Writing an SXC Parser

Added by Dan Diephouse, last edited by Dan Diephouse on Mar 19, 2007  (view change)

Writing an SXC parser is fairly simple. You tell SXC what type of XML you are expecting and then attach actions to it. Lets look at a simple example. We have a Customer object with two properties "id" and "name". We want to map this XML to it:

<customer id="1">
 <name>Dan Diephouse</name>
</customer>

Here is an example of the parser that we would create:

// Create a Parser/Writer Builder 
Builder builder = new BuilderImpl();
ElementParserBuilder b = builder.getParserBuilder();

// Get the CodeModel - an API for building Java classes
JCodeModel model = builder.getCodeModel();
JType cusClass = model._ref(Customer.class);

// Tell SXC to expect a <customer> element
ElementParserBuilder root = b.expectElement(new QName("customer"));
// When we see <customer> create a new Customer object
CodeBody body = root.getBody();
JVar var = body.decl(cusClass, "customer", JExpr._new(model._ref(Customer.class)));
// Return the customer object once we're done parsing
body._return(var);

// Tell SXC to expect an attribute "id" on the <customer> element
ParserBuilder idBuilder = root.expectAttribute(new QName("id"));
// Pass the customer object to the ParserBuilder that handles the ID
JVar methodVar = idBuilder.passParentVariable(var);
// Read the attribute as a int. 
JVar attVar = idBuilder.as(int.class);
// pass this variable to setId on the customer object
idBuilder.getBody().add(methodVar.invoke("setId").arg(attVar));

// Handle the <name> element
ElementParserBuilder nameBuilder = root.expectElement(new QName("name"));
// Pass the Customer object to this builder
methodVar = nameBuilder.passParentVariable(var);
// Read the element as a non nillable String
JVar name = nameBuilder.as(String.class, false);
// Call setName with this String as an argument
nameBuilder.getBody().add(methodVar.invoke("setName").arg(name));

// Compile the written classes
Context context = builder.compile();

// unmarshal the xml
Reader reader = context.createReader();
Object object = reader.read(getClass().getResourceAsStream("customer.xml"));

assertTrue(object instanceof Customer);

Customer c = (Customer) object;
assertEquals(1, c.getId());
assertEquals("Dan Diephouse", c.getName());

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