创建第一个属于自己的JavaWeb小程序吧

需要使用的技术工具：

idea 2022 开发工具
MySql 5.6 数据库工具
Apache Tomcat 8.5.85 web应用部署工具

主要功能有：

用户登录
用户注册
展示列表信息

涉及到的知识：

Servlet
JDBC
过滤器

先打开数据库创建一个数据库然后创建对应的表结构

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,
  `address` varchar(255) NOT NULL,
  `info` varchar(255) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
 
INSERT INTO `user` VALUES ('1', '123', '123', '女', '北京', '123');
INSERT INTO `user` VALUES ('2', '111, '111', '男', '北京', '123123');

然后打开 idea 创建以下几个目录：

com.filter //过滤器解决中文字符集乱码
com.util //数据库连接工具类
com.entity //实体类
com.dao //数据操作类
com.servlet //servlet类

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

package com.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;
 
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");
    }
 
}

然后到web.xml下进行对EncodingFilter相应的 xml配置

<?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">

    <!--  设置编码格式  -->
    <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>com.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> <!--* 为过滤所有-->
    </filter-mapping>

    <!--  设置首页为登录页 首页从默认的 index.jsp 换成 login.jsp  -->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>

</web-app>

在util下新建一个DBconn类用来处理对数据库的连接操作（用户名和密码需要对照自己的数据库进行更改）

package com.util;

import java.sql.*;

public class DBConnection {
    //定义连接数据库的属性
    private static String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static String url = "jdbc:mysql://localhost:3306/demo";

    // 用户 密码
    private static String username = "root";
    private static String pwd = "123456";
    private static Connection conn = null;

    static ResultSet rs = null;
    static PreparedStatement ps =null;
    
    public static void init(){
        try {
            Class.forName(JDBC_DRIVER);
            conn = DriverManager.getConnection(url,username,pwd);
        } catch (Exception e) {
            System.out.println("init [SQL驱动程序初始化失败！]");
            e.printStackTrace();
        }
    }

    public static int addUpdDel(String sql){
        int i = 0;
        try {
            PreparedStatement ps =  conn.prepareStatement(sql);
            i =  ps.executeUpdate();
        } catch (SQLException 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(sql);
        } catch (SQLException e) {
            System.out.println("数据库查询异常");
            e.printStackTrace();
        }
        return rs;
    }

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

在entity下新建一个User实体类对应数据库中的每个字段

package com.entity;

public class User {
    private int id;
    private String name;
    private String pwd;
    private String sex;
    private String address;
    private String info;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getInfo() {
        return info;
    }

    public void setInfo(String info) {
        this.info = info;
    }
}

在dao下新建一个UserDao接口以及对应的方法实现类规范开发需要使用接口及实现类

UserDao.java

package com.dao;

import com.entity.User;

import java.util.List;

public interface UserDao {
    public boolean login(String name,String pwd);//登录
    public boolean register(User user);//注册
    public List<User> getUserAll();//返回用户信息集合
    public boolean delete(int id) ;//根据id删除用户
    public boolean update(int id,String name, String pwd,String sex, String home,String info) ;//更新用户信息
}

在写一个 UserDaoImpl.java 实现UserDao接口，及未实现的方法

package com.dao;

import com.entity.User;
import com.util.DBConnection;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDaoImpl implements UserDao {
    DBConnection DBconn = new DBConnection();

    // 注册用户
    @Override
    public boolean register(User user) {
        boolean flag = false;
        DBconn.init();
        int i =DBconn.addUpdDel("insert into user(name,pwd,sex,address,info) " +
                "values('"+user.getName()+"','"+user.getPwd()+"','"+user.getSex()+"','"+user.getAddress()+"','"+user.getInfo()+"')");
        if(i>0){
            flag = true;
        }
        DBconn.closeConn();
        return flag;
    }

    // 查询 登录用户是否存在
    @Override
    public boolean login(String name, String pwd) {
        boolean flag = false;
        try {
            DBconn.init();
            ResultSet rs = DBconn.selectSql("select * from user where name='"+name+"' and pwd='"+pwd+"'");
            while(rs.next()){
                if(rs.getString("name").equals(name) && rs.getString("pwd").equals(pwd)){
                    flag = true;
                }
            }
            DBconn.closeConn();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return flag;
    }

