web核心(Tomcat,项目部署,Servlet,Request,Response,解决两者的中文乱码问题,sqlSessionFactory工具类的提取)

小咪咪 2024-03-27 09:16 20阅读 0赞

**目录**

一、web核心介绍

二、HTTP

三、Web服务器------Tomcat

四、Servlet

4.1 快速入门

4.2 Servlet的执行流程

4.3 Servlet生命周期

4.4 Servlet方法

4.5 Servlet体系结构

4.5 Servlet urlPattern配置

4.6 XML配置方式编写Servlet

五、Request

5.1 Request继承体系

5.2 Request请求数据

5.21 通用方式获取请求参数

5.22 请求参数中文乱码处理

5.3 Request请求转发

六、Response

6.1 Response设置响应数据功能介绍

6.2 Response重定向

6.3 资源路径问题

6.4 Response响应数据

6.4.1 Response响应字符数据

6.4.2 Response响应字节数据

七、用户登录&&用户注册案例

7.1 用户登录案例

7.2 用户注册案例

八、代码优化---SqlSessionFactory工具类提取

--------------------

### 一、web核心介绍 ###

![d98ae467e9e44eadb45f80cc042caf63.png][]

**JavaWeb技术栈**

![691ae591dbe6460488ccc7f16fea372d.png][]

## 二、HTTP ##

## ![386bbe0373854f88ac8ff42344a5cef4.png][]![9d930a02e1ba4e7fa9ef66146154d482.png][] ##

![f1f47bd9e7074bec83ebe8c9710b7f87.png][]

![6681d530833a45159c2efb4bbf74fcec.png][]

## 三、Web服务器------Tomcat ##

![bad9fd8729fa4d4d8cb033e159d6e7f6.png][]

![b247afb9fd6742779a067a89f3c5d52d.png][]

![87fddb948d0145139c58e9a2af75bdb8.png][]

![74543bca8ab94bb1abe79a12ef989c73.png][]

![038f8f80b07a4c7192add2ff90e5fdb2.png][] Tomcat控制台编码默认为uft-8，而window为gbk，因此会出现乱码，将tomcat目录下的conf下的logging.properties改为gbk即可。![4a07dad8dbba4e90822fc24bb659471e.png][]

![3aa7e933f5c246d7baa55fbe2b3307cb.png][]

![3bf3ebb648f8449badaa3b9fc25d2291.png][]

![e6a9498596584486a0771aeabaf15750.png][]

![2369190d0e04497b86cecfbcd484038b.png][]

![1e2a36a31c3c42208dfb82969188651d.png][]

![0e69a34e5e8b46ebb4a6b86e88e5360a.png][]

![263929f05b70405383eebdf822d97d50.png][] ![05f5a3feda224c29b71dccc2f5a09245.png][]

注意： alt+insert:导入插件模板(此处用到了maven helper插件)

![966c8899be074aebba035ce9d869ab56.png][]

![1b55a1eea4174f299a8b50bccff70d60.png][]

## 四、Servlet ##

![01c9c5e91c2747babf10cb67cf8331c2.png][]

### 4.1 快速入门 ###

![02c6332a9b7a42cea456a81ad5c12123.png][]

<dependencies>
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>javax.servlet-api</artifactId>
                <version>3.1.0</version>
                
                <scope>provided</scope>
            </dependency>
        </dependencies>

### 4.2 Servlet的执行流程 ###

![22e1ae6b797941ccaeca04ff23732dfd.png][]

### 4.3 Servlet生命周期 ###

### ![3591f6aa6e114a9e87786a28ce03a8fd.png][] ###

### 4.4 Servlet方法 ###

### ![c3b72385424644cbac4786a4fd6cf5c9.png][] 4.5 Servlet体系结构 ###

![823ac7fd69ce4eb4964f3d12f231ebc2.png][]

### ![f225ce0a54bf483eb0195e858fc2dcab.png][]![518d43adb5f04f57bf3f2cffeea53b4d.png][] ###

public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
            //需要根据请求方式的不同，进行分别处理
    
            //强制类型转换，只有在HTTP协议下才能获取请求方式
            HttpServletRequest request = (HttpServletRequest) servletRequest;
    
            //1.获取请求方式
            String method = request.getMethod();
            //2.判断
            if ("GET".equals(method)){
                //get方式的处理逻辑
    
