java留言管理系統中模糊查詢實例分享

本文分享了一個基於MVC+DAO的留言管理系統，包含增刪改查，其中查詢，有全部查詢和按關鍵字進行模糊查詢的功能，具體內容如下
NoteDAO.Java

 package cn.mldn.lxh.note.dao ; import java.util.* ; import cn.mldn.lxh.note.vo.* ; public interface NoteDAO { // 增加操作public void insert(Note note) throws Exception ; // 修改操作public void update(Note note) throws Exception ; // 刪除操作public void delete(int id) throws Exception ; // 按ID查詢，主要為更新使用public Note queryById(int id) throws Exception ; // 查詢全部public List queryAll() throws Exception ; // 模糊查詢public List queryByLike(String cond) throws Exception ; };

NoteDAOImpl.java

 package cn.mldn.lxh.note.dao.impl ; import java.sql.* ; import java.util.* ; import cn.mldn.lxh.note.vo.* ; import cn.mldn.lxh.note.dao.* ; import cn.mldn.lxh.note.dbc.* ; public class NoteDAOImpl implements NoteDAO { // 增加操作public void insert(Note note) throws Exception { String sql = "INSERT INTO note(id,title,author,content) VALUES(note_sequ.nextVal,?,?,?)" ; PreparedStatement pstmt = null ; DataBaseConnection dbc = null ; dbc = new DataBaseConnection() ; try { pstmt = dbc.getConnection().prepareStatement(sql) ; pstmt.setString(1,note.getTitle()) ; pstmt.setString(2,note.getAuthor()) ; pstmt.setString(3,note.getContent()) ; pstmt.executeUpdate() ; pstmt.close() ; } catch (Exception e) { // System.out.println(e) ; throw new Exception("操作中出現錯誤！！！") ; } finally { dbc.close() ; } } // 修改操作public void update(Note note) throws Exception { String sql = "UPDATE note SET title=?,author=?,content=? WHERE id=?" ; PreparedStatement pstmt = null ; DataBaseConnection dbc = null ; dbc = new DataBaseConnection() ; try { pstmt = dbc.getConnection().prepareStatement(sql) ; pstmt.setString(1,note.getTitle()) ; pstmt.setString(2,note.getAuthor()) ; pstmt.setString(3,note.getContent()) ; pstmt.setInt(4,note.getId()) ; pstmt.executeUpdate() ; pstmt.close() ; } catch (Exception e) { throw new Exception("操作中出現錯誤！ ！ ！ ") ; } finally { dbc.close() ; } } // 刪除操作public void delete(int id) throws Exception { String sql = "DELETE FROM note WHERE id=?" ; PreparedStatement pstmt = null ; DataBaseConnection dbc = null ; dbc = new DataBaseConnection() ; try { pstmt = dbc.getConnection().prepareStatement(sql) ; pstmt.setInt(1,id) ; pstmt.executeUpdate() ; pstmt.close() ; } catch (Exception e) { throw new Exception("操作中出現錯誤！！！") ; } finally { dbc.close() ; } } // 按ID查詢，主要為更新使用public Note queryById(int id) throws Exception { Note note = null ; String sql = "SELECT id,title,author,content FROM note WHERE id=?" ; PreparedStatement pstmt = null ; DataBaseConnection dbc = null ; dbc = new DataBaseConnection() ; try { pstmt = dbc.getConnection().prepareStatement(sql) ; pstmt.setInt(1,id) ; ResultSet rs = pstmt.executeQuery() ; if(rs.next()) { note = new Note() ; note.setId(rs.getInt(1)) ; note.setTitle(rs.getString(2)) ; note.setAuthor(rs.getString(3)) ; note.setContent(rs.getString(4)) ; } rs.close() ; pstmt.close() ; } catch (Exception e) { throw new Exception("操作中出現錯誤！ ！ ！ ") ; } finally { dbc.close() ; } return note ; } // 查詢全部public List queryAll() throws Exception { List all = new ArrayList() ; String sql = "SELECT id,title,author,content FROM note" ; PreparedStatement pstmt = null ; DataBaseConnection dbc = null ; dbc = new DataBaseConnection() ; try { pstmt = dbc.getConnection().prepareStatement(sql) ; ResultSet rs = pstmt.executeQuery() ; while(rs.next()) { Note note = new Note() ; note.setId(rs.getInt(1)) ; note.setTitle(rs.getString(2)) ; note.setAuthor(rs.getString(3)) ; note.setContent(rs.getString(4)) ; all.add(note) ; } rs.close() ; pstmt.close() ; } catch (Exception e) { System.out.println(e) ; throw new Exception("操作中出現錯誤！！！") ; } finally { dbc.close() ; } return all ; } // 模糊查詢public List queryByLike(String cond) throws Exception { List all = new ArrayList() ; String sql = "SELECT id,title,author,content FROM note WHERE title LIKE ? or AUTHOR LIKE ? or CONTENT LIKE ?" ; PreparedStatement pstmt = null ; DataBaseConnection dbc = null ; dbc = new DataBaseConnection() ; try { pstmt = dbc.getConnection().prepareStatement(sql) ; pstmt.setString(1,"%"+cond+"%") ; pstmt.setString(2,"%"+cond+"%") ; pstmt.setString(3,"%"+cond+"%") ; ResultSet rs = pstmt.executeQuery() ; while(rs.next()) { Note note = new Note() ; note.setId(rs.getInt(1)) ; note.setTitle(rs.getString(2)) ; note.setAuthor(rs.getString(3)) ; note.setContent(rs.getString(4)) ; all.add(note) ; } rs.close() ; pstmt.close() ; } catch (Exception e) { System.out.println(e) ; throw new Exception("操作中出現錯誤！ ！ ！ ") ; } finally { dbc.close() ; } return all ; } };

