Dynamic Query Mapping using Toplink Entity

Question

Hi,
We have a requirement that the column names of the table dynamically gets changed for different customers.
eg;
Client 1 , will have
Select EMP_ID, EMP_NAME from EMPLOYEE
Client 2 will have
SELECT CEMP_ID, EMP_NAME, CEMP_ADDR from EMPLOYEE
Is it possible to make a Toplink Entity Employee object to support both the queries at runtime ?ie; we should not modify the java entity object for each customer.
With normal JDBC , we can perform SELECT * from EMPLOYEE ,get the resultset , and using metadata , we can find the column names and process it accordingly.
Is this functionality possible with toplink JPA at all ?
Thanks
prabu

Answer 1

Hi,
I am trying to use DynamicEntity class. Is Joined Table Inheritance supported in DynamicEntity ? Since I need to create an HybridEntity on the fly by selecting all the fields from TABLE A and TABLE B by joining key fields, whose fields will dynamically change based upon the customer. Below is what I am currently trying to do. But the Entity Object that I got contains fields only from TABLE A and not from TABLE B
EntityManagerFactory emf = new EntityManagerFactoryImpl(setup,EclipseLinkJPATest.getEMFProperties());
SchemaManager manager = new SchemaManager(JpaHelper.getServerSession(emf));
Vector <DatabaseRecord>tableAEntityFieldNames = manager.getAllColumnNames("TABLE A");
Vector <DatabaseRecord>tableBFieldNames = manager.getAllColumnNames("TABLE B");
EntityType tableAType = EntityTypeFactory.create("TableAEntity","DynamicEntity$TableAEntity", "TABLE A", loader);
String columnName = null;
for(DatabaseRecord tableAObj: tableAEntityFieldNames){
columnName = tableAObj.get("COLUMN_NAME").toString();
EntityTypeFactory.addBasicProperty(tableAType, columnName, columnName,
"TABLE A_ID".equals(columnName) ? Long.class : String.class, "TABLE A_ID".equals(columnName) ? true : false);
EntityTypeFactory.addToPersistenceUnit(emf, tableAType);
EntityType stepType = EntityTypeFactory.create("TableBEntity","DynamicEntity$TableBEntity", "TABLE B", loader);
for(DatabaseRecord tableBObj: tableBEntityFieldNames) { 
columnName = tableBObj.get("COLUMN_NAME").toString();
EntityTypeFactory.addBasicProperty(tableBType, columnName, columnName,"TABLE B_ID".equals(columnName) ? Long.class : String.class, "TABLE B_ID".equals(columnName) ? true : false);
EntityTypeFactory.addToPersistenceUnit(emf, tableBType);
EntityManager em = emf.createEntityManager();
List <DynamicEntity> entityList = null;
entityList = em.createQuery("select s from TableAEntity s, TableBEntity st where s.TABLE A_ID= st.TABLE B_IDand s.TABLE A_ID=?1")
          .setParameter(1, 1397)
          .getResultList();
System.out.println("entityList..."+entityList);
Thanks
Prabu