21天精通Java,这是一本英文书

				package data;
				
				import java.rmi.*;
				import java.sql.*;
				import java.util.*;
				import javax.ejb.*;
				import javax.naming.*;
				import javax.sql.*;
				
				public class LocationBean implements EntityBean
				{
					private DataSource dataSource;
					private String name;
					private String description;
				
					public String getName () {
						return name;
					}
					
					public String getDescription () {
						return description;
					}
					
					public void setDescription (String description) {
						this.description = description;
					}
				
					// EJB methods start here
				
					public void ejbPostCreate (String name, String description) {}
				
					public String ejbCreate (String name, String description) throws CreateException {
						try {
							ejbFindByPrimaryKey(name);
							throw new CreateException("Duplicate location name: "+name);
						}
						catch (FinderException ex) {}
						
						Connection con = null;
						PreparedStatement stmt = null;
						try {
							con = dataSource.getConnection();
							stmt = con.prepareStatement(
							"INSERT INTO Location (name,description) VALUES (?,?)");
				
							stmt.setString(1, name);
							stmt.setString(2, description);
							stmt.executeUpdate();
						}
						catch (SQLException e) {
							error("Error creating Location "+name,e);
						}
						finally {
							closeConnection(con, stmt, null);
						}
						this.name = name;
						this.description = description;
						return name;
					}
					
					public String ejbFindByPrimaryKey(String name) throws FinderException {
						Connection con = null;
						PreparedStatement stmt = null;
						ResultSet rs = null;
						try {
							con = dataSource.getConnection();
							stmt = con.prepareStatement(
							"SELECT name FROM Location WHERE name = ?");
				
							stmt.setString(1, name);
							rs = stmt.executeQuery();
				
							if (!rs.next()) {
								throw new FinderException("Unknown location: "+name);
							}
							return name;
						}
						catch (SQLException e) {
							error("Error in findByPrimaryKey for "+name,e);
						}
						finally {
							closeConnection(con, stmt, rs);
						}
						return null;
					}
					
					public Collection ejbFindAll() throws FinderException {
						Connection con = null;
						PreparedStatement stmt = null;
						ResultSet rs = null;
						try {
							con = dataSource.getConnection();
							stmt = con.prepareStatement(
							"SELECT name FROM Location ORDER BY name");
				
							rs = stmt.executeQuery();
				
							Collection col = new ArrayList();
							while (rs.next()) {
								col.add(rs.getString(1));
							}
							return col;
						}
						catch (SQLException e) {
							error("Error in findAll",e);
						}
						finally {
							closeConnection(con, stmt, rs);
						}
						return null;
					}
				
					public void ejbLoad(){
						name = (String)ctx.getPrimaryKey();
						Connection con = null;
						PreparedStatement stmt = null;
						ResultSet rs = null;
						try {
							con = dataSource.getConnection();
							stmt = con.prepareStatement(
							"SELECT name,description FROM Location WHERE name = ?");
				
							stmt.setString(1, name);
							rs = stmt.executeQuery();
				
							if (!rs.next()) {
								error("No data found in ejbLoad for "+name,null);
							}
							this.name = rs.getString(1);
							this.description = rs.getString(2);
						}
						catch (SQLException e) {
							error("Error in ejbLoad for "+name,e);
						}
						finally {
							closeConnection(con, stmt, rs);
						}
					}
				
					public void ejbStore(){
						Connection con = null;
						PreparedStatement stmt = null;
						try {
							con = dataSource.getConnection();
							stmt = con.prepareStatement(
							"UPDATE Location SET description = ? WHERE name = ?");
				
							stmt.setString(1, description);
							stmt.setString(2, name);
							stmt.executeUpdate();
						}
						catch (SQLException e) {
							error("Error in ejbStore for "+name,e);
						}
						finally {
							closeConnection(con, stmt, null);
						}
					}
				
					public void ejbPassivate(){
						name = null;
						description = null;
					}
				
					public void ejbActivate(){
					}
				
					public void ejbRemove(){
						name = (String)ctx.getPrimaryKey();
						
						Connection con = null;
						PreparedStatement stmt = null;
						try {
							con = dataSource.getConnection();
						  
							stmt = con.prepareStatement(
							"DELETE FROM Location WHERE name = ?");
				
							stmt.setString(1, name);
							stmt.executeUpdate();
						}
						catch (SQLException e) {
							error("Error removing location "+name,e);
						}
						finally {
							closeConnection(con, stmt, null);
						}
						name = null;
						description = null;
					}
				
					private EntityContext ctx;
					
					public void setEntityContext(EntityContext ctx) {
						this.ctx = ctx;
						InitialContext ic = null;
						try {
							ic = new InitialContext();
							dataSource = (DataSource)ic.lookup("java:comp/env/jdbc/Agency");
						}
						catch (NamingException ex) {
							error("Error connecting to java:comp/env/jdbc/Agency:",ex);
							return;
						}
					}	
				
					public void unsetEntityContext() {
						this.ctx = null;
						dataSource = null;
					}	
				
					private void closeConnection (Connection con, PreparedStatement stmt, ResultSet rslt) {
						if (rslt != null) {
							try {
								rslt.close();
							}
							catch (SQLException e) {}
						}
						if (stmt != null) {
							try {
								stmt.close();
							}
							catch (SQLException e) {}
						}
						if (con != null) {
							try {
								con.close();
							}
							catch (SQLException e) {}
						}
					}
				
					private void error (String msg, Exception ex) {
						String s = "LocationBean: "+msg + "\n" + ex;
						System.out.println(s);
						throw new EJBException(s,ex);
					}
					
				}