How to return Response in XML in JAX-RS web service?
Question
I'm developing a REST service using JAX-RS with Java 6 and Jersey 1.8 and my server is JBoss 5.1.0 GA , I've started with a simple endpoint that receives a parameter and return a null value.
Following this article , I mapped my expected exceptions with ExceptionMapper to three classes: AppException for exceptions within the scope of the project, NotFoundException for exceptions of records not found and GenericException for any other exception outside the expected errors.
I can return the exceptions as application/json responses just fine, but when I try to return a response as an application/xml , I get an HTML page from my server with HTTP 500 status code.
For example, if I don't send the required parameter to my endpoint, I get a HTTP 400 status code with its JSON response correctly:
{
"status": 400,
"message": "org.xml.sax.SAXParseException: Premature end of file.",
"developerMessage": "javax.ws.rs.WebApplicationException: org.xml.sax.SAXParseException: Premature end of file.... 40 more\r\n"
}
But if I try to return a XML response I get this HTML page:
<html>
<head>
<title>JBoss Web/2.1.3.GA - Informe de Error</title>
</head>
<body>
<h1>Estado HTTP 500 - </h1>
<HR size="1" noshade="noshade">
<p>
<b>type</b> Informe de estado
</p>
<p>
<b>mensaje</b>
<u></u>
</p>
<p>
<b>descripción</b>
<u>El servidor encontró un error interno () que hizo que no pudiera rellenar este requerimiento.</u>
</p>
<HR size="1" noshade="noshade">
<h3>JBoss Web/2.1.3.GA</h3>
</body>
</html>
My ErrorMessage class looks as described in the article I linked:
import java.lang.reflect.InvocationTargetException;
import javax.ws.rs.core.Response;
import org.apache.commons.beanutils.*;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import com.sun.jersey.api.NotFoundException;
@XmlRootElement(name = "errorMessage")
public class ErrorMessage {
@XmlElement(name = "status")
int status;
@XmlElement(name = "message")
String message;
@XmlElement(name = "developerMessage")
String developerMessage;
public int getStatus() {
return status;
}
public void setStatus(int status) {
this.status = status;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public String getDeveloperMessage() {
return developerMessage;
}
public void setDeveloperMessage(String developerMessage) {
this.developerMessage = developerMessage;
}
public ErrorMessage(AppException ex) {
try {
BeanUtils.copyProperties(this, ex);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
public ErrorMessage(NotFoundException ex) {
this.status = Response.Status.NOT_FOUND.getStatusCode();
this.message = ex.getMessage();
}
public ErrorMessage() {
}
@Override
public String toString(){
return "ErrorMessage{" + "status=" + status + ", message='" + message + '\'' + ", developerMessage='" + developerMessage + "'}";
}
}
Why am I unable to return a XML response when specified?
This is the GenericExceptionMapper class I'm using
@Provider
public class GenericExceptionMapper implements ExceptionMapper<Throwable> {
@Override
public Response toResponse(Throwable exception) {
ErrorMessage errorMessage = new ErrorMessage();
setHttpStatus(exception, errorMessage);
errorMessage.setMessage(exception.getMessage());
StringWriter errorStackTrace = new StringWriter();
exception.printStackTrace(new PrintWriter(errorStackTrace));
errorMessage.setDeveloperMessage(errorStackTrace.toString());
// The only change is the MediaType.APPLICATION_XML, originally it was MediaType.APPLICATION_JSON
return Response.status(errorMessage.getStatus()).entity(errorMessage).type(MediaType.APPLICATION_XML).build();
}
private void setHttpStatus(Throwable ex, ErrorMessage errorMessage) {
if(ex instanceof WebApplicationException ) {
errorMessage.setStatus(((WebApplicationException)ex).getResponse().getStatus());
} else {
errorMessage.setStatus(Response.Status.INTERNAL_SERVER_ERROR.getStatusCode());
}
}
}
1 answers
solution1
4 ACCPTED 2015-02-04 20:43:07
Providing the @XmlAccessorType(XmlAccessType.FIELD) above your ErrorMessage class should solve the problem :
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class ErrorMessage {
/** contains the same HTTP Status code returned by the server */
@XmlElement(name = "status")
int status;
This JAXB annotation will tell the server to bind attributes instead of getters to your XML. Otherwise an error will be generated as this causes your XML response to have duplicate properties for XML binding(like duplicate code elements).
WHY?
By default, if @XmlAccessorType on a class is absent, and none of its super classes is annotated with @XmlAccessorType, then the following default on the class is assumed:
@XmlAccessorType(XmlAccessType.PUBLIC_MEMBER)
Next if we look into the documentation on XmlAccessType to understand PUBLIC_MEMBER here is what it has to say:
Every public getter/setter pair and every public field will be automatically bound to XML, unless annotated by XmlTransient.
So the code of ErrorMessage became conflicting as XmlElement was also used to map JavaBean property to XML. Therefore for example the property code was not only bound by XmlElement but also by it's getter method.
To overcome this problem we have two options:
Option 1 :We can use XmlAccessType.FIELD so that only the fields are used and getters are omitted.
Option 2 :Simply remove the XmlElement annotations from the class in which case the getters will only decide the binding.
Also, don't forget to update the toResponse message of your mapper class to reflect the output is XML:
@Override
public Response toResponse(AppException ex) {
return Response.status(ex.getStatus())
.entity(new ErrorMessage(ex))
.type(MediaType.APPLICATION_XML).
build();
}
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