創建第一個屬于自己的JavaWeb小程式吧-有解無憂

需要使用的技術工具：

idea 2022 開發工具
MySql 5.6 資料庫工具
Apache Tomcat 8.5.85 web應用部署工具

主要功能有：

用戶登錄
用戶注冊
展示串列資訊

涉及到的知識：

Servlet
JDBC
過濾器

先打開資料庫創建一個資料庫然后創建對應的表結構

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');

然后打開 idea 創建以下幾個目錄：

com.filter //過濾器解決中文字符集亂碼
com.util //資料庫連接工具類
com.entity //物體類
com.dao //資料操作類
com.servlet //servlet類

在filter下新建一個EncodingFilter用來解決中文字符集亂碼，需要實作Filter介面，并且重寫doFilter函式

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("過濾器構造");
    }
    public void destroy() {
        System.out.println("過濾器銷毀");
    }
    public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding("utf-8"); //將編碼改為utf-8
        response.setContentType("text/html;charset=utf-8");
        chain.doFilter(request, response);
    }
 
    public void init(FilterConfig arg0) throws ServletException {
        System.out.println("過濾器初始化");
    }
 
}

然后到web.xml下進行對EncodingFilter相應的 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">

    <!--  設定編碼格式  -->
    <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>com.filter.EncodingFilter</filter-class><!--全路徑 從根包開始一直到類名-->
    </filter>
    <filter-mapping>
        <filter-name>EncodingFilter</filter-name>
        <url-pattern>/*</url-pattern> <!--* 為過濾所有-->
    </filter-mapping>

    <!--  設定首頁為登錄頁 首頁從默認的 index.jsp 換成 login.jsp  -->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>

</web-app>

在util下新建一個DBconn類用來處理對資料庫的連接操作（用戶名和密碼需要對照自己的資料庫進行更改）

package com.util;

import java.sql.*;

public class DBConnection {
    //定義連接資料庫的屬性
    private static String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static String url = "jdbc:mysql://localhost:3306/demo";

    // 用戶 密碼
    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驅動程式初始化失敗！]");
            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("資料庫增刪改例外");
            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("資料庫查詢例外");
            e.printStackTrace();
        }
        return rs;
    }

    public static void closeConn(){
        try {
            conn.close();
        } catch (SQLException e) {
            System.out.println("資料庫關閉例外");
            e.printStackTrace();
        }
    }
}

在entity下新建一個User物體類對應資料庫中的每個欄位

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下新建一個UserDao介面以及對應的方法實作類規范開發需要使用介面及實作類

UserDao.java

package com.dao;

import com.entity.User;

import java.util.List;

public interface UserDao {
    public boolean login(String name,String pwd);//登錄
    public boolean register(User user);//注冊
    public List<User> getUserAll();//回傳用戶資訊集合
    public boolean delete(int id) ;//根據id洗掉用戶
    public boolean update(int id,String name, String pwd,String sex, String home,String info) ;//更新用戶資訊
}

在寫一個 UserDaoImpl.java 實作UserDao介面，及未實作的方法

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();

    // 注冊用戶
    @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;
    }

    // 查詢 登錄用戶是否存在
    @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;
    }

    // 獲取用戶
    @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;
    }

    // 更新用戶資料
    @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;
    }

    // 洗掉用戶
    @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下創建DengluServlet用來實作對用戶登錄的操作，實作Servlet具體內容，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 = "https://www.cnblogs.com/signinServlet")
public class Signin extends HttpServlet { // serverlet 需要繼承 HttpServerlet  并重寫doGet和doPost方法
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doPost(request, response);  //將資訊使用doPost方法執行   對應jsp頁面中的form表單中的method
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name"); //得到jsp頁面傳過來的引數
        String pwd = request.getParameter("pwd");

        UserDao ud = new UserDaoImpl();

        if(ud.login(name, pwd)){
            request.setAttribute("xiaoxi", "歡迎用戶"+name); //向request域中放置資訊
            request.getRequestDispatcher("/success.jsp").forward(request, response);//轉發到成功頁面
        }else{
            response.sendRedirect("index.jsp"); //重定向到首頁
        }

    }
}

兩點要注意的地方：

一：getParameter與getAttribute兩者的區別

request.setAttribute("xiaoxi", "歡迎用戶"+name);//向request域中放置資訊（鍵值對的形式）名字為xiaoxi 內容為"歡迎用戶"+name

request.getAttribute("xiaoxi");//得到request域中放置名字為xiaoxi的資訊

request.getParameter("name");//得到request域的引數資訊（得到jsp頁面傳過來的引數）

getAttribute表示從request范圍取得設定的屬性，必須要先setAttribute設定屬性，才能通過getAttribute來取得，設定與取得的為Object物件型別，

getParameter表示接收引數，引數為頁面提交的引數，包括：表單提交的引數、URL重寫（就是xxx?id=1中的id）傳的引數等，因此這個并沒有設定引數的方法（沒有setParameter），而且接收引數回傳的不是Object，而是String型別

