mybatis-plus CRUD常用方法

mybatisplus CRUD常用方法

查询

单个主键查询

//通过单个主键查询
Student student = studentMapper.selectById("1414125536583036929");
System.out.println(student);

多个主键查询

//通过多个主键查询
List<Student> students = studentMapper.selectBatchIds(Arrays.asList(
    "1414125536583036929", "1414132766216757250", "1414133065828499457"));
students.forEach(System.out::println);

map条件查询

HashMap<String, Object> map = new HashMap<>();
map.put("stuName","溪风");
map.put("stuAge",20);
//条件查询
List<Student> students = studentMapper.selectByMap(map);
students.forEach(System.out::println);
//生成的语句如下
//SELECT stuId,stuName,stuSex,stuAddress,stuAge,version,create_time AS createTime,update_time AS updateTime FROM student WHERE stuName = ? AND stuAge = ?	

分页查询

添加分页拦截

@Configuration
@MapperScan("com.lwp.study.dao")
@EnableTransactionManagement  //开启事务
public class MybatisPlusConfig {
    /**
     * 拦截器处理乐观锁和分页
     * @return
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        //添加分页拦截
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

代码实操

//参数1：第几页（1开始,传入0和1一样），参数2：每页显示数量
IPage<Student> page=new Page(2,2);
studentMapper.selectPage(page,null);
//获取分页后的记录数
page.getRecords().forEach(System.out::println);
//获取当前的页数
System.out.println(page.getCurrent());
//当前分页的总页数
System.out.println(page.getPages());
//获取当前每页显示多少条
System.out.println(page.getSize());
//当前满足条件总行数，既select count(*) from xx where xxx=xxx的值
System.out.println(page.getTotal());

删除

物理删除

//通过单个主键删除
int i = studentMapper.deleteById("1414204070248828930");
//通过多个主键删除
int i1 = studentMapper.deleteBatchIds(Arrays.asList(
    "1b0a2643082c63db81a182f144967d9f",
    "87107e33b1c2ac3486d19c4d3a18ce08"
));
//通过条件删除
HashMap<String, Object> map = new HashMap<>();
map.put("stuName","呵呵");
int i2 = studentMapper.deleteByMap(map);

逻辑删除

添加逻辑删除标识字段

@TableLogic  //标识逻辑删除注解，字段名和yaml配置的全局一致，可不需要该注解
private Integer deleted;

配置yaml

mybatis-plus:
  global-config:
    db-config:
      logic-delete-field: deleted  # 全局逻辑删除的实体字段名(since 3.3.0,配置后可以忽略不配置步骤2)
      logic-delete-value: 1 # 逻辑已删除值(默认为 1)
      logic-not-delete-value: 0 # 逻辑未删除值(默认为 0)

测试

//通过单个主键删除
int i = studentMapper.deleteById("1414133065828499457");
//实际执行的语句
//UPDATE student SET deleted=1 WHERE stuId=? AND deleted=0

注意点

插入: 不作限制
查找: 追加where条件过滤掉已删除数据,且使用 wrapper.entity 生成的where条件会忽略该字段
更新: 追加where条件防止更新到已删除数据,且使用 wrapper.entity 生成的where条件会忽略该字段
删除: 转变为 更新

例如：
删除: update user set deleted=1 where id = 1 and deleted=0
查找: select id,name,deleted from user where deleted=0

新增

//会根据传入的参数拼接动态sql进行新增
Student stu=new Student();
stu.setStuName("呵呵");
stu.setStuAge(18);
//返回受影响的行数
int resultValue = studentMapper.insert(stu);

修改

//会根据传入的参数拼接动态sql进行修改
Student student = studentMapper.selectById("1414125536583036929");
student.setStuName("魔尊");
studentMapper.updateById(student1);