Gemfire JavaDocs

public interface PdxSerializable

When a domain class implements PdxSerializable it marks itself as a PDX. The implementation of toData provides the serialization code and fromData provides the deserialization code. These methods also define each field name and field type of the PDX. Domain classes should serialize and deserialize all its member fields in the same order in toData and fromData method. Also fromData and toData must read and write the same fields each time they are called. A domain class that implements this interface must also have a public zero-arg constructor which is used during deserialization.

Simple example:

 public class User implements PdxSerializable {
   private String name;
   private int userId;

   public User() {}

   public void toData(PdxWriter out) {
     out.writeString("name", this.name);
     out.writeInt("userId", this.userId);
   }

   public void fromData(PdxReader in) {
     this.name = in.readString("name");
     this.userId = in.readInt("userId");
   }
 }