jaxb tutorial

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JAXB Tutorial

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Table of Contents

1. How to Marshal and Unmarshal XML .......................................... 2

2. Customized Namespace Prefixes Example using NamespacePrefixMapper .............................................................. 10

a. Introduction ............................................................................................ 3 b. Spring’s Jaxb2Marshaller ...................................................................... 4 c. Java’s XML Packages ........................................................................... 6

a. Introduction ........................................................................................... 11 b. Dependencies ...................................................................................... 12 c. NamespacePrefixMapper ..................................................................... 13 d. Configure .............................................................................................. 16


How to Marshal and

Unmarshal XML


This JAXB tutorial describes how to use JAXB to marshal and unmarshal XML strings using either Spring or the standard javax.xml.bind interfaces.

The samples below are using XML strings instead of files, but could easily be adapted to files if needed.

Introduction


Configuration To use Spring’s Jaxb2Marshaller, you will need the spring-oxm dependency, which you may already have, since it is used by other major spring components.

To configure the Jaxb2Marshaller in your Spring context, add the config XML below. Be sure to add all root packages that contain the JAXB classes.

Spring’s Jaxb2Marshaller


Unmarshalling To unmarshal an XML string into a JAXB object, just inject the Jaxb2Marshaller and call the unmarshal() method.

Marshalling To marshal a JAXB object into an XML string, you will need to create a StringResult and pass that to the marshal() method.


Java 6 and later have the standard JAXB interfaces and factories for processing xml available in the java.xml.bind package. You can find more info about JAXB on the JAXB project web site.

Unmarshalling To unmarshal an xml string into a JAXB object, you will need to create an Unmarshaller from the JAXBContext, then call the unmarshal() method with a source/reader and the expected root object.

Java’s XML Packages

JAXB project web site

https://jaxb.java.net/


Marshalling To marshal a JAXB object into an XML string, you will need to create a a Marshallerfrom the JAXBContext and pass a Writer target to the marshal() method.


As you can see, the Spring mechanisms are pretty clean, but if you are not using Spring, the Java mechanisms are easy to work with as well.

Next up in this JAXB tutorial, we’ll see how to configure the namespace prefixes.

JAXB Tutorial Side Note If you’ve ever wondered about the correct spelling of marshalling (vs marshaling), there’s a brief summary on Stack Overflow… (2 l’s is acceptable) Stack Overflow

http://stackoverflow.com/questions/4434590/marshall-or-marshal-marshalling-or-marshaling

Customized Namespace

Prefixes Example using

NamespacePrefixMapper



Do you need to specify what namespace prefixes are used in your JAXB marshaled XML? For example, do you want to see <soap:envelope/> in the generated XML instead of <ns1:envelope/>? If so, this JAXB tutorial will walk you through those steps.

If you are using the default JAXB implementation provided with Java 6 or later, you can configure the namespace prefixes by extending the NamespacePrefixMapper and setting a property to tell the marshaller to use your extension.

Introduction


Since you need to extend a class that is defined in the JAXB API’s Reference Implemenation (RI), you must pull it in as a dependency.

You can download the libraries directly from jaxb.java.net, or you can add the Maven dependencies.

Dependencies

jaxb.java.net

https://jaxb.java.net/


Once you have the JAXB libraries, you can extend the com.sun.xml.bind.marshaller.NamespacePrefixMapper class. This is the core class that provides the mapping of XML namespaces to the desired prefix.

NamespacePrefixMapper


Sample extension (using Java 8 syntax)


Set the “com.sun.xml.bind.namespacePrefixMapper” property on the marshaller to an instance of your mapper. Once set, any time you marshal your JAXB object to XML, it will use your mapper to get the prefix for a given namespace.

Spring’s Jaxb2Marshaller To configure Spring’s Jaxb2Marshaller to use your NamespacePrefixMapper, you should set the marshallerProperties map on the Jaxb2Marshaller bean.

Configure


Java’s Marshaller To configure the javax.xml.bind.Marshaller, you can set the property directly on the marshaller by calling marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper", new DefaultNamespacePrefixMapper());


Example: (line 25)

Note: If you use the same mappings across your application, you can create one instance of the mapper and share it.


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