Binding to JSON & XML - Handling Collections

One of EclipseLink JAXB (MOXy)'s strengths is the ability to map an object model to both JSON and XML with a single set of metadata.  The one weakness had been that you needed to compromise on the JSON key or XML element for collection properties.  I'm happy to say that this issue has been solved in EclipseLink 2.5 (and EclipseLink 2.4.2), and I will demonstrate below with an example.

You can try this out today by downloading an EclipseLink 2.5.0 (or EclipseLink 2.4.2) nightly build starting on March 15, 2013 from:

• http://www.eclipse.org/eclipselink/downloads/nightly.php

JAXB and java.util.Map

Is it ironic that it can be difficult to map the java.util.Map class in JAXB (JSR-222)?  In this post I will cover some items that will make it much easier.

MOXy's @XmlInverseReference is now Truly Bidirectional

EclipseLink JAXB (MOXy)'s @XmlInverseReference annotation enables you to map a back pointer during the unmarshal operation (useful when mapping JPA entities).  The problem was it acted like @XmlTransient during the marshal operation.  This means that previously it could only be used in one direction.  Now I'm happy to announce in EclipseLink 2.5.0 we have expanded @XmlInverseReference so that the corresponding property may be writeable enabling it to be used in both directions.

You can try this out today by downloading one EclipseLink 2.5.0 nightly downloads starting on March 1, 2013 from:

• http://www.eclipse.org/eclipselink/downloads/nightly.php

Leveraging MOXy in your Web Service via JAX-WS Provider

In previous articles I demonstrated how EclipseLink JAXB (MOXy) is directly integrated into the JAX-WS implementations in WebLogic (as of 12.1.1) and in GlassFish (as of 3.1.2).  In this post I'll demonstrate how to leverage MOXy in any application server by using the JAX-WS Provider class.

JAXB's @XmlAnyElement(lax=true) Explained

In a previous post I introduced how the @XmlAnyElement(lax=true) annotation could be used to create a very flexible mapping.  In this post I'll dig a bit deeper into how it relates to both the @XmlRootElement and @XmlElementDecl.

JAXB - Representing Null and Empty Collections

In this post I will cover how to differentiate between null and empty collections in the XML representation with JAXB (JSR-222).

Creating a Generic List Wrapper in JAXB

To marshal/unmarshal a list with a JAXB (JSR-222) implementation you need to create a wrapper object to hold the list. People find this onerous having to create multiple wrapper objects for this purpose.  Below I'll demonstrate that in reality you only need to create one. This post is based on an answer I gave on Stack Overflow.

Using JAXB With XSLT to Produce HTML

JAXB (JSR-222) enables Java to treat a domain model as XML.  In this post I will demonstrate how to leverage this by applying an XSLT stylesheet to a JAXB model to produce HTML.  This approach is often leveraged when creating JAX-RS applications.

Applying a Namespace During JAXB Unmarshal

For some an XML schema is a strict set of rules for how the XML document must be structured.  But for others it is a general guideline to indicate what the XML should look like.  This means that sometimes people want to accept input that doesn't conform to the XML schema for some reason.  In this example I will demonstrate how this can be done by leveraging a SAX XMLFilter.

Removing JAXBElement From Your Domain Model

JAXBElement is a JAXB (JSR-222) mechanism that stores name and namespace information in situations where this can not be determined from the value or mapping.  For example in the class below the elements billing-address and shipping-address both correspond to the Address class.  In order to be able to round trip the data we need to keep track of which element we unmarshalled.

import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.*;

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {

    @XmlElementRefs({
        @XmlElementRef(name = "billing-address"),
        @XmlElementRef(name = "shipping-address")
    })
    private JAXBElement<Address> address;

}

While useful JAXBElement can get in the way if you want to use your domain model with something like JPA (which doesn't know what to do with it).  In this post I will demonstrate how you can eliminate the need for JAXBElement through the use of an XmlAdapter.

Handle the Middle of a XML Document with JAXB and StAX

Recently I have come across a lot of people asking how to read data from, or write data to the middle of an XML document.  In this post I will demonstrate how this can be done using JAXB with StAX.  Note:  JAXB (JSR-222) and StAX (JSR-173) implementations are included in the JDK/JRE since Java SE 6.

