使用IDEA练习一个最基础的java web项目(适合新手)
使用Servlet、JDBC、Maven和IDEA完成最基础的增删改查，整体逻辑浅显易懂，希望能帮助到各位更好的学习web基础，如果有问题欢迎留言，
完整代码免费下载地址：https://wwa.lanzous.com/ih0tRhfneba
目录
- 主要功能
- 整体架构
- 1.新建mysql表
- 2.IDEA新建maven项目
- 3.整理pom.xml文件
- 4.过滤器
- 5.实体类User
- 6.数据库工具类DBCoon
- 7.UserDao接口和实现类
- 8.servlet
-
- 登录LoginServlet
- 注册RegisterServlet
- 查询所有SearchAllServlet
- 删除DeleteServlet
- 更新UpdateServlet
- 9.在web.xml里注册servlet
- 10.jsp页面
-
- 登录login.jsp
- 注册register.jsp
- 操作成功success.jsp
- 操作失败error.jsp
- 显示所有用户信息showAll.jsp
- 可能会遇到的一些坑
- 进阶
-
- 搜索功能的实现
- 分页功能的实现
- 搜索加分页功能
- 验证码的实现
- 文件上传功能
- 购物车功能
- 总结
主要功能
1.用户注册
2.用户登录
3.用户列表展示
4.用户信息修改
5.用户信息删除
整体架构
1.新建mysql表
CREATE TABLE `user` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(255) NOT NULL,
`pwd` varchar(255) NOT NULL,
`sex` varchar(255) NOT NULL,
`home` varchar(255) NOT NULL,
`info` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
/*添加两个值用于测试*/
INSERT INTO `user` VALUES ('1', '123', '123', '男', '北京', '123');
INSERT INTO `user` VALUES ('2', '123123', '123123', '男', '北京', '123123');
2.IDEA新建maven项目
这里选择设置好的maven环境
在src下建立项目包结构
3.整理pom.xml文件
注意：
1.删除没用的内容
2.导入需要使用的依赖
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0modelVersion>
<groupId>org.examplegroupId>
<artifactId>csdn3artifactId>
<version>1.0-SNAPSHOTversion>
<packaging>warpackaging>
<dependencies>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.20version>
dependency>
<dependency>
<groupId>javax.servletgroupId>
<artifactId>javax.servlet-apiartifactId>
<version>4.0.0version>
dependency>
<dependency>
<groupId>javax.servlet.jspgroupId>
<artifactId>javax.servlet.jsp-apiartifactId>
<version>2.3.3version>
dependency>
<dependency>
<groupId>javax.servlet.jsp.jstlgroupId>
<artifactId>jstl-apiartifactId>
<version>1.2version>
dependency>
<dependency>
<groupId>taglibsgroupId>
<artifactId>standardartifactId>
<version>1.1.2version>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<version>1.18.12version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.11version>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.pluginsgroupId>
<artifactId>maven-clean-pluginartifactId>
<version>3.0.0version>
plugin>
plugins>
build>
project>
4.过滤器
作用：过滤所有页面解决乱码问题
注意：在web.xml里注册
package com.filter;
import javax.servlet.*;
import java.io.IOException;
public class EncodingFilter implements Filter {
public EncodingFilter() {
System.out.println("执行过滤器");
}
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=UTF-8");
filterChain.doFilter(request, response);
}
public void destroy() {
}
}
5.实体类User
作用：映射数据库创建的user表
注意：这里我使用到了lombok包，需要先下载lombok插件再在pom.xml里导入lombok依赖，在方法上加上**@Data**就会生成这个类所有属性的setter和getter方法，在左侧Structure里可以看到生成的方法，也可以手动生成setter和getter方法，二者没区别
package com.entiy;
import lombok.Data;
@Data
public class User {
private int id;
private String name;
private String pwd;
private String sex;
private String home;
private String info;
}
6.数据库工具类DBCoon
作用：用于连接数据库,执行SQL语句和返回执行结果
注：我使用了PreparedStatement 预编译SQL方法通过遍历Object数组的方式传递SQL参数，原作者使用的是字符串拼接的方式，比较复杂且易错
package com.util;
import java.sql.*;
/*数据库工具类：
* 1.连接数据库
* 2.增删改查
* 3.执行SQL语句并返回执行结果
* 4.关流
* */
public class DBCoon {
//serverTimezone=UTC设置连接时区，不设置可能会报时区错误
static String url = "jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8";
static String username = "root";
//密码换成自己的
static String password = "root";
static Connection conn = null;
static ResultSet rs = null;