            }else if("POST".equals(method)){
                //post的处理逻辑
    
            }
        }

### 4.5 Servlet urlPattern配置 ###

![e35278807f324ca986201f999a31e7de.png][]

![4dbc4673f01c465ea119f229f96c634b.png][]

### 4.6 XML配置方式编写Servlet ###

![0d4f0c01443d4a2db8b8aee6102079e8.png][]

<servlet>
            <servlet-name>demo13</servlet-name>
            <servlet-class>com.itheima.ServletDemo13</servlet-class>
        </servlet>
        
        
        <servlet-mapping>
            <servlet-name>demo13</servlet-name>
            <url-pattern>/demo13</url-pattern>
        </servlet-mapping>

## 五、Request ##

![3dcd39042799460c85bbd7d5046f6bdb.png][]

### 5.1 Request继承体系 ###

![f2897819141040d4b80a9925c5114001.png][]

### 5.2 Request请求数据 ###

#### ![cb19c0be8c924d218cad7c403aa2b925.png][] ####

/**
     * request 获取请求数据
     */
    @WebServlet("/req1")
    public class RequestDemo1 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            // String getMethod()：获取请求方式： GET
            String method = req.getMethod();
    
            System.out.println(method);//GET
            // String getContextPath()：获取虚拟目录(项目访问路径)：/request-demo
            String contextPath = req.getContextPath();
            System.out.println(contextPath);
            // StringBuffer getRequestURL(): 获取URL(统一资源定位符)：http://localhost:8080/request-demo/req1
            StringBuffer url = req.getRequestURL();
            System.out.println(url.toString());
            // String getRequestURI()：获取URI(统一资源标识符)： /request-demo/req1
            String uri = req.getRequestURI();
            System.out.println(uri);
            // String getQueryString()：获取请求参数（GET方式）： username=zhangsan
            String queryString = req.getQueryString();
            System.out.println(queryString);
    
    
            //------------
            // 获取请求头：user-agent: 浏览器的版本信息
            String agent = req.getHeader("user-agent");
            System.out.println(agent);
    
    
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            //获取post 请求体：请求参数
    
            //1. 获取字符输入流
            BufferedReader br = req.getReader();
            //2. 读取数据
            String line = br.readLine();
            System.out.println(line);
    
    
        }
    }

#### 5.21 通用方式获取请求参数 ####

![1e04baf2f26f4b82b1a8afbebd9c967b.png][]

![c925e05d6b574572b9ee5fb385baf6d7.png][]

![9ad6a7ba79d1497dba7ef9d07c44a0ed.png][]

#### 5.22 请求参数中文乱码处理 ####

![225a5c909d7949359411af3a02baf581.png][]

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1.解决乱码Post,getReader()，tomcat默认这个流的编码是ISO-8859-1
            request.setCharacterEncoding("UTF-8");//设置字符输入流的编码
    
            //2.获取username
            String username = request.getParameter("username");
            System.out.println("解决乱码前："+username);
    
            //3 GET，获取参数方式：getQueryString
            //乱码原因:tomcat进行URL解码，默认的字符集ISI-8859-1
    
            /*//3.1 先对乱码数据进行编码，转为字节数组
            byte[] bytes = username.getBytes(StandardCharsets.ISO_8859_1);
            //3.2 字节数组解码
            username = new String(bytes, StandardCharsets.UTF_8);*/
    
            username = new String(username.getBytes(StandardCharsets.ISO_8859_1),StandardCharsets.UTF_8);
    
            System.out.println("解决乱码后："+username);
    
        }

![cfafb5ea0f3a49ba83561e8c6ba0d380.png][]

### 5.3 Request请求转发 ###

![b20d829d08bb4085b49d7ad629eb22ec.png][]

## 六、Response ##

![50b4b603b7f94d99844f642b1a5dd724.png][]

### 6.1 Response设置响应数据功能介绍 ###

![b814c82bc90d43f1a3907a41898d4035.png][]

### 6.2 Response重定向 ###

![97a8f5e129a8472588e0d36b95db4431.png][]

@WebServlet("/response1")
    public class Response1 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            System.out.println("response1...");
    
            //重定向
           /* //1.设置响应状态码302
            response.setStatus(302);
            //2.设置响应头
            response.setHeader("Location","/request-demo/response2");*/
    
            //简化方式完成重定向
            //response.sendRedirect("/request-demo/response2");
    
            //动态获取虚拟目录
            String contextPath = request.getContextPath();
            response.sendRedirect(contextPath+"/response2");
    