NoteServlet.java

 package cn.mldn.lxh.note.servlet ; import java.io.* ; import javax.servlet.* ; import javax.servlet.http.* ; import cn.mldn.lxh.note.factory.* ; import cn.mldn.lxh.note.vo.* ; public class NoteServlet extends HttpServlet { public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException { this.doPost(request,response) ; } public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException { request.setCharacterEncoding("GB2312") ; String path = "errors.jsp" ; // 接收要操作的參數值String status = request.getParameter("status") ; if(status!=null) { // 參數有內容，之後選擇合適的方法// 查詢全部操作if("selectall".equals(status)) { try { request.setAttribute("all",DAOFactory.getNoteDAOInstance().queryAll()) ; } catch (Exception e) { } path = "list_notes.jsp" ; } // 插入操作if("insert".equals(status)) { // 1、接收插入的信息String title = request.getParameter("title") ; String author = request.getParameter("author") ; String content = request.getParameter("content") ; // 2、實例化VO對象Note note = new Note() ; note.setTitle(title) ; note.setAuthor(author) ; note.setContent(content) ; // 3、調用DAO完成數據庫的插入操作boolean flag = false ; try { DAOFactory.getNoteDAOInstance().insert(note) ; flag = true ; } catch (Exception e) {} request.setAttribute("flag",new Boolean(flag)) ; path = "insert_do.jsp" ; } // 按ID查詢操作，修改之前需要將數據先查詢出來if("selectid".equals(status)) { // 接收參數int id = 0 ; try { id = Integer.parseInt(request.getParameter("id")) ; } catch(Exception e) {} try { request.setAttribute("note",DAOFactory.getNoteDAOInstance().queryById(id)) ; } catch (Exception e) { } path = "update.jsp" ; } // 更新操作if("update".equals(status)) { int id = 0 ; try { id = Integer.parseInt(request.getParameter("id")) ; } catch(Exception e) {} String title = request.getParameter("title") ; String author = request.getParameter("author") ; String content = request.getParameter("content") ; Note note = new Note() ; note.setId(id) ; note.setTitle(title) ; note.setAuthor(author) ; note.setContent(content) ; boolean flag = false ; try { DAOFactory.getNoteDAOInstance().update(note) ; flag = true ; } catch (Exception e) {} request.setAttribute("flag",new Boolean(flag)) ; path = "update_do.jsp" ; } // 模糊查詢if("selectbylike".equals(status)) { String keyword = request.getParameter("keyword") ; try { request.setAttribute("all",DAOFactory.getNoteDAOInstance().queryByLike(keyword)) ; } catch (Exception e) { } path = "list_notes.jsp" ; } // 刪除操作if("delete".equals(status)) { // 接收參數int id = 0 ; try { id = Integer.parseInt(request.getParameter("id")) ; } catch(Exception e) {} boolean flag = false ; try { DAOFactory.getNoteDAOInstance().delete(id) ; flag = true ; } catch (Exception e) {} request.setAttribute("flag",new Boolean(flag)) ; path = "delete_do.jsp" ; } } else { // 則表示無參數，非法的客戶請求} request.getRequestDispatcher(path).forward(request,response) ; } }; /* <servlet> <servlet-name>note</servlet-name> <servlet-class>cn.mldn.lxh.note.servlet.NoteServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>note</servlet-name> <url-pattern>/note/note_mvc/Note</url-pattern> </servlet-mapping> */

