Multiple JAXBContext instances

java jaxb marshalling

20,259

From the Javadoc for JAXBContext:

A client application normally obtains new instances of this class using one of these
two styles for newInstance methods, although there are other specialized forms of the
method available:

JAXBContext.newInstance( "com.acme.foo:com.acme.bar" )
The JAXBContext instance is initialized from a list of colon separated Java package
names. Each java package contains JAXB mapped classes, schema-derived classes and/or
user annotated classes. Additionally, the java package may contain JAXB package annotations
that must be processed. (see JLS 3rd Edition, Section 7.4.1. Package Annotations).

JAXBContext.newInstance( com.acme.foo.Foo.class )
The JAXBContext instance is intialized with class(es) passed as parameter(s) and
classes that are statically reachable from these class(es). See newInstance(Class...)
for details.

You can use a shared context and initialize it with a list of package names.

Code Example:

package test.jaxb.one;

@XMLRootElement
@XMLType(name = "test.jaxb.one.SimpleObject")
@XMLAccessorType(XMLAccessType.FIELD)
public class SimpleObject implements Serializable {
    private static final long serialVersionUID = 54536613717262557148L;

    @XmlElement(name = "Name")
    private String name;

    // Constructor, Setters/Getters
}

and this one:

package test.jaxb.two;

@XMLRootElement
@XMLType(name = "test.jaxb.two.SimpleObject")
@XMLAccessorType(XMLAccessType.FIELD)
public class SimpleObject implements Serializable {
    private static final long serialVersionUID = -4073071224211934153L;

    @XmlElement(name = "Name")
    private String name;

    // Constructor, Setters/Getters
}

Finally:

public class JAXBTest {
    @Test
    public void testContextLoad() throws Exception {
        final JAXBContext context = JAXBContext
            .newInstance("test.jaxb.one:test.jaxb.two");
        Assert.assertNotNull(context);
    }
}

20,259

Author by

Spring

Updated on May 25, 2020

Comments

Spring almost 4 years
By using XJC, I create 2 different JAXB metadata packages with an ObjectFactory class in each package (I dont know if this approach is OK, I have 2 different XSD's to work on )

It is recommended to create only one JAXBContext per operation, because it is costy. So I wonder if what I'm doing here is valid and good practise?
```
    JAXBContext jaxbContext = JAXBContext.newInstance("com.package.one");
    Unmarshaller jaxbUnmarshaller1 = jaxbContext.createUnmarshaller();

    JAXBContext jaxbContext2 = JAXBContext.newInstance("com.package.two");
    Unmarshaller jaxbUnmarshaller2 = jaxbContext2.createUnmarshaller();
```
EDIT when i try to initialize 2 packages together i get an exception "The element name {}Value has more than one mapping." Value is a class in both packages.
```
 JAXBContext jaxbContext = JAXBContext.newInstance("com.package.one:com.package.two");
```
Spring over 11 years

thnx so its not a problem that those packages to contain classes with same name?
Perception over 11 years

JAXB uses FQN (fully qualified names) while processing, so no, its not a problem if classes have the same (simple) name.
Spring over 11 years

@Perception when i try to initialize 2 packages together i get an exception "The element name {}Value has more than one mapping." But they work well seperatly. Value is a class in both packages. So whats is the problem?
Perception over 11 years

@tibtof - The OP already realizes that creating multiple JAXB context objects is the wrong approach, my answer tells him how to use one context and accomplish the same goal. The intent is clear.
Perception over 11 years

@Spring - are you getting the exception when initializing the JAXB context, or when executing the unmarshal?
Spring over 11 years

@Perception I get exception while initializing the JAXB context. Tested by removing the unmarshall code
Spring over 11 years

@tibtof tnx could you give a reference on sharing same JAXB context is trouble when unmarshalling?
Spring over 11 years

@tibtof changing namespaces solved the crash. But do you have a reference on your claim that "FQN is only valid for marshalling?" you can edit your answer with this information and i will remove the downvote
Perception over 11 years

@Spring - you just need to add an XMLType annotation to the top of the classes with the same simple name. I would recommend using the FQN as the type name.
Spring over 11 years

I changed the namespaces from objectFactory classes, is that a bad approach?
Perception over 11 years

let us continue this discussion in chat