Note: I’m the EclipseLink JAXB (MOXy) lead and a member of the JAXB 2 (JSR-222) expert group.
A .episode file is generated by the XJC (XML Schema to Java) compiler. It is a schema bindings that associates schema types with existing classes. It is useful when you have one XML schema that is imported by other schemas as it prevents the model from being regenerated. Below is an example:
Product.xsd
<?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.
xjc -d out -episode product.episode Product.xsd
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.
xjc -d out ProductPurchaseRequest.xsd -extension -b product.episode
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
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