Java XML and JSON Binding: MOXy as Your JAX-RS JSON Provider

In a previous post I demonstrated how you can implement a MessageBodyReader/MessageBodyWriter to leverage EclipseLink JAXB (MOXy)'s JSON binding in a JAX-RS service. MOXy now includes an implementation (MOXyJsonProvider) that can be used directly or extended to make the integration even easier.

Using MOXyJsonProvider

Default Behaviour

You can use a JAX-RS Application class to specify that MOXyJsonProvider should be used with your JAX-RS application.

package org.example;

import java.util.*;
import javax.ws.rs.core.Application;
import org.eclipse.persistence.jaxb.rs.MOXyJsonProvider;

public class CustomerApplication  extends Application {

    @Override
    public Set<Class<?>> getClasses() {
        HashSet<Class<?>> set = new HashSet<Class<?>>(2);
        set.add(MOXyJsonProvider.class);
        set.add(CustomerService.class);
        return set;
    }

}

Configuration Options

You can also use a JAX-RS Application class to specify an instance of MOXyJsonProvider to be used with your JAX-RS application. This approach allows you customize the different configuration options offered by the MOXyJsonProvider.

package org.example;

import java.util.*;
import javax.ws.rs.core.Application;
import org.eclipse.persistence.jaxb.rs.MOXyJsonProvider;

public class CustomerApplication  extends Application {

    @Override
    public Set<Class<?>> getClasses() {
        HashSet<Class<?>> set = new HashSet<Class<?>>(1);
        set.add(ExampleService.class);
        return set;
    }

    @Override
    public Set<Object> getSingletons() {
        MOXyJsonProvider moxyJsonProvider = new MOXyJsonProvider();

        moxyJsonProvider.setAttributePrefix("@");
        moxyJsonProvider.setFormattedOutput(true);
        moxyJsonProvider.setIncludeRoot(true);
        moxyJsonProvider.setMarshalEmptyCollections(false);
        moxyJsonProvider.setValueWrapper("$");

        Map<String, String> namespacePrefixMapper = new HashMap<String, String>(1);
        namespacePrefixMapper.put("http://www.example.org/customer", "cust");
        moxyJsonProvider.setNamespacePrefixMapper(namespacePrefixMapper);
        moxyJsonProvider.setNamespaceSeparator(':');

        HashSet<Object> set = new HashSet<Object>(1);
        set.add(moxyJsonProvider);
        return set;
    }

}

WEB-INF/web.xml

A web.xml file is used to configure the Application class. Below is a web.xml I used in a previous example (see Creating a RESTful Web Service - Part 4/5) extended to reference the CustomerApplication class from this post.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <servlet>
        <servlet-name>Jersey Web Application</servlet-name>
        <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer
        </servlet-class>
        <load-on-startup>1</load-on-startup>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>org.example.CustomerApplication</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>Jersey Web Application</servlet-name>
        <url-pattern>/rest/*</url-pattern>
    </servlet-mapping>
    <persistence-context-ref>
        <persistence-context-ref-name>persistence/em</persistence-context-ref-name>
        <persistence-unit-name>CustomerService</persistence-unit-name>
    </persistence-context-ref>
</web-app>

Extending MOXyJsonProvider

You can also extend MOXyJsonProvider to create your own MessageBodyReader/MessageBodyWriter. The preReadFrom and preWriteTo methods can be overridden to customize the Unmarshaller/Marshaller that will be used by MOXy.

package org.example;

import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

import javax.ws.rs.*;
import javax.ws.rs.core.*;
import javax.ws.rs.ext.Provider;
import javax.xml.bind.*;

import org.eclipse.persistence.jaxb.MarshallerProperties;
import org.eclipse.persistence.jaxb.rs.MOXyJsonProvider;

@Provider
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class CustomerJSONProvider extends MOXyJsonProvider {

    @Override
    public boolean isReadable(Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType) {
        return getDomainClass(genericType) == Customer.class;
    }

    @Override
    public boolean isWriteable(Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType) {
        return isReadable(type, genericType, annotations, mediaType);
    }

    @Override
    protected void preReadFrom(Class<Object> type, Type genericType,
            Annotation[] annotations, MediaType mediaType,
            MultivaluedMap<String, String> httpHeaders,
            Unmarshaller unmarshaller) throws JAXBException {
        unmarshaller.setProperty(MarshallerProperties.JSON_VALUE_WRAPPER, "$");
    }

    @Override
    protected void preWriteTo(Object object, Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType,
            MultivaluedMap<String, Object> httpHeaders, Marshaller marshaller)
            throws JAXBException {
        marshaller.setProperty(MarshallerProperties.JSON_VALUE_WRAPPER, "$");
    }

}

Further Reading

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