static PreparedStatement ps = null;
/*连接数据库*/
public static void init() {
try {
/*1.加载驱动获得驱动管理器*/
Class.forName("com.mysql.cj.jdbc.Driver");
/*2.连接数据库*/
conn = DriverManager.getConnection(url, username, password);
System.out.println("数据库连接成功");
} catch (Exception e) {
e.printStackTrace();
System.out.println("数据库连接失败");
}
}
/*查询数据(传递参数)*/
public static ResultSet searchSql(String sql,Object[] args){
try {
ps = conn.prepareStatement(sql);
for (int j = 0; j < args.length; j++) {
ps.setObject(j+1, args[j]);
}
rs = ps.executeQuery();
System.out.println("数据查询成功");
} catch (SQLException e) {
e.printStackTrace();
System.out.println("数据查询失败");
}
return rs;
}
/*增删改查数据(传递参数)*/
public static int addUpdDel(String sql,Object[] args){
int i = 0;
try{
ps = conn.prepareStatement(sql);
for (int j = 0; j < args.length; j++) {
ps.setObject(j+1, args[j]);
}
i = ps.executeUpdate();
System.out.println("增删改成功");
} catch (SQLException e) {
e.printStackTrace();
System.out.println("增删改失败");
}
return i;
}
/*不传递参数查询所有用户信息*/
public static ResultSet getUsers(String sql){
try {
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
System.out.println("数据查询成功");
} catch (SQLException e) {
e.printStackTrace();
System.out.println("数据查询失败");
}
return rs;
}
/*关流*/
public static void close() {
try {
if (rs != null){
rs.close();
}
if (ps != null) {
ps.close();
}
if (conn != null){
conn.close();
}
}catch (SQLException e) {
System.out.println("数据流关闭异常");
}
}
7.UserDao接口和实现类
注意：接口是为了使代码更简洁规范,注意每个方法传递的参数意义
package com.dao;
import com.entiy.User;
import java.util.List;
public interface UserDao {
/*获取前台的账号密码判断能否登录成功*/
public boolean login(String name, String pwd);
/*获取前台的注册信息，封装成user对象*/
public boolean register(User user);
/*返回所有的用户信息*/
public List<User> searchAll();
/*根据获取到的内容更新用户信息*/
public boolean update(int id,String name, String pwd,String sex, String home,String info) ;//更新用户信息
/*获取前台传递的id删除用户*/
public boolean delete(int id);
}
package com.dao;
import com.entiy.User;
import com.util.DBCoon;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
public class UserDaoImpl implements UserDao {
/*创建一个返回值标志*/
static boolean flag = false;
/*提高sql作用域，每个方法里都要编写sql语句*/
static String sql = null;
public boolean login(String name, String pwd) {
try {
DBCoon.init();
sql = "select * from user where name= ? and pwd = ?";
/*使用预编译SQL传递参数*/
Object[] args = {
name,pwd};
ResultSet rs = DBCoon.searchSql(sql, args);
/*遍历数据库里的账号密码与从jsp传来的账号密码作对比*/
while (rs.next()) {
if (rs.getString("name").equals(name)&&rs.getString("pwd").equals(pwd)){
flag = true;
System.out.println("登录成功");
}
}
}catch (Exception e) {
System.out.println("登录失败");
e.printStackTrace();
} finally {
DBCoon.close();
}
return flag;
}
public boolean register(User user) {
try {
DBCoon.init();
sql="insert into user(name,pwd,sex,home,info)"+"values(?,?,?,?,?)";
Object[] args = {
user.getName(),user.getPwd(),user.getSex(),user.getHome(),user.getInfo()};
int i = DBCoon.addUpdDel(sql,args);
if (i>0){
flag = true;
System.out.println("注册成功");
}
}catch (Exception e) {
e.printStackTrace();
System.out.println("注册失败");
}finally {
DBCoon.close();
}
return flag;
}
public List<User> searchAll() {
List<User> list = new ArrayList<User>();
try {
DBCoon.init();
sql = "select * from user";
ResultSet rs = DBCoon.getUsers(sql);
System.out.println("获取所有用户信息成功");
while (rs.next()) {
User user = new User();
