javaweb--JDBC
本文基于JDBC的讲解，演示登录注销案例
第一个JDBC程序
public class MyJDBC {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
//1、加载驱动 连接信息
Class.forName("com.mysql.jdbc.Driver");
//2、连接数据库
String url="jdbc:mysql://localhost:3306/smbms?useSSL=true&&useUnicode=true&characterEncoding=utf8";
String username="root";
String password="123456";
Connection connection = DriverManager.getConnection(url, username, password);
//3、获得执行对象statement
Statement statement = connection.createStatement();
String sql="select * from smbms.smbms_user";
//4、获得返回的结果集
ResultSet resultSet = statement.executeQuery(sql);
while (resultSet.next()){
System.out.println("id"+resultSet.getInt("id"));
System.out.println("userName"+resultSet.getString("userName"));
System.out.println("userCode"+resultSet.getString("userCode"));
System.out.println("userPassword"+resultSet.getString("userPassword"));
System.out.println("==================================");
}
//5、释放连接
resultSet.close();
statement.close();
connection.close();
}
本程序基于以下数据库：
CREATE DATABASE `smbms`;
USE `smbms`;
DROP TABLE IF EXISTS `smbms_user`;
CREATE TABLE `smbms_user` (
`id` BIGINT(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
`userCode` VARCHAR(15) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT '用户编码',
`userName` VARCHAR(15) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT '用户名称',
`userPassword` VARCHAR(15) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT '用户密码',
`gender` INT(10) DEFAULT NULL COMMENT '性别（1:女、 2:男）',
`birthday` DATE DEFAULT NULL COMMENT '出生日期',
`phone` VARCHAR(15) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT '手机',
`address` VARCHAR(30) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT '地址',
`userRole` BIGINT(20) DEFAULT NULL COMMENT '用户角色（取自角色表-角色id）',
`createdBy` BIGINT(20) DEFAULT NULL COMMENT '创建者（userId）',
`creationDate` DATETIME DEFAULT NULL COMMENT '创建时间',
`modifyBy` BIGINT(20) DEFAULT NULL COMMENT '更新者（userId）',
`modifyDate` DATETIME DEFAULT NULL COMMENT '更新时间',
PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
INSERT INTO `smbms_user`(`id`,`userCode`,`userName`,`userPassword`,`gender`,`birthday`,`phone`,`address`,`userRole`,`createdBy`,`creationDate`,`modifyBy`,`modifyDate`) VALUES (1,'admin','系统管理员','1234567',1,'1983-10-10','13688889999','北京市海淀区成府路207号',1,1,'2013-03-21 16:52:07',NULL,NULL),(2,'liming','李明','0000000',2,'1983-12-10','13688884457','北京市东城区前门东大街9号',2,1,'2014-12-31 19:52:09',NULL,NULL),(5,'hanlubiao','韩路彪','0000000',2,'1984-06-05','18567542321','北京市朝阳区北辰中心12号',2,1,'2014-12-31 19:52:09',NULL,NULL),(6,'zhanghua','张华','0000000',1,'1983-06-15','13544561111','北京市海淀区学院路61号',3,1,'2013-02-11 10:51:17',NULL,NULL),(7,'wangyang','王洋','0000000',2,'1982-12-31','13444561124','北京市海淀区西二旗辉煌国际16层',3,1,'2014-06-11 19:09:07',NULL,NULL),(8,'zhaoyan','赵燕','0000000',1,'1986-03-07','18098764545','北京市海淀区回龙观小区10号楼',3,1,'2016-04-21 13:54:07',NULL,NULL),(10,'sunlei','孙磊','0000000',2,'1981-01-04','13387676765','北京市朝阳区管庄新月小区12楼',3,1,'2015-05-06 10:52:07',NULL,NULL),(11,'sunxing','孙兴','0000000',2,'1978-03-12','13367890900','北京市朝阳区建国门南大街10号',3,1,'2016-11-09 16:51:17',NULL,NULL),(12,'zhangchen','张晨','0000000',1,'1986-03-28','18098765434','朝阳区管庄路口北柏林爱乐三期13号楼',3,1,'2016-08-09 05:52:37',1,'2016-04-14 14:15:36'),(13,'dengchao','邓超','0000000',2,'1981-11-04','13689674534','北京市海淀区北航家属院10号楼',3,1,'2016-07-11 08:02:47',NULL,NULL),(14,'yangguo','杨过','0000000',2,'1980-01-01','13388886623','北京市朝阳区北苑家园茉莉园20号楼',3,1,'2015-02-01 03:52:07',NULL,NULL),(15,'zhaomin','赵敏','0000000',1,'1987-12-04','18099897657','北京市昌平区天通苑3区12号楼',2,1,'2015-09-12 12:02:12',NULL,NULL);
本程序为查询用户信息，查询结果如下图：
提取为工具类
//工具类 简化操作
public class JdbcUtils {
//静态代码块实现，一调用该类就加载
private static String driver=null;
private static String url=null;
private static String username=null;
private static String password=null;
static {
try {
//加载配置文件
InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
Properties properties = new Properties();
