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<p><strong>Table of Contents</strong></p>
<img class="editor-inline-macro" src="/plugins/servlet/confluence/placeholder/macro?definition=e3RvY30&amp;locale=en_GB&amp;version=2" data-macro-name="toc">

<h1>Groovy 1.8 release notes</h1>

<p>The 1.8 release of Groovy comes with many new features that greatly enhance</p>
<ul>
	<li>the dynamic expressiveness of Groovy, specifically for defining DSLs</li>
	<li>runtime performance</li>
	<li>concurrent and parallel execution</li>
	<li>design by contract</li>
	<li>functional programming style</li>
	<li>first-class JSON support</li>
	<li>compile-time meta programming</li>
	<li>and more helpers and library additions</li>
</ul>

<p>These features have undergone the Groovy developer process with formal descriptions, discussion, and voting (GEP - Groovy Enhancement Proposal) for core parts and less formal developer discussions and JIRA voting for additional parts.</p>

<p>Our goal has stayed the same, though: to give the Java developer a tool that makes him more productive, allows him to achieve his goals faster and with a smaller margin of error, and extend the scalability of the Java platform from full-blown enterprise projects to everyday &quot;getting things done&quot; tasks.</p>

<h2>Command chains for nicer Domain-Specific Languages</h2>

<p>Thanks to its flexible syntax and its compile-time and runtime metaprogramming capabilities, Groovy is well known for its Domain-Specific Language capabilities. However, we felt that we could improve upon the syntax further by removing additional punctuation symbols when users chain method calls. This allows DSL implementors to develop command descriptions that read almost like natural sentences.</p>

<p>Before Groovy 1.8, we could omit parentheses around the arguments of a method call for top-level statements. But we couldn't chain method calls. The new &quot;command chain&quot; feature allows us to chain such parentheses-free method calls, requiring neither parentheses around arguments, nor dots between the chained calls. The general idea is that a call like <code>a b c d</code> will actually be equivalent to <code>a(b).c(d)</code>. This also works with multiple arguments, closure arguments, and even named arguments. Furthermore, such command chains can also appear on the right-hand side of assignments. Let's have a look at some examples supported by this new syntax:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
turn left then right                           // equivalent to: turn(left).then(right)
take 2.pills of chloroquinine after 6.hours    // equivalent to: take(2.pills).of(chloroquinine).after(6.hours)
paint wall with red, green and yellow          // equivalent to: paint(wall).with(red, green).and(yellow)

// with named parameters too
check that: margarita tastes good             // equivalent to: check(that: margarita).tastes(good)

// with closures as parameters
given { } when { } then { }                    // equivalent to: given({}).when({}).then({})
</pre></td></tr></table>

<p>It is also possible to use methods in the chain which take no arguments, but in that case, the parentheses are needed:</p>

<p>If your command chain contains an odd number of elements, the chain will be composed of method / arguments, and will finish by a final property access:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
take 3 cookies                                 // equivalent to: take(3).cookies
                                               // and also this: take(3).getCookies()
</pre></td></tr></table>

<p>This new command chain approach opens up interesting possibilities in terms of the much wider range of DSLs which can now be written in Groovy. This new feature has been developed thanks to the Google Summer of Code program, where our student, Lidia, helped us modify the Groovy Antlr grammar to extend top-level statements to accept that command chain syntax.</p>

<p>The above examples illustrate using a command chain based DSL but not how to create one. You will be able to find some <a href="http://groovyconsole.appspot.com/tag/gep3">further examples</a> of &quot;command chains&quot; on the Groovy Web Console but to illustrate creating such a DSL, we will show just a couple of examples - first using maps and Closures:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
show = { println it }
square_root = { Math.sqrt(it) }

def please(action) {
  [the: { what ->
    [of: { n -> action(what(n)) }]
  }]
}

please show the square_root of 100             // equivalent to: please(show).the(square_root).of(100)
// ==> 10.0
</pre></td></tr></table>

<p>Or if you prefer Japanese and a metaprogramming style (see <a href="http://d.hatena.ne.jp/uehaj/20100919/1284906117">here</a> for more details):</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
// Japanese DSL using GEP3 rules
Object.metaClass.を =
Object.metaClass.の = { clos -> clos(delegate) }

まず = { it }
表示する = { println it }
平方根 = { Math.sqrt(it) }

まず 100 の 平方根 を 表示する  // First, show the square root of 100
// => 10.0
</pre></td></tr></table>

<p>As a second example, consider how you might write a DSL for simplifying one of your existing APIs. Maybe you need to put this code in front of customers, business analysts or testers who might be not hard-core Java developers. We'll use the <code>Splitter</code> from the Google <a href="http://code.google.com/p/guava-libraries/">Guava libraries</a> project as it already has a nice Fluent API. Here is how we might use it out of the box:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@Grab('com.google.guava:guava:r09')
import com.google.common.base.*
def result = Splitter.on(',').trimResults(CharMatcher.is('_' as char)).split("_a ,_b_ ,c__").iterator().toList()
assert result == ['a ', 'b_ ', 'c']
</pre></td></tr></table>
<p>It reads fairly well for a Java developer but if that is not your target audience or you have many such statements to write, it could be considered a little verbose. Again, there are many options for writing a DSL. We'll keep it simple with Maps and Closures. We'll first write a helper method:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def split(string) {
  [on: { sep ->
    [trimming: { trimChar ->
      Splitter.on(sep).trimResults(CharMatcher.is(trimChar as char)).split(string).iterator().toList()
    }]
  }]
}
</pre></td></tr></table>
<p>now instead of this line from our original example:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def result = Splitter.on(',').trimResults(CharMatcher.is('_' as char)).split("_a ,_b_ ,c__").iterator().toList()
</pre></td></tr></table>
<p>we can write this:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def result = split "_a ,_b_ ,c__" on ',' trimming '_'
</pre></td></tr></table>

