java留言管理系统中模糊查询实例分享

本文分享了一个基于MVC+DAO的留言管理系统，包含增删改查，其中查询，有全部查询和按关键字进行模糊查询的功能，具体内容如下
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 ;
  // 删除操作
  public void delete(int id) throws Exception ;
  // 按ID查询，主要为更新使用
  public Note queryById(int id) throws Exception ;
  // 查询全部
  public List queryAll() throws Exception ;
  // 模糊查询
  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("操作中出现错误！！！") ;
    }
    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("操作中出现错误！！！") ;
    }
    finally
    {
      dbc.close() ;
    }
  }
  // 删除操作
  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("操作中出现错误！！！") ;
    }
    finally
    {
      dbc.close() ;
    }
  }
  // 按ID查询，主要为更新使用
  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("操作中出现错误！！！") ;
    }
    finally
    {
      dbc.close() ;
    }
    return note ;
  }
  // 查询全部
  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("操作中出现错误！！！") ;
    }
    finally
    {
      dbc.close() ;
    }
    return all ;
  }
  // 模糊查询
  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("操作中出现错误！！！") ;
    }
    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" ;
    // 接收要操作的参数值
    String status = request.getParameter("status") ;
    if(status!=null)
    {
      // 参数有内容，之后选择合适的方法
      // 查询全部操作
      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、实例化VO对象
        Note note = new Note() ;
        note.setTitle(title) ;
        note.setAuthor(author) ;
        note.setContent(content) ;
        // 3、调用DAO完成数据库的插入操作
        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查询操作，修改之前需要将数据先查询出来
      if("selectid".equals(status))
      {
        // 接收参数
        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" ;
      }
      // 模糊查询
      if("selectbylike".equals(status))
      {
        String keyword = request.getParameter("keyword") ;
        try
        {
          request.setAttribute("all",DAOFactory.getNoteDAOInstance().queryByLike(keyword)) ;
        }
        catch (Exception e)
        {
        }
        path = "list_notes.jsp" ;
      }
      // 删除操作
      if("delete".equals(status))
      {
        // 接收参数
        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
    {
      // 则表示无参数，非法的客户请求
    }
    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——登陆</title>
</head>
<body>
<center>
  <h1>留言管理范例 —— MVC + DAO实现</h1>
  <hr>
  <br>
  <%
    // 编码转换
    request.setCharacterEncoding("GB2312") ;
    if(session.getAttribute("uname")!=null)
    {
      // 用户已登陆
  %>
  <%
    // 如果有内容，则修改变量i，如果没有，则根据i的值进行无内容提示
    int i = 0 ;
    String keyword = request.getParameter("keyword") ;
    List all = null ;
    all = (List)request.getAttribute("all") ;
  %>
<form action="Note" method="POST">
  请输入查询内容：<input type="text" name="keyword">
  <input type="hidden" name="status" value="selectbylike">
  <input type="submit" value="查询">
</form>
</h3><a href="insert.jsp">添加新留言</a></h3>
<table width="80%" border="1">
  <tr>
    <td>留言ID</td>
    <td>标题</td>
    <td>作者</td>
    <td>内容</td>
    <td>删除</td>
  </tr>
  <%
      Iterator iter = all.iterator() ;
      while(iter.hasNext())
      {
        Note note = (Note)iter.next() ;
        i++ ;
        // 进行循环打印，打印出所有的内容，以表格形式
        // 从数据库中取出内容
        int id = note.getId() ;
        String title = note.getTitle() ;
        String author = note.getAuthor() ;
        String content = note.getContent() ; 

        // 因为要关键字返红，所以此处需要接收查询关键字
        // String keyword = request.getParameter("keyword") ;
        if(keyword!=null)
        {
          // 需要将数据返红
          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">删除</a></td>
        </tr>
  <%
      }
      // 判断i的值是否改变，如果改变，则表示有内容，反之，无内容
      if(i==0)
        {
      // 进行提示
  %>
        <tr>
          <td colspan="5">没有任何内容！！！</td>
        </tr>
  <%
      }
  %>
</table> 

  <%
    }
    else
    {
      // 用户未登陆，提示用户登陆，并跳转
      response.setHeader("refresh","2;URL=login.jsp") ;
  %>
      您还未登陆，请先登陆！！！<br>
      两秒后自动跳转到登陆窗口！！！<br>
      如果没有跳转，请按<a href="login.jsp">这里</a>！！！<br>
  <%
    }
  %>
</center>
</body>
</html>

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