JavaEE MyBatis-Plus 基本CRUD

MyBatis-Plus中的基本CRUD在内置的BaseMapper中都已得到了实现，我们可以直接使用，接口如下：

public interface BaseMapper<T> extends Mapper<T> {
    int insert(T entity);

    int deleteById(Serializable id);

    int deleteById(T entity);

    int deleteByMap(@Param("cm") Map<String, Object> columnMap);

    int delete(@Param("ew") Wrapper<T> queryWrapper);

    int deleteBatchIds(@Param("coll") Collection<?> idList);

    int updateById(@Param("et") T entity);

    int update(@Param("et") T entity, @Param("ew") Wrapper<T> updateWrapper);

    T selectById(Serializable id);

    List<T> selectBatchIds(@Param("coll") Collection<? extends Serializable> idList);

    List<T> selectByMap(@Param("cm") Map<String, Object> columnMap);

    default T selectOne(@Param("ew") Wrapper<T> queryWrapper) {
        List<T> ts = this.selectList(queryWrapper);
        if (CollectionUtils.isNotEmpty(ts)) {
            if (ts.size() != 1) {
                throw ExceptionUtils.mpe("One record is expected, but the query result is multiple records", new Object[0]);
            } else {
                return ts.get(0);
            }
        } else {
            return null;
        }
    }

    default boolean exists(Wrapper<T> queryWrapper) {
        Long count = this.selectCount(queryWrapper);
        return null != count && count > 0L;
    }

    Long selectCount(@Param("ew") Wrapper<T> queryWrapper);

    List<T> selectList(@Param("ew") Wrapper<T> queryWrapper);

    List<Map<String, Object>> selectMaps(@Param("ew") Wrapper<T> queryWrapper);

    List<Object> selectObjs(@Param("ew") Wrapper<T> queryWrapper);

    <P extends IPage<T>> P selectPage(P page, @Param("ew") Wrapper<T> queryWrapper);

    <P extends IPage<Map<String, Object>>> P selectMapsPage(P page, @Param("ew") Wrapper<T> queryWrapper);
}

每个接口的应用例子：

@SpringBootTest
public class MybatisPlusTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelectList(){
    //selectList()根据MP内置的条件构造器查询一个list集合，null表示没有条件，即查询所有
        userMapper.selectList(null).forEach(System.out::println);
    }

    //int insert(T entity);
    @Test
    public void testInsert(){
        User user = new User(null, "张三", 23, "zhangsan@qcby.com");
        //INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? )
        int result = userMapper.insert(user);
        System.out.println("受影响行数："+result);
        //1475754982694199298
        System.out.println("id自动获取："+user.getId());
    }

    //int deleteById(Serializable id);
    //int deleteById(T entity);
    @Test
    public void testDeleteById(){
        //通过id删除用户信息
        //DELETE FROM user WHERE id=?
        int result = userMapper.deleteById(6L);
        System.out.println("id删除受影响行数："+result);

        //实体
        User user = new User(6L, "张三", 23, "zhangsan@qcby.com");
        result = userMapper.deleteById(user);
        System.out.println("实体删除受影响行数："+result);
    }

    //int deleteByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);
    @Test
    public void testDeleteByMap(){
        //根据map集合中所设置的条件删除记录
        //DELETE FROM user WHERE name = ? AND age = ?
        Map<String, Object> map = new HashMap<>();
        map.put("age", 23);
        map.put("name", "张三");
        int result = userMapper.deleteByMap(map);
        System.out.println("受影响行数："+result);
    }

    //int delete(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
    @Test
    public void testDeleteByQueryWrapper(){
        // 创建 QueryWrapper 对象
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        // 添加查询条件：age 等于指定值
        queryWrapper.eq("age", 23);
        int result = userMapper.delete(queryWrapper);
        System.out.println("受影响行数："+result);
    }

    //int deleteBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);
    @Test
    public void testDeleteByList(){
        List<Long> idList = Arrays.asList(5L, 6L);
        int result = userMapper.deleteBatchIds(idList);
        System.out.println("受影响行数："+result);
    }

    //int updateById(@Param(Constants.ENTITY) T entity);
    @Test
    public void testUpdateById(){
        User user = new User(4L, "admin", 22, null);
        //UPDATE user SET name=?, age=? WHERE id=?
        int result = userMapper.updateById(user);
        System.out.println("受影响行数："+result);
    }

    //int update(@Param(Constants.ENTITY) T entity, @Param(Constants.WRAPPER) Wrapper<T> updateWrapper);
    @Test
    public void testUpdateAgeByName(){
        User user = new User();
        user.setAge(26);

        // 创建 QueryWrapper 对象，构建更新条件
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("name", "张三");

        int result = userMapper.update(user , queryWrapper);
        System.out.println("受影响行数："+result);
    }

    //T selectById(Serializable id);
    @Test
    public void testSelectById(){
        User user = userMapper.selectById(1);
        System.out.println("aaaaaaaaaaaaaa"+user);
    }

    //List<T> selectBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);
    @Test
    public void testSelectByList(){
        List<Long> idList = Arrays.asList(1L, 2L, 3L);
        List<User> users = userMapper.selectBatchIds(idList);
        for (User user : users) {
            System.out.println(user);
        }
    }

    //List<T> selectByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);
    @Test
    public void testSelectByMap(){
        Map<String, Object> map = new HashMap<>();
        map.put("age", 26);
        map.put("name", "张三");
        List<User> users = userMapper.selectByMap(map);
        System.out.println(users);
    }

    //List<T> selectList(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
    @Test
    public void testSelectAllList(){
        //查询所有用户信息
        //SELECT id,name,age,email FROM user
        List<User> list = userMapper.selectList(null);
        list.forEach(System.out::println);
    }

    //default T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper){}
    @Test
    public void testSelectOne(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("name", "Tom");
        User user = userMapper.selectOne(queryWrapper);
        System.out.println(user);
    }

    //Long selectCount(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
    @Test
    public void testSelectCount(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("age", 26);
        Long numbers = userMapper.selectCount(queryWrapper);
        System.out.println("年龄为26的人数为："+numbers);
    }

    //List<Object> selectObjs(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
    @Test
    public void testselectObjs(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("age", 26);
        List<Object> ids = userMapper.selectObjs(queryWrapper);
        System.out.println("年龄为 26 的用户的第一个字段值列表:"+ids);
    }

    //<P extends IPage<T>> P selectPage(P page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
    @Test
    public void testSelectPage(){
        int currentPage = 2;
        int pageSize = 1;
        Page<User> page = new Page<>(currentPage, pageSize);
        // 创建 QueryWrapper 对象，构建查询条件
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("age", 26);

        IPage<User> userPage = userMapper.selectPage(page, queryWrapper);
        System.out.println("当前页码: " + userPage.getCurrent());
        System.out.println("每页记录数: " + userPage.getSize());
    }

    //<P extends IPage<Map<String, Object>>> P selectMapsPage(P page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
    @Test
    public void testSelectMapsPage(){
        int currentPage = 2;
        int pageSize = 1;
        Page<Map<String,Object>> page = new Page<>(currentPage, pageSize);
        // 创建 QueryWrapper 对象，构建查询条件
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("age", 26);

        IPage<Map<String, Object>> userPage = userMapper.selectMapsPage(page, queryWrapper);
        System.out.println("当前页码: " + userPage.getCurrent());
        System.out.println("每页记录数: " + userPage.getSize());
    }
}

注：

Wrapper类型的形参：条件构造器，可针 对于SQL语句设置不同的条件，若没有条件，则可以为该形参赋值null，即查询（删除/修改）所有数据