<h2>Performance improvements</h2>

<p>Groovy's flexible metaprogramming model involves numerous decision points when making method calls or accessing properties to determine whether any metaprogamming hooks are being utilized. During complex expression calculations, such decision points involved identical checks being executed numerous times. Recent performance improvements allow some of these checks to be bypassed during an expression calculation once certain initial assumptions have been checked. Basically if certain preconditions hold, some streamlining can take place.</p>

<p>Groovy 1.8.0 contains two main streams of optimization work:</p>
<ul>
	<li>There are several optimizations for basic operations on integers like plus, minus, multiply, increment, decrement and comparisons. This version doesn't support the mixed usage of different types. If an expression contains different types, then it falls back to the classical way of performing the operation, i.e. no streamlining occurs.</li>
	<li>There is also an optimization for direct method calls. Such a method call is done directly if it is done on &quot;this&quot; and if the argument types are a direct match with the parameter types of the method we may call. Since this is an operation that does not behave too well with a method call logic based on runtime types we select only methods where the primitive types match, the parameter types are final or for methods that take no arguments. Currently methods with a variable parameter list are not matched in general, unless a fitting array is used for the method call.</li>
</ul>

<p>Those two areas of optimization are only the beginning of further similar improvements. Upcoming versions of the Groovy 1.8.x branch will see more optimizations coming. In particular, primitive types other than integers should be expected to be supported shortly.</p>

<h2>GPars bundled within the Groovy distribution</h2>

<p>The <a href="http://gpars.codehaus.org">GPars</a> project offers developers new intuitive and safe ways to handle Java or Groovy tasks concurrently, asynchronously, and distributed by utilizing the power of the Java platform and the flexibility of the Groovy language. Groovy 1.8 now bundles GPars 0.11 in the libraries of the Groovy installation, so that you can leverage all the features of the library for<br />
Fork/Join, Map/Filter/Reduce, DataFlow, Actors, Agents, and more with all the Groovy goodness.</p>

<p>To learn more about GPars, head over to the <a href="http://gpars.codehaus.org/">GPars website</a>, read the <a href="http://gpars.org/guide/index.html">detailed online user guide</a>, or check out chapter 17 of <a href="http://www.manning.com/koenig2">Groovy in Action, 2nd Edition (MEAP)</a>.</p>

<h2>Closure enhancements</h2>

<p>Closures are a central and essential piece of the Groovy programming language and are used in various ways throughout the Groovy APIs. In Groovy 1.8, we introduce the ability to use closures as annotation parameters. Closures are also a key part of what gives Groovy its functional flavor.</p>

<h3>Closure annotation parameters</h3>

<p>In Java, there's a limited set of types you can use as annotation parameters (String, primitives, annotations, classes, and arrays of these). But in Groovy 1.8, we're going further and let you use closures as annotation parameters – which are actually transformed into a class parameter for compatibility reasons.</p>

@Retention(RetentionPolicy.RUNTIME)
@interface Invariant {
    Class value() // will hold a closure class
}

@Invariant({ number >= 0 })
class Distance {
    float number
    String unit
}

def d = new Distance(number: 10, unit: "meters")

def anno = Distance.getAnnotation(Invariant)
def check = anno.value().newInstance(d, d)

assert check(d)
</pre></td></tr></table>

<p>Closure annotation parameters open up some interesting possibilities for framework authors! As an example, the <a href="https://github.com/andresteingress/gcontracts/wiki/">GContracts</a> project, which brings the &quot;Design by Contract&quot; paradigm to Groovy makes heavy use of annotation parameters to allow preconditions, postconditions and invariants to be declared.</p>

<h3>Closure functional flavors</h3>

<h4>Closure composition</h4>

<p>If you recall your math lessons, function composition may be a concept you're familiar with. And in turn, <strong>Closure composition</strong> is about that: the ability to compose Closures together to form a new Closure which chains the call of those Closures. Here's an example of composition in action:</p>

def times3plus2 = plus2 &lt;&lt; times3
assert times3plus2(3) == 11
assert times3plus2(4) == plus2(times3(4))

def plus2times3 = times3 &lt;&lt; plus2
assert plus2times3(3) == 15
assert plus2times3(5) == times3(plus2(5))

// reverse composition
assert times3plus2(3) == (times3 >> plus2)(3)
</pre></td></tr></table>

<p>To see more examples of Closure composition and reverse composition, please have a look at our <a href="http://svn.codehaus.org/groovy/trunk/groovy/groovy-core/src/test/groovy/ClosureComposeTest.groovy">test case</a>.</p>

<h4>Closure trampoline</h4>

<p>When writing recursive algorithms, you may be getting the infamous stack overflow exceptions, as the stack starts to have a too high depth of recursive calls. An approach that helps in those situations is by using Closures and their new <a href="http://en.wikipedia.org/wiki/Tail_call#Through_trampolining">trampoline</a> capability.</p>

<p>Closures are wrapped in a <code>TrampolineClosure</code>. Upon calling, a trampolined Closure will call the original Closure waiting for its result. If the outcome of the call is another instance of a <code>TrampolineClosure</code>, created perhaps as a result to a call to the <code>trampoline()</code> method, the Closure will again be invoked. This repetitive invocation of returned trampolined Closures instances will continue until a value other than a trampolined Closure is returned. That value will become the final result of the trampoline. That way, calls are made serially, rather than filling the stack.</p>

