Reusing Generated JAXB Classes
Join the DZone community and get the full member experience.
Join For FreeIn this post I will demonstrate how to leverage the -episode XJC extension
to reuse classes previously generated from.an XML schema. This is
useful when an XML schema is imported by other XML schemas and you do
not want the same classes generated each time.
Imported Schema (Product.xsd)
The following XML schema represents basic information about a product. Product is a common concept in this example domain so I have decided to define one representation that can be leveraged by other schemas, rather than having each schema define its own representation of product information.
<?xml version="1.0" encoding="UTF-8"?>
<schema
xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.example.org/Product"
xmlns:tns="http://www.example.org/Product"
elementFormDefault="qualified">
<element name="product">
<complexType>
<sequence>
<element name="id" type="string"/>
<element name="name" type="string"/>
</sequence>
</complexType>
</element>
</schema>
Since multiple XML schemas import Product.xsd we can leverage episode files so that the classes corresponding to Product.xsd are only generated once. The following XJC call demonstrates how to generate an episode file called product.episode along with the generated classes:
xjc -d out -episode product.episode Product.xsd
Importing Schema (ProductPurchaseRequest.xsd)
Below is an example of an XML schema that imports Product.xsd:
<?xml version="1.0" encoding="UTF-8"?>
<schema
xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.example.org/ProductPurchaseRequest"
xmlns:tns="http://www.example.org/ProductPurchaseRequest"
xmlns:prod="http://www.example.org/Product"
elementFormDefault="qualified">
<import namespace="http://www.example.org/Product" schemaLocation="Product.xsd"/>
<element name="purchase-request">
<complexType>
<sequence>
<element ref="prod:product" maxOccurs="unbounded"/>
</sequence>
</complexType>
</element>
</schema>When we generate
classes from this XML schema we will reference the episode file we
created when we generated Java classes from Product.xsd. If we do not
specify the episode file then classes will be generated for both ProductPurchaseRequest.xsd and Product.xsd:
xjc -d out ProductPurchaseRequest.xsd -extension -b product.episode
Another Importing Schema (ProductQuoteRequest.xsd)
Below is another example of an XML schema that imports Product.xsd:
<?xml version="1.0" encoding="UTF-8"?>
<schema
xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.example.org/ProductQuoteRequest"
xmlns:tns="http://www.example.org/ProductQuoteRequest"
xmlns:prod="http://www.example.org/Product"
elementFormDefault="qualified">
<import namespace="http://www.example.org/Product" schemaLocation="Product.xsd"/>
<element name="quote">
<complexType>
<sequence>
<element ref="prod:product"/>
</sequence>
</complexType>
</element>
</schema>Again when we
generate classes from this XML schema we will reference the episode file
we created when we generated Java classes from Product.xsd.
xjc -d out ProductQuoteRequest.xsd -extension -b product.episode
How Does it Work? (product.episode)
For
those of you curious how this works. The episode file generated by XJC
is really just a standard JAXB bindings file that is used to customize
the class generation. This generated bindings/episode file contains
entries that tells XJC that a class already exists for this type. You
could write this file by hand, but -episode flag to XJC does it for you.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<bindings version="2.1" xmlns="http://java.sun.com/xml/ns/jaxb">
<!--
This file was generated by the JavaTM Architecture for XML Binding
(JAXB) Reference Implementation, vJAXB 2.1.10 in JDK 6 See
<a href="http://java.sun.com/xml/jaxb">http://java.sun.com/xml/jaxb</a>
Any modifications to this file will be lost upon recompilation of the
source schema.
Generated on: 2011.11.02 at 03:40:10 PM EDT
-->
<bindings scd="x-schema::tns"
xmlns:tns="http://www.example.org/Product">
<schemaBindings map="false"/>
<bindings scd="tns:product">
<class ref="org.example.product.Product"/>
</bindings>
</bindings>
</bindings>
From http://blog.bdoughan.com/2011/12/reusing-generated-jaxb-classes.html
Schema
XML
Opinions expressed by DZone contributors are their own.
Comments