JSON Serialization loop (infinite recursion) in Wildfly

Question

I am developing a straightforward maven-based JavaEE application in IntelliJ IDEA, and obviously I would like to use Wildfly 8 for both development and production. I simply need to expose some entities through some RESTful web services. Those entities have bidirectional relationships, which leads to a loop when they are going to be serialized into JSON.

Newer versions of Jackson are able to handle this kind of situation with a special annotation. To get that to work, I need to exclude Wildfly's built-in JSON serializer / jackson provider / whatever it is and use the newer version that comes bundled with my application. I have followed the instructions I have found on the web and came up with this jboss-deployment-structure.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<jboss-deployment-structure>
    <deployment>
        <exclusions>
            <module name="org.codehaus.jackson.jackson-jaxrs" />
            <module name="org.codehaus.jackson.jackson-core-asl" />
            <module name="org.codehaus.jackson.jackson-mapper-asl" />
            <module name="org.codehaus.jackson.jackson-xc" />
        </exclusions>
    </deployment>
</jboss-deployment-structure>

The problem is, it doesn't work. Even when I set my pom.xml to something like this:

<dependencies>
    <dependency>
        <groupId>javax</groupId>
        <artifactId>javaee-api</artifactId>
        <version>7.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.3.1</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.3.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.jboss.resteasy</groupId>
        <artifactId>resteasy-jackson2-provider</artifactId>
        <version>3.0.6.Final</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

which clearly indicates that nothing should come bundled with my application, I still get this StackOverflowError (caused by the infinite loop) which roots in org.codehaus.jackson package. This is turn means that built-in version of Jackson is still in the works and is not excluded. How can I fix this?

Thanks in advance.

UPDATES

I changed the title because I guess the problem is even bigger. Either I am doing something terribly wrong or there is a serious problem with Wildfly.

I have created a pom.xml with all the jackson 2 libraries (com.fasterxml.jackson*) with a "compile" scope. The libraries are included in the WEB-INF/lib folder. I wrote a @Provider according to Jackson JAX-RS FAQ and I can verify that it is actually read by the JAX-RS implementation (RestEasy), simply because the deployment fails if I do not include jackson libraries in WEB-INF/lib with a ClassNotFoundException. However, I am still getting infinite recursion errors with org.codehaus.X (Jackson 1).

I don't care how, I just need a solution to fix this infinite recursion in Wildfly.

Answer 1

The solution is to create a class which implement MessageBodyWriter<Object> using Jackson's ObjectMapper:

@Provider
@Produces("application/json")
public class JacksonMapper implements MessageBodyWriter<Object> {

    @Override
    public boolean isWriteable(Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType) {
        return true;
    }

    @Override
    public long getSize(Object object, Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType) {
        return 0;
    }

    @Override
    public void writeTo(Object object, Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> stringObjectMultivaluedMap, OutputStream outputStream)
            throws IOException, WebApplicationException {
        outputStream.write(new ObjectMapper().writeValueAsBytes(object));
    }

}

There's no need for any exclusion or Wildfly-specific descriptors.

It doesn't matter if you include the dependencies or not (compile or provided scopes both work fine) as Jackson 2 is included in Wildfly. However, for an unknown reason, it is near to impossible to deactivate Jackson 1.

This solution brings Jackson 2 into the works. Now you can easily avoid serialization loops using the @JsonIdentityInfo annotation. More info here.