mybatis-plus 使用 mybatis-plus 使用

官网: https://mp.baomidou.com/guide/

#引入依赖

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.22</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.1</version>
        </dependency>

#控制台打印sql

方法一

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl #开启log日志

方法二

logging:
  level:
    com.chz.mapper: debug

#使用

查询 select

• 通过查询, 查询所有

    @Test 
    public void tests1() {
        List<Employee> employees = employeeDao.selectList(null);
        employees.forEach(System.out::println);

    }

• 按id查询

    @Test 
    public void tests2() {
        Employee employee = employeeDao.selectById(13);
        System.out.println(employee);
    }

• 查询一个

    @Test 
    public void tests3() {
        QueryWrapper<Employee> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("name","zs")
        Employee employee = employeeDao.selectOne(queryWrapper);
        System.out.println(employee);
    }

• 使用map作为条件查询

    @Test 
    public void tests4() {
        HashMap<String, Object> map = new HashMap<>();
        //key对应字段名, value对应字段值
        map.put("last_name", "z3f");
        List<Employee> employees = employeeDao.selectByMap(map);
        System.out.println(employees);
    }

• 一条记录对应一个map

    @Test 
    public void tests5() {
        QueryWrapper<Employee> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("gender", 1);
        List<Map<String, Object>> maps = employeeDao.selectMaps(queryWrapper);
        maps.forEach(System.out::println);
    }

• 查询多个id

    @Test
    public void test5() {
        List<Integer> list = Arrays.asList(1, 2, 3);
        List<Employee> employees = employeeDao.selectBatchIds(list);
        employees.forEach(System.out::println);
    }

• 分页查询

  必须配置分页插件

	@Test 
    public void test6() {
        Page<Employee> page = new Page<>(0, 2);
        //queryWrapper可以是null
        IPage<Employee> employeeIPage = employeeDao.selectPage(page, null);
        //要通过getRecords()拿到结果
        System.out.println(employeeIPage.getRecords());
    }

​ 分页插件

    @Bean
    public PaginationInterceptor paginationInterceptor() {
        PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
        return paginationInterceptor;
    }

• 条加查询

    @Test
    public void test7() {
        QueryWrapper<Employee> wrapper = new QueryWrapper<Employee>().select("age", "gender").eq("last_name", "z3f");
        System.out.println(employeeDao.selectOne(wrapper));
    }

• 排序

 	@Test
    public void test8() {
        List<Employee> age = employeeDao.selectList(new QueryWrapper<Employee>().
                orderBy(true, true, "age"));
        System.out.println(age);
    }

• 查询列数

    @Test
    public void test9() {
        //查询带条件的count
        Integer integer = employeeDao.selectCount(new QueryWrapper<Employee>().eq("gender", 1));
        //查询所有的count
        Integer integer1 = employeeDao.selectCount(null);
    }

插入 insert

    @Test
    public void test10() {
        Employee employee = new Employee();
        employee.setLastName("Oka").setEmail("oka@").setGender(2).setAge(3).setSalary(1000D);
        employee.setLastName("z3").setGender(1);
        //insert显示sql当前赋过值的字段
        int num = employeeDao.insert(employee);
        //mp直接会回显主键
        //mybatis需要配置useGeneratedKeys,keyProperty才能回显主键
        Integer id = employee.getId();
        System.out.println("生效行数:" + num + "	主键值:" + id);
    }

更新 upadate

    @Test
    public void test11() {
        Employee employee = new Employee();
        //如果不想修改某个字段,不赋值即可
        employee.setId(13).setLastName("z3f").setAge(33);
        int i = employeeDao.updateById(employee);
        System.out.println("生效行数:" + i);
    }

支持lambda表达式

@Test
public void tests11() {
    UpdateWrapper<Employee> updateWrapper = new UpdateWrapper<>();
    //where条件
    updateWrapper.lambda()
            .eq(Employee::getLastName, "Black")
            .eq(Employee::getGender, 1);
    Employee employee = new Employee();
    //想要修改的值
    employee.setEmail("black123@qq");
    employeeDao.update(employee, updateWrapper);
}

删除 delete

    @Test 
    public void test12() {
        int i = employeeDao.deleteById(6);
        System.out.println("生效行数:" + i);
    }

    @Test //deleteByMap
    public void test13() {
        HashMap<String, Object> map = new HashMap<>();
        //封装条件
        map.put("age", 22);
        employeeDao.deleteByMap(map);
    }

#条件

条件	描述
ge	great equal 大于等于
gt	great than 大于
le	less equal小于等于
lt	less than小于
isNull	空值
isNotNull	不为空值
eq	equal 等于
ne	not equal 不等于
between	包含
notBetween	不在区间内
allEq	所有相同
like	模糊查询
notLike
in	包含
notIn	不包含
exists	存在
notExists	不存在
or	不调用or默认使用and
and	默认使用and拼接
orderBy	按指定方式排序
orderByDesc	降序
orderByAsc	升序
last	直接拼接到sql的最后, 有sql注入的风险