Mybatis-Plus(Service CRUD 接口)(+24篇MyBatis-Plus文章)

亦凉 2023-09-28 08:04 50阅读 0赞

<table> 
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   <td>MyBatis-Plus</td> 
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</table>

--------------------

### 文章目录 ###

*   *  1、简介
     *  2、 Save
     *  3、 SaveOrUpdate
     *  4、 Remove
     *  5、 Update
     *  6、 Get
     *  7、 List
     *  8、 Page
     *  9、 Count
     *  10、 Chain
     *   *  10.1 查询
         *  10.2 更新

--------------------

## 1、简介 ##

说明:

*  通用 Service CRUD 封装IService接口，进一步封装 CRUD 采用 `get 查询单行` `remove 删除` `list 查询集合` `page 分页` 前缀命名方式区分 `Mapper` 层避免混淆，
 *  泛型 `T` 为任意实体对象
 *  建议如果存在自定义通用 Service 方法的可能，请创建自己的 `IBaseService` 继承 `Mybatis-Plus` 提供的基类
 *  对象 `Wrapper` 为 条件构造器

[官网地址:][Link 1]

https://baomidou.com/pages/49cc81/#service-crud-%E6%8E%A5%E5%8F%A3

## 2、 Save ##

// 插入一条记录（选择字段，策略插入）
    boolean save(T entity);
    // 插入（批量）
    boolean saveBatch(Collection<T> entityList);
    // 插入（批量）
    boolean saveBatch(Collection<T> entityList, int batchSize);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">T</td> 
   <td align="center">entity</td> 
   <td align="center">实体对象</td> 
  </tr> 
  <tr> 
   <td align="center">Collection</td> 
   <td align="center">entityList</td> 
   <td align="center">实体对象集合</td> 
  </tr> 
  <tr> 
   <td align="center">int</td> 
   <td align="center">batchSize</td> 
   <td align="center">插入批次数量</td> 
  </tr> 
 </tbody> 
</table>

案例：

MyUser user01 = MyUser.builder().name("张三").age(12).address("北京").build();
    MyUser user02 = MyUser.builder().name("李四").age(26).address("上海").build();
    ArrayList<MyUser> myUsers = new ArrayList<>();
    myUsers.add(user01);
    myUsers.add(user02);
    //  插入一条记录（选择字段，策略插入）
    boolean save = myUserService.save(user01);
    // 插入（批量）
    boolean b = myUserService.saveBatch(myUsers);
    // 插入（批量）（batchSize）插入批次数量
    boolean c = myUserService.saveBatch(myUsers, 1);

## 3、 SaveOrUpdate ##

// TableId 注解存在更新记录，否插入一条记录
    boolean saveOrUpdate(T entity);
    // 根据updateWrapper尝试更新，否继续执行saveOrUpdate(T)方法
    boolean saveOrUpdate(T entity, Wrapper<T> updateWrapper);
    // 批量修改插入
    boolean saveOrUpdateBatch(Collection<T> entityList);
    // 批量修改插入
    boolean saveOrUpdateBatch(Collection<T> entityList, int batchSize);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">