properties.load(in);
driver=properties.getProperty("driver");
url=properties.getProperty("url");
username=properties.getProperty("username");
password=properties.getProperty("password");
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
//获得连接
public static Connection getConnection(){
Connection connection=null;
try {
connection = DriverManager.getConnection(url, username, password);
} catch (SQLException e) {
e.printStackTrace();
}
return connection;
}
//释放资源
public static void closeResource(Connection connection, Statement statement, ResultSet resultSet){
if (resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (statement!=null){
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection!=null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
配置文件为
db.properties
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?useSSL=true&&useUnicode=true&characterEncoding=utf8
username=root
password=123456
则第一个程序改为以下程序：
public class JDBCTest {
public static void main(String[] args) {
Connection connection =null;
Statement statement=null;
ResultSet resultSet=null;
try {
connection= JdbcUtils.getConnection();
statement= connection.createStatement();
String sql="select * from smbms.smbms_user";
resultSet = statement.executeQuery(sql);
while (resultSet.next()){
System.out.println("id"+resultSet.getInt("id"));
System.out.println("userName"+resultSet.getString("userName"));
System.out.println("userCode"+resultSet.getString("userCode"));
System.out.println("userPassword"+resultSet.getString("userPassword"));
System.out.println("==================================");
}
JdbcUtils.closeResource(connection,statement,resultSet);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
上文基于的是statement对象，Jdbc中的statement对象用于向数据库发送SQL语句，想完成对数据库的增删改查，只需要通过这个对象向数据库发送增删改查语句即可。
Statement对象的executeUpdate方法，用于向数据库发送增、删、改的sql语句，executeUpdate执行完后，将会返回一个整数（即增删改语句导致了数据库几行数据发生了变化）。
Statement.executeQuery方法用于向数据库发送查询语句executeQuery方法返回代表查询结果的ResultSet对象。
但是存在sql注入的问题，故接下来使用PreparedStatement， 可以防止SQL注入。
PreparedStatement对象
PreparedStatement对象是继承的Statement，可以扩展优良特性，防止sql注入！
增加用户
public class JDBCTest3 {
public static void main(String[] args) {
Connection connection =null;
PreparedStatement ps=null;
ResultSet resultSet=null;
try {
connection= JdbcUtils.getConnection();
//使用预编译
String sql="insert into smbms_user(id,userCode,userPassword)values(?,?,?)";
ps = connection.prepareStatement(sql);//先进行预编译，再进行赋值
ps.setInt(1,2);//参数从1开始
ps.setString(2,"zhouzhou");
ps.setString(3,"112233");
int i = ps.executeUpdate();
if (i>0){
System.out.println("插入成功");
}
JdbcUtils.closeResource(connection,ps,resultSet);
} catch (Exception e) {
e.printStackTrace();
}
}
}
删除用户
public class JDBCTest4 {
public static void main(String[] args) {
Connection connection =null;
PreparedStatement ps=null;
ResultSet resultSet=null;
try {
connection= JdbcUtils.getConnection();
//使用预编译
String sql="delete from smbms.smbms_user where id=?";
ps = connection.prepareStatement(sql);
ps.setInt(1,2);
int i = ps.executeUpdate();
if (i>0){
System.out.println("删除成功");
}
JdbcUtils.closeResource(connection,ps,resultSet);
} catch (Exception e) {
e.printStackTrace();
}
}
}
查询用户：
public class JDBCTest5 {
public static void main(String[] args) {
Connection connection =null;
PreparedStatement ps=null;
ResultSet resultSet=null;
try {
connection= JdbcUtils.getConnection();
//使用预编译
String sql="select * from smbms.smbms_user where id=?";
ps = connection.prepareStatement(sql);
ps.setInt(1,1);
resultSet = ps.executeQuery();
if (resultSet.next()){
System.out.println("id"+resultSet.getInt("id"));
System.out.println("userName"+resultSet.getString("userName"));
System.out.println("==================================");
}
JdbcUtils.closeResource(connection,ps,resultSet);
} catch (Exception e) {
e.printStackTrace();
}
}
}
PreparedStatement与Statement最大的不同是先预编译sql，之后再讲参数一个个进行赋值，注意参数编号要从1开始！
登录注销项目
1、新建maven项目，然后导入一下依赖
由于mysql驱动无法导入成功，所以在后面手动建立了lib，并把驱动添加到了类库中.
