搭建一个完整的javaweb项目

开发环境与工具

1.IntelliJ IDEA 2020（Ultimate Edition）（Mac版本）
2.Mysql 8.0.8
3.jdk8
4.Tomcat for mac ( 安装教程 )

功能:

用户登录
新用户注册
用户列表展示
用户信息删除
用户信息更新

操作步骤

1.在mysql建立一个新表Student，里面有name,password,id（为了简化操作，所以只有三列并且都是String类型）

create table if not exists Student (name varchar(10) primary key,
password varchar(10) not  null,
id varchar(10) not null);

2.插入数据

insert into Student(name,password,id) values("005",123,5);
insert into Student(name,password,id) values("004",123,4);
insert into Student(name,password,id) values("003",123,3);
insert into Student(name,password,id) values("002",123,2);
insert into Student(name,password,id) values("001",123,1);

3.整理pom.xml文件
导入需要使用的依赖

4.建立对应的包结构
filter //过滤器，解决中文字符集乱码
util //数据库连接工具类
entity //实体类
dao //数据操作类
servlet //servlet类

5.在filter下新建一个EncodingFilter用来解决中文字符集乱码，它需要实现Filter接口，并重写doFilter函数

package filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

//在filter下新建一个EncodingFilter用来解决中文字符集乱码，它需要实现Filter接口，并重写doFilter函数
public class EncodingFilter implements Filter {
    public EncodingFilter() {
        System.out.println("过滤器构造");
    }
    
    public void destroy() {
        System.out.println("过滤器销毁");
    }
    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding("utf-8"); //将编码改为utf-8
        response.setContentType("text/html;charset=utf-8");
        chain.doFilter(request, response);
    }
    
    public void init(FilterConfig arg0) throws ServletException {
        System.out.println("过滤器初始化");
    }
}

web.xml的全部配置信息

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
         
    <display-name></display-name>
    
    <filter><!-- 过滤器配置-->
        <filter-name>EncodingFilter</filter-name>
        <filter-class>filter.EncodingFilter</filter-class><!--全路径 从根包开始一直到类名-->
    </filter>

    <filter-mapping>
        <filter-name>EncodingFilter</filter-name>
        <url-pattern>/*</url-pattern> <!--*即为过滤所有-->
    </filter-mapping>
    
    <servlet><!--servlet类路径配置-->
        <servlet-name>loginServlet</servlet-name>
        <servlet-class>servlet.loginServlet</servlet-class>
    </servlet>

    <servlet>
        <servlet-name>registerServlet</servlet-name>
        <servlet-class>com.servlet.registerServlet</servlet-class>
    </servlet>
    
    <servlet>
        <servlet-name>showAllServlet</servlet-name>
        <servlet-class>servlet.showAllServlet</servlet-class>
    </servlet>
    
    <servlet>
        <servlet-name>deleteServlet</servlet-name>
        <servlet-class>com.servlet.deleteServlet</servlet-class>
    </servlet>
    
    <servlet>
        <servlet-name>updateServlet</servlet-name>
        <servlet-class>servlet.updateServlet</servlet-class>
    </servlet>
    
    <servlet-mapping><!--servlet类映射配置-->
        <servlet-name>loginServlet</servlet-name>
        <url-pattern>/loginServlet</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>registerServlet</servlet-name>
        <url-pattern>/registerServlet</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>showAllServlet</servlet-name>
        <url-pattern>/showAllServlet</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>deleteServlet</servlet-name>
        <url-pattern>/deleteServlet</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>updateServlet</servlet-name>
        <url-pattern>/updateServlet</url-pattern>
    </servlet-mapping>
    
    <welcome-file-list><!--默认首页地址-->
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
    
</web-app>

在util下新建一个DBconnect类用来处理对数据库的连接操作（用户名或密码按照自己的数据库更改）

package com.util;
import java.sql.*;
public class DBconnect
{
    static String url="jdbc:mysql://localhost:3306/DataTest?useSSL=false";
    static String user="root";
    static String pw = "12345678";
    static Connection conn=null;
    static PreparedStatement ps=null;
    static ResultSet rs=null;
    static Statement st=null;

    public static void init() throws SQLException, ClassNotFoundException {//SQl程序初始化
        try{
            Class.forName("com.mysql.jdbc.Driver");//注册驱动
            conn= DriverManager.getConnection(url, user, pw);  //建立连接
        }catch (Exception e){
            System.out.println("SQL程序初始化失败");
            e.printStackTrace();
        }
    }

    public static int addUpdateDelete(String sql){
        int i=0;
        try{
            ps=conn.prepareStatement(sql);
            boolean flag= ps.execute();
            if(flag==false){//如果第一个结果是结果集对象，则返回true;如果第一个结果是更新计数或者没有结果，则返回false
                i++;
            }
        }catch(Exception e){
            System.out.println("数据库增删改异常 ");
            e.printStackTrace();
        }
        return i;
    }

    public static ResultSet selectSql(String sql){
        try{
            ps=conn.prepareStatement(sql);
            rs=ps.executeQuery();

