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

Question

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?

Answer 1

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:
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.
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.
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:
http://blog.bdoughan.com/2012/05/moxy-as-your-jax-rs-json-provider.html