<dependencies>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.12version>
dependency>
<dependency>
<groupId>javax.servletgroupId>
<artifactId>javax.servlet-apiartifactId>
<version>3.0.1version>
dependency>
<dependency>
<groupId>javax.servlet.jspgroupId>
<artifactId>jsp-apiartifactId>
<version>2.1version>
dependency>
<dependency>
<groupId>javax.servlet.jsp.jstlgroupId>
<artifactId>jstl-apiartifactId>
<version>1.2version>
dependency>
<dependency>
<groupId>taglibsgroupId>
<artifactId>standardartifactId>
<version>1.1.2version>
dependency>
dependencies>
具体的包结构：
2、编写操作数据库的公共类
有了前面的基础，就很好编写了！
数据库配置文件db.properties：
# driver=com.mysql.jdbc.Driver
# driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?useSSL=true&useUnicode=true&characterEncoding=utf-8
#user=root
password=123456
#号表示注释，可以直接在下面的程序中写成固定的
//操作数据库的公共类
public class BaseDao {
private static String driver;
private static String url;
private static String username;
private static String password;
//静态代码块，类加载的时候就初始化了
static {
Properties properties = new Properties();
//通过类加载器读取对应的资源
InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
try {
properties.load(is);
} catch (IOException e) {
e.printStackTrace();
}
// driver = properties.getProperty("driver");
driver="com.mysql.jdbc.Driver";
url = properties.getProperty("url");
// username = properties.getProperty("user");
username="root";
password = properties.getProperty("password");
}
//获取数据库的链接
public static Connection getConnection(){
Connection connection = null;
try {
Class.forName(driver);
connection = DriverManager.getConnection(url, username, password);
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
//编写查询公共方法
public static ResultSet execute(Connection connection, String sql, Object[] params, ResultSet resultSet, PreparedStatement preparedStatement) throws SQLException {
//预编译的sql，在后面直接执行就可以了
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < params.length; i++) {
//setObject,占位符从1开始，但是我们的数组是从0开始！
preparedStatement.setObject(i+1,params[i]);
}
resultSet = preparedStatement.executeQuery();
return resultSet;
}
//编写增删改公共方法
public static int execute(Connection connection,String sql,Object[] params,PreparedStatement preparedStatement) throws SQLException {
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < params.length; i++) {
//setObject,占位符从1开始，但是我们的数组是从0开始！
preparedStatement.setObject(i+1,params[i]);
}
int updateRows = preparedStatement.executeUpdate();
return updateRows;
}
//释放资源
public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
boolean flag = true;
if (resultSet!=null){
try {
resultSet.close();
//GC回收
resultSet = null;
} catch (SQLException e) {
e.printStackTrace();
flag = false;
}
}
if (preparedStatement!=null){
try {
preparedStatement.close();
//GC回收
preparedStatement = null;
} catch (SQLException e) {
e.printStackTrace();
flag = false;
}
}
if (connection!=null){
try {
connection.close();
//GC回收
connection = null;
} catch (SQLException e) {
e.printStackTrace();
flag = false;
}
}
return flag;
}
}
3、编写与数据库对应的实体类
package com.zhou.pojo;
import java.util.Date;
public class User {
private Integer id; //id
private String userCode; //用户编码
private String userName; //用户名称
private String userPassword; //用户密码
private Integer gender; //性别
private Date birthday; //出生日期
private String phone; //电话
private String address; //地址
private Integer userRole; //用户角色
private Integer createdBy; //创建者
private Date creationDate; //创建时间
private Integer modifyBy; //更新者
private Date modifyDate; //更新时间
private Integer age;//年龄
private String userRoleName; //用户角色名称
