SpringBoot入门九（整合之通用mapper）

目标：配置通用Mapper组件到Spring Boot项目中并使用 Mapper<T>接口

分析：通用Mapper:可以实现自动拼接sql语句，所有的mapper都不用编写任何方法也就是不用编写sql语句，可以提高效率

1.添加启动器依赖
2.改造UserMapper继承Mapper<User>
3.修改启动器引导类Application中的Mapper扫描注解
4.修改User实体类添加jpa注解
5.改造UserService实现业务功能

注意：在启动引导类上面的mapper扫描注解一定要修改为通用mapper的扫描注解（不然mapper找不到）
==========

1.添加启动器依赖

        <!--通用mapper-->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper-spring-boot-starter</artifactId>
            <version>2.1.5</version>
        </dependency>

2.改造UserMapper继承Mapper<User>

package com.cc8w.home.mapper;

import com.cc8w.com.cc8w.entity.User;
import org.apache.ibatis.session.RowBounds;
import tk.mybatis.mapper.common.Mapper;

import java.util.List;

public interface UserMapper extends Mapper<User> {
    
}

3.修改启动器引导类Application中的Mapper扫描注解

package com.cc8w;

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

/**
 * spring boot 工程都有一个启动引导类，
 * 并且添加 @SpringBootApplication 组合注解
 */
@SpringBootApplication
//@MapperScan("com.cc8w.home.mapper") //扫描mapper接口
@MapperScan("com.cc8w.home.mapper")//使用通用mapper
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class,args);
    }
}

4.修改User实体类添加jpa注解

package com.cc8w.com.cc8w.entity;

import lombok.Data;
import tk.mybatis.mapper.annotation.KeySql;

import javax.persistence.Column;
import javax.persistence.Id;
import javax.persistence.Table;

@Data
@Table(name="t_users")
public class User {
    @Id
    @KeySql(useGeneratedKeys = true) //id回填
    private int id;
    @Column(name="user_name")//符合驼峰命名可以不用
    private String userName;
    private String passWord;
}

5.改造UserService实现业务功能

package com.cc8w.home.service;

import com.cc8w.com.cc8w.entity.User;
import com.cc8w.home.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    //根据id查询
    public User queryById(int id){
        return userMapper.selectByPrimaryKey(id);
    }
    //保存用户
    @Transactional
    public void saveUser(User user){
        userMapper.insertSelective(user);
        System.out.println("保存..");
    }
}

试一下查询用户

package com.cc8w.home.controller;

import com.cc8w.com.cc8w.entity.User;
import com.cc8w.home.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.sql.DataSource;

@RestController
@RequestMapping("home/test")
public class JdbcTest {

    @Autowired
    private DataSource dataSource;
    @Autowired
    private UserService userService;

    @RequestMapping("jtest")
    public String jTest(){

        System.out.println(dataSource);
        System.out.println("jTest22");
        User user = userService.queryById(1);
        System.out.println(user);

        return "null";
    }

}