Spring @ResponseBody Json Cyclic Reference

Question

I am trying to use Spring 3.x @ResponseBody to generate json/xml response, I am using JPA 2.0 ORM when there is many-many relation b/w tables then json is throwing LazyInitializationException

If I give "eager fetch" then it is going into cyclic reference.

This may not be the answer you're looking for, but I've also run into this issue, and I've had to solve it by writing a custom `ObjectMapper` and `JsonSerializer` that dealt with relationship. — bvulaj, Mar 15 '12 at 20:33
can anybody give solution to my problem, this is still holding my development — Sandeep Manne, Mar 16 '12 at 09:45
I see two solutions that have been posted. Have you tried either? — bvulaj, Mar 20 '12 at 20:49
custom wrapper I didnt tried, its the last option I am trying to consider, yes I am calling the methods to initialize the child - like user.getGroups() - where groups has many-many relationship and it again has userList which I cant intialize because it will cause cyclic problem again. — Sandeep Manne, Mar 21 '12 at 08:09
I dont need but @ManytoMany annotation is creating that, I just need user and list of groups — Sandeep Manne, Mar 21 '12 at 13:15

score 3 · Accepted Answer · edited May 23 '17 at 12:15

I recently encountered a similar problem: Jackson - serialization of entities with birectional relationships (avoiding cycles)

So the solution is to upgrade to Jackson 2.0, and add to classes the following annotation:

@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, 
                  property = "@id")
public class SomeEntityClass ...

Then the problem is that Spring doesn't work with Jackson 2.0. This has been solved in the following way:

<bean id="jacksonMessageConverter"
          class="own.implementation.of.MappingJacksonHttpMessageConverter"/>

<bean class="org.springframework.web.servlet.mvc
             .annotation.AnnotationMethodHandlerAdapter">
        <property name="messageConverters">
            <list>
                <ref bean="jacksonMessageConverter"/>
            </list>
        </property>
        <property name="requireSession" value="false"/>
    </bean>

And the own.implementation.of.MappingJacksonHttpMessageConverter is based on this:

http://www.jarvana.com/jarvana/view/org/springframework/spring-web/3.0.0.RELEASE/spring-web-3.0.0.RELEASE-sources.jar!/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java?format=ok

But use ObjectMapper and other Jackson classes from Jackson 2.0 instead of Jackson 1.*

score 3 · Answer 2 · answered Mar 21 '12 at 14:09

Judging by your comments, just create a custom Serializer.

Your JsonSerializer. You can have these for each object type you're trying to serialize.

public class MyObjectJsonSerializer extends JsonSerializer<MyObject> {

@Override
public Class<MyObject> handledType() {
    return MyObject.class;
}

@Override
public void serialize(MyObject myObject, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
    jgen.writeStartObject();
    jgen.writeNumberField("id", myObject.getId());
    // whatever else you need
    jgen.writeEndObject();
}

}

Your ObjectMapper.

public class MyObjectMapper extends ObjectMapper {

public MyObjectMapper() {
    SimpleModule module = new SimpleModule("My Module", new Version(1, 0, 0, "SNAPSHOT"));
    module.addSerializer(new MyObjectJsonSerializer());

    this.registerModule(module);
}

}

And then in your spring-config.xml.

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
            <property name="objectMapper" ref="myObjectMapper" />
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

<bean id="myObjectMapper" class="com.manne.app.objectmapper.MyObjectMapper" />

score 1 · Answer 3 · answered Mar 18 '12 at 14:39

1

Sounds like you are serializing an ORM-managed object to JSON, but haven't initialized all of the child associations, leading to the LazyInitializationException, as your Controller doesn't have a handle to the DB connection. 2 choices:

Initialize all of the objects' child associations in the DAO layer
Convert the ORM-managed object to a TO and pass that to the Controller for conversion to JSON

answered Mar 18 '12 at 14:39

atrain

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In my scenario I have users and groups with many-many relation-ship, if I initialize group child objects in user then again that group has users as child objects if I initialize that it will go into cycle – Sandeep Manne Mar 21 '12 at 08:11

Spring @ResponseBody Json Cyclic Reference

3 Answers3

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