public String getUserRoleName() {
return userRoleName;
}
public void setUserRoleName(String userRoleName) {
this.userRoleName = userRoleName;
}
public Integer getAge() {
Date date = new Date();
Integer age = date.getYear()-birthday.getYear();
return age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUserCode() {
return userCode;
}
public void setUserCode(String userCode) {
this.userCode = userCode;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserPassword() {
return userPassword;
}
public void setUserPassword(String userPassword) {
this.userPassword = userPassword;
}
public Integer getGender() {
return gender;
}
public void setGender(Integer gender) {
this.gender = gender;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Integer getUserRole() {
return userRole;
}
public void setUserRole(Integer userRole) {
this.userRole = userRole;
}
public Integer getCreatedBy() {
return createdBy;
}
public void setCreatedBy(Integer createdBy) {
this.createdBy = createdBy;
}
public Date getCreationDate() {
return creationDate;
}
public void setCreationDate(Date creationDate) {
this.creationDate = creationDate;
}
public Integer getModifyBy() {
return modifyBy;
}
public void setModifyBy(Integer modifyBy) {
this.modifyBy = modifyBy;
}
public Date getModifyDate() {
return modifyDate;
}
public void setModifyDate(Date modifyDate) {
this.modifyDate = modifyDate;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", userCode='" + userCode + '\'' +
", userName='" + userName + '\'' +
", userPassword='" + userPassword + '\'' +
", gender=" + gender +
", birthday=" + birthday +
", phone='" + phone + '\'' +
", address='" + address + '\'' +
", userRole=" + userRole +
", createdBy=" + createdBy +
", creationDate=" + creationDate +
", modifyBy=" + modifyBy +
", modifyDate=" + modifyDate +
", age=" + age +
", userRoleName='" + userRoleName + '\'' +
'}';
}
}
4、在dao层编写用户登录的接口和实现类
public interface UserDao {
//得到要登录的用户
public User getLoginUser(Connection connection, String userCode) throws SQLException;
}
package com.zhou.dao.User;
import com.zhou.dao.BaseDao;
import com.zhou.pojo.User;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class UserDaoImpl implements UserDao {
//得到要登录的用户
public User getLoginUser(Connection connection, String userCode) throws SQLException {
PreparedStatement pstm = null;
ResultSet rs = null;
User user = null;
if (connection!=null){
String sql = "select * from smbms_user where userCode=?";
Object[] params = {userCode};
rs = BaseDao.execute(connection,sql, params,rs,pstm);
if (rs.next()){
user = new User();
user.setId(rs.getInt("id"));
user.setUserCode(rs.getString("userCode"));
user.setUserName(rs.getString("userName"));
user.setUserPassword(rs.getString("userPassword"));
user.setGender(rs.getInt("gender"));
user.setBirthday(rs.getDate("birthday"));
user.setPhone(rs.getString("phone"));
user.setAddress(rs.getString("address"));
user.setUserRole(rs.getInt("userRole"));
user.setCreatedBy(rs.getInt("createdBy"));
user.setCreationDate(rs.getTimestamp("creationDate"));
user.setModifyBy(rs.getInt("modifyBy"));
user.setModifyDate(rs.getTimestamp("modifyDate"));
}
BaseDao.closeResource(null,pstm,rs);
}
return user;
}
}
5、编写service层：
public interface UserService {
//用户登录
public User login(String userCode, String password);
}
package com.zhou.service.User;
import com.zhou.dao.BaseDao;
import com.zhou.dao.User.UserDao;
import com.zhou.dao.User.UserDaoImpl;
import com.zhou.pojo.User;
import java.sql.Connection;
import java.sql.SQLException;
