JAXB XJC code generation - adding @XmlRootElement and Joda DateTime

Question

Here's an interesting scenario that I encountered the other day. I did eventually reach a solution on my own. However, I'd welcome any comments and better approaches.

The requirements

I want to generate JAXB objects based on a collection of XSDs using XJC as part of a Maven build. I'll be using JAXB-RI 2.1 as the implementation.

In addition, I want to make sure that all objects implement a signature interface (e.g. MySignature) which has no methods. Also, I want to avoid using XmlGregorianCalendar and have Joda DataTime instead (with a suitable adapter that I'll provide called DateUtils with parse() and format() methods).

Finally, I want to be able to select certain objects to act as root elements so I'll need to selectively add @XmlRootElement to some objects, and I have suitable XPath expressions to locate them.

I can't make any changes to the XSDs.

The approach

Step 1 - Configuring the pom.xml

Configure Maven to use the XJC plugin as follows:

<build>
    <plugins>
      <plugin>
        <groupId>org.jvnet.jaxb2.maven2</groupId>
        <artifactId>maven-jaxb2-plugin</artifactId>
        <version>0.7.4</version>
        <executions>
          <execution>
            <id>generate-domain1</id>
            <goals>
              <goal>generate</goal>
            </goals>
            <configuration>
              <strict>false</strict>
              <schemaIncludes>
                <value>domain1.xsd</value>
              </schemaIncludes>
              <bindingIncludes>
                <include>domain1-bindings.xjb</include>
              </bindingIncludes>
              <extension>true</extension>
              <generatePackage>org.example.domain1</generatePackage>
              <generateDirectory>${project.build.directory}/generated-sources/domain1</generateDirectory>
              <args>
                <arg>-Xannotate</arg>
               </args>                  
               <plugins>
                <plugin>
                  <groupId>org.jvnet.jaxb2_commons</groupId>
                  <artifactId>jaxb2-basics</artifactId>
                  <version>0.6.0</version>
                </plugin>
                <plugin>
                  <groupId>org.jvnet.jaxb2_commons</groupId>
                  <artifactId>jaxb2-basics-annotate</artifactId>
                  <version>0.6.0</version>
                </plugin>
              </plugins>
            </configuration>
          </execution>
        </executions>
      </plugin>
   </plugins>
</build>

The use of a dedicated execution configuration is there to allow additional mutually exclusive XSDs to be built using a different target output path.

Step 2 - Configure the bindings

Include the following as src/main/resources/domain1-bindings.xjb.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<jaxb:bindings
  xmlns:jaxb="http://java.sun.com/xml/ns/jaxb" xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:annox="http://annox.dev.java.net"
  xsi:schemaLocation="http://java.sun.com/xml/ns/jaxb http://java.sun.com/xml/ns/jaxb/bindingschema_2_0.xsd"
  jaxb:extensionBindingPrefixes="xjc annox"
  version="2.1">

  <jaxb:globalBindings>
    <jaxb:serializable uid="1"/>
    <!-- All generated classes must have MySignature interface (supplied in dependencies) -->
    <xjc:superInterface name="org.example.MySignature"/>
    <!-- All temporal fields are implemented as Joda DateTime and use DateUtils as an adapter -->
    <jaxb:javaType
      name="org.joda.time.DateTime"
      xmlType="xs:time"
      parseMethod="org.example.DateUtils.parseDateTime"
      printMethod="org.exmaple.DateUtils.formatDateTime"
      />
  </jaxb:globalBindings>

  <!-- Application of annotations to selected classes within schemas -->

  <!-- org.example.SomeRootType @XmlRootElement -->
  <jaxb:bindings schemaLocation="domain1.xsd" node="/xs:schema">
    <jaxb:bindings node="xs:complexType[@name='SomeRootType']">
      <annox:annotate>
        <annox:annotate annox:class="javax.xml.bind.annotation.XmlRootElement" name="SomeRootType"/>
      </annox:annotate>
    </jaxb:bindings>
  </jaxb:bindings>

</jaxb:bindings>

Troubleshooting

If you encounter the infamous

Unsupported binding namespace "". Perhaps you meant "http://annox.dev.java.net"

then you need to examine your bindings.xjb to make sure that you're using the correct namespace URIs (as defined above) and have included them into extensionBindingPrefixes.

Answer 1

The <jaxb:javaType /> tag generates a new org.w3._2001.xmlschema.AdapterN class for each new javaType definition. So a better approach would be:

• Create a class extending XmlAdapter<String, _To_>. In it you will have to override the both methods defined. So in example, the class could be org.example.DateUtilsAdapter.

• Use this tag instead:

  <xjc:javaType
      name="org.joda.time.DateTime"
      xmlType="xs:time"
      adapter="org.example.DateUtilsAdapter" />
  

Source

Answer 2

I tried your example in Eclipse and got a warning:

cvc-complex-type.3.2.2: Attribute 'jaxb:extensionBindingPrefixes' is not allowed to appear in 
 element 'jaxb:bindings'.

When I changed the URL from 2.0 to 2.1 it removed the warning.

Before: http://java.sun.com/xml/ns/jaxb/bindingschema_2_0.xsd
After: http://java.sun.com/xml/ns/jaxb/bindingschema_2_1.xsd

<jaxb:bindings
  xmlns:jaxb="http://java.sun.com/xml/ns/jaxb" xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:annox="http://annox.dev.java.net"
  xsi:schemaLocation="http://java.sun.com/xml/ns/jaxb http://java.sun.com/xml/ns/jaxb/bindingschema_2_1.xsd"
  jaxb:extensionBindingPrefixes="xjc annox"
  version="2.1">