Virtual hosts

Contact the core Jetty developers at www.webtide.com
private support for your internal/customer projects ... custom extensions and distributions ... versioned snapshots for indefinite support ... scalability guidance for your apps and Ajax/Comet projects ... development services from 1 day to full product delivery

Using Virtual Hosts

A virtual host is an alternative name, registered in DNS, for an IP address. A single IP address may have many such alternative names.

Multi-homed hosts, that is machines with more than one network interface, may have a different name for each IP address. This is also refered to as "virtual hosting".

Essentially, "virtual hosting" concerns the resolution of a DNS registered name to an IP address - many names may resolve to the same IP address, and 1 or more IP addresses may reside on the same physical machine.

Jetty users often want to configure their web applications taking into account these different virtual hosts. Frequently, a machine with a single IP address will have different DNS resolvable names associated with it, and a webapp deployed on it must be reachable from all of the alternative names.

Other possibilities are to serve different web applications from different virtual hosts.

Let's examine these possibilities.

Configuration of virtual hosts

When configuring a web application, you can supply a list of IP addresses and names at which the web application will be reachable. Suppose we have a machine with these IP addresses and DNS resolvable names:

  • 333.444.555.666
  • 127.0.0.1
  • www.blah.com
  • www.blah.net
  • www.blah.org

Suppose we have a webapp, xxx.war that we want to be served from all of the above names and addresses. Then we would configure the webapp like so:

    <New class="org.mortbay.jetty.webapp.WebAppContext">
      <Arg><Ref id="Contexts"/></Arg>
      <Arg><SystemProperty name="jetty.home"/>/webapps/xxx.war</Arg>
      <Arg>/xxx</Arg>
      <Set name="defaultsDescriptor"><SystemProperty name="jetty.home" default="."/>/etc/webdefault.xml</Set>
      <Set name="VirtualHosts">
        <Array type="java.lang.String">
          <Item>333.444.555.666</Item>
          <Item>127.0.0.1</Item>
          <Item>www.blah.com</Item>
          <Item>www.blah.net</Item>
          <Item>www.blah.org</Item>
        </Array>
      </Set>
    </New>

Assuming we'd configured a connector listening on port 8080, then webapp xxx.war would be available at all of the following addresses:

Configuring different webapps for different virtual hosts

This is accomplished simply by supplying a different list of virtual hosts for each webapp. For example, suppose our imaginary machine has these DNS names and IP addresses:

  • 333.444.555.666
  • 127.0.0.1
  • www.blah.com
  • www.blah.net
  • www.blah.org
  • 777.888.888.111
  • www.other.com
  • www.other.net
  • www.other.org

Suppose also we have another webapp, zzz.war. We want xxx.war to be deployed as above, and zzz.war to be deployed only from 777.888.888.111, www.other.com, www.other.net and www.other.org:


    <!-- webapp xxx.war -->
    <New class="org.mortbay.jetty.webapp.WebAppContext">
      <Arg><Ref id="Contexts"/></Arg>
      <Arg><SystemProperty name="jetty.home"/>/webapps/xxx.war</Arg>
      <Arg>/xxx</Arg>
      <Set name="defaultsDescriptor"><SystemProperty name="jetty.home" default="."/>/etc/webdefault.xml</Set>
      <Set name="VirtualHosts">
        <Array type="java.lang.String">
          <Item>333.444.555.666</Item>
          <Item>127.0.0.1</Item>
          <Item>www.blah.com</Item>
          <Item>www.blah.net</Item>
          <Item>www.blah.org</Item>
        </Array>
      </Set>
    </New>

    <!-- webapp zzz.war -->
    <New class="org.mortbay.jetty.webapp.WebAppContext">
      <Arg><Ref id="Contexts"/></Arg>
      <Arg><SystemProperty name="jetty.home"/>/webapps/zzz.war</Arg>
      <Arg>/zzz</Arg>
      <Set name="defaultsDescriptor"><SystemProperty name="jetty.home" default="."/>/etc/webdefault.xml</Set>
      <Set name="VirtualHosts">
        <Array type="java.lang.String">
          <Item>777.888.888.111</Item>
          <Item>www.other.com</Item>
          <Item>www.other.net</Item>
          <Item>www.other.org</Item>
        </Array>
      </Set>
    </New>

Webapp xxx.war is still available at:

But now webapp zzz.war is available at:

Configuring different webapps for different virtual hosts, but at the same context path

In our example above, we have made webapp zzz.war avilable not only at a certain set of virtual hosts, but also at the context path /zzz, whilst our other webapp is available at both a different set of virtual hosts, and at a different context path. What happens if we want them at the same context path, but still at different sets of virtual hosts?

Very simply, we just supply the same context path for each webapp, leaving the disjoint set of virtual host definitions as before:

    <New class="org.mortbay.jetty.webapp.WebAppContext">
      <Arg><Ref id="Contexts"/></Arg>
      <Arg><SystemProperty name="jetty.home"/>/webapps/xxx.war</Arg>
      <Arg>/</Arg>
      <Set name="defaultsDescriptor"><SystemProperty name="jetty.home" default="."/>/etc/webdefault.xml</Set>
      <Set name="VirtualHosts">
        <Array type="java.lang.String">
          <Item>333.444.555.666</Item>
          <Item>127.0.0.1</Item>
          <Item>www.blah.com</Item>
          <Item>www.blah.net</Item>
          <Item>www.blah.org</Item>
        </Array>
      </Set>
    </New>

    <New class="org.mortbay.jetty.webapp.WebAppContext">
      <Arg><Ref id="Contexts"/></Arg>
      <Arg><SystemProperty name="jetty.home"/>/webapps/zzz.war</Arg>
      <Arg>/</Arg>
      <Set name="defaultsDescriptor"><SystemProperty name="jetty.home" default="."/>/etc/webdefault.xml</Set>
      <Set name="VirtualHosts">
        <Array type="java.lang.String">
          <Item>777.888.888.111</Item>
          <Item>www.other.com</Item>
          <Item>www.other.net</Item>
          <Item>www.other.org</Item>
        </Array>
      </Set>
    </New>

Now, webapp xxx.war is available at:

and webapp zzz.war is available at:

Enter labels to add to this page:
Please wait 
Looking for a label? Just start typing.

Comments (1)

 

  1. Dec 01, 2007

    Maximilian Böhm says:

    Hi, i'm configuring jetty with some helper-methods. One problem is, that i have...

    Hi,

    i'm configuring jetty with some helper-methods. One problem is, that i have to restart jetty to overtake the changes i've done with context.setVirtualHosts. Is there a mistake by me or doesn't it work else?

    Thanks in advance 

    Greetz

    PS.: Here the code:

       public void addVirtualHost(Context context, String sDomain) throws Exception{
      int nOldVHosts = context.getVirtualHosts().length+1;
      String[] nNewVHosts = new String[nOldVHosts];
      for (int i = 0; i < context.getVirtualHosts().length; i++) {
         nNewVHosts[i] = context.getVirtualHosts()[i];
      }
      nNewVHosts[nOldVHosts-1] = sDomain;
     
      context.setVirtualHosts(nNewVHosts);
     
      server.stop();
      server.start();
   }
   
Contact the core Jetty developers at www.webtide.com
private support for your internal/customer projects ... custom extensions and distributions ... versioned snapshots for indefinite support ... scalability guidance for your apps and Ajax/Comet projects ... development services from 1 day to full product delivery