public class UserServiceImpl implements UserService {
//业务层都会调用dao层，所以我们要引入Dao层；
private UserDao userDao;
public UserServiceImpl(){
userDao = new UserDaoImpl();
}
public User login(String userCode, String password) {
Connection connection = null;
User user = null;
try {
connection = BaseDao.getConnection();
//通过业务层调用对应的具体的数据库操作
user = userDao.getLoginUser(connection, userCode);
} catch (SQLException e) {
e.printStackTrace();
}finally {
BaseDao.closeResource(connection,null,null);
}
return user;
}
}
6、编写控制层调用业务层：
登录：
public class LoginServlet extends HttpServlet {
//Servlet:控制层，调用业务层代码
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("LoginServlet--start....");
//获取用户名和密码
String userCode = req.getParameter("userCode");
String userPassword = req.getParameter("userPassword");
System.out.println("用户名和密码为"+userCode+"="+userPassword);
//和数据库中的密码进行对比，调用业务层；
UserService userService = new UserServiceImpl();
User user = userService.login(userCode, userPassword); //这里已经把登录的人给查出来了
System.out.println("登录的用户为"+user);
if (user!=null){ //查有此人，可以登录
//将用户的信息放到Session中;
req.getSession().setAttribute(Constants.USER_SESSION,user);
//跳转到主页
resp.sendRedirect("/jsp/frame.jsp");
}else {
//转发回登录页面，顺带提示它，用户名//查无此人，无法登录或者密码错误；
req.setAttribute("error","用户名或者密码不正确");
req.getRequestDispatcher("/login.jsp").forward(req,resp);
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
注册到web.xml 中
<servlet>
<servlet-name>LoginServletservlet-name>
<servlet-class>com.zhou.servlet.user.LoginServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>LoginServletservlet-name>
<url-pattern>/login.dourl-pattern>
servlet-mapping>
注销：
public class LogoutServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//移除用户的Constants.USER_SESSION
req.getSession().removeAttribute(Constants.USER_SESSION);
resp.sendRedirect("/login.jsp");//返回登录页面
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<servlet>
<servlet-name>LogoutServletservlet-name>
<servlet-class>com.zhou.servlet.user.LogoutServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>LogoutServletservlet-name>
<url-pattern>/jsp/logout.dourl-pattern>
servlet-mapping>
7、过滤器
字符乱码过滤器：
public class CharacterEncodingFilter implements Filter {
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
chain.doFilter(request,response);
}
public void init(FilterConfig filterConfig) throws ServletException {
}
public void destroy() {
}
}
<filter>
<filter-name>CharacterEncodingFilterfilter-name>
<filter-class>com.zhou.filter.CharacterEncodingFilterfilter-class>
filter>
<filter-mapping>
<filter-name>CharacterEncodingFilterfilter-name>
<url-pattern>/*url-pattern>
filter-mapping>
权限控制过滤器：
public class SysFilter implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
//过滤器，从Session中获取用户，
User user = (User) request.getSession().getAttribute(Constants.USER_SESSION);
System.out.println("过滤器");
if (user==null){ //已经被移除或者注销了，或者未登录
response.sendRedirect("/error.jsp");
}else {
chain.doFilter(req,resp);
}
}
public void destroy() {
}
}
<filter>
<filter-name>SysFilterfilter-name>
<filter-class>com.zhou.filter.SysFilterfilter-class>
filter>
<filter-mapping>
<filter-name>SysFilterfilter-name>
<url-pattern>/jsp/*url-pattern>
filter-mapping>
8、前端编写：
登录页面：
login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
登录页面
<welcome-file-list>
<welcome-file>login.jspwelcome-file>
welcome-file-list>
首页：frame.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
首页
错误页面：error.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
错误页面
错误页面
点我，返回首页
接下来只要数据库中，存在此用户，就可以成功登陆！！！
登陆注销流程图：