        }

### 6.3 资源路径问题 ###

![61f6519775a147f58580b1f4a6cd6248.png][]

//动态获取虚拟目录
        String contextPath = request.getContextPath();
        response.sendRedirect(contextPath+"/response2");

### 6.4 Response响应数据 ###

#### 6.4.1 Response响应字符数据 ####

![58b527ef8733441f806be059556a49a7.png][]

@Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置响应数据格式以及字符集
            response.setContentType("text/html;charset=utf-8");
            //1.获取字符输出流
            PrintWriter writer = response.getWriter();
            //2.contebtype
            //response.setHeader("content-type","text/html");
    
            writer.write("你好");
            writer.write("<h1>aaa</h1>");
    
            //细节:流不需要关闭
    
        }

#### 6.4.2 Response响应字节数据 ####

![d3ceaf57863449929d647b7627ca1a96.png][]

## 七、用户登录&&用户注册案例 ##

### 7.1 用户登录案例 ###

![862a11dd2d0a4c0a9e16891c82f6029a.png][]

pom.xm配置文件：

<?xml version="1.0" encoding="UTF-8"?>
    <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>4.0.0</modelVersion>
    
        <groupId>org.example</groupId>
        <artifactId>request-demo</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <packaging>war</packaging>
    
        <properties>
            <maven.compiler.source>8</maven.compiler.source>
            <maven.compiler.target>8</maven.compiler.target>
        </properties>
    
    
    
        <dependencies>
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>javax.servlet-api</artifactId>
                <version>3.1.0</version>
                <scope>provided</scope>
            </dependency>
    
    
            <dependency>
                <groupId>commons-io</groupId>
                <artifactId>commons-io</artifactId>
                <version>2.6</version>
            </dependency>
    
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.5</version>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.34</version>
            </dependency>
    
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.tomcat.maven</groupId>
                    <artifactId>tomcat7-maven-plugin</artifactId>
                    <version>2.2</version>
                   
                </plugin>
            </plugins>
        </build>
    
    
    </project>

Mybatis配置文件：

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        
        <typeAliases>
            <package name="com.itheima.pojo"/>
        </typeAliases>
    
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    
                    <property name="url" value="jdbc:mysql:///db1?useSSL=false&useServerPrepStmts=true"/>
                    <property name="username" value="root"/>
                    <property name="password" value="    "/>
                </dataSource>
            </environment>
        </environments>
    
        <mappers>
            
            <package name="com.itheima.mapper"/>
        </mappers>
    
    </configuration>

CSS页面：

* {
        margin: 0;
        padding: 0;
    }
    
    html {
        height: 100%;
        width: 100%;
        overflow: hidden;
        margin: 0;
        padding: 0;
        background: url(../imgs/Desert.jpg) no-repeat 0px 0px;
        background-repeat: no-repeat;
        background-size: 100% 100%;
        -moz-background-size: 100% 100%;
    }
    
    body {
        display: flex;
        align-items: center;
        justify-content: center;
        height: 100%;
    }
    
    #loginDiv {
        width: 37%;
        display: flex;
        justify-content: center;
        align-items: center;
        height: 300px;
        background-color: rgba(75, 81, 95, 0.3);
        box-shadow: 7px 7px 17px rgba(52, 56, 66, 0.5);
        border-radius: 5px;
    }
    
    #name_trip {
        margin-left: 50px;
        color: red;
    }
    
    p {
        margin-top: 30px;
        margin-left: 20px;
        color: azure;
    }
    
    input {
        margin-left: 15px;
        border-radius: 5px;
        border-style: hidden;
        height: 30px;
        width: 140px;
        background-color: rgba(216, 191, 216, 0.5);
        outline: none;
        color: #f0edf3;
        padding-left: 10px;
    }
    #username{
        width: 200px;
    }
    #password{
        width: 202px;
    }
    .button {
        border-color: cornsilk;
        background-color: rgba(100, 149, 237, .7);
        color: aliceblue;
        border-style: hidden;
        border-radius: 5px;
        width: 100px;
        height: 31px;
        font-size: 16px;
    }
    
    #subDiv {
        text-align: center;
        margin-top: 30px;
    }
    #loginMsg{
        text-align: center;color: aliceblue;
    }

<!DOCTYPE html>
    <html lang="en">
    
    <head>
        <meta charset="UTF-8">
        <title>login</title>
        <link href="css/login.css" rel="stylesheet">
    </head>
    