<p>Here's an example of the use of <code>trampoline()</code> to implement the factorial function:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def factorial
factorial = { int n, def accu = 1G ->
    if (n &lt; 2) return accu
    factorial.trampoline(n - 1, n * accu)
}
factorial = factorial.trampoline()

assert factorial(1)    == 1
assert factorial(3)    == 1 * 2 * 3
assert factorial(1000) == 402387260... // plus another 2560 digits
</pre></td></tr></table>

<h4>Closure memoization</h4>

<p>Another improvement to Closures is the ability to <a href="http://en.wikipedia.org/wiki/Memoization">memoize</a> the outcome of previous (ideally side-effect free) invocations of your Closures. The return values for a given set of Closure parameter values are kept in a cache, for those memoized Closures. That way, if you have an expensive computation to make that takes seconds, you can put the return value in cache, so that the next execution with the same parameter will return the same result – again, we assume results of an invocation are the same given the same set of parameter values.</p>

<p>There are three forms of memoize functions:</p>
<ul>
	<li>the standard <code>memoize()</code> which caches all the invocations</li>
	<li><code>memoizeAtMost(max)</code> call which caches a maximum number of invocations</li>
	<li><code>memoizeAtLeast(min)</code> call which keeps at least a certain number of invocation results</li>
	<li>and <code>memoizeBetween(min, max)</code> which keeps a range results (between a minimum and a maximum)</li>
</ul>

<p>Let's illustrate that:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def plus = { a, b -> sleep 1000; a + b }.memoize()
assert plus(1, 2) == 3 // after 1000ms
assert plus(1, 2) == 3 // return immediately
assert plus(2, 2) == 4 // after 1000ms
assert plus(2, 2) == 4 // return immediately
 
// other forms:

// at least 10 invocations cached
def plusAtLeast = { ... }.memoizeAtLeast(10)

// at most 10 invocations cached
def plusAtMost = { ... }.memoizeAtMost(10)

// between 10 and 20 invocations cached
def plusAtLeast = { ... }.memoizeBetween(10, 20)
</pre></td></tr></table>

<h3>Currying improvements</h3>

<p>Currying improvements have also been backported to recent releases of Groovy 1.7, but it's worth outlining here for reference. Currying used to be done only from left to right, but it's also possible to do it from right to left, or from a given index, as the following examples demonstrate:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
// right currying
def divide = { a, b -> a / b }
def halver = divide.rcurry(2)
assert halver(8) == 4
 
// currying n-th parameter
def joinWithSeparator = { one, sep, two ->
    one + sep + two
}
def joinWithComma =
    joinWithSeparator.ncurry(1, ', ')
assert joinWithComma('a', 'b') == 'a, b'
</pre></td></tr></table>

<h2>Native JSON support</h2>

<p>With the ubiquity of JSON as an interchange format for our applications, it is natural that Groovy added support for JSON, in a similar fashion as the support Groovy's always had with XML. So Groovy 1.8 introduces a JSON builder and parser.</p>

<h3>Reading JSON</h3>

<p>A <code>JsonSlurper</code> class allows you to parse JSON payloads, and access the nested Map and List data structures representing that content. JSON objects and arrays are indeed simply represented as Maps and Lists, giving you access to all the GPath expression benefits (subscript/property notation, find/findAll/each/inject/groupBy/etc.). Here's an example showing how to find all the recent commit messages on the Grails project:</p>

def payload = new URL("http://github.com/api/v2/json/commits/list/grails/grails-core/master").text

def slurper = new JsonSlurper()
def doc = slurper.parseText(payload)

doc.commits.message.each { println it }
</pre></td></tr></table>

<p>If you want to see some more examples of the usage of the JSON parser, you can have a look at the <a href="http://svn.codehaus.org/groovy/branches/GROOVY_1_8_X/src/test/groovy/json/JsonSlurperTest.groovy">JsonSlurper tests</a> in our code base.</p>

<h3>JSON builder</h3>

<p>Parsing JSON data structures is one thing, but we should also be able to produce JSON content just like we create markup with the <code>MarkupBuilder</code>. The following example:</p>

def json = new JsonBuilder()

json.person {
    name "Guillaume"
    age 33
    pets "Hector", "Felix"
}

println json.toString()
</pre></td></tr></table>

<p>Will create the JSON output:</p>

<p>You can find some more usages of the JSON builder in our <a href="http://svn.codehaus.org/groovy/branches/GROOVY_1_8_X/src/test/groovy/json/JsonBuilderTest.groovy">JsonBuilder tests</a>.</p>

<h3>Pretty printing JSON content</h3>

<p>When given a JSON data structure, you may wish to pretty-print it, so that you can more easily inspect it, with a more friendly layout. So for instance, if you want to pretty print the result of the previous example, you could do:</p>

println JsonOutput.prettyPrint('''{"person":{"name":"Guillaume","age":33,"pets":["Hector","Felix"]}}''')
</pre></td></tr></table>

<p>Which would result in the following pretty-printed output:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
{
    "person": {
        "name": "Guillaume",
        "age": 33,
        "pets": [
            "Hector",
            "Felix"
        ]
    }
}
</pre></td></tr></table>

<h2>New AST Transformations</h2>

<p>The Groovy compiler reads the source code, builds an Abstract Syntax Tree (AST) from it, and then puts the AST into bytecode. With AST transformations, the programmer can hook into this process. A general description of this process, an exhaustive description of all available transformations, and a guide of how to write you own ones can be found for example in <a href="http://www.manning.com/koenig2">Groovy in Action, 2nd Edition (MEAP)</a>, chapter 9.</p>

