javaweb连接mysql数据库 JavaWeb连接数据库MySQL的操作技巧
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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.getUserName());
pstmt.setString(2, user.getPwd());
pstmt.setString(3, 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, HttpServletResponse response)
throws ServletException, 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,
editor : 'text',
align : 'center'
},
{
field : 'displayName',
title : '级别',
width : 100,
height : 100,
editor : 'text',
align : 'center'
},
{
field : 'option',
title : '操作',
width : 100,
align : 'center',
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,
pwd : pwd,
displayName : dname
}, 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网站的支持！
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