GWT RPC warn Checking all subtypes

Question

I have a gwt aplication, during compilation I get the error:

Scanning for additional dependencies: file:/D:/projects/healthplanel_trunk/clinics-gwt-client/src/com/clinics/gwt/shared/UserServiceAsync.java Computing all possible rebind results for 'com.clinics.gwt.shared.UserService' Rebinding com.clinics.gwt.shared.UserService Invoking generator com.google.gwt.user.rebind.rpc.ServiceInterfaceProxyGenerator Generating client proxy for remote service interface 'com.clinics.gwt.shared.UserService' Analyzing 'com.clinics.gwt.shared.UserService' for serializable types Analyzing methods: public abstract com.clinics.gwt.shared.query.GQueryResult listAdmins(com.clinics.gwt.shared.query.GQueryParams queryParams) Parameter: com.clinics.gwt.shared.query.GQueryParams queryParams com.clinics.gwt.shared.query.GQueryParams Verifying instantiability com.clinics.gwt.shared.query.GQueryParams Analyzing the fields of type 'com.clinics.gwt.shared.query.GQueryParams' that qualify for serialization private java.util.List> filters java.util.List> Verifying instantiability java.util.Vector> Checking parameters of 'java.util.Vector>' Checking type argument 0 of type 'java.util.Vector' because it is directly exposed in this type or in one of its subtypes com.clinics.gwt.shared.query.GFilterBy Verifying instantiability com.clinics.gwt.shared.query.GFilterBy Checking parameters of 'com.clinics.gwt.shared.query.GFilterBy' Checking type argument 0 of type 'com.clinics.gwt.shared.query.GFilterBy' because it is directly exposed in this type or in one of its subtypes java.io.Serializable Verifying instantiability java.util.HashMap [WARN] Checking all subtypes of Object which qualify for serialization

My code is:

public class GQueryParams implements IsSerializable {
private static final long serialVersionUID = 1L;
private int offset = 0;
private int maxCount = -1; // -1 means all
private ArrayList<GOrderBy> orders = new ArrayList<GOrderBy>();
private ArrayList<NoSqlOrderBy> noSqlOrders = new ArrayList<NoSqlOrderBy>();
private ArrayList<GFilterBy<?>> filters = new ArrayList<GFilterBy<?>>();

And:

public class GFilterBy<T extends Serializable> implements Serializable {
private static final long serialVersionUID = 1L;
private String id;
private GFilterOperation operation;
private T value;

What's wrong, could you please help me with it?

Answer 1

GFilterBy<?> basically accepts everything (everything that implements Serializable), so the generator has to scan the whole classpath for every applicable class and generate the appropriate ser/deserialization code for each of them.

This is generally not what you want, hence the warning.

The rule of thumb is to always be as specific as possible in types sent over the wire with GWT-RPC; and ? obviously violates that rule.