JAXB's @XmlTransient and Property Order

In previous articles I wrote about how the @XmlTransient annotation can be used at the type level to have a class excluded from the inheritance hierarchy, or at the field/property level to unmap a field/property.  In this article I'll demonstrate how doing this impacts the propOrder setting on the @XmlType annotation.

JAXB and Root Elements

@XmlRootElement is an annotation that people are used to using with JAXB (JSR-222).  It's purpose is to uniquely associate a root element with a class.  Since JAXB classes map to complex types, it is possible for a class to correspond to multiple root elements. In this case @XmlRootElement can not be used and people start getting a bit confused.  In this post I'll demonstrate how @XmlElementDecl can be used to map this use case.

JAXB - No Annotations Required

There appears to be a misconception that annotations are required on the model in order to use a JAXB (JSR-222) implementation.  The truth is that JAXB is configuration by exception, so annotations are only required when you want to override default behaviour.  In this example I'll demonstrate how to use JAXB without providing any metadata.

Extending JAXB - Representing Metadata as JSON

In previous posts I have described the XML mapping document and JSON-binding extensions in EclipseLink JAXB (MOXy).   Since MOXy has a JAXB model for its mapping document we were able to eat our own dog food, and now MOXy offers a JSON mapping document.

An external metadata representation is useful when:

• You cannot modify the domain model (it may come from a 3rd party).
• You do not want to introduce compile dependencies on JAXB APIs (if you are using a version of Java prior to Java SE 6).
• You want to apply multiple JAXB mappings to a domain model (you are limited to one representation with annotations).
• Your object model already contains so many annotations from other technologies that adding more would make the class unreadable.

Binding to JSON & XML - Handling Null

In a previous post I demonstrated how EclipseLink MOXy can be leveraged to produce both XML and JSON representations of your domain model.  The same metadata is used for both representations and MOXy applies it to leverage the capabilities of the media type.  In this post I'll focus on how null is handled in each of these representations.

JAXB and Unmapped Properties

JAXB (JSR-222) is configuration by exception, meaning that there is a default mapping applied to domain objects.  This means that sometimes you need to explicitly exclude a field/property.  In this post I'll discuss how this can be done using @XmlTransient or @XmlAccessorType(XmlAccessType.NONE) and when each option is appropriate.

MOXy as Your JAX-RS JSON Provider - Client Side

Recently I posted how to leverage EclipseLink JAXB (MOXy)'s JSON binding to create a RESTful service.  In this post I will demonstrate how easy it is to take advantage of MOXy's JSON binding on the client side.

• MOXy as Your JAX-RS JSON Provider - Server Side
• MOXy as Your JAX-RS JSON Provider - Client Side
• MOXy as Your JAX-RS JSON Provider - MOXyJsonProvider 

MOXy as Your JAX-RS JSON Provider - Server Side

In a previous series of posts I covered how EclipseLink JAXB (MOXy) can be leveraged to create a RESTful data access service.  In this post I will cover how easy it is to leverage MOXy's JSON binding on the server side to add support for JSON messages based on JAXB mappings.

• MOXy as Your JAX-RS JSON Provider - Server Side
• MOXy as Your JAX-RS JSON Provider - Client Side 

UPDATE

MOXy now includes an implementation of MessageBodyReader/MessageBodyWriter to make it even easier to leverage MOXy's JSON binding in a JAX-RS application.

•  MOXy as Your JAX-RS JSON Provider - MOXyJsonProvider

GlassFish 3.1.2 is Full of MOXy (EclipseLink JAXB)

I am very happy to announce that EclipseLink JAXB (MOXy) is now a JAXB (JSR-222) provider in GlassFish 3.1.2.  I would like to thank the EclipseLink and GlassFish committers for all their hard work to make this happen.

In this post I will introduce how MOXy can be leveraged to create a JAX-WS service.  In future posts I will cover more of the extensions in greater detail.

GlassFish can be downloaded from the following link:

• http://glassfish.java.net/public/downloadsindex.html