    // 获取用户
    @Override
    public List<User> getUserAll() {
        List<User> list = new ArrayList<User>();
        try {
            DBconn.init();
            ResultSet rs = DBconn.selectSql("select * from user");
            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.setAddress(rs.getString("address"));
                user.setInfo(rs.getString("info"));
                list.add(user);
            }
            DBconn.closeConn();
            return list;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    // 更新用户数据
    @Override
    public boolean update(int id, String name, String pwd, String sex, String home, String info) {
        boolean flag = false;
        DBconn.init();
        String sql ="update user set name ='"+name
                +"' , pwd ='"+pwd
                +"' , sex ='"+sex
                +"' , home ='"+home
                +"' , info ='"+info+"' where id = "+id;
        int i =DBconn.addUpdDel(sql);
        if(i>0){
            flag = true;
        }
        DBconn.closeConn();
        return flag;
    }

    // 删除用户
    @Override
    public boolean delete(int id) {
        boolean flag = false;
        DBconn.init();
        String sql = "delete  from user where id="+id;
        int i =DBconn.addUpdDel(sql);
        if(i>0){
            flag = true;
        }
        DBconn.closeConn();
        return flag;
    }


}

在servlet下创建DengluServlet用来实现对用户登录的操作，实现Servlet具体内容，然后需要去WEB_INF下的web.xml去配置servlet

package com.servlet;

import com.dao.UserDao;
import com.dao.UserDaoImpl;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "signinServlet", value = "/signinServlet")
public class Signin extends HttpServlet { // serverlet 需要继承 HttpServerlet  并重写doGet和doPost方法
    @Override
    protected 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
    }

    @Override
    protected 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 pwd = request.getParameter("pwd");

        UserDao ud = new UserDaoImpl();

        if(ud.login(name, pwd)){
            request.setAttribute("xiaoxi", "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("index.jsp"); //重定向到首页
        }

    }
}

两点要注意的地方：

一：getParameter与getAttribute两者的区别

request.setAttribute("xiaoxi", "欢迎用户"+name);//向request域中放置信息（键值对的形式）名字为xiaoxi 内容为"欢迎用户"+name

request.getAttribute("xiaoxi");//得到request域中放置名字为xiaoxi的信息

request.getParameter("name");//得到request域的参数信息（得到jsp页面传过来的参数）

getAttribute表示从request范围取得设置的属性，必须要先setAttribute设置属性，才能通过getAttribute来取得，设置与取得的为Object对象类型。

getParameter表示接收参数，参数为页面提交的参数，包括：表单提交的参数、URL重写（就是xxx?id=1中的id）传的参数等，因此这个并没有设置参数的方法（没有setParameter），而且接收参数返回的不是Object，而是String类型

二：转发与重定向的区别

（1）.重定向的执行过程：Web服务器向浏览器发送一个http响应--》浏览器接受此响应后再发送一个新的http请求到服务器--》服务器根据此请求寻找资源并发送给浏览器。它可以重定向到任意URL，不能共享request范围内的数据。
（2）.重定向是在客户端发挥作用，通过新的地址实现页面转向。
（3）.重定向是通过浏览器重新请求地址，在地址栏中可以显示转向后的地址。
（4）.转发过程：Web服务器调用内部方法在容器内部完成请求和转发动作--》将目标资源发送给浏览器，它只能在同一个Web应用中使用，可以共享request范围内的数据。
（5）.转发是在服务器端发挥作用，通过forward()方法将提交信息在多个页面间进行传递。
（6）.转发是在服务器内部控制权的转移，客户端浏览器的地址栏不会显示出转向后的地址。

在servlet下创建一个ZhuceServlet用来实现用户注册的操作

package com.servlet;

import com.dao.UserDao;
import com.dao.UserDaoImpl;
import com.entity.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "LogonServlet", value = "/LogonServlet")
public class Logon extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name"); //获取jsp页面传过来的参数
        String pwd = req.getParameter("pwd");
        String sex = req.getParameter("sex");
        String address = req.getParameter("address");
        String info = req.getParameter("info");

        User user = new User(); //实例化一个对象，组装属性
        user.setName(name);
        user.setPwd(pwd);
        user.setSex(sex);
        user.setAddress(address);
        user.setInfo(info);

        UserDao ud = new UserDaoImpl();

        if( ud.register(user) ){
            req.setAttribute("username", name);  //向req域中放置参数
            req.setAttribute("xiaoxi", "注册成功");
            req.getRequestDispatcher("/login.jsp").forward(req, resp);  //转发到登录页面
        }else{
            resp.sendRedirect("login.jsp");//重定向到首页
        }
    }
}