<p>Below is a list of all new transformations that come with Groovy 1.8. They save you from writing repetitive code and help avoiding common errors.</p>

<p>You can annotate your classes with the @Log transformation to automatically inject a logger in your Groovy classes, under the <code>log</code> property. Four kind of loggers are actually available:</p>
<ul>
	<li><code>@Log</code> for java.util.logging</li>
	<li><code>@Commons</code> for Commons-Logging</li>
	<li><code>@Log4j</code> for Log4J</li>
	<li><code>@Slf4j</code> for SLF4J</li>
</ul>

<p>Here's a sample usage of the @Log transformation:</p>

@Log
class Car {
    Car() {
        log.info 'Car constructed'
    }
}

def c = new Car()
</pre></td></tr></table>

<p>You can change the name of the logger by specifying a different name, for instance with <code>@Log('myLoggerName')</code>.</p>

<p>Another particularity of these logger AST transformations is that they take care of wrapping and safe-guarding logger calls with the usual <code>isSomeLevelEnabled()</code> calls. So when you write <code>log.info 'Car constructed'</code>, the generated code is actually equivalent to:</p>

<h3>@Field</h3>

<p>When defining variables in a script, those variables are actually local to the script's run method, so they are not accessible from other methods of the script. A usual approach to that problem has been to store variables in the binding, by not def'ining those variables and by just assigning them a value. Fortunately, the <code>@Field</code> transformation provides a better alternative: by annotating your variables in your script with this annotation, the annotated variable will become a private field of the script class.</p>

<p>More concretely, you'll be able to do as follows:</p>

<h3>@PackageScope enhancements</h3>

<p>The @PackageScope annotation can be placed on classes, methods or fields and is used for turning off Groovy's visibility conventions and reverting back to Java conventions. This ability is usually only needed when using 3rd party libraries which rely on the package scope visibility. When adding the <code>@PackageScope</code> annotation to a field, Groovy will assign package scope access to the field rather than automatically treating it as a property (and adding setters/getters). Annotating a class or method with <code>@PackageScope</code> will cause Groovy to revert to Java's convention of leaving the class/method as package scoped rather than automatically promoting it to public scope. The class variant can also take one or more parameters to allow nested setting of visibility of attributes within the class - see the Javadoc for more details. Recent releases of Groovy 1.7 have had a more limited version of this annotation.</p>

<h3>@AutoClone</h3>

<p>The <code>@AutoClone</code> annotation is placed on classes which you want to be <code>Cloneable</code>. The annotation instructs the compiler to execute an AST transformation which adds a public <code>clone()</code> method and adds <code>Cloneable</code> to the classes implements list of interfaces. Because the JVM doesn't have a one-size-fits-all cloning strategy, several customizations exist for the cloning implementation:</p>
<ul>
	<li>By default, the <code>clone()</code> method will call <code>super.clone()</code> before calling <code>clone()</code> on each <code>Cloneable</code> property of the class. Example usage:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.AutoClone

@AutoClone
class Person {
    String first, last
    List favItems
    Date since
}
</pre></td></tr></table>
Which will create a class of the following form:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
class Person implements Cloneable {
    ...
    public Object clone() throws CloneNotSupportedException {
        Object result = super.clone()
        result.favItems = favItems.clone()
        result.since = since.clone()
        return result
    }
    ...
}
</pre></td></tr></table></li>
	<li>Another popular cloning strategy is known as the copy constructor pattern. If any of your fields are <code>final</code> and <code>Cloneable</code> you should set <code>style=COPY_CONSTRUCTOR</code> which will then use the copy constructor pattern.</li>
	<li>As a final alternative, if your class already implements the <code>Serializable</code> or <code>Externalizable</code> interface, you might like to set <code>style=SERIALIZATION</code> which will then use serialization to do the cloning.</li>
</ul>

<p>See the Javadoc for <code>AutoClone</code> for further details.</p>

<h3>@AutoExternalizable</h3>

<p>The <code>@AutoExternalizable</code> class annotation is used to assist in the creation of <code>Externalizable</code> classes. The annotation instructs the compiler to execute an AST transformation which adds <code>writeExternal()</code> and <code>readExternal()</code> methods to a class and adds <code>Externalizable</code> to the interfaces which the class implements. The <code>writeExternal()</code> method writes each property (or field) for the class while the <code>readExternal()</code> method will read each one back in the same order. Properties or fields marked as <code>transient</code> are ignored. Example usage:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.*

@AutoExternalize
class Person {
    String first, last
    List favItems
    Date since
}
</pre></td></tr></table>
<p>Which will create a class of the following form:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
class Person implements Externalizable {
    ...
    void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(first)
        out.writeObject(last)
        out.writeObject(favItems)
        out.writeObject(since)
    }

void readExternal(ObjectInput oin) {
        first = oin.readObject()
        last = oin.readObject()
        favItems = oin.readObject()
        since = oin.readObject()
    }
    ...
}
</pre></td></tr></table>

<h3>Controlling the execution of your code</h3>

<p>When integrating user-provided Groovy scripts and classes in your Java application, you may be worried about code that would eat all your CPU with infinite loops, or that call methods like <code>System.exit(0)</code> (for the latter, check the section on compiler customizers, and particularly the <code>SecureASTCustomizer</code>). It would be interesting to have a wait to control the execution of that Groovy code, to be able to interrupt its execution when the thread is interrupted, when a certain duration has elapsed, or when a certain condition is met (lack of resources, etc).</p>

