重生之 SpringBoot3 入门保姆级学习（17、整合SSM）

4、数据访问

4.1 整合 ssm

• pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.3.0</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.zhong</groupId>
    <artifactId>boot3-05-ssm</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>boot3-05-ssm</name>
    <description>boot3-05-ssm</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <!--SpringBoot Web 启动器-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!--MySQL 驱动-->
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>

        <!--MyBatis 依赖-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>3.0.3</version>
        </dependency>

        <!--类注解插件-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

• application.properties

# 1、MySQL相关配置
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.type=com.zaxxer.hikari.HikariDataSource
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=123456

# 2、整合 MyBatis
# mybatis.config-location 告诉 MyBatis 每个接口的 xml 在哪里
mybatis.mapper-locations=classpath:/mapper/*.xml
mybatis.configuration.map-underscore-to-camel-case=true

• 准备数据库

CREATE TABLE `t_user`
(
	`id` BIGINT(20) NOT NULL AUTO_INCREMENT COMMENT '编号',
	`login_name` VARCHAR(200) NULL DEFAULT NULL COMMENT '用户名称' COLLATE 'utf8_general_ci',	 
	`nick_name`  VARCHAR(200) NULL DEFAULT NULL COMMENT '用户昵称' COLLATE 'utf8_general_ci',	 
	`password`   VARCHAR(200) NULL DEFAULT NULL COMMENT '用户密码' COLLATE 'utf8_general_ci',
	PRIMARY KEY (`id`)	 
);
insert into t_user(login_name,nick_name,password) values ('xiaozhong','小钟','123456');
insert into t_user(login_name,nick_name,password) values ('xiaowang','小王','123456');

• 运行成功后请刷新数据库

• 添加 Tuser 实体类映射数据库字段

package com.zhong.ssm.bean;

import lombok.Data;

/**
 * @ClassName : Tuser
 * @Description :
 * @Author : zhx
 * @Date: 2024-06-02 17:40
 */
@Data
public class TUser {
    private Long id;
    private String loginName;
    private String nickName;
    private String password;
}

• 安装插件 MyBatisX

• 写 UserMapper 接口

package com.zhong.ssm.bean.mapper;

/**
 * @ClassName : UserMapper
 * @Description :
 * @Author : zhx
 * @Date: 2024-06-02 17:47
 */
public interface UserMapper {

}

• 按键盘 Alt + Enter 选择 [MybatisX] Generate of xml 选择当前项目的 resource 目录下的 mapper 文件夹 点击确定

• 自动生成了对应的 xml 文件

• 快速生成：新建方法 getUserById 按键盘 Alt + Enter 直接回车

package com.zhong.ssm.bean.mapper;

import com.zhong.ssm.bean.TUser;
import org.apache.ibatis.annotations.Param;

/**
 * @ClassName : UserMapper
 * @Description :
 * @Author : zhx
 * @Date: 2024-06-02 17:47
 */
public interface UserMapper {
    /**
     * 1、每个方法都在 mapper 文件有一个 sql 标签对应的
     * 2、所有参数都应该用 @Param(name) 进行签名 SQL 中才可用 #{name} 取值
     * @param id
     * @return
     */
    TUser getUserById(@Param("id") Long id);
}

• 添加查询语句

<?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.zhong.ssm.bean.mapper.UserMapper">

    <select id="getUserById" resultType="com.zhong.ssm.bean.TUser">
        select * from t_user where id=#{id}
    </select>
</mapper>

• 添加包扫描路径

package com.zhong.ssm;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@MapperScan(basePackages = "com.zhong.ssm.bean.mapper")
@SpringBootApplication
public class Boot305SsmApplication {

    public static void main(String[] args) {
        SpringApplication.run(Boot305SsmApplication.class, args);
    }

}

• 添加 controller

package com.zhong.ssm.controller;

import com.zhong.ssm.bean.TUser;
import com.zhong.ssm.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

/**
 * @ClassName : UserController
 * @Description :
 * @Author : zhx
 * @Date: 2024-06-02 19:15
 */
@RestController
public class UserController {
    @Autowired
    UserMapper userMapper;

    @GetMapping("/user/{id}")
    public TUser getUser(@PathVariable("id") Long id) {
        return userMapper.getUserById(id);
    }
}

• 浏览器测试

http://localhost:8080/user/1

http://localhost:8080/user/2