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JavaWeb连接数据库MySQL的操作技巧

发布时间：2020-12-14 14:32:40 所属栏目：Java 来源：网络整理
导读：数据库是编程中重要的一部分，它囊括了数据操作，数据持久化等各方面。在每一门编程语言中都占有相当大的比例。 本次，我以MySQL为例，使用MVC编程思想(请参阅我之前的博客)。简单演示一下JavaWeb对数据库的操作。 1：我们需要掌握简单的SQL语句，并且会简单

数据库是编程中重要的一部分，它囊括了数据操作，数据持久化等各方面。在每一门编程语言中都占有相当大的比例。

本次，我以MySQL为例，使用MVC编程思想(请参阅我之前的博客)。简单演示一下JavaWeb对数据库的操作。

1：我们需要掌握简单的SQL语句，并且会简单操作图形化的数据库。我们在数据库建一个表(Users)可以在里面随便添加几条数据。

2：接下来，我们获得驱动并连接到MySQL。

package com.joker.web.db; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.SQLException; 
public class DBConnection { 
  private static Connection con = null; 
  // 驱动程序名 
  private static String driverName = "com.mysql.jdbc.Driver"; 
  // 数据库用户名 
  private static String userName = "root"; 
  // 密码 1 
  private static String userPasswd = "*****"; 
  // 数据库名 
  private static String dbName = "jokertest"; 
  // 联结字符串 
  private static String url = "jdbc:mysql://localhost/" + dbName + "?user=" 
      + userName + "&password=" + userPasswd 
      + "&useUnicode=true&characterEncoding=gbk"; 
  public static Connection getConnection() { 
    try { 
      // 1.驱动 
      Class.forName(driverName); 
      // 2. 连接数据库 保持连接 
      con = DriverManager.getConnection(url); 
    } catch (ClassNotFoundException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } 
    return con; 
  } 
  public static void closeConnection() { 
    if (con != null) { 
      try { 
        con.close(); 
      } catch (SQLException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
      } 
    } 
  } 
}<span style="font-size:18px;color:#990000;"> 
</span>

3.写我们的Dao文件,即对数据库的增删改查

package com.joker.web.dao; 
import java.sql.*; 
import java.util.*; 
import com.joker.web.db.DBConnection; 
import com.joker.web.entity.User; 
public class UserDao { 
  // 查找所有数据，返回List集合 
  public List<User> selectAll() { 
    Connection con = DBConnection.getConnection();// 连接数据库 保持连接 
    Statement stmt; 
    List<User> list = new ArrayList<User>(); 
    try { 
      stmt = con.createStatement();// 执行SQL语句 
      ResultSet rs = stmt.executeQuery("SELECT * FROM users");// 查找 
                                  // 数据返回结果集 
      while (rs.next()) { 
        User user = new User(); 
        user.setId(rs.getInt("id")); 
        user.setUserName(rs.getString("USER_NAME")); 
        user.setDisplayName(rs.getString("DISPLAY_NAME")); 
        user.setPwd(rs.getString("PWD")); 
        list.add(user); 
      } 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      DBConnection.closeConnection(); 
    } 
    return list; 
  } 
  // 按条件查找 
  // where USER_NAME='"+ name + "' and PWD='" + pwd + "' 
  public User selectWhere(String whereOption) { 
    Connection con = DBConnection.getConnection();// 连接数据库 保持连接 
    Statement stmt; 
    User user = null; 
    try { 
      stmt = con.createStatement();// 执行SQL语句 
      String sql = "SELECT * FROM users "; 
      if (!whereOption.equals("")) { 
        sql += whereOption; 
      } 
      // 查找数据返回结果集 
      ResultSet rs = stmt.executeQuery(sql); 
      while (rs.next()) { 
        user = new User(); 
        user.setUserName(rs.getString("USER_NAME")); 
        user.setDisplayName(rs.getString("DISPLAY_NAME")); 
        user.setPwd(rs.getString("PWD")); 
      } 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      DBConnection.closeConnection(); 
    } 
    return user; 
  } 
  // 新增 
  public int insert(User user) { 
    Connection con = DBConnection.getConnection(); 
    PreparedStatement pstmt = null; 
    String sql = " insert into users(user_name,pwd,display_name) values(?,?,?)"; 
    // 增加用prepareStatement 
    int count = 0; 
    try { 
      pstmt = con.prepareStatement(sql); 
      pstmt.setString(1,user.getUserName()); 
      pstmt.setString(2,user.getPwd()); 
      pstmt.setString(3,user.getDisplayName()); 
      count = pstmt.executeUpdate(); 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      try { 
        pstmt.close(); 
      } catch (SQLException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
      } 
      DBConnection.closeConnection(); 
    } 
    return count; 
  } 
  // 修改 
  public int upDate(User user) { 
    Connection con = DBConnection.getConnection(); 
    PreparedStatement pstmt = null; 
    String sql = " update users " + " set user_name = ?," + " pwd = ?," 
        + " display_name= ? " + " where id= ? "; 
    int count = 0; 
    try { 
      pstmt = con.prepareStatement(sql); 
      pstmt.setString(1,user.getDisplayName()); 
      pstmt.setInt(4,user.getId()); 
      count = pstmt.executeUpdate(); 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      try { 
        pstmt.close(); 
      } catch (SQLException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
      } 
      DBConnection.closeConnection(); 
    } 
    return count; 
  } 
  // 删除 
  public int delete(int id) { 
    Connection con = DBConnection.getConnection(); 
    PreparedStatement pstmt = null; 
    String sql = " delete from users where id = ?"; 
    int count = 0; 
    try { 
      pstmt = con.prepareStatement(sql); 
      pstmt.setInt(1,id); 
      count = pstmt.executeUpdate(); 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      try { 
        pstmt.close(); 
      } catch (SQLException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
      } 
      DBConnection.closeConnection(); 
    } 
    return count; 
  } 
  public List<User> selectPage(int from,int rows) { 
    Connection con = DBConnection.getConnection();// 连接数据库 保持连接 
    Statement stmt; 
    List<User> list = new ArrayList<User>(); 
    try { 
      stmt = con.createStatement();// 执行SQL语句 
      ResultSet rs = stmt.executeQuery("SELECT * FROM users LIMIT " 
          + from + "," + rows); 
      while (rs.next()) { 
        User user = new User(); 
        user.setId(rs.getInt("id")); 
        user.setUserName(rs.getString("USER_NAME")); 
        user.setDisplayName(rs.getString("DISPLAY_NAME")); 
        user.setPwd(rs.getString("PWD")); 
        list.add(user); 
      } 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      DBConnection.closeConnection(); 
    } 
    return list; 
  } 
// 返回所有数剧条数 
  public int selectCount() { 
    Connection con = DBConnection.getConnection();// 连接数据库 保持连接 
    Statement stmt; 
    int count =0 ; 
    try { 
      stmt = con.createStatement();// 执行SQL语句 
      ResultSet rs = stmt.executeQuery("SELECT count(1) count FROM users"); 
      while (rs.next()) { 
        count = rs.getInt("count"); 
      } 
    } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } finally { 
      DBConnection.closeConnection(); 
    } 
    return count; 
  } 
}<span style="font-size:18px;color:#990000;"> 
</span>