<p>Groovy 1.8 introduces three transformations for those purposes, as we shall see in the following sections. By default, the three transformations add some checks in at the beginning of each method body, and each closure body, to check whether a condition of interruption is met or not.</p>

<p>Note that those transformations are local (triggered by an annotation). If you want to apply them transparently, so that the annotation doesn't show up, I encourage you to have a look at the <code>ASTTransformationCustomizer</code> explained at the end of this article.</p>

<p>Cédric Champeau, our most recent Groovy committer, who implemented those features, has a <a href="http://www.jroller.com/melix/entry/upcoming_groovy_goodness_automatic_thread">very nice blog post</a> covering those code interruption transformations.</p>

<h4>@ThreadInterrupt</h4>

<p>You don't need to write checks in your scripts for whether the current thread of execution has been interrupted or not, by default, the transformation will add those checks for you for scripts and classes, at the beginning of each method body and closure body:</p>

while (true) {
    // eat lots of CPU
}
</pre></td></tr></table>

<p>You can specify a <code>checkOnMethodStart</code> annotation parameter (defaults to true) to customize where checks are added by the transformation (adds an interrupt check by default as the first statement of a method body). And you can also specify the <code>applyToAllClasses</code> annotation parameter (default to true) if you want to specify whether only the current class or script should have this interruption logic applied or not.</p>

<h4>@TimedInterrupt</h4>

<p>With <code>@TimedInterrupt</code>, you can interrupt the script after a certain amount of time:</p>

while (true) {
    // eat lots of CPU
}
</pre></td></tr></table>

<p>In addition to the previous annotation parameters we mentioned for <code>@ThreadInterrupt</code>, you should specify <code>value</code>, the amount of time to wait, and <code>unit</code> (defaulting to <code>TimeUnit.SECONDS</code>) to specify the unit of time to be used.</p>

<h4>@ConditionalInterrupt</h4>

<p>An example of <code>@ConditionalInterrupt</code> which leverages the closure annotation parameter feature, and the <code>@Field</code> transformation as well:</p>

@Field int counter = 0

100.times {
    println 'executing script method...'
}
</pre></td></tr></table>

<p>You can imagine defining any kind of condition: on counters, on resource availability, on resource usage, and more.</p>

<h3>@ToString</h3>

<p>Provides your classes with a default <code>toString()</code> method which prints out the values of the class' properties (and optionally the property names and optionally fields). A basic example is here:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.ToString

@ToString
class Person {
    String name
    int age
}

println new Person(name: 'Pete', age: 15)
// => Person(Pete, 15)
</pre></td></tr></table>
<p>And here's another example using a few more options:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@ToString(includeNames = true, includeFields = true)
class Coord {
    int x, y
    private z = 0
}
println new Coord(x:20, y:5)
// => Coord(x:20, y:5, z:0)
</pre></td></tr></table>

<h3>@EqualsAndHashCode</h3>

<p>Provides your classes with <code>equals()</code> and <code>hashCode()</code> methods based on the values of the class' properties (and optionally fields and optionally super class values for <code>equals()</code> and <code>hashCode()</code>).</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.EqualsAndHashCode

@EqualsAndHashCode
class Coord {
    int x, y
}

def c1 = new Coord(x:20, y:5)
def c2 = new Coord(x:20, y:5)

assert c1 == c2
assert c1.hashCode() == c2.hashCode()
</pre></td></tr></table>

<h3>@TupleConstructor</h3>

<p>Provides a tuple (ordered) constructor. For POGOs (plain old Groovy objects), this will be in addition to Groovy's default &quot;named-arg&quot; constructor.</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.TupleConstructor

@TupleConstructor
class Person {
    String name
    int age
}

def p1 = new Person(name: 'Pete', age: 15) // map-based
def p2 = new Person('Pete', 15)            // tuple-based

assert p1.name == p2.name
assert p1.age == p2.age
</pre></td></tr></table>

<h3>@Canonical</h3>

<p>Allows you to combine <code>@ToString</code>, <code>@EqualsAndHashCode</code> and <code>@TupleConstructor</code>. For those familiar with Groovy's <code>@Immutable</code> transform, this provides similar features but for mutable objects.</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.Canonical

@Canonical
class Person {
    String name
    int age
}

def p1 = new Person(name: 'Pete', age: 15)
def p2 = new Person('Paul', 15)

p2.name = 'Pete'
println "${p1.equals(p2)} $p1 $p2"
// => true Person(Pete, 15) Person(Pete, 15)
</pre></td></tr></table>

<p>By default, <code>@Canonical</code> gives you vanilla versions for each of the combined annotations. If you want to use any of the special features that the individual annotations give you, simply include the individual annotation as well.</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import groovy.transform.*

@Canonical
@ToString(includeNames = true)
class Person {
    String name
    int age
}

def p = new Person(name: 'Pete', age: 15)
println p
// => Person(name:Pete, age:15)
</pre></td></tr></table>

<p>You will find a great <a href="http://prystash.blogspot.com/2011/04/groovy-18-playing-with-new-canonical.html">write-up on @Canonical, @ToString, @EqualsAndHashCode and @TupleConstructor</a> on John Prystash's weblog.</p>

<h3>@InheritConstructors</h3>

<p>Sometimes, when you want to subclass certain classes, you also need to override all the constructors of the parent, even if only to call the super constructor. Such a case happens for instance when you define your own exceptions, you want your exceptions to also have the constructors taking messages and throwable as parameters. But instead of writing this kind of boilerplate code each time for your exceptions:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
class CustomException extends Exception {
    CustomException() { super() }
    CustomException(String msg) { super(msg) }
    CustomException(String msg, Throwable t) { super(msg, t) }
    CustomException(Throwable t) { super(t) }
}
</pre></td></tr></table>

