JAVA WEB 开发详解（JSP+Serlet)

package org.sunxin.guestbook.beans; import java.io.*; import java.sql.*; import javax.naming.*; import javax.sql.*; import org.sunxin.guestbook.*; public class GuestbookDB implements Serializable { private DataSource ds=null; public GuestbookDB() { try { Context ctx = new InitialContext(); ds = (DataSource) ctx.lookup("java:comp/env/jdbc/guestbook"); } catch (NamingException ne) { System.err.println(ne.toString()); } } /** * 得到数据库连接。 */ public Connection getConnection() throws SQLException { return ds.getConnection(); } /** * 关闭连接对象。 */ protected void closeConnection(Connection conn) { if(conn!=null) { try { conn.close(); conn=null; } catch (SQLException ex) { System.err.println(ex.toString()); } } } /** * 关闭Statement对象。 */ protected void closeStatement(Statement stmt) { if(stmt!=null) { try { stmt.close(); stmt=null; } catch (SQLException ex) { System.err.println(ex.toString()); } } } /** * 关闭PreparedStatement对象。 */ protected void closePreparedStatement(PreparedStatement pstmt) { if(pstmt!=null) { try { pstmt.close(); pstmt=null; } catch (SQLException ex) { System.err.println(ex.toString()); } } } /** * 关闭ResultSet对象。 */ protected void closeResultSet(ResultSet rs) { if(rs!=null) { try { rs.close(); rs=null; } catch (SQLException ex) { System.err.println(ex.toString()); } } } /** * 注册用户。 */ public void registerUser(User user) throws UserException { Connection conn=null; ResultSet rs=null; PreparedStatement pstmt=null; try { conn = getConnection(); pstmt = conn.prepareStatement( "select username from users where username=?"); pstmt.setString(1,user.getUsername()); rs=pstmt.executeQuery(); if(rs.next()) throw new UserException("用户名已经存在"); pstmt = conn.prepareStatement( "insert into users values(?,?,?,?)"); pstmt.setString(1, user.getUsername()); pstmt.setString(2, user.getPassword()); pstmt.setString(3, user.getEmail()); pstmt.setString(4, user.getStyle()); pstmt.executeUpdate(); } catch(SQLException se) { System.err.println(se.toString()); throw new UserException("用户注册失败！"); } finally { closeResultSet(rs); closePreparedStatement(pstmt); closeConnection(conn); } } /** * 对登录用户进行验证。 */ public String validateUser(User user) throws UserException { Connection conn=null; ResultSet rs = null; PreparedStatement pstmt = null; try { conn = getConnection(); pstmt = conn.prepareStatement( "select style from users where username=? and password=?"); pstmt.setString(1, user.getUsername()); pstmt.setString(2, user.getPassword()); rs = pstmt.executeQuery(); if (rs.next()) return rs.getString(1); else return ""; } catch (SQLException se) { System.err.println(se.toString()); throw new UserException("服务器忙，无法验证用户，请联系管理员。"); } finally { closeResultSet(rs); closePreparedStatement(pstmt); closeConnection(conn); } } /** * 保存留言。 */ public void saveMessage(Message msg) throws GuestbookException { Connection conn = null; PreparedStatement pstmt = null; try { conn = getConnection(); pstmt = conn.prepareStatement( "insert into gst(gst_user,gst_title,gst_content,gst_ip) values(?,?,?,?)"); pstmt.setString(1, msg.getUsername()); pstmt.setString(2, msg.getTitle()); pstmt.setString(3, msg.getContent()); pstmt.setString(4, msg.getIp()); pstmt.executeUpdate(); } catch (SQLException se) { System.err.println(se.toString()); throw new GuestbookException("保存留言失败！"); } finally { closePreparedStatement(pstmt); closeConnection(conn); } } /** * 获取所有留言。 * @return ResultSet */ public ResultSet getMessages() throws GuestbookException { Connection conn = null; Statement stmt = null; ResultSet rs=null; try { conn = getConnection(); stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY); rs=stmt.executeQuery("select * from gst order by gst_time desc"); return rs; } catch (SQLException se) { System.err.println(se.toString()); throw new GuestbookException("获取留言操作失败，请联系管理员。"); } } /** * 对管理员登录进行验证。 */ public boolean validateManager(User user) throws UserException { Connection conn=null; ResultSet rs = null; PreparedStatement pstmt = null; try { conn = getConnection(); pstmt = conn.prepareStatement( "select username from managers where username=? and password=?"); pstmt.setString(1, user.getUsername()); pstmt.setString(2, user.getPassword()); rs = pstmt.executeQuery(); if (rs.next()) return true; else return false; } catch (SQLException se) { System.err.println(se.toString()); throw new UserException("服务器忙，无法验证用户。"); } finally { closeResultSet(rs); closePreparedStatement(pstmt); closeConnection(conn); } } /** * 删除指定的留言。 */ public void deleteMessage(int id) throws GuestbookException { Connection conn = null; PreparedStatement pstmt = null; try { conn = getConnection(); pstmt = conn.prepareStatement( "delete from gst where gst_id = ?"); pstmt.setInt(1, id); pstmt.executeUpdate(); } catch (SQLException se) { System.err.println(se.toString()); throw new GuestbookException("删除留言失败！"); } finally { closePreparedStatement(pstmt); closeConnection(conn); } } }