Chapter 1. First steps
Prev   Next

Chapter 1. First steps

Table of Contents

Generating Java Code
Creating a JaxMe Schema
Running The Generator
Working with XML
Writing XML Documents
Reading XML

This chapter introduces the first steps of using JaxMe. In what follows, we will create some simple examples. All examples deal with addresses stored in XML documents like the following (quoted from the file examples/misc/address.xml in the JaxMe 2 distribution): 

<?xml version="1.0"?>
<!-- A sample document for the Address.xsd schema. This
     sample document is used in the docs, see
     docs/GenerateJava.html. -->

<Address xmlns="http://ws.apache.org/jaxme/examples/misc/address">
  <Name>
    <First>Jane</First>
    <Middle>Lee</Middle>
    <Middle>Chris</Middle>
    <Last>Doe</Last>
    <Initials>(JD)</Initials>
  </Name>
  ... further details omitted for brevity ...
</Address>

Our target is to convert this into convenient, standard Java bean code, much like the following: 

      Address address = new Address();
      Name name = new Name();
      address.setName(name);
      name.setFirst("Jane");
      name.addMiddle("Lee");
      name.addMiddle("Chris");
      name.setSur("Doe");
      name.setInitials("JD");
      ...

Generating Java Code

After you've downloaded JaxMe, you're ready to use it. In this section we will demonstrate how to generate sources.

Creating a JaxMe Schema

The usual way to use JaxMe is to start from a schema and generate source code from that schema. So (with the address example in mind) we create an XML Schema from which the sources will be generated. When using JaxMe in the wild sometimes the schema will already exist, in other cases the application developer will develop the schema as the application develops. In either case, the way that JaxMe is used is very similar.

The schema can be regarded as a description of compliant document instances (in our case addresses). For example (examples/misc/address.xsd in the JaxMe 2 distribution): 


<?xml version="1.0" encoding="UTF-8"?>

<xs:schema
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xml:lang="EN"
    targetNamespace="http://ws.apache.org/jaxme/examples/misc/address"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">
  <xs:element name="Address">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Name">
          <xs:annotation><xs:documentation>
              A name consists of two required (first and last name)
              and two optional parts (middle name and initials).
          </xs:documentation></xs:annotation>
          <xs:complexType>
            <xs:sequence>
              <xs:element name="First" type="xs:string"/>
              <xs:element name="Middle" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
              <xs:element name="Last" type="xs:string"/>
              <xs:element name="Initials" minOccurs="0" type="xs:string"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
        ... further details omitted for brevity ...
      </xs:sequence>
      <xs:attribute name="id"/>
    </xs:complexType>
  </xs:element>
</xs:schema>
You will easily note that xs:element is used to define elements. An attribute is added using xs:attribute, and so on. XML schema are very expressive (which is why they support source generation so well) but with this expressiveness comes complexity. Getting to grips with the XML schema standard is worth the effort but some users may choose to use one of the numerous tools that help with XML schema generation.

Running The Generator

The easiest way to run the generator is by invoking an Ant task. Here is a typical ant target: 

    <target name="taskdef">
      <!--
      Set up the classpath for the generation task.
      Include all the standard jaxme jars.
      -->
      <path id="generate.class.path">
        <pathelement location="jaxme2.jar"/>
        <pathelement location="jaxmejs.jar"/>
        <pathelement location="jaxmexs.jar"/>
        <pathelement location="jaxmeapi.jar"/>
      </path>
      <!--
      Defines the generation task using that classpath.
      -->
      <taskdef name="xjc"
        classname="org.apache.ws.jaxme.generator.XJCTask"
        classpathref="generate.class.path"/>
      <!--
      Generate source code.
      The 'schema' attribute gives the path to the schema the sources
      will be generated from.
      The 'target' attribute specifies the base directory that the source
      will be generated into. Sources will be created in subdirectories
      corresponding to the package structure.
      -->
      <xjc 
        schema="examples/misc/address.xsd" 
        target="build/src">
            <!--
            The source files being created. The xjc task uses these for
            a check, whether they are uptodate. If so, the generation is
            skipped, for improved speed.
            Specifying the package isn't necessary, unless you have other
            files in the target directory as well, for example manually
            written files or files created by another generator or xjc call.
            If so, these need to be excluded from the uptodate check.
            -->
            <produces includes="org/apache/ws/jaxme/examples/misc/address/*.java"/>
      </xjc>
    </target>

The example demonstrates how a classpath called generate.class.path is created and used to define a new ant task called "xjc". This new task is used to compile a schema file called examples/misc/address.xsd. The generated sources will reside in the directory build/src. The target package is org.apache.ws.jaxme.examples.misc.address, hence the effective location is build/src/org/apache/ws/jaxme/examples/misc/address.

After running the task, looking into that directory, we find that the following files have been created:

Files Generated by the JaxMe Binding Compiler

Address.java

Contains the Java interface describing the document type Address. This interface extends the interface specified by AddressType.java.

AddressType.java

Contains the Java interface describing the inner contents of the document type Address. The best way to think of it is to assume that they are the same, except that the latter is anonymous and doesn't have an element name.

Configuration.xml

This file is used by the JaxMe runtime internally. Typically you'll never notice that it is even there (though you will need to ensure that it remains on the classpath). The main task of the file is a mapping between XML element names (like Address in namespace http://ws.apache.org/jaxme/examples/misc/address) and Java classes.

Tip

In theory you are able to replace the implementations generated by JaxMe with your own classes. This is particularly useful, if you want to modify a certain behaviour by deriving a subclass.

jaxb.properties

The JAXB standard uses this file. Typically you'll never even notice that it exists (though again, it must be found on the classpath). The task of the file is to ensure that the JAXB runtime correctly initializes the JaxMe runtime.

impl/AddressHandler.java

A SAX2 ContentHandler, which can convert XML documents of type Address into implementations of the Java interface Address. This is rarely called directly. Usually it will be created and invoked automatically by the JAXB Marshaller.

impl/AddressImpl.java

Default implementation of the Address interface.

impl/AddressType.java

Default implementation of the AddressType interface.

impl/AddressTypeHandler.java

Similar to its subclass AddressHandler, this is a SAX2 ContentHandler for reading instances of AddressType. The main difference to the subclass is that the subclass doesn't have a fixed element name.

impl/AddressTypeImpl.java

Default implementation of AddressType.

impl/AddressTypeSerializer.java

Converts instances of AddressType into XML documents. It is also used to convert instances of Address.

Prev   Next
Introduction Home Working with XML