<p>Simply use the @InheritConstructors transformation which takes care of overriding the base constructors for you:</p>

@InheritConstructors
class CustomException extends Exception {}
</pre></td></tr></table>

<h3>@WithReadLock and @WithWriteLock</h3>

<p>Those two transformations, combined together, simplify the usage of <code>java.util.concurrent.locks.ReentrantReadWriteLock</code>, are safer to use than the <code>synchronized</code> keyword, and improve upon the <code>@Synchronized</code> transformation with a more granular locking.</p>

<p>More concretely, with an example, the following:</p>

class ResourceProvider {
    private final Map&lt;String, String> data = new HashMap&lt;&gt;()

@WithReadLock
    String getResource(String key) {
        return data.get(key)
    }

@WithWriteLock
    void refresh() {
        //reload the resources into memory
    }
}
</pre></td></tr></table>
<p>Will generate code as follows:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import java.util.concurrent.locks.ReentrantReadWriteLock
import java.util.concurrent.locks.ReadWriteLock

class ResourceProvider {
    private final ReadWriteLock $reentrantlock = new ReentrantReadWriteLock()
    private final Map&lt;String, String> data = new HashMap&lt;String, String>()

String getResource(String key) {
        $reentrantlock.readLock().lock()
        try {
            return data.get(key)
        } finally {
            $reentrantlock.readLock().unlock()
        }
    }

void refresh() throws Exception {
        $reentrantlock.writeLock().lock()
        try {
            //reload the resources into memory
        } finally {
            $reentrantlock.writeLock().unlock()
        }
    }
}
</pre></td></tr></table>

<h3>@ListenerList</h3>

<p>If you annotate a Collection type field with @ListenerList, it generates everything that is needed to follow the bean event pattern. This is kind of an EventType independent version of what @Bindable is for PropertyChangeEvents.</p>

<p>This example shows the most basic usage of the @ListenerList annotation. The easiest way to use this annotation is to annotate a field of type List and give the List a generic type. In this example we use a List of type MyListener. MyListener is a one method interface that takes a MyEvent as a parameter. The following code is some sample source code showing the simplest scenario.</p>

class MyEvent {
    def source
    String message

MyEvent(def source, String message) {
        this.source = source
        this.message = message
    }
}
class MyBeanClass {
    @ListenerList
    List&lt;MyListener> listeners
}
</pre></td></tr></table>

<ul>
	<li>+ addMyListener(MyListener) : void - This method is created based on the generic type of your annotated List field. The name and parameter type is are based on the List field's generic parameter.</li>
	<li>+ removeMyListener(MyListener) : void- This method is created based on the generic type of your annotated List field. The name and parameter type is are based on the List field's generic parameter.</li>
	<li>+ getMyListeners() : MyListener[] - This method is created based on the generic type of your annotated List field.The name is the plural form of the List field's generic parameter, and the return type is an array of the generic parameter.</li>
	<li>+ fireEventOccurred(MyEvent) : void - This method is created based on the type that the List's generic type points to. In this case, MyListener is a one method interface with an eventOccurred(MyEvent) method. The method name is fire[MethodName of the interface] and the parameter is the parameter list from the interface. A fireX method will be generated for each public method in the target class, including overloaded methods. </li>
</ul>

<h2>Alignments with JDK 7</h2>

<p>Groovy 1.9 will be the version which will align as much as possible with the upcoming JDK 7, so beyond those aspects already covered in Groovy (like strings in switch and others), most of those &quot;Project Coin&quot; proposals will be in 1.9, except the &quot;diamond operator&quot; which was added in 1.8, as explained in the following paragraph.</p>

<h3>Diamond operator</h3>

<p>Java 7 will introduce the &quot;diamond&quot; operator in generics type information, so that you can avoid the usual repetition of the parameterized types. Groovy decided to adopt the notation before JDK 7 is actually released. So instead of writing:</p>

<p>You can &quot;omit&quot; the parameterized types and just use the pointy brackets, which now look like a diamond:</p>

<h2>New DGM methods</h2>

<ul>
	<li>count Closure variants
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def isEven = { it % 2 == 0 }
assert [2,4,2,1,3,5,2,4,3].count(isEven) == 5
</pre></td></tr></table></li>
	<li>countBy
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
assert [0:2, 1:3] == [1,2,3,4,5].countBy{ it % 2 }
assert [(true):2, (false):4] == 'Groovy'.toList().countBy{ it == 'o' }
</pre></td></tr></table></li>
	<li>plus variants specifying a starting index
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
assert [10, 20].plus(1, 'a', 'b') == [10, 'a', 'b', 20]
</pre></td></tr></table></li>
	<li>equals for Sets and Maps now do flexible numeric comparisons (on values for Maps)
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
assert [1L, 2.0] as Set == [1, 2] as Set
assert [a:2, b:3] == [a:2L, b:3.0]
</pre></td></tr></table></li>
	<li>toSet for primitive arrays, Strings and Collections
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
assert [1, 2, 2, 2, 3].toSet() == [1, 2, 3] as Set
assert 'groovy'.toSet() == ['v', 'g', 'r', 'o', 'y'] as Set
</pre></td></tr></table></li>
	<li>min / max methods for maps taking closures<br />
(also available in Groovy 1.7)
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def map = [a: 1, bbb: 4, cc: 5, dddd: 2]

assert map.max { it.key.size() }.key == 'dddd'
assert map.min { it.value }.value == 1
</pre></td></tr></table></li>
	<li>map withDefault{}<br />
Oftentimes, when using a map, for example for counting the frequency of words in a document, you need to check that a certain key exists, before doing something with the associating value (like incrementing it). Nothing really complex, but we could improve upon that with a new method, called <code>withDefault</code>. So instead of writing code like below:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def words = "one two two three three three".split()
def freq = [:]
words.each {
    if (it in freq)
        freq[it] += 1
    else
        freq[it] = 1
}
</pre></td></tr></table>
Thanks to the new method (also backported to 1.7), you can write the example as follows:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def words = "one two two three three three".split()
def freq = [:].withDefault { k -> 0 }
words.each {
        freq[it] += 1
}
</pre></td></tr></table></li>
</ul>

