J2EE实现电子通讯录

package com.my.struts.model; import java.sql.*; import com.my.struts.db.*; public class FriendInfoDAO { Connection con=null; Statement stmt=null; PreparedStatement pstmt=null; ResultSet rs=null; ConDB db=null; public FriendInfoDAO() { } //查询是否存在指定好朋友：根据朋友姓名查询，得到查询结果是布尔型 public boolean search(String friendName) { boolean result=false; try { db=new ConDB(); String sql="select * from friendInfo where name=?"; con=db.getConnection(); pstmt=con.prepareStatement(sql); pstmt.setString(1, friendName); rs=pstmt.executeQuery(); if(rs.next()) { result=true; } } catch(Exception e) { e.printStackTrace(); } finally { try { if(rs!=null) rs.close(); if(pstmt!=null) pstmt.close(); if(con!=null) con.close(); } catch(SQLException e) { e.printStackTrace(); } } return result; } public boolean insert(String friendName,String phone,String address) { boolean result=false; try { String sql="insert friendInfo values(?,?,?)"; db=new ConDB(); con=db.getConnection(); pstmt=con.prepareStatement(sql); pstmt.setString(1,friendName); pstmt.setString(2,phone); pstmt.setString(3,address); int i=pstmt.executeUpdate(); if(i>0) { result=true; } } catch(SQLException e) { e.printStackTrace(); } finally { try { if(pstmt!=null) pstmt.close(); if(con!=null) con.close(); } catch(SQLException e) { e.printStackTrace(); } } return result; } public String display(String sql) { StringBuffer st=new StringBuffer(); try { db=new ConDB(); con=db.getConnection(); stmt=con.createStatement(); rs=stmt.executeQuery(sql); st.append("<table border='1' width='60%' align='center'>"); st.append("<th>FriendName</th>"); st.append("<th>Phone</th>"); st.append("<th>Address</th>"); while(rs.next()) { st.append("<tr>"); String friendName=rs.getString("name"); String phone=rs.getString("phone"); String address=rs.getString("address"); st.append("<td>"); st.append(friendName); st.append("</td>"); st.append("<td>"); st.append(phone); st.append("</td>"); st.append("<td>"); st.append(address); st.append("</td>"); st.append("</tr>"); } st.append("</table>"); } catch(SQLException e) { e.printStackTrace(); } finally { try { if(rs!=null) rs.close(); if(stmt!=null) stmt.close(); if(con!=null) con.close(); } catch(SQLException e) { e.printStackTrace(); } } System.out.println("st="+st); return st.toString(); } }