A Universal Model for Designing the Entity EJB Layer
by Jonathon Leibundguth, Michael Pease, and Andrei Povodyrev


Example 1: 

Universum findByPrimaryKey(UniversumPK pk) throws FinderException, RemoteException;
Universum create(UniversumData data, UniversumPK pk) throws RemoteException, CreateException; 
Collection findBySQLWhere(String where, UniversumPK pk) throws FinderException, RemoteException;

Example 2: 

public static java.util.Collection findByName(String qst, UniversumHome home) 
                throws SQLException, FinderException, RemoteException{
        String where = " FIRST_NAME = '" + qst + "'";    
        return home.findBySQLWhere(where, UserPK.getInstance());
}

Example 3: 

void setBeanAttributes(EntityBeanData ebw) throws RemoteException; 
EntityBeanData getBeanAttributes() throws RemoteException;

Example 4: 

// First we need to insert a record into the database.
// Define the data elements of the record to insert

HashMap hm = new HashMap();
hm.put("ID", new Integer(102)); 
hm.put("FIRST_NAME","JP");
hm.put("LAST_NAME","LEIBUNDGUTH");
hm.put("ZIP_CODE","22182");
hm.put("PHONE","571-633-8645");

UniversumHome home;

// Lookup home interface for Universum Bean with appropriate JNDI string
// Convert our HashMap of data to the Value object for Universum Bean
UniversumData ebd = new UniversumData(hm);

// Use the create method on the home interface to insert the record
Universum user = home.create(ebd, UserPK.getInstance());    

// Next, retrieve the first name of the user we just created.
UniversumData data = user.getBeanAttributes());
String name = (String) data.get("FIRST_NAME");
    
// Finally, change the user's phone number and update the record
HashMap hm = new HashMap();
hm.put("PHONE","703-770-3000"); 
user.setBeanAttributes(new UniversumData(hm));


Listing One
package org.article.entitybean;
import java.sql.*;
import org.article.util.UniversumData;
import java.util.*;

/* Universal EJB primary key class that defines an interface that each 
 * concrete primary key class must implement.
 * @version: 1.0
 * @author: Andrei Povodyrev
 */
public interface UniversumPK    extends java.io.Serializable{
    public int hashCode(); //required by EJB specs   
    public String toString(); //required by EJB specs
    /* Implement this to determine primary key equality with another of 
     * same type, required by EJB specs
     * @param   obj  another UniversumPK
     * @return     true if the primary keys are the same
     */
    public boolean equals(Object obj);   
    public UniversumPK insert(UniversumData beanAttributes, Connection con)
        throws SQLException;
    /* Called to delete the row represented by this primary key
     * @exception   SQLException  
     */
    public void delete(Connection con) throws SQLException;

    /* Called to update the row represented by this primary key
     * @exception   SQLException  
     */
    public  void update(UniversumData beanAttributes, Connection con)
        throws SQLException;

    /* Called to select the row represented by this primary key
     * @return UniversumData
     * @exception   SQLException  
     */         
    public UniversumData select(Connection con) throws SQLException;

    /* Called to test for existance of the record represented by 
     * this primary key
     * @return     true if the record exists
     * @exception   SQLException  
     */
    public boolean exists(Connection con) throws SQLException;     
    /* Finds records using a SQL where clause
     * @param   where  the SQL where clause
     * @return     an enumeration of records
     * @exception   SQLException  
     */
    public Collection findBySQLWhere(String where, 
                                     Connection con) throws SQLException;
    /* Validates entry data which keys must match those specified by 
     * the concrete primary key class
     * @return     true if entry data valid
     **/
    public boolean validate(UniversumData attributes)throws SQLException;  
    }


Listing Two
package org.article.util;
import java.util.*;
/* Sun's recomendation for value objects: 
 *  fine-grained, dependent, i.e controlled by another object,
 *  and immutable, i.e. fields are not independently modifiable **/
public class UniversumData implements java.io.Serializable, Cloneable
{
    private HashMap _attributeMap;
    public UniversumData(HashMap map){      this.setMap(map);   }
    protected void setMap(HashMap map) { _attributeMap = map;   }
    public HashMap getMap(){        return _attributeMap;   }
    public Object get(String key){
        return _attributeMap == null?null:_attributeMap.get(key);   
  }
    public Object clone() throws CloneNotSupportedException{ 
// implement clone ...
    }




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