<h2>Miscellaneous</h2>

<h3>Slashy strings</h3>

<p>Slashy strings are now multi-line:</p>

assert poem.readLines().size() == 4
</pre></td></tr></table>
<p>This is particularly useful for multi-line regexs when using the regex free-spacing comment style (though you would still need to escape slashes):</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
// match yyyy-mm-dd from this or previous century
def dateRegex = /(?x)     # enable whitespace and comments
((?:19|20)\d\d)           # year (group 1) (non-capture alternation for century)
-                         # seperator
(0[1-9]|1[012])           # month (group 2)
-                         # seperator
(0[1-9]|[12][0-9]|3[01])  # day (group 3)
/

assert '04/04/1988' == '1988-04-04'.find(dateRegex) { all, y, m, d -> [d, m, y].join('/') }
</pre></td></tr></table>

<h3>Dollar slashy strings</h3>

<p>A new string notation has been introduced: the &quot;dollar slashy&quot; string. This is a multi-line GString similar to the slashy string, but with slightly different escaping rules. You are no longer required to escape slash (with a preceding backslash) but you can use '$$' to escape a '$' or '$/' to escape a slash if needed. Here's an example of its usage:</p>

def dollarSlashy = $/
    Hello $name,
    today we're ${date}
    $ dollar-sign
    $$ dollar-sign
    \ backslash
    / slash
    $/ slash
/$

println dollarSlashy
</pre></td></tr></table>

<p>This form of string is typically used when you wish to embed content that may naturally contains slashes or backslashes and you don't want to have to rework the content to include all of the necessary escaping. Some examples are shown below:</p>

<ul>
	<li>Embedded XML fragments with backslashes:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def tic = 'tic'

def xml = $/
  &lt;xml>
  $tic\tac
  &lt;/xml>
/$

assert "\n&lt;xml>\ntic\\tac\n&lt;/xml>\n" == xml
</pre></td></tr></table>
Better than a normal (now multi-line) slashy string where you would have to escape the slashes or a triple quote (&quot;&quot;&quot;) GString where you would have to escape the backslashes.</li>
</ul>

<ul>
	<li>Or windows pathnames containing a slash at the end:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def dir = $/C:\temp\/$
</pre></td></tr></table>
Previously, triple quote (&quot;&quot;&quot;) GString required extra escaping, and the above sequence was illegal for a normal slashy string. Now, ugly workarounds are not needed.</li>
</ul>

<ul>
	<li>Embedding multi-line regexs when using the regex free-spacing comment style (particularly ones which contain slashes):
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
// match yyyy-mm-dd from current or previous century
def dateRegex = $/(?x)    # enable whitespace and comments
((?:19|20)\d\d)           # year (group 1) (non-capture alternation for century)
[- /.]                    # seperator
(0[1-9]|1[012])           # month (group 2)
[- /.]                    # seperator
(0[1-9]|[12][0-9]|3[01])  # day (group 3)
/$

assert '04/04/1988' == '1988-04-04'.find(dateRegex) { all, y, m, d -> [d, m, y].join('/') }
assert '10-08-1989' == '1989/08/10'.find(dateRegex) { all, y, m, d -> [d, m, y].join('-') }
</pre></td></tr></table>
So, you can cut and paste most PERL regex examples without further escaping.</li>
</ul>

<ul>
	<li>Or Strings which are themselves Groovy code fragments containing slashes:
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def alphabet = ('a'..'z').join('')
def code = $/
    def normal = '\b\t\n\r'
    def slashy = /\b\t\n\r/
    assert '$alphabet'.size() == 26
    assert normal.size() == 4
    assert slashy.size() == 8
/$
println code
Eval.me(code)
</pre></td></tr></table>
Again allowing you to cut and paste many slashy string Groovy examples and have them embedded within dollar slashy strings without further escaping.</li>
</ul>

<h3>Compilation customizers</h3>

<p>The compilation of Groovy code can be configured through the <code>CompilerConfiguration</code> class, for example for setting the encoding of your sources, the base script class, the recompilation parameters, etc). <code>CompilerConfiguration</code> now has a new option for setting <em>compilation customizers</em> (belonging to the <code>org.codehaus.groovy.control.customizers</code> package). Those customizers allow to customize the compilation process in three ways:</p>
<ul>
	<li>adding default imports with the <code>ImportCustomizer</code>: so you don't have to always add the same imports all over again</li>
	<li>securing your scripts and classes with the <code>SecureASTCustomizer</code>: by allowing/disallowing certain classes, or special AST nodes (Abstract Syntax Tree), filtering imports, you can secure your scripts to avoid malicious code or code that would go beyond the limits of what the code should be allowed to do.</li>
	<li>applying AST transformations with the <code>ASTTransformationCustomizer</code>: lets you apply transformations to all the class nodes of your compilation unit.</li>
</ul>

