MyBatis-Plus实用篇超完整教程

@Mapper
public interface UserMapper extends BaseMapper<User> {}

/**
  * UserService继承IService模板提供的基础功能 
  */
public interface UserService extends IService<User> {}

/**
  * ServiceImpl实现了IService，提供了IService中基础功能的实现 
  * 若ServiceImpl无法满足业务需求，则可以使用自定的UserService定义方法，并在实现类中实现
  */
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper,User> implements UserService{}

@Data
@TableName("t_user")
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

mybatis-plus:
  global-config:
    db-config:
      # 设置实体类所对应的表的统一前缀
      table-prefix: t_

@Data
public class User {
    @TableId(value = "tid")
    private Long uid;
    private String name;
    private Integer age;
    private String email;
}

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long uid;
    private String name;
    private Integer age;
    private String email;
}

//指定数据库字段名称
@TableField(value = "email")
private string mail

// 执行的sql语句就变成`关键字`，这样sql就不会报错了
@TableField(value = "`desc`")
private string desc

@TableField(exist = false)
private Boolean checked;

@TableField(select = false)
private String password;

// 实体注解-实现模糊查询
@TableField(condition = SqlCondition.LIKE)
private String name;
// 业务代码
User user = new User();
user.setName("张");
userService.lambdaQuery(user).list();
// 打印sql
SELECT id,user_name,age FROM user WHERE name LIKE CONCAT('%',?,'%')

userService.lambdaQuery().eq(User::getName,"张").list();

// 方式三：
// 实体注解-实现修改字段时候，前后添加“**” 其中 %s 会填充为字段
@TableField(update = "CONCAT('**',%s,'**')")
private String name;
// 业务代码
User user = new User();
user.setId(1);
user.setName("张三");
userService.updateById(user);
// 打印sql
UPDATE user SET name=CONCAT('**',name,'**') WHERE id=?

userService.lambdaQuery().eq(User::getName,"张").list();

// 实体字段注解
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;
// 枚举类
public enum FieldFill {
    /**
     * 默认不处理
     */
    DEFAULT,
    /**
     * 插入填充字段
     */
    INSERT,
    /**
     * 更新填充字段
     */
    UPDATE,
    /**
     * 插入和更新填充字段
     */
    INSERT_UPDATE
}

@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
	Date date = new Date();
    @Override
    public void insertFill(MetaObject metaObject) {
        this.strictInsertFill(metaObject, "createTime", Date.class, date);
        this.strictInsertFill(metaObject, "updateTime", Date.class, date);
    }
    @Override
    public void updateFill(MetaObject metaObject) {
        this.strictUpdateFill(metaObject, "updateTime", Date.class, date);
    }
}

public enum FieldStrategy {
    /**
     * 忽略判断，所有字段都进行更新和插入
     * 无论什么值，直接拼接，没有值，则拼接null
     */
    IGNORED,
    /**
     * 只更新和插入非NULL值
     * 相当于添加if判断，不为null才操作
     * <if test="columnProperty != null">column=#{columnProperty}</if>
     */
    NOT_NULL,
    /**
     * 只更新和插入非NULL值且非空字符串
     * 相当于添加if判断，不为null而且不是空字符串才操作
     * <if test="columnProperty != null and columnProperty!=''">column=#{columnProperty}</if>
     */
    NOT_EMPTY,
    /**
     * 默认NOT_NULL
     */
    DEFAULT,
    /**
     * 永远不进行更新和插入
     */
    NEVER
}

public void testDeleteById(){
    int result = userMapper.deleteById(1527472864163348482L);
    System.out.println(result > 0 ? "删除成功！" : "删除失败！");
    System.out.println("受影响的行数为：" + result);
}

public void testSelectList(){
    List<User> users = userMapper.selectList(null);
}

 /** 组装修改条件  将(年龄大于20并且用户名中包含有a)或邮箱为null的用户信息修改 **/
@Test
public void test01() {
    /*
        UPDATE t_user SET user_name=?, email=?
        age > ? AND user_name LIKE ? OR email IS NOT NULL
     */
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.gt("age", 20)
            .like("user_name", "a")
            .or()
            .isNotNull("email");
    User user = new User();
    user.setName("小明");
    user.setEmail("test@atguigu.com");
    int result = userMapper.update(user, queryWrapper);
    System.out.println("result = " + result);
}
/** 条件优先级  将用户名中包含a并且(年龄大于20或邮箱为null)的用户信息修改 **/
@Test
public void test02() {
    // lambda中条件优先级
    /*
        UPDATE t_user SET user_name=?, email=?
        WHERE user_name LIKE ? AND (age > ? OR email IS NULL)
     */
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.like("user_name", "a")
            .and(i -> i.gt("age", 20).or().isNull("email"));
    User user = new User();
    user.setName("小红");
    user.setEmail("test@atguigu.com");
    int result = userMapper.update(user, queryWrapper);
    System.out.println("result = " + result);
}

@Test
public void test3() {
    /*
        SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user
        WHERE user_name LIKE ? AND age <= ?
     */
    String username = "a";
    Integer ageBegin = null;
    Integer ageEnd = 30;
    //组装set子句
    LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
    //避免使用字符串表示字段，防止运行时错误
    queryWrapper.like(StringUtils.isNotBlank(username), User::getName, username)
            .gt(ageBegin != null, User::getAge, ageBegin)
            .le(ageEnd != null, User::getAge, ageEnd);
    List<User> list = userMapper.selectList(queryWrapper);
    list.forEach(System.out::println);
}
@Test
public void test4() {
    /*
        UPDATE t_user SET user_name=?,email=?
        WHERE user_name LIKE ? AND (age > ? OR email IS NULL)
     */
    LambdaUpdateWrapper<User> updateWrapper = new LambdaUpdateWrapper<>();
    updateWrapper.like(User::getName, "a")
            //lambda表达式内的逻辑优先运算
            .and(i -> i.gt(User::getAge, 20).or().isNull(User::getEmail)); 
    updateWrapper.set(User::getName, "小黑").set(User::getEmail, "abc@atguigu.com");
    int result = userMapper.update(null, updateWrapper);
    System.out.println("result = " + result);
}

 @Test
 public void test1(){
 	 // 单个查询，多个报错
     User user = userService.lambdaQuery().eq(User::getName, "Tom").one();
	 // 集合查询
     List<User> userList = userService.lambdaQuery().like(User::getName, "J").eq(User::getAge,20).list();
     // 记录数查询
     Integer count = userService.lambdaQuery().like(User::getAge, 20).select(User::getName, User::getAge).count();
  }

  @Test
  public void test2() {
	  // set修改某些属性
      userService.lambdaUpdate().eq(User::getName, "Tom").set(User::getId, 110).set(User::getAge, 15).update();
      // 修改整个对象
      User user = new User();
      user.setId(110L);
      user.setAge(15);
      userService.lambdaUpdate().eq(User::getName, "Tom").update(user);
      // 根据名称删除
      userService.lambdaUpdate().eq(User::getName, "Jack").remove();
   }

@Test
void testDbGet() {
    User user = Db.getById(1L, User.class);
    System.out.println(user);
}
​
@Test
void testDbList() {
    // 利用Db实现复杂条件查询
    List<User> list = Db.lambdaQuery(User.class)
            .like(User::getUsername, "o")
            .ge(User::getBalance, 1000)
            .list();
}
​
@Test
void testDbUpdate() {
    Db.lambdaUpdate(User.class)
            .set(User::getBalance, 2000)
            .eq(User::getUsername, "Rose");
}

/**
* 根据年龄查询用户列表，分页显示
*/
Page<User> selectPageVo(@Param("page") Page<User> page,@Param("age") Integer age);

<select id="selectPageVo" resultType="User">
    select id,username as name,age,email from t_user where age > #{age}
</select>

@Test
public void testSelectPageVo(){ //设置分页参数
    Page<User> page = new Page<>(1, 5); 
    userMapper.selectPageVo(page, 20);
    //获取分页数据
    List<User> list = page.getRecords(); 
    list.forEach(System.out::println); 
    System.out.println("当前页:"+page.getCurrent()); 
    System.out.println("每页显示的条数:"+page.getSize()); 
    System.out.println("总记录数:"+page.getTotal()); 
    System.out.println("总页数:"+page.getPages()); 
    System.out.println("是否有上一页:"+page.hasPrevious()); 
    System.out.println("是否有下一页:"+page.hasNext());
}

@Select("select * from student where age = #{age} and user_name = #{userName}")
Student getStudent( @Param("age") Integer age, @Param("userName") String userName);

// 单表查询
@Select("select * from student ${ew.customSqlSegment}")
Student getStudentById( @Param("ew") QueryWrapper<Student> wrapper);
// 多表查询
@Select("SELECT u.* FROM student u INNER JOIN address a ON u.id = a.student_id ${ew.customSqlSegment}")
List<Student> queryStudentListByWrapper(@Param("page") Page<Student> page, @Param("ew")QueryWrapper<User> wrapper);

// 情况1：如果查询条件中有address的字段，比如模糊查询地址名称
// 情况2：如果查询条件的字段，两个表都有，这里会有问题
// 自动分页的查询count(*)时候，就会抛出以上异常
@Select("SELECT u.* FROM student u LEFT JOIN address a ON u.id = a.student_id ${ew.customSqlSegment}")
List<Student> queryStudentListByWrapper(@Param("page") Page<Student> page, @Param("ew")QueryWrapper<User> wrapper);

@Select("SELECT * FROM (SELECT u.* FROM student u LEFT JOIN address a ON u.id = a.student_id) as result ${ew.customSqlSegment}")
List<Student> queryStudentListByWrapper(@Param("page") Page<Student> page, @Param("ew")QueryWrapper<User> wrapper);

// 分页查询
Page<UserEntity> userPage = super.lambdaQuery().page(new Page<>(request.getCurrent(), request.getSize()));
// entity转换为vo
IPage<UserVO> infoResPage = userPage.convert(item -> Convert.convert(UserVO.class, item));

// 方式一
List<String> nameList = SimpleQuery.list(
        new LambdaQueryWrapper<Student>().like(Student::getUserName, "张"),
        Student::getUserName
);
// 方式二
List<Student> list = studentService.list();
List<String> nameList2 = SimpleQuery.list2List(list, Student::getUserName);

List<String> nameList = SimpleQuery.list(
        new LambdaQueryWrapper<Student>().like(Student::getUserName, "李"),
        Student::getUserName,
        new Consumer<Student>() {
            @Override
            public void accept(Student student) {
                student.setUserName("**"+student.getUserName()+"**");
            }
        }
);

Map<String, Integer> map = SimpleQuery.map(
        new LambdaQueryWrapper<>(), 
        Student::getUserName, 
        Student::getAge
);

Map<String, List<Student>> group = SimpleQuery.group(
        new LambdaQueryWrapper<Student>(), 
        Student::getUserName
);

@Data
@TableName(value = "student")
public class Student extends Model<Student> {
    /**
     * 主键id
     */
    private Long id;
    /**
     * 姓名
     */
    private String userName;
    /**
     * 年龄
     */
    private Integer age;
}
@Test
void activeRecordAddQ{
	Student student = new Student();
	student.setUserName("李四");
	student.setAge(12);
	student.insert();
}

@Configuration
public class MybatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        //注意使用哪种数据库
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}