Serialization and de-serialization for deep object graphs (references and cyclic dependencies).

Features:

• high-performance graph serialization
• handles cyclic dependencies and polymorphic pojos (interface and abstract classes)

Limitations:

• When a root message is serialized/deserialized, its nested messages should not contain references to it.

Example:

message ClubFounder {
    optional string name = 1;
    optional Club club = 2;
}

message Club {
    optional string name = 1;
    repeated Student student = 2;
    repeated Club partner_club = 3;
}

message Student {
    optional string name = 1;
    repeated Club club = 2;
}

You cannot directly serialize Club since it can potentially have a reference to itself.

The solution is to wrap the target message.

message ClubWrapper {
    optional Club club = 1;
}

On the other hand, you can serialize ClubFounder.

Schema<ClubFounder> schema = RuntimeSchema.getSchema(ClubFounder.class);
ClubFounder founder = new ClubFounder();

// fill with cyclic club and student objects

byte[] data = GraphIOUtil.toByteArray(founder, schema);

ClubFounder cf = new ClubFounder();
GraphIOUtil.mergeFrom(data, cf, schema);

// check if cf retains the graph

For a more complex example, take a look at PolymorphicRuntimeGraphTest.java

Note that if you have collection fields that can potentially be cyclic, you need to enable the system property below:

-Dprotostuff.runtime.collection_schema_on_repeated_fields=true

E.g

class Foo
{
    List<Bar> barList;
    List<Baz> anotherBarList; // if this points to barList, it will be cyclic.

}

Doing so treats the collection field as a standalone message (which is handled on cyclic graph serialization).

Source document: https://code.google.com/p/protostuff/wiki/SerializingObjectGraphs