<p>For example, if you want to apply the @Log transformation to all the classes and scripts, you could do:</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import org.codehaus.groovy.control.CompilerConfiguration
import org.codehaus.groovy.control.customizers.*
import groovy.util.logging.Log

def configuration = new CompilerConfiguration()
configuration.addCompilationCustomizers(new ASTTransformationCustomizer(Log))

def shell = new GroovyShell(configuration)
shell.evaluate("""
    class Car {
        Car() {
            log.info 'Car constructed'
        }
    }

log.info 'Constructing a car'
    def c = new Car()
""")
</pre></td></tr></table>

<p>This will log the two messages, the one from the script, and the one from the Car class constructor, through java.util.logging. No need to apply the @Log transformation manually to both the script and the class: the transformation is applied to all class nodes transparently. This mechanism can also be used for adding global transformations, just for the classes and scripts that you compile, instead of those global transformations being applied to all scripts and classes globally.</p>

<p>If you want to add some default imports (single import, static import, star import, star static imports, and also aliased imports and static imports), you can use the import customizer as follows:</p>

def configuration = new CompilerConfiguration()
def custo = new ImportCustomizer()
custo.addStaticStar(Math.name)
configuration.addCompilationCustomizers(custo)

def shell = new GroovyShell(configuration)
shell.evaluate("""
    cos PI/3
""")
</pre></td></tr></table>

<p>When you want to evaluate Math expressions, you don't need anymore to use the <code>import static java.lang.Math.*</code> star static import to import all the Math constants and static functions.</p>

<h3>(G)String to Enum coercion</h3>

<p>Given a String or a GString, you can coerce it to Enum values bearing the same name, as the sample below presents:</p>

// coercion with as
def r = "red" as Color

// implicit coercion
Color b = "blue"

// with GStrings too
def g = "${'green'}" as Color
</pre></td></tr></table>

<h3>Maps support isCase()</h3>

<p>Maps now support <code>isCase()</code>, so you can use maps in your switch/case statements, for instance:</p>

switch (val) {
    case m: "key in map"; break
    // equivalent to // case { val in m }: ...
    default: "not in map"
}
</pre></td></tr></table>

<h3>Grape/Grab Improvements</h3>

<h4>Shorter notation for @GrabResolver</h4>

<p>When you need to specify a special grab resolver, for when the artifacts you need are not stored in Maven central, you could use:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@GrabResolver(name = 'restlet.org', root = 'http://maven.restlet.org')
@Grab('org.restlet:org.restlet:2.0.6')
import org.restlet.Restlet
</pre></td></tr></table>
<p>Groovy 1.8 adds a shorter syntax as well:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@GrabResolver('http://maven.restlet.org')
@Grab('org.restlet:org.restlet:2.0.6')
import org.restlet.Restlet
</pre></td></tr></table>

<h4>Compact form for optional Grab attributes</h4>

<p>The <code>@Grab</code> annotation has numerous options. For example, to download the Apache commons-io library (where you wanted to set the <code>transitive</code> and <code>force</code> attributes - not strictly needed for this example but see the Grab or Ivy documentation for details on what those attributes do) you could use a grab statement similar to below:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@Grab(group='commons-io', module='commons-io', version='2.0.1', transitive=false, force=true)
</pre></td></tr></table>

<p>The compact form for grab which allows the artifact information to be represented as a string now supports specifying additional attributes. As an example, the following script will download the commons-io jar and the corresponding javadoc jar before using one of the commons-io methods.</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
@Grab('commons-io:commons-io:2.0.1;transitive=false;force=true')
@Grab('commons-io:commons-io:2.0.1;classifier=javadoc')
import static org.apache.commons.io.FileSystemUtils.*
assert freeSpaceKb() > 0
</pre></td></tr></table>

<h3>Sql improvements</h3>

<p>The <code>eachRow</code> and <code>rows</code> methods in the <code>groovy.sql.Sql</code> class now support paging.  Here's an example:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
sql.eachRow('select * from PROJECT', 2, 2) { row ->
  println "${row.name.padRight(10)} ($row.url)"
}
</pre></td></tr></table>

<p>Which will start at the second row and return a maximum of 2 rows. Here's an example result from a database containing numerous projects with their URLs:</p>
<table class="wysiwyg-macro" data-macro-name="noformat" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e25vZm9ybWF0fQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
Grails     (http://grails.org)
Griffon    (http://griffon.codehaus.org)
</pre></td></tr></table>

<h3>Storing AST node metadata</h3>

<p>When developing AST transformations, and particularly when using a visitor to navigate the AST nodes, it is sometimes tricky to keep track of information as you visit the tree, or if a combination of transforms need to be sharing some context. The <code>ASTNode</code> base class features 4 methods to store node metadata:</p>
<ul>
	<li><code>public Object getNodeMetaData(Object key)</code></li>
	<li><code>public void copyNodeMetaData(ASTNode other)</code></li>
	<li><code>public void setNodeMetaData(Object key, Object value)</code></li>
	<li><code>public void removeNodeMetaData(Object key)</code></li>
</ul>

<h3>Ability to customize the GroovyDoc templates</h3>

<p>GroovyDoc uses hard-coded templates to create the JavaDoc for your Groovy classes. Three templates are used: top-level templates, a package-level template, a class template. If you want to customize these templates, you can subclass the <code>Groovydoc</code> Ant task and override the <code>getDocTemplates()</code>, <code>getPackageTemplates()</code>, and <code>getClassTemplates()</code> methods pointing at your own templates. Then you can use your custom GroovyDoc Ant task in lieu of Groovy's original one.</p>