EJB 模拟银行ATM流程及操作源代码

package Account; import java.sql.*; import javax.ejb.*; import java.util.Collection; import java.util.Vector; // 这个管理持久化实体Bean表示一个银行账户 public class AccountBean implements EntityBean { protected EntityContext ctx; // Bean的状态域 private String accountID; // 本例中的主键 private String ownerName; private double balance; public AccountBean() { } // 商务逻辑方法 //存款 public void deposit(double amt) throws AccountException { balance += amt; } // 取款，如果amt>余额，抛出异常 public void withdraw(double amt) throws AccountException { if (amt > balance) { throw new AccountException(余额不够"); } balance -= amt; } // 实体Bean上的获得器/设置器方法 public double getBalance() { System.out.println("getBalance()"); return balance; } public void setOwnerName(String name) { System.out.println("setOwnerName()" + accountID); ownerName = name; } public String getOwnerName() { System.out.println("getOwnerName() on" + accountID); return ownerName; } public String getAccountID() { System.out.println("getAccountID() on" + accountID); return accountID; } public void setAccountID(String id) { System.out.println("setAccountID() on " + accountID); this.accountID = id; } // 返回所有账户的余额 public double ejbHomeGetTotalBankValue() throws AccountException { PreparedStatement pstmt = null; Connection conn = null; try { // 和数据库连接 conn = getConnection(); // 执行查询操作，得到所有账户余额总和 pstmt = conn.prepareStatement( "select sum(balance) as total from accounts"); ResultSet rs = pstmt.executeQuery(); if (rs.next()) { return rs.getDouble("total"); } } catch (Exception e) { e.printStackTrace(); throw new AccountException(e); } finally {// 释放数据库资源 try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } throw new AccountException("Error!"); } // EJB必须实现的方法 public void ejbActivate() { System.out.println("ejbActivate()"); } // 从数据库中移除实体Bean public void ejbRemove() throws RemoveException { System.out.println("ejbRemove()"); // 一个实体Bean可以表示不同的数据实例 // 我们应该通过主键来判断删除哪个数据实例 AccountPK pk = (AccountPK) ctx.getPrimaryKey(); String id = pk.accountID; PreparedStatement pstmt = null; Connection conn = null; try { // 获得新的数据库连接 conn = getConnection(); // 从数据库中删除账号 pstmt = conn.prepareStatement("delete from accounts where id = ?"); pstmt.setString(1, id); // 操作数据库失败，抛出一个系统级错误 if (pstmt.executeUpdate() == 0) { throw new RemoveException("Account " + pk + " failed to be removed from the database"); } } catch (Exception ex) { throw new EJBException(ex.toString()); } finally { // 释放数据库连接 try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } // 钝化，为了挂起释放的资源 public void ejPassivate() { System.out.println("ejbPassivate ()on " + accountID); } // 更新内存中的实体Bean对象，反映数据库中的当前值 public void ejbLoad() { System.out.println("ejbLoad() on " + accountID); // 得到实体主键，这样我们知道那个实例被加载 AccountPK pk = (AccountPK) ctx.getPrimaryKey(); String id = pk.accountID; PreparedStatement pstmt = null; Connection conn = null; try { // 获得新的数据库连接 conn = getConnection(); // 通过ID查询，得到数据库中的账号 pstmt = conn.prepareStatement( "select ownerName, balance from accounts where id = ?"); pstmt.setString(1, id); ResultSet rs = pstmt.executeQuery(); rs.next(); ownerName = rs.getString("ownerName"); balance = rs.getDouble("balance"); } catch (Exception ex) { throw new EJBException("Account " + pk + " failed to load from database", ex); } finally { // 释放数据库连接 try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } // 更新数据库，反映当前内存中的值 public void ejbStore() { System.out.println("ejbStore() on " + accountID); PreparedStatement pstmt = null; Connection conn = null; try { // 获得新的数据库连接 conn = getConnection(); // 往数据库存储账户 pstmt = conn.prepareStatement( "update accounts set ownerName = ?, balance = ? where id = ?"); pstmt.setString(1, ownerName); pstmt.setDouble(2, balance); pstmt.setString(3, accountID); pstmt.executeUpdate(); } catch (Exception ex) { throw new EJBException("Account " + accountID + " failed to save to database", ex); } finally { // 释放数据库连接 try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } // 把一个Bean实例和一个特定的环境对象关联起来 public void setEntityContext(EntityContext ctx) { System.out.println("setEntityContext called"); this.ctx = ctx; } // 把一个Bean和它的环境变量分离 public void unsetEntityContext() { System.out.println("unsetEntityContext called on " + accountID); this.ctx = null; } // 在ejbCreate()调用后，Bean可以从它的环境中提取EJB对象 // 并当作一个this参数传递 public void ejbPostCreate(String accountID, String ownerName) { } // 此方法对应Home中的create()方法 // 当客户端调用本地对象(Home)的create()方法时， // 本地对象调用ejbCreate()方法 public AccountPK ejbCreate(String accountID, String ownerName) throws CreateException { PreparedStatement pstmt = null; Connection conn = null; try { System.out.println("ejbCreate() called on " + accountID); this.accountID = accountID; this.ownerName = ownerName; this.balance = 0; // 获得数据库的连接 conn = getConnection(); // 插入账号 pstmt = conn.prepareStatement( "insert into accounts (id, ownerName, balance) values (?, ?, ?)"); pstmt.setString(1, accountID); pstmt.setString(2, ownerName); pstmt.setDouble(3, balance); pstmt.executeUpdate(); // 产生一个主键，并返回 return new AccountPK(accountID); } catch (Exception e) { throw new CreateException(e.toString()); } finally { //释放数据库的连接 try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } // 通过主键找到一个账号 public AccountPK ejbFindByPrimaryKey(AccountPK key) throws FinderException { PreparedStatement pstmt = null; Connection conn = null; try { Sys