在servlet下创建SearchallServlet用来返回数据库中所有用户信息 Searchall.java

package com.servlet;

import com.dao.UserDao;
import com.dao.UserDaoImpl;
import com.entity.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet(name = "SearchallServlet", value = "/SearchallServlet")
public class Searchall extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        UserDao ud = new UserDaoImpl();
        List<User> userAll = ud.getUserAll();
        req.setAttribute("userAll", userAll);
        req.getRequestDispatcher("/showall.jsp").forward(req, resp);
    }
}

在servlet下创建DeleteServlet用来删除用户操作 DeleteServlet.java

package com.servlet;

import com.dao.UserDao;
import com.dao.UserDaoImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "DeleteServlet", value = "/DeleteServlet")
public class Delete extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String id = req.getParameter("id");
        int userId = Integer.parseInt(id);

        UserDao ud = new UserDaoImpl();

        if(ud.delete(userId)){
            req.setAttribute("xiaoxi", "删除成功");
            req.getRequestDispatcher("/Searchall").forward(req, resp);
        }else{
            resp.sendRedirect("index.jsp");
        }
    }
}

在servlet下创建UpdateServlet操作用来更新用户信息 UpdateServlet.java

package com.servlet;


import com.dao.UserDao;
import com.dao.UserDaoImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "UpdateServlet", value = "/UpdateServlet")
public class Update extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(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");

        System.out.println("------------------------------------"+userId);

        UserDao ud = new UserDaoImpl();

        if(ud.update(userId, name, pwd, sex, home, info)){
            req.setAttribute("xiaoxi", "更新成功");
            req.getRequestDispatcher("/Searchall").forward(req, resp);
        }else{
            resp.sendRedirect("index.jsp");
        }
    }
}

配置servlet

<?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">

    <!--  设置编码格式  -->
    <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>com.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> <!--* 为过滤所有-->
    </filter-mapping>


    <servlet><!--servlet类路径配置-->
        <servlet-name>LogonServlet</servlet-name>
        <servlet-class>com.servlet.Logon</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>SigninServlet</servlet-name>
        <servlet-class>com.servlet.Signin</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>SearchallServlet</servlet-name>
        <servlet-class>com.servlet.Searchall</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>DeleteServlet</servlet-name>
        <servlet-class>com.servlet.Delete</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>UpdateServlet</servlet-name>
        <servlet-class>com.servlet.Update</servlet-class>
    </servlet>

    <!--配置Servlet 类-->
    <servlet-mapping>
        <servlet-name>LogonServlet</servlet-name>
        <url-pattern>/LogonServlet</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>SigninServlet</servlet-name>
        <url-pattern>/SigninServlet</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>SearchallServlet</servlet-name>
        <url-pattern>/SearchallServlet</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>

    <!--  设置首页为登录页  -->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
</web-app>

新建jsp页面 login

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

<form action="SigninServlet" method="post">
    用户名：<input type="text" name="name"value=""><br><br>
    密码：  <input type="password" name="pwd"value=""><br><br>
    <input type="submit"value="登录"name="denglu"><input type="reset"value="重置"><br>
</form>
<form action="zhuce.jsp">
    <input type="submit"value="新用户注册">
</form>

</body>
</html>

zhuce.jsp 用户注册页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
<head>
    <title>My JSP 'BB.jsp' starting page</title>
</head>
<body >
<form action="LogonServlet"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:<input type="radio"name="sex"value="男"checked>男
    <input type="radio"name="sex"value="女">女<br><br>
    选择家乡:
    <select name="address">
        <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>
    <textarea name="info" row="5"cols="30"></textarea><br>
    <input type="reset"value="重置"><input type="submit"value="注册">
</form>
</body>
</html>

失败页面 index.jsp

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

success.jsp 成功页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>My JSP 'success.jsp' starting page</title>
</head>
<body>
    ${xiaoxi} <br>
    <a href="showall.jsp">查看所有用户</a>
</body>
</html>

完成以上工作就可以运行 Tomcat服务，然后运行啦

本博文参考大佬 http://blog.csdn.net/qq_23994787/article/details/73612870

posted @ 2023-03-05 16:09 萧熙阅读(98) 评论(0) 编辑收藏举报

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