    <body>
    <div id="loginDiv">
        <form action="/request-demo/loginServlet" method="post" id="form">
            <h1 id="loginMsg">LOGIN IN</h1>
            <p>Username:<input id="username" name="username" type="text"></p>
    
            <p>Password:<input id="password" name="password" type="password"></p>
    
            <div id="subDiv">
                <input type="submit" class="button" value="login up">
                <input type="reset" class="button" value="reset">   
                <a href="register.html">没有账号？点击注册</a>
            </div>
        </form>
    </div>
    
    </body>
    </html>

user实体类：

package com.itheima.pojo;
    
    public class User {
    
        private Integer id;
        private String username;
        private String password;
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    '}';
        }
    }

mapper接口：

/**
         * 根据用户名和密码查询用户对象
         * @param username
         * @param password
         * @return
         */
        @Select("select * from tb_user where username = #{username} and password = #{password}")
        User select(@Param("username") String username,@Param("password")  String password);

LoginServlet:

package com.itheima.web;
    
    import com.itheima.mapper.UserMapper;
    import com.itheima.pojo.User;
    import com.itheima.util.SqlSessionFactoryUtils;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.PrintWriter;
    
    @WebServlet("/loginServlet")
    public class LoginServlet extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1. 接收用户名和密码
            String username = request.getParameter("username");
            String password = request.getParameter("password");
    
            //2. 调用MyBatis完成查询
            //2.1 获取SqlSessionFactory对象
           /* String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);*/
    
            SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();
            //2.2 获取SqlSession对象
            SqlSession sqlSession = sqlSessionFactory.openSession();
            //2.3 获取Mapper
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            //2.4 调用方法
            User user = userMapper.select(username, password);
            //2.5 释放资源
            sqlSession.close();
    
    
            //获取字符输出流，并设置content type
            response.setContentType("text/html;charset=utf-8");
            PrintWriter writer = response.getWriter();
            //3. 判断user释放为null
            if(user != null){
                // 登陆成功
                writer.write("登陆成功");
            }else {
                // 登陆失败
                writer.write("登陆失败");
            }
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            this.doGet(request, response);
        }
    }

### 7.2 用户注册案例 ###

![99b05179040f48189490a4a54a30172a.png][]

pom.xm配置文件：

Mybatis配置文件：

CSS页面：

* {
        margin: 0;
        padding: 0;
        list-style-type: none;
    }
    .reg-content{
        padding: 30px;
        margin: 3px;
    }
    a, img {
        border: 0;
    }
    
    body {
        background-image: url("../imgs/reg_bg_min.jpg") ;
        text-align: center;
    }
    
    table {
        border-collapse: collapse;
        border-spacing: 0;
    }
    
    td, th {
        padding: 0;
        height: 90px;
    
    }
    .inputs{
        vertical-align: top;
    }
    
    .clear {
        clear: both;
    }
    
    .clear:before, .clear:after {
        content: "";
        display: table;
    }
    
    .clear:after {
        clear: both;
    }
    
    .form-div {
        background-color: rgba(255, 255, 255, 0.27);
        border-radius: 10px;
        border: 1px solid #aaa;
        width: 424px;
        margin-top: 150px;
        margin-left:1050px;
        padding: 30px 0 20px 0px;
        font-size: 16px;
        box-shadow: inset 0px 0px 10px rgba(255, 255, 255, 0.5), 0px 0px 15px rgba(75, 75, 75, 0.3);
        text-align: left;
    }
    
    .form-div input[type="text"], .form-div input[type="password"], .form-div input[type="email"] {
        width: 268px;
        margin: 10px;
        line-height: 20px;
        font-size: 16px;
    }
    
    .form-div input[type="checkbox"] {
        margin: 20px 0 20px 10px;
    }
    
    .form-div input[type="button"], .form-div input[type="submit"] {
        margin: 10px 20px 0 0;
    }
    
    .form-div table {
        margin: 0 auto;
        text-align: right;
        color: rgba(64, 64, 64, 1.00);
    }
    
    .form-div table img {
        vertical-align: middle;
        margin: 0 0 5px 0;
    }
    
    .footer {
        color: rgba(64, 64, 64, 1.00);
        font-size: 12px;
        margin-top: 30px;
    }
    
