Postgres stored procedure call from java, table to return

I made a Postgres stored procedure:

CREATE OR REPLACE FUNCTION GetUser(ipUserId integer)
RETURNS setof users AS $$
BEGIN
  IF ipUserId is null THEN
    return query select * from users A order by modifieddate desc;
  END IF;
  return query select * from users where iduser = ipUserId;
END;
$$ LANGUAGE plpgsql;

I tried to use it in java like this:

    StoredProcedureQuery query = entityManager.createStoredProcedureQuery("GetUser").
            registerStoredProcedureParameter("ipUserId",
                    Integer.class, ParameterMode.IN)
            .registerStoredProcedureParameter("users",
                    List.class, ParameterMode.OUT)
            .setParameter("postId", 1);

or

 StoredProcedureQuery query = entityManager.createStoredProcedureQuery("GetUser")
                .registerStoredProcedureParameter(1,void.class, ParameterMode.REF_CURSOR)
                .registerStoredProcedureParameter(2,Integer.class, ParameterMode.IN)
                .setParameter(2, ipIdUser);

I want to store the result in a List.

What and how should i do, because i'm getting all kind of errors?

Update :

Those are the errors :

javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: Error calling CallableStatement.getMoreResults
Caused by: org.hibernate.exception.SQLGrammarException: Error calling CallableStatement.getMoreResults
    at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:106)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
    at org.hibernate.result.internal.OutputsImpl.convert(OutputsImpl.java:79)
    at org.hibernate.result.internal.OutputsImpl.<init>(OutputsImpl.java:56)
    at org.hibernate.procedure.internal.ProcedureOutputsImpl.<init>(ProcedureOutputsImpl.java:34)
    at org.hibernate.procedure.internal.ProcedureCallImpl.buildOutputs(ProcedureCallImpl.java:453)
    at org.hibernate.procedure.internal.ProcedureCallImpl.getOutputs(ProcedureCallImpl.java:404)
    at org.hibernate.procedure.internal.ProcedureCallImpl.outputs(ProcedureCallImpl.java:663)
    at org.hibernate.procedure.internal.ProcedureCallImpl.getResultList(ProcedureCallImpl.java:751)
    ... 21 more
Caused by: org.postgresql.util.PSQLException: A CallableStatement was executed with an invalid number of parameters

I found a much simple solution, just make a SQL Query to call the procedure with hibernate.

    String SqlString = "select * from GetUser({0})";

    if (ipIdUser == null )
        SqlString = MessageFormat.format(SqlString, "NULL");
    else
        SqlString = MessageFormat.format(SqlString, ipIdUser);

    LOGGER.info("SqlSting =" + SqlString);

    return entityManager.createNativeQuery(SqlString, User.class)
            .getResultList();