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.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,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,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,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,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> 
*/