一个较初级的EJB商业应用的例子

package order.ejb; import order.common.*; import java.sql.*; import javax.sql.*; import java.util.*; import javax.ejb.*; import javax.naming.*; public class OrderEJB implements EntityBean{ public String order_id; // 定购编号 public String user_id; // 用户帐号 public int totalPrice; // 订单价格 public ArrayList orderItems; // 订单项目的数组对象 private Connection con; private String dbJndi="java:comp/env/jdbc/ExampleDB"; // 连接数据库的id,password private String dbId="guest"; private String dbPassword="guest123"; private EntityContext context; // 取得数据库连接 public void setEntityContext(EntityContext context){ this.context=context; try{ getConnection(); } catch(Exception ex){ throw new EJBException("Connect to DB failed:"+ex.getMessage()); } } // 释放数据库连接 public void unsetEntityContext(){ try{ con.close(); } catch(SQLException ex){ throw new EJBException("Close DB Connection failed:"+ex.getMessage()); } } // 添加订单到ordertbl表，添加订单细目到itemtbl表 public String ejbCreate(String user_id, int totalPrice, ArrayList orderItems) throws CreateException{ if(orderItems==null||orderItems.size()==0) throw new CreateException("ejbCreate exception : no any item"); try{// 取得订单编号 this.order_id=genOrder_id(); // 添加一笔订单到ordertbl表格 insertOrder(this.order_id, user_id, totalPrice); // 添加订单细目到itemtbl表格 insertItems(orderItems); } catch(Exception ex){ throw new EJBException("ejbCreate exception: "+ex.getMessage()); } this.user_id=user_id; this.totalPrice=totalPrice; this.orderItems=orderItems; // 返回订单编号 return order_id; } public void ejbPostCreate(String user_id, int totalPrice, ArrayList orderItems){ } // 通过一个主键查找订单 public String ejbFindByPrimaryKey(String orderId)throws FinderException{ boolean result; try{ result=selectByPrimaryKey(orderId); } catch(Exception ex){ throw new EJBException("ejbFindByPrimaryKey exception:"+ex.getMessage()); } if(result) return orderId; else throw new ObjectNotFoundException("Row for id "+orderId+" not found."); } // 根据订购的账号查找一个订购者的所有订单 public Collection ejbFindByUserId(String userId) throws FinderException { Collection result; try{ result=selectByUserId(userId); } catch(Exception ex){ throw new EJBException(ex.getMessage()); } if(result.isEmpty()){ throw new ObjectNotFoundException("No rows found."); } else{ return result; } } // 查找所有订单 public Collection ejbFindAll()throws FinderException { Collection result; try{ result=selectAll(); } catch(Exception ex){ throw new EJBException(ex.getMessage()); } if(result.isEmpty()){ throw new ObjectNotFoundException("No rows found."); } else{ return result; } } // 读取数据库订单内容和订单细目到内存字段变量 public void ejbLoad(){ try{ loadOrder(); loadItems(); } catch(Exception ex){ throw new EJBException("ejbLoad exception:"+ex.getMessage()+"....."); } } // 写入内存字段变量到数据库表 public void ejbStore(){ try{ storeOrder(); deleteItems(); insertItems(orderItems); } catch(Exception ex) { throw new EJBException("ejbLoad exception:"+ex.getMessage()); } } // 获得订单细目 public ArrayList getOrderItems(){ return orderItems; } // 取得用户id public String getUser_id(){ return user_id; } // 获得订单总价 public int getTotalPrice(){ return totalPrice; } // 设定订单总价 public void setTotalPrice(int totalPrice){ this.totalPrice=totalPrice; } // 设定订单编号 public String getOrder_id(){ return order_id; } // 设定订单细目 public void setOrderItems(ArrayList orderItems){ if(orderItems==null||orderItems.size()==0) throw new EJBException("setOrderItems exception : no any item"); this.orderItems=orderItems; } // 在激活执行前，先去的主键 public void ejbActivate(){ order_id=(String)context.getPrimaryKey(); } // 钝化，将Bean实例放回Bean池 public void ejbPassivate(){ order_id=null; } // 删除订单和订单细目 public void ejbRemove(){ try{ deleteOrder(); deleteItems(); } catch(Exception ex){ throw new EJBException("ejbRemove exception:"+ex.getMessage()); } } // 取得数据库连结 private void getConnection() throws NamingException, SQLException{ InitialContext ic=new InitialContext(); DataSource ds=(DataSource) ic.lookup(dbJndi); con= ds.getConnection(dbId, dbPassword); } // 取得订单编号 private String genOrder_id() throws SQLException{ ResultSet rs; String order_id; String selectStatement ="select order_id "+"from OrderTBL where order_id=? "; PreparedStatement ps = con.prepareStatement(selectStatement); try{ do{ order_id=OrderId.genOrderId(); ps.setString(1, order_id); rs=ps.executeQuery(); }while(rs.next()); return order_id; } finally{ ps.close(); } } // 插入订单到ordertbl private void insertOrder(String order_id, String user_id, int totalPrice) throws SQLException{ String insertStatement ="insert into OrderTBL values(? ,? ,?)"; PreparedStatement ps= con.prepareStatement(insertStatement); try{ ps.setString(1, order_id); ps.setString(2, user_id); ps.setInt(3, totalPrice); ps.executeUpdate(); } finally{ ps.close(); } } // 插入订单细目到itemtbl private void insertItems(ArrayList orderItems) throws SQLException{ String insertStatement ="insert into ItemTBL values(? ,? ,?)"; PreparedStatement ps=con.prepareStatement(insertStatement); try{ // 逐笔将订单细目新增至ITEMTBL表格 ps.setString(1, this.order_id); for(int i=0; i<orderItems.size(); i++){ OrderItem item=(OrderItem)orderItems.get(i); ps.setString(2, item.getProduct_id()); ps.setInt(3, item.getQuantity()); ps.executeUpdate(); } } finally{ ps.close(); } } private boolean selectByPrimaryKey(String primaryKey) throws SQLException{ String selectStatement ="select order_id "+"from OrderTBL where order_id=?"; PreparedStatement ps =con.prepareStatement(selectStatement); try{ ps.setString(1, primaryKey); ResultSet rs=ps.executeQuery(); return rs.next(); } finally{ ps.close(); } } private Collection selectAll() throws SQLException{ String sqlStatement="select order_id from OrderTBL"; PreparedStatement ps=con.prepareStatement(sqlStatement); try{ ResultSet rs=ps.executeQuery(); ArrayList al=new ArrayList(); while(rs.next()){ String id=rs.getString(1); al.add(id); } return al; }finally{ ps.close(); } } private Collection selectByUserId(String userId) throws SQLException{ String sqlStatement="select order_id from OrderTBL "+"where user_id=?"; PreparedStatement ps=con.prepareStatement(sqlStatement); try{ ps.setString(1, userId); ResultSet rs=ps.executeQuery(); ArrayList al=new ArrayList(); while(rs.next()){ String id=rs.getString(1); al.add(id); } return al; } finally{ ps.close(); } } // 删除一笔订单细目 private void deleteItems() throws SQLException{ String deleteStatement = "delete from ItemTBL "+"where order_id=?"; PreparedStatement ps =con.prepareStatement(deleteStatement); try{ ps.setString(1, order_id); ps.executeUpdate();