    .form-div .buttons {
        float: right;
    }
    
    input[type="text"], input[type="password"], input[type="email"] {
        border-radius: 8px;
        box-shadow: inset 0 2px 5px #eee;
        padding: 10px;
        border: 1px solid #D4D4D4;
        color: #333333;
        margin-top: 5px;
    }
    
    input[type="text"]:focus, input[type="password"]:focus, input[type="email"]:focus {
        border: 1px solid #50afeb;
        outline: none;
    }
    
    input[type="button"], input[type="submit"] {
        padding: 7px 15px;
        background-color: #3c6db0;
        text-align: center;
        border-radius: 5px;
        overflow: hidden;
        min-width: 80px;
        border: none;
        color: #FFF;
        box-shadow: 1px 1px 1px rgba(75, 75, 75, 0.3);
    }
    
    input[type="button"]:hover, input[type="submit"]:hover {
        background-color: #5a88c8;
    }
    
    input[type="button"]:active, input[type="submit"]:active {
        background-color: #5a88c8;
    }
    .err_msg{
        color: red;
        padding-right: 170px;
    }
    #password_err,#tel_err{
        padding-right: 195px;
    }
    
    #reg_btn{
        margin-right:50px; width: 285px; height: 45px; margin-top:20px;
    }

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>欢迎注册</title>
        <link href="css/register.css" rel="stylesheet">
    </head>
    <body>
    
    <div class="form-div">
        <div class="reg-content">
            <h1>欢迎注册</h1>
            <span>已有帐号？</span> <a href="login.html">登录</a>
        </div>
        <form id="reg-form" action="/request-demo/registerServlet" method="post">
    
            <table>
    
                <tr>
                    <td>用户名</td>
                    <td class="inputs">
                        <input name="username" type="text" id="username">
                        <br>
                        <span id="username_err" class="err_msg" style="display: none">用户名不太受欢迎</span>
                    </td>
    
                </tr>
    
                <tr>
                    <td>密码</td>
                    <td class="inputs">
                        <input name="password" type="password" id="password">
                        <br>
                        <span id="password_err" class="err_msg" style="display: none">密码格式有误</span>
                    </td>
                </tr>
    
            </table>
    
            <div class="buttons">
                <input value="注 册" type="submit" id="reg_btn">
            </div>
            <br class="clear">
        </form>
    
    </div>
    </body>
    </html>

user实体类：

mapper接口：

/**
         * 根据用户名查询用户对象
         * @param username
         * @return
         */
        @Select("select * from tb_user where username = #{username}")
        User selectByUsername(String username);
    
        /**
         * 添加用户
         * @param user
         */
        @Insert("insert into tb_user values(null,#{username},#{password})")
        void add(User user);

RegisterServlet:

package com.itheima.web;
    
    import com.itheima.mapper.UserMapper;
    import com.itheima.pojo.User;
    import com.itheima.util.SqlSessionFactoryUtils;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    import java.io.IOException;
    import java.io.InputStream;
    
    @WebServlet("/registerServlet")
    public class RegisterServlet extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1. 接收用户数据
            String username = request.getParameter("username");
            String password = request.getParameter("password");
    
            //封装用户对象
            User user = new User();
            user.setUsername(username);
            user.setPassword(password);
    
            //2. 调用mapper 根据用户名查询用户对象
            //2.1 获取SqlSessionFactory对象
           /* String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);*/
            SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();
    
            //2.2 获取SqlSession对象
            SqlSession sqlSession = sqlSessionFactory.openSession();
            //2.3 获取Mapper
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    
            //2.4 调用方法
            User u = userMapper.selectByUsername(username);
    
            //3. 判断用户对象释放为null
            if( u == null){
                // 用户名不存在，添加用户
                userMapper.add(user);
    
                // 提交事务
                sqlSession.commit();
                // 释放资源
                sqlSession.close();
            }else {
                // 用户名存在，给出提示信息
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("用户名已存在");
            }
    
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            this.doGet(request, response);
        }
    }

## 八、代码优化---SqlSessionFactory工具类提取 ##

![b00688fd82f242ed828e74734109b16d.png][]

package com.itheima.util;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    public class SqlSessionFactoryUtils {
    
        private static SqlSessionFactory sqlSessionFactory;
    
        static {
            //静态代码块会随着类的加载而自动执行，且只执行一次
    
            try {
                String resource = "mybatis-config.xml";
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
    
        public static SqlSessionFactory getSqlSessionFactory(){
            return sqlSessionFactory;
        }
    }

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