Search code examples
jsonrestjaxbcxf

JSON Provider builds wrong String field, when value is 'true' or 'false'

I have a problem. Could you please help me. I have an application: CXF+Spring+JAXB+REST. And I try to generate Response using JSONProvider class There is a bean class:

@XmlRootElement
class Foo {
@XmlElement
private String bar;
}

When I set to the field value:

setBar("true")

or

setBar("false");

JSONProvider returns to me:

"bar":false

But, I expect 

"bar":"false"

Because I use String type. What should I do with that?

Solution

  • Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

    The JAXB (JSR-222) specification does not cover JSON-binding. In a REST/JAX-RS context it is up to the provider to apply the JAXB mapping rules to a JSON representation. There are 3 different approaches that are being used today:

    1. Use a JAXB implementation with a library like Jettison. Jettison implements the StAX interfaces but interprets JSON. The advantage of this approach is that it can be used with any JAXB implementation to produce/consume JSON, the disadvantage of this approach is that Jettison does not have enough information to do a perfect JSON representation. Jettison receives the String "true" without knowing what the corresponding Java type was, so it decides to represent it as a JSON boolean, since it is probably the desired output most of the time.
    2. REST/JAX-RS implementation leverages a specific JAXB implementation to produce JSON. This approach is similar to the first, except that the REST/JAX-RS provider makes proprietary calls to the JAXB provider to make more educated guesses to what the JSON representation should be.
    3. The JAXB implementation provides the JSON-binding implementation. Currently EclipseLink MOXy is the only JAXB implementation to support JSON-binding.

    MOXy EXAMPLE

    Root

    Below is a domain object with String and boolean fields. I've also added fields annotated with @XmlSchemaType which can be used to override the default representation.

    package forum11145933;

import javax.xml.bind.annotation.*;

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

    String barString;

    boolean barBoolean;

    @XmlSchemaType(name="boolean")
    String barStringWithXmlTypeBoolean;

    @XmlSchemaType(name="string")
    boolean barBooleanWithXmlTypeString;

}

    jaxb.properties

    To specify MOXy as your JAXB provider you need to add a file called jaxb.properties in the same package as your domain model with the following entry:

    javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

    Demo

    The following code demonstrates how to marshal the domain object to JSON. Note that there are no compile time dependencies on MOXy.

    package forum11145933;

import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Root root = new Root();
        root.barString = "true";
        root.barBoolean = true;
        root.barStringWithXmlTypeBoolean = "true";
        root.barBooleanWithXmlTypeString = true;

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty("eclipselink.media-type", "application/json");
        marshaller.marshal(root, System.out);
    }

}

    Output

    The following is the output from running the Demo code. Note how the boolean and String properties are written out correctly. Also notice how the use of the @XmlSchemaType annotation allows us to marshal a boolean as a String and vice versa. 

    {
   "root" : {
      "barString" : "true",
      "barBoolean" : true,
      "barStringWithXmlTypeBoolean" : true,
      "barBooleanWithXmlTypeString" : "true"
   }
}

    MOXy & JAX-RS

    MOXy includes MOXyJsonProvider which can be used to enable MOXy as the JSON provider in your JAX-RS environment: