MyBatis-Plus 使用说明介绍

先看一下和MyBatis 不同点说明：

    @GetMapping("/select_sql")
    public Object getUserBySql() {
        User user=new User(1L);
        User selectUser=user.selectById();
        user.deleteById(user);
        return userService.selectListBySQL();  //普通走法
    }

最大的不同点在entity层直接可以调用superEntity，直接实现默认的一些增删改查

/**
 * 用户表
 */
@SuppressWarnings("serial")
public class User extends SuperEntity<User> {

    /**
     * 名称
     */
    private String name;
    /**
     * 年龄
     */
    private AgeEnum age;
    /**
     * 这里故意演示注解可无
     */
    @TableField("test_type")
    @TableLogic
    private Integer testType;

    /**
     * 测试插入填充
     */
    @TableField(fill = FieldFill.INSERT)
    private Date testDate;

    private Long role;
    private PhoneEnum phone;

    public User() {
    }
    public User(Long id){
        this.setId(id);
    }

    public User(Long id, String name, AgeEnum age, Integer testType) {
        this.setId(id);
        this.name = name;
        this.age = age;
        this.testType = testType;
    }

    public User(String name, AgeEnum age, Integer testType) {
        this.name = name;
        this.age = age;
        this.testType = testType;
    }


    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public AgeEnum getAge() {
        return this.age;
    }

    public void setAge(AgeEnum age) {
        this.age = age;
    }

    public Integer getTestType() {
        return this.testType;
    }

    public void setTestType(Integer testType) {
        this.testType = testType;
    }

    public Long getRole() {
        return this.role;
    }

    public void setRole(Long role) {
        this.role = role;
    }

    public PhoneEnum getPhone() {
        return this.phone;
    }

    public void setPhone(PhoneEnum phone) {
        this.phone = phone;
    }

    public Date getTestDate() {
        return testDate;
    }

    public void setTestDate(Date testDate) {
        this.testDate = testDate;
    }

    @Override
    public String toString() {
        return "User [id=" + this.getId() + ", name=" + name + ", age=" + age
                + ", testType=" + testType + ", testDate="
                + testDate + ", role=" + role + ", phone=" + phone + "]";
    }

SuperEntity 继承Model  ，Model默认实现了简单的增删改查，不需要再去实现mapper层。

/**
 * 演示实体父类
 */
public class SuperEntity<T extends Model> extends Model<T> {

    /**
     * 主键ID , 这里故意演示注解可以无
     */
    @TableId("test_id")
    private Long id;
    private Long tenantId;

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public Long getTenantId() {
        return tenantId;
    }

    public SuperEntity setTenantId(Long tenantId) {
        this.tenantId = tenantId;
        return this;
    }

    @Override
    protected Serializable pkVal() {
        return this.id;
    }
}

2.对于原生service层改造实现，默认实现baseMapper， baseMapper 默认实现了mapper的常规使用写法方式。

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IUserService {

	@Override
	public boolean deleteAll() {
		return retBool(baseMapper.deleteAll());
	}

	@Override
	public List<User> selectListBySQL() {
		return baseMapper.selectListBySQL();
	}

	@Override
	public List<User> selectListByWrapper(Wrapper wrapper) {
		return baseMapper.selectListByWrapper(wrapper);
		//baseMapper.selectma
	}
}

3.UserMapper 继承 superMapper，而superMapper继承baseMapper，你可以把一些公共的方法放在superMapper里，从而实现公用。

/**
 * User 表数据库控制层接口
 */
public interface UserMapper extends SuperMapper<User> {

    /**
     * 自定义注入方法
     */
    int deleteAll();

    @Select("select test_id as id, name, age, test_type from user")
    List<User> selectListBySQL();

    List<User> selectListByWrapper(@Param("ew") Wrapper wrapper);

}

最后的XML是一些不常用的sql可以写在这里给予调用。

<?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.baomidou.springboot.mapper.UserMapper">

    <!-- 通用查询结果列 -->
    <sql id="Base_Column_List">
        test_id AS testId, name, age, test_type AS testType, role, phone
    </sql>

    <delete id="deleteAll">
        DELETE FROM USER
    </delete>

    <select id="selectListByWrapper" resultType="com.baomidou.springboot.entity.User">
        SELECT * FROM USER
        <!-- 判断 wrapper 是否为空 emptyOfWhere -->
        <where>
            ${ew.sqlSegment}
        </where>
    </select>
</mapper>

可以看到他们的关系是一层一层过滤设计的，用了公共代码方便了公用，也达到了解耦合。