4.使用Servlet当控制器，在Servlet对网页上的数据进行操作。

package com.joker.web.servlet; 
import java.io.IOException; 
import java.io.PrintWriter; 
import java.util.*; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import net.sf.json.JSONArray; 
import net.sf.json.JSONObject; 
import com.joker.web.dao.UserDao; 
import com.joker.web.entity.User; 
public class UserServlet extends HttpServlet { 
  /** 
   * Constructor of the object. 
   */ 
  public UserServlet() { 
    super(); 
  } 
  /** 
   * Destruction of the servlet. <br> 
   */ 
  public void destroy() { 
    super.destroy(); // Just puts "destroy" string in log 
    // Put your code here 
  } 
  public void doGet(HttpServletRequest request,HttpServletResponse response) 
      throws ServletException,IOException { 
    this.doPost(request,response); 
  } 
  public void doPost(HttpServletRequest request,IOException { 
    request.setCharacterEncoding("utf-8"); 
    response.setContentType("text/html;charset=utf-8"); 
    String action = request.getParameter("action"); 
    if (action.equals("select")) { 
      select(request,response); 
    } else if (action.equals("update")) { 
      update(request,response); 
    } else if (action.equals("add")) { 
      insert(request,response); 
    } else if (action.equals("delete")) { 
      delete(request,response); 
    } 
  } 
  // 新增 
  private void insert(HttpServletRequest request,HttpServletResponse response)  
      throws IOException { 
    String uName = request.getParameter("userName"); 
    String pwd = request.getParameter("user"); 
    String dName = request.getParameter("displayName"); 
    User user = new User(); 
    user.setUserName(uName); 
    user.setPwd(pwd); 
    user.setDisplayName(dName); 
    UserDao uDao = new UserDao(); 
    int affCount = uDao.insert(user); 
    PrintWriter out = response.getWriter(); 
    // 将受影响数据的数量返回给jsp 
    out.print(affCount); 
  } 
  // 删除 
  private void delete(HttpServletRequest request,HttpServletResponse response) 
      throws IOException { 
    String[] ids = request.getParameterValues("uid[]"); 
    UserDao ud = new UserDao(); 
    int count = 0; 
    for (int i = 0; i < ids.length; i++) { 
      count += ud.delete(Integer.parseInt(ids[i])); 
    } 
    PrintWriter out = response.getWriter(); 
    out.print(count); 
  } 
  /** 
   * Initialization of the servlet. <br> 
   * 
   * @throws ServletException 
   *       if an error occurs 
   */ 
  public void init() throws ServletException { 
    System.out.println("处室执行！！！！！！！！！！！！！！！"); 
  } 
  // 查询 
  public void select(HttpServletRequest request,HttpServletResponse response) 
      throws IOException { 
    String page = request.getParameter("page"); 
    String rows = request.getParameter("rows"); 
    System.out.println("page:" + page + " rows:" + rows); 
    UserDao ud = new UserDao(); 
    int rowsCount = Integer.parseInt(rows); 
    int from = (Integer.parseInt(page) - 1) * rowsCount; 
    List<User> list = ud.selectPage(from,rowsCount); 
    HashMap<String,Object> map = new HashMap<String,Object>(); 
    map.put("total",ud.selectCount()); 
    map.put("rows",list); 
    // JSONArray ja = JSONArray.fromObject(list); 
    JSONObject jo = JSONObject.fromObject(map);// 单条数据 
    PrintWriter out = response.getWriter(); 
    System.out.println(jo.toString()); 
    // 将json数据返回给jspData-grid的url。 
    out.println(jo.toString()); 
  } 
  // 修改 
  public void update(HttpServletRequest request,HttpServletResponse response) 
      throws IOException { 
    String id = request.getParameter("id"); 
    String uName = request.getParameter("userName"); 
    String pwd = request.getParameter("pwd"); 
    String dName = request.getParameter("displayName"); 
    User user = new User(); 
    user.setId(Integer.parseInt(id)); 
    user.setUserName(uName); 
    user.setPwd(pwd); 
    user.setDisplayName(dName); 
    UserDao uDao = new UserDao(); 
    int affCount = uDao.upDate(user); 
    PrintWriter out = response.getWriter(); 
    // 将受影响数据的数量返回给jsp 
    out.print(affCount); 
  } 
}<span style="font-size:18px;color:#990000;"> 
</span>