list_notes.jsp

 <%@ page contentType="text/html;charset=gb2312"%> <%@ page import="java.util.*"%> <%@ page import="cn.mldn.lxh.note.vo.*"%> <html> <head> <title>MVC+DAO 留言管理程序――登陸</title> </head> <body> <center> <h1>留言管理範例―― MVC + DAO實現</h1> <hr> <br> <% // 編碼轉換request.setCharacterEncoding("GB2312") ; if(session.getAttribute("uname")!=null) { // 用戶已登陸%> <% // 如果有內容，則修改變量i，如果沒有，則根據i的值進行無內容提示int i = 0 ; String keyword = request.getParameter("keyword") ; List all = null ; all = (List)request.getAttribute("all") ; %> <form action="Note" method="POST"> 請輸入查詢內容：<input type="text" name="keyword"> <input type="hidden" name="status" value="selectbylike"> <input type="submit" value="查詢"> </form> </h3><a href="insert.jsp">添加新留言</a></h3> <table> <tr> <td>留言ID</td> <td>標題</td> <td>作者</td> <td>內容</td> <td>刪除</td> </tr> <% Iterator iter = all.iterator() ; while(iter.hasNext()) { Note note = (Note)iter.next() ; i++ ; // 進行循環打印，打印出所有的內容，以表格形式// 從數據庫中取出內容int id = note.getId() ; String title = note.getTitle() ; String author = note.getAuthor() ; String content = note.getContent() ; // 因為要關鍵字返紅，所以此處需要接收查詢關鍵字// String keyword = request.getParameter("keyword") ; if(keyword!=null) { // 需要將數據返紅title = title.replaceAll(keyword,"<font color=/"red/">"+keyword+"</font>") ; author = author.replaceAll(keyword,"<font color=/"red/">"+keyword +"</font>") ; content = content.replaceAll(keyword,"<font color=/"red/">"+keyword +"</font>") ; } %> <tr> <td><%=id%></td> <td><a href="Note?id=<%=id%>&status=selectid"><%=title%></a></td> <td><%=author%></td> <td><%=content%></td> <td><a href="Note?id=<%=id%>&status=delete">刪除</a></td> </tr> <% } // 判斷i的值是否改變，如果改變，則表示有內容，反之，無內容if(i==0) { // 進行提示%> <tr> <td colspan="5">沒有任何內容！ ！ ！ </td> </tr> <% } %> </table> <% } else { // 用戶未登陸，提示用戶登陸，並跳轉response.setHeader("refresh","2;URL=login.jsp") ; %> 您還未登陸，請先登陸！ ！ ！ <br> 兩秒後自動跳轉到登陸窗口！ ！ ！ <br> 如果沒有跳轉，請按<a href="login.jsp">這裡</a>！ ！ ！ <br> <% } %> </center> </body> </html>

以上就是本文的全部內容，希望對大家的學習有所幫助。