user.setId(rs.getInt("id"));
user.setName(rs.getString("name"));
user.setPwd(rs.getString("pwd"));
user.setSex(rs.getString("sex"));
user.setHome(rs.getString("home"));
user.setInfo(rs.getString("info"));
list.add(user);
}
}catch (Exception e){
System.out.println("获取所有用户信息失败");
e.printStackTrace();
}finally{
DBCoon.close();
}
return list;
}
public boolean update(int id, String name, String pwd, String sex, String home, String info) {
try {
DBCoon.init();
sql = "update user set name=?,pwd=?,sex=?,home=?,info=? where id=?";
Object[] args={
name,pwd,sex,home,info,id};
int i = DBCoon.addUpdDel(sql,args);
if (i>0){
flag=true;
System.out.println("数据更新成功");
}
}catch (Exception e) {
System.out.println("数据更新失败");
e.printStackTrace();
}finally {
DBCoon.close();
}
return flag;
}
public boolean delete(int id) {
try {
DBCoon.init();
sql = "delete from user where id = ?";
Object[] args = {
id};
int i = DBCoon.addUpdDel(sql,args);
if (i>0){
flag=true;
System.out.println("删除成功");
}
}catch (Exception e) {
System.out.println("删除失败");
e.printStackTrace();
}finally {
DBCoon.close();
}
return flag;
}
}
8.servlet
注意：
1.这里用到了请求转发和重定向，二者的不同可以看下这篇文章，详细介绍了什么时候用转发和重定向https://blog.csdn.net/weixin_40001125/article/details/88663468
2.req.getParameter获取前台输入框的值即input框里的name属性的值
3.req.setAttribute向request域中添加名为msg值为object对象类型的信息，前台可以通过el表达式${msg}获取对象的值
登录LoginServlet
package com.servlet;
import com.dao.UserDao;
import com.dao.UserDaoImpl;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
/*req.getParameter获取前台输入框的值即input框里的name属性的值*/
String name = req.getParameter("name");
String pwd = req.getParameter("pwd");
UserDao ud = new UserDaoImpl();
if(ud.login(name,pwd)){
/*如果要获取request存放的参数则使用请求转发，路径加不加/都行 */
System.out.println("用户"+name+"登录成功");
/*req.setAttribute向request域中添加名为msg对象object为string类型的信息*/
req.setAttribute("msg","用户"+name+"登录成功");
req.getRequestDispatcher("success.jsp").forward(req, resp);
}else {
/*如果不获取参数则使用重定向到错误页面*/
resp.sendRedirect("error.jsp");
}
}
}
注册RegisterServlet
package com.servlet;
import com.dao.UserDao;
import com.dao.UserDaoImpl;
import com.entiy.User;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class RegisterServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String name = req.getParameter("name");
String pwd = req.getParameter("pwd");
String sex = req.getParameter("sex");
String home = req.getParameter("home");
String info = req.getParameter("info");
//实例化一个对象，组装属性
User user = new User();
user.setName(name);
user.setPwd(pwd);
user.setSex(sex);
user.setHome(home);
user.setInfo(info);
UserDao ud = new UserDaoImpl();
if (ud.register(user)){
System.out.println("用户"+name+"注册成功");
req.setAttribute("msg","用户"+name+"注册成功");
req.getRequestDispatcher("success.jsp").forward(req, resp);
}else {
resp.sendRedirect("error.jsp");
}
}
}
查询所有SearchAllServlet
package com.servlet;
import com.dao.UserDao;
import com.dao.UserDaoImpl;
import com.entiy.User;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
public class SearchAllServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
UserDao ud = new UserDaoImpl();
List<User> users = ud.searchAll();
req.setAttribute("users",users);
System.out.println("查询全部用户成功");
req.getRequestDispatcher("/showAll.jsp").forward(req, resp);
}
}
删除DeleteServlet
package com.servlet;
import com.dao.UserDao;