5.使用Easy-UI框架，是数据库内容在页面进行显示

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 
<% 
  String path = request.getContextPath(); 
  String basePath = request.getScheme() + "://" 
      + request.getServerName() + ":" + request.getServerPort() 
      + path + "/"; 
%> 
 
<!DOCTYPE HTML> 
<html> 
<head> 
<base href="<%=basePath%>" rel="external nofollow" > 
<title>main.jsp</title> 
<meta http-equiv="pragma" content="no-cache"> 
<meta http-equiv="cache-control" content="no-cache"> 
<link rel="stylesheet" href="CSS/easyui.css" rel="external nofollow" type="text/css"></link> 
<link rel="stylesheet" href="CSS/icon.css" rel="external nofollow" type="text/css"></link> 
<script type="text/javascript" src="JS/jquery-1.8.2.min.js"></script> 
<script type="text/javascript" src="JS/jquery.easyui.min.js"></script> 
<script type="text/javascript"> 
  var addFlags = true; 
  $(function() { 
    $('#dg') 
        .datagrid( 
            { 
              title : '用户列表',url : 'servlet/UserServlet?action=select',fitColumns : true,/* 自适应宽度 */ 
              striped : true,/* 斑马线效果 */ 
              pagination : true,/* 底部显示分页工具栏 */ 
              singleSelect : false,/* 只允许选择一行 */ 
              rownumbers : true,/* 显示一个行号列 */ 
              ctrlSelect : true,/* 允许使用Ctrl键+鼠标点击的方式进行多选操作 */ 
              iconCls : 'icon-ok',checkOnSelect : true,/* 点击行的时候该复选框就会被选中或取消选中 */ 
              selectOnCheck : true,/* 单击复选框将永远选择行 */ 
              pagination : true,nowrap : true,rownumbers : true,collapsible : true,//是否可折叠的 
              pageSize : 5,//每页显示的记录条数，默认为10  
              pageList : [ 2,4,5],//可以设置每页记录条数的列表  
              toolbar : [ 
                  { 
                    text : '查询',iconCls : 'icon-search',handler : function() { 
                      $('#dg').datagrid('reload'); 
                    } 
                  },'-',{ 
                    text : '修改',iconCls : 'icon-edit',handler : function() { 
                      alert('帮助按钮'); 
                    } 
                  },{ 
                    text : '添加',iconCls : 'icon-add',handler : function() { 
                      if(addFlags){ 
                        $('#dg').datagrid('insertRow',{ 
                      index: 0,// 索引从0开始 
                     row: {} 
                     }); 
                      var editIndex = 0; 
                      $('#dg').datagrid('selectRow',editIndex) 
                          .datagrid('beginEdit',editIndex); 
                        addFlags = false; 
                      } 
                      /*,$('#dlg').dialog('open') 
                          .dialog('center').dialog( 
                              'setTitle','New User'); 
                      $('#fm').form('clear') */ 
                    } 
                  },{ text : '删除',iconCls : 'icon-remove',handler : function() { 
                 $.messager.confirm("信息确认","确定删除吗?",function(ret) { 
                          if (ret) { 
                          var row = $("#dg").datagrid("getSelections"); 
                        if (row.length == 0) { 
                          $.messager.alert("提示:","请选择删除的数据"); 
                              return; 
                            } 
                            var ids = []; 
                        for ( var i = 0; i < row.length; i++) { 
                              ids.push(row[i].id); 
                            } 
                          $.post("servlet/UserServlet?action=delete",{uid : ids},function(data) { 
                                if (data > 0) { 
                              $('#dg').datagrid('reload'); 
                                  alert("删除成功"); 
                                } else { 
                                alert("删除失败"); 
                                } 
