3. 将处理之后的结果,按照特定的要求?返回给用户(返回) SpringMVC Controller

?过程

1.数据库（内容可自行添加）

建表语句：

CREATE TABLE demo_user (

id int(11) NOT NULL AUTO_INCREMENT,

name char(40) DEFAULT NULL,

age int(11) DEFAULT NULL,

sex char(40) DEFAULT NULL,

PRIMARY KEY (id),

KEY cc (id),

KEY user_index (name)

) ENGINE=InnoDB AUTO_INCREMENT=234 DEFAULT CHARSET=utf8

数据库示例：

2.搭建后端项目（IDEA）

2.1 目录结构（创建 Maven 项目）

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2.2? 配置 pom 文件 添加依赖

<parent>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-parent</artifactId>

<version>2.5.2</version>

<relativePath/>

</parent>

<properties>

<java.version>1.8</java.version>

<!--跳过测试类打包-->

<skipTests>true</skipTests>

</properties>

<dependencies>

<dependency>

    <groupId>org.springframework.boot</groupId>

    <!--springboot启动项(器)在包的内部SpringBoot

    已经完成了项目的"整合"(配置) 用户拿来就用

    web导入SpringMVC

    -->

    <artifactId>spring-boot-starter-web</artifactId>

</dependency>

<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-test</artifactId>

    <scope>test</scope>

</dependency>

<!--支持热部署 -->

<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-devtools</artifactId>

</dependency>

<!--添加lombok依赖-->

<dependency>

    <groupId>org.projectlombok</groupId>

    <artifactId>lombok</artifactId>

</dependency>

<!--引入数据库驱动 -->

<dependency>

    <groupId>mysql</groupId>

    <artifactId>mysql-connector-java</artifactId>

    <scope>runtime</scope>

</dependency>

<!--springBoot数据库连接  -->

<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-jdbc</artifactId>

</dependency>

<!--导入MP包之后,删除原有的Mybatis的包 -->

<dependency>

    <groupId>com.baomidou</groupId>

    <artifactId>mybatis-plus-boot-starter</artifactId>

    <version>3.4.3</version>

</dependency>

</dependencies>

<build>

<plugins>

    <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

        <version>2.5.2</version>

    </plugin>

</plugins>

</build>

2.3 配置 application.yml 文件

server:

port: 8090

spring:

datasource:

driver-class-name: com.mysql.cj.jdbc.Driver

url: jdbc:mysql://127.0.0.1:3306/jt?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true

username: root

password: root

#SpringBoot 整合 MP

mybatis-plus:

type-aliases-package: com.jt.pojo

mapper-locations: classpath:/mybatis/*.xml

configuration:

map-underscore-to-camel-case: true

Mapper 接口执行 打印 Sql 日志

logging:

level:

com.jt.mapper: debug 

2.4 配置映射文件 UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.jt.mapper.UserMapper">

</mapper>

2.5 启动类

@SpringBootApplication

@MapperScan("com.jt.mapper") //Spring 容器内部为接口创建代理对象

//JDK 的动态代理对象

public class SpringBootRun {

//标准写法