import com.dao.UserDaoImpl;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class DeleteServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String id = req.getParameter("id");
System.out.println("删除的用户id为："+id);
/*获取到的id是一个引用数据类型即对象，需要变成基本数据类型作为参数传输*/
int userId = Integer.parseInt(id);
/*调用dao层，返回值是一个整形数字*/
UserDao ud = new UserDaoImpl();
/*delete方法的参数为int id，所以必须把从jsp页面获取到的id转换成基本数据类型*/
if(ud.delete(userId)){
/*站内转发：请求转发到searchAll的servlet*/
req.getRequestDispatcher("searchAll").forward(req, resp);
}else{
/*站外转发：重定向到首页*/
resp.sendRedirect("error.jsp");
}
}
}
更新UpdateServlet
package com.servlet;
import com.dao.UserDao;
import com.dao.UserDaoImpl;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class UpdateServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String id = req.getParameter("id");
int userId = Integer.parseInt(id);
String name = req.getParameter("name");
String pwd = req.getParameter("pwd");
String sex = req.getParameter("sex");
String home = req.getParameter("home");
String info = req.getParameter("info");
UserDao ud = new UserDaoImpl();
if(ud.update(userId, name, pwd, sex, home, info)){
req.getRequestDispatcher("searchAll").forward(req, resp);
}else{
resp.sendRedirect("error.jsp");
}
}
}
9.在web.xml里注册servlet
注意：设置好的名字，这是访问servlet的入口，建议复制
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<filter>
<filter-name>EncodingFilterfilter-name>
<filter-class>com.filter.EncodingFilterfilter-class>
filter>
<filter-mapping>
<filter-name>EncodingFilterfilter-name>
<url-pattern>/*url-pattern>
filter-mapping>
<servlet>
<servlet-name>loginservlet-name>
<servlet-class>com.servlet.LoginServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>loginservlet-name>
<url-pattern>/loginurl-pattern>
servlet-mapping>
<servlet>
<servlet-name>searchAllservlet-name>
<servlet-class>com.servlet.SearchAllServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>searchAllservlet-name>
<url-pattern>/searchAllurl-pattern>
servlet-mapping>
<servlet>
<servlet-name>deleteservlet-name>
<servlet-class>com.servlet.DeleteServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>deleteservlet-name>
<url-pattern>/deleteurl-pattern>
servlet-mapping>
<servlet>
<servlet-name>updateservlet-name>
<servlet-class>com.servlet.UpdateServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>updateservlet-name>
<url-pattern>/updateurl-pattern>
servlet-mapping>
<servlet>
<servlet-name>registerservlet-name>
<servlet-class>com.servlet.RegisterServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>registerservlet-name>
<url-pattern>/registerurl-pattern>
servlet-mapping>
<welcome-file-list>
<welcome-file>login.jspwelcome-file>
welcome-file-list>
web-app>
10.jsp页面
登录login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录title>
head>
<body>
<form action="login" method="post" style="margin: 0 auto;">
账号：<input type="text" name="name"><br><br>
密码: <input type="password" name="pwd"><br><br>
<br>
form>
<a href="register.jsp">新用户注册a>
body>
html>
注册register.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>注册title>
head>
<body>
<%--action后面跟的就是要访问的servlet路径--%>
<form action="register" method="post" style="padding-top:-700px;">
输入用户名:<input name="name" type="text"><br><br>
输入密码:<input name="pwd" type="password"><br><br>
选择性别:男
女<br><br>
选择家乡:
<select name="home">
<option value="上海">上海option>
<option value="北京" selected>北京option>
<option value="纽约">纽约option>
select><br>
填写个人信息:<br>