        }catch(Exception e){
            System.out.println("数据库查询异常");
            e.printStackTrace();
        }
        return rs;
    }

    public static  void closeConn(){
        try{
            conn.close();
        }catch(Exception e){
            System.out.println("数据库关闭异常");
            e.printStackTrace();
        }
    }
}

在entity下新建一个MyUser实体类（实体即抽象出来的用户对象，对应数据库中的Student表,表中每个字段在实体中为一个属性，也可以理解为一个User对象对应数据库中的Student表一条记录）

package entity;

public class MyUser {
    private String name;
    private String password;
    private String id;
    
    public MyUser(){}

    public MyUser(String name,String password,String id){
        this.name=name;
        this.password=password;
        this.id=id;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
    

    public MyUser(String name, String password) {
        this.name = name;
        this.password = password;
    }

    public String getName() {
        return name;
    }

    public void setName(String username) {
        this.name = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }


}

在dao下新建一个UserDao接口 以及对应的方法实现类（使用接口类是为了规范开发）
UserDao类

package dao;
import java.util.List;
import entity.MyUser;

public interface UserDao {
    public boolean login(String name,String password);
    public boolean register(MyUser user);
    public List<MyUser> getUserAll();//返回用户信息集合
    public boolean delete(String id);//根据id删除
    public boolean update(String name, String id);
}

UserDaoImplement类

package dao;

import entity.MyUser;
import util.DBconnect;

import java.lang.invoke.MutableCallSite;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDaoImplement implements UserDao {
    public boolean login(String name, String password) {
        boolean flag = false;
        try {
            try{
                DBconnect.init();
            }catch (Exception e){
                e.printStackTrace();
            }
            //注意查询语句中的单引号双引号
            ResultSet rs = DBconnect.selectSql("select * from student where name='" + name + " 'and password='" + password + "';");
            while (rs.next()) {
                if (rs.getString("name").equals(name) && rs.getString("password").equals(password)) {
                    flag = true;
                }
            }
            DBconnect.closeConn();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return flag;
    }

    public boolean register(MyUser user) {
        boolean flag = false;
        try{
            DBconnect.init();
        }catch (Exception e){
            e.printStackTrace();
        }
        int i = DBconnect.addUpdateDelete("insert into student(name,password,id) " +
                "values('" + user.getName() + "','" + user.getPassword() + "','"+user.getId()+" ' )");
        if (i > 0) {
            flag = true;
        }
        DBconnect.closeConn();
        return flag;
    }

    public List<MyUser> getUserAll() {//返回用户信息集合
        List<MyUser> list = new ArrayList<>();
        try {
            try{
                DBconnect.init();
            }catch (Exception e){
                e.printStackTrace();
            }
            ResultSet rs = DBconnect.selectSql("select * from student");
            while (rs.next()) {
                String nameone=rs.getString("name");
                String passwordone=rs.getString("password");
                String idone=rs.getString("id");
                MyUser user=new MyUser(nameone,passwordone,idone);
                list.add(user);
            }
            DBconnect.closeConn();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return list;
    }

    public boolean delete(String id) {//根据id删除{
        boolean flag = false;
        try{
            DBconnect.init();
        }catch (Exception e){
            e.printStackTrace();
        }
        String sql = "delete from student where id='" + id+"'";
        int i = DBconnect.addUpdateDelete(sql);//i的意义：
        if (i > 0) {
            flag = true;
        }
        DBconnect.closeConn();
        return flag;
    }

    public boolean update(String name, String id) {
        boolean flag = false;
        try{
            DBconnect.init();
        }catch (Exception e){
            e.printStackTrace();
        }
        String sql = "update student set name ='" + name

                +"'"+"where id = '" + id+"'";

        int i = DBconnect.addUpdateDelete(sql);
        System.out.println("1"+" "+i);
        if (i > 0) {
            flag = true;
        }
        DBconnect.closeConn();
        return flag;
    }

}

在servlet下创建loginServlet用来实现对用户登录的操作

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dao.UserDao;
import dao.UserDaoImplement;

public class loginServlet extends HttpServlet {  //需要继承HttpServlet  并重写doGet  doPost方法

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);  //将信息使用doPost方法执行   对应jsp页面中的form表单中的method
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name"); //得到jsp页面传过来的参数
        String password = request.getParameter("password");

        UserDao ud = new UserDaoImplement();

        if (ud.login(name, password)) {
            //request.setAttribute("hello", "欢迎用户" + name); //向request域中放置信息
          request.getRequestDispatcher("/success.jsp").forward(request, response);//转发到成功页面
        } else {
            response.sendRedirect("login.jsp"); //重定向到首页
        }
    }
}