                               }); 
                            } 
                        }); 
                    } 
                  } ],columns : [ [ 
                  { 
                    field : 'ck',checkbox : true,width : 50,},{ 
                    field : 'id',hidden : true,{ 
                    field : 'userName',title : '用户名',align : 'center',editor : 'text',width : 100 
                  },{ 
                    field : 'pwd',title : '密码',width : 100,align : 'center' 
                  },{ 
                    field : 'displayName',title : '级别',height : 100,{ 
                    field : 'option',title : '操作',formatter : function(value,row,index) { 
                      if (row.editing) { 
                        var s = '<a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" style="text-decoration:none" onclick="saverow(' 
                            + index + ')">保存</a>'+' ' 
                            +'<a href = "javascript:void(0);" style="text-decoration:none" onclick="canclerow(' 
                            + index + ')">取消</a>'; 
                        return s; 
                      } else { 
                        var e = '<a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" style="text-decoration:none" onclick="editrow(' 
                            + index + ')">编辑</a>'; 
                        return e; 
                      } 
                    } 
                  } ] ],onBeforeEdit : function(index,row) { 
                row.editing = true; 
                $("#dg").datagrid("refreshRow",index); 
              },onAfterEdit : function(index,row) { 
                row.editing = false; 
                $("#dg").datagrid("refreshRow",index); 
              } 
            }); 
    //设置分页控件  
    var p = $('#dg').datagrid('getPager'); 
    $(p).pagination({ 
      beforePageText : '第',//页数文本框前显示的汉字  
      afterPageText : '页  共 {pages} 页',displayMsg : '当前显示 {from} - {to} 条记录  共 {total} 条记录' 
    }); 
  }); 
  function editrow(index) { 
    var row = $("#dg").datagrid("getSelected"); 
    if (row == null) { 
      alert("请选择您要编辑的行"); 
      return; 
    } 
    $("#dg").datagrid("beginEdit",index); 
  } 
  function saverow(index) { 
    $("#dg").datagrid("endEdit",index); 
    var row = $("#dg").datagrid("getSelected"); 
    if(addFlags) { 
     dbSave(row); 
    } else { 
     dbAdd(row); 
    } 
    addFlags = true; 
  } 
  function canclerow(index) { 
    $("#dg").datagrid("rejectChanges"); 
    $('#dg').datagrid('reload'); 
    addFlags = true; 
  } 
  function dbSave(row) { 
    var name = row.userName; 
    var uid = row.id; 
    var pwd = row.pwd; 
    var dname = row.displayName; 
    $.post("servlet/UserServlet?action=update",{ 
      id : uid,userName : name,pwd : pwd,displayName : dname 
    },function(data) { 
      if (data == "1") { 
        alert("修改成功"); 
      } else { 
        alert("修改失败"); 
      } 
    }); 
    alert(row.userName + "-" + row.pwd + "-" + row.displayName); 
  } 
    function dbAdd(row) { 
    var name = row.userName; 
    var pwd = row.pwd; 
    var dname = row.displayName; 
    $.post("servlet/UserServlet?action=add",{ 
      userName : name,function(data) { 
      if (data == "1") { 
        alert("添加成功"); 
      } else { 
        alert("添加失败"); 
      } 
    }); 
  } 
</script> 
<body> 
  <%-- ${sessionScope.user.userName} 
  ${sessionScope.user.dislayName} --%> 
  <table class="easyui-datagrid" id="dg"> 
  </table> 
</body> 
</html><span style="font-size:18px;color:#990000;"> 
</span>

6.各个操作具体图片:

6.1添加:添加（张三 666 学生 这条数据）默认显示五条数据



6.2 删除刚刚插入的数据

6.3 修改数据(修改的ID主键为10的数据)





以上所述是小编给大家介绍的JavaWeb连接数据库MySQL的操作技巧，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对编程小技巧网站的支持！

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