二：轉發與重定向的區別

（1）.重定向的執行程序：Web服務器向瀏覽器發送一個http回應--》瀏覽器接受此回應后再發送一個新的http請求到服務器--》服務器根據此請求尋找資源并發送給瀏覽器，它可以重定向到任意URL，不能共享request范圍內的資料，
（2）.重定向是在客戶端發揮作用，通過新的地址實作頁面轉向，
（3）.重定向是通過瀏覽器重新請求地址，在地址欄中可以顯示轉向后的地址，
（4）.轉發程序：Web服務器呼叫內部方法在容器內部完成請求和轉發動作--》將目標資源發送給瀏覽器，它只能在同一個Web應用中使用，可以共享request范圍內的資料，
（5）.轉發是在服務器端發揮作用，通過forward()方法將提交資訊在多個頁面間進行傳遞，
（6）.轉發是在服務器內部控制權的轉移，客戶端瀏覽器的地址欄不會顯示出轉向后的地址，

在servlet下創建一個ZhuceServlet用來實作用戶注冊的操作

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 = "https://www.cnblogs.com/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"); //獲取jsp頁面傳過來的引數
        String pwd = req.getParameter("pwd");
        String sex = req.getParameter("sex");
        String address = req.getParameter("address");
        String info = req.getParameter("info");

        User user = new User(); //實體化一個物件，組裝屬性
        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域中放置引數
            req.setAttribute("xiaoxi", "注冊成功");
            req.getRequestDispatcher("/login.jsp").forward(req, resp);  //轉發到登錄頁面
        }else{
            resp.sendRedirect("login.jsp");//重定向到首頁
        }
    }
}

在servlet下創建SearchallServlet用來回傳資料庫中所有用戶資訊 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 = "https://www.cnblogs.com/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下創建DeleteServlet用來洗掉用戶操作 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 = "https://www.cnblogs.com/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", "洗掉成功");
            req.getRequestDispatcher("/Searchall").forward(req, resp);
        }else{
            resp.sendRedirect("index.jsp");
        }
    }
}

在servlet下創建UpdateServlet操作用來更新用戶資訊 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 = "https://www.cnblogs.com/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">

    <!--  設定編碼格式  -->
    <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>com.filter.EncodingFilter</filter-class><!--全路徑 從根包開始一直到類名-->
    </filter>
    <filter-mapping>
        <filter-name>EncodingFilter</filter-name>
        <url-pattern>/*</url-pattern> <!--* 為過濾所有-->
    </filter-mapping>


    <servlet><!--servlet類路徑配置-->
        <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 類-->
    <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>

    <!--  設定首頁為登錄頁  -->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
</web-app>

新建jsp頁面 login

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

<form action="SigninServlet" method="post">
    用戶名：<input type="text" name="name"value=""><br><br>
    密碼：  <input type="password" name="pwd"value=""><br><br>
    <input type="submit"value="https://www.cnblogs.com/xiaoxiblog/archive/2023/03/05/登錄"name="denglu"><input type="reset"value="https://www.cnblogs.com/xiaoxiblog/archive/2023/03/05/重置"><br>
</form>
<form action="zhuce.jsp">
    <input type="submit"value="https://www.cnblogs.com/xiaoxiblog/archive/2023/03/05/新用戶注冊">
</form>

</body>
</html>

zhuce.jsp 用戶注冊頁面

<%@ 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;">
    輸入用戶名:<input name="name" type="text"><br><br>
    輸入密碼:<input name="pwd" type="password"><br><br>
    選擇性別:<input type="radio"name="sex"value="男"checked>男
    <input type="radio"name="sex"value="女">女<br><br>
    選擇家鄉:
    <select name="address">
        <option value="上海">上海</option>
        <option value="北京" selected>北京</option>
        <option value="紐約">紐約</option>
    </select><br>
    填寫個人資訊:<br>
    <textarea name="info" row="5"cols="30"></textarea><br>
    <input type="reset"value="重置"><input type="submit"value="注冊">
</form>
</body>
</html>

失敗頁面 index.jsp

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

success.jsp 成功頁面

<%@ 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">查看所有用戶</a>
</body>
</html>

完成以上作業就可以運行 Tomcat服務，然后運行啦

本博文參考大佬 http://blog.csdn.net/qq_23994787/article/details/73612870

本文來自博客園，作者：蕭熙，轉載請注明原文鏈接：https://www.cnblogs.com/xiaoxiblog/p/17180633.html

轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/545830.html

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