在servlet下创建一个registerServlet用来实现用户注册的操作

```javascript
package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.text.*;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.UserDao;
import dao.UserDaoImplement;
import entity.MyUser;

public class registerServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String name = request.getParameter("name"); //获取jsp页面传过来的参数
        String pwd = request.getParameter("password");
        String id = request.getParameter("id");

        MyUser user = new MyUser(); //实例化一个对象，组装属性
        user.setName(name);
        user.setPassword(pwd);
        user.setId(id);

        UserDao ud = new UserDaoImplement();

        if(ud.register(user)){
            request.setAttribute("name", name);  //向request域中放置参数
            request.getRequestDispatcher("/login.jsp").forward(request, response);  //转发到登录页面
        }else{
            response.sendRedirect("register.jsp");//注册失败则返回注册页面，但是缺少提示"注册失败"
        }
    }
}

在servlet下创建shouAllServlet用来返回数据库中所有用户信息

package servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.UserDao;
import dao.UserDaoImplement;
import entity.MyUser;

public class showAllServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html;charset=utf-8");
        UserDao ud = new UserDaoImplement();
        List<MyUser> userAll = ud.getUserAll();
        request.setAttribute("all", userAll);
        request.getRequestDispatcher("showAll.jsp").forward(request, response);
    }
}

在servlet下创建updateServlet用来更新用户信息(在此仅仅根据id来更新用户姓名，逻辑性很弱

package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.text.ParseException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dao.UserDao;
import dao.UserDaoImplement;
import entity.MyUser;

public class updateServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String id = request.getParameter("id");

        String name = request.getParameter("name"); //获取jsp页面传过来的参数

        UserDao ud = new UserDaoImplement();

        if(ud.update(name, id)){
            request.getRequestDispatcher("/addUpdateDeleteSuccess.jsp").forward(request, response);
        }else{
            response.sendRedirect("addUpdateDeleteFail.jsp");
        }
    }
}

补充：在servlet下创建deleteServlet用来删除用户信息

package servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.UserDao;
import dao.UserDaoImplement;

public class deleteServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String id = request.getParameter("id");

        UserDao ud = new UserDaoImplement();

        if (ud.delete(id)) {
            request.getRequestDispatcher("addUpdateDeleteSuccess.jsp").forward(request, response);
        } else {
            response.sendRedirect("addUpdateDeleteFail.jsp");
        }
    }
}

新建各种jsp页面
login.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
<head>
    <title>登录注册页面</title>
</head>
<body >

<form action="loginServlet"  method="post"  style="padding-top:-700px;">
    用户名：<input type="text" name="name"value=""><br><br>
    密码：  <input type="password" name="password"value=""><br><br>
    <input type="submit"value="登录"name="login"><input type="reset"value="重置"><br>
</form>

<form action="register.jsp">
    <input type="submit"value="新用户注册">
</form>

</body>
</html>

success.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <title>My JSP 'success.jsp' starting page</title>
</head>
<body>
<br>
<a href="showAllServlet">查看所有用户</a>
</body>
</html>

register.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <title>My JSP  starting page</title>
</head>
<body >
<form action="registerServlet"method="post" style="padding-top:-700px;">
    输入姓名:<input name="name" type="text"><br><br>
    输入密码:<input name="password" type="password"><br><br>
    输入id:<input name="id" type="text" ><br><br>

    <input type="reset"value="重置"><input type="submit"value="注册">
</form>
</body>
</html>

showAll.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page import="com.entity.MyUser" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="com.dao.UserDao" %>
<%@ page import="com.dao.UserDaoImplement" %>
<%@ page import="java.lang.ref.ReferenceQueue" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>所有用户页面</title>
  </head>

<body>

<!--以下两段代码放在body中不要放在<html>之外-->
<%
String path=request.getContextPath();
String basepath=request.getScheme()+"://"+ request.getServerName()+":"+request.getServerPort()+"/";
%>
<!-- 使用from提交数据，不能在不刷新页面的情况下直接在当前页面显示处理过的后台数据-->
 <c:forEach var="U" items="${requestScope.all}"  >
      <form action="updateServlet" method="post">
       <tr>
	       <td><input type="text" value="${U.name}" name="name" ></td>
	       <td><input type="text" value="${U.password}" name="password"></td>
            <td><input type="text" value="${U.id}" name="id"></td>
           <td><a href="deleteServlet?id=${U.id}">删除</a> <input type="submit" value="更新"/></td>
	   </tr>
    </form>
    </c:forEach>
</body>
</html>

addUpdateDeleteFail.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>addUpdatedDeleteFail</title>
</head>
<body>
<p>addUpdateDeleteFail</p>
</body>
</html>

addUpdateDeleteSuccess.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>addUpdateDeleteSuccess</title>
</head>
<body>
<a href="showAllServlet">查看所有用户</a>
</body>
</html>

操作截图

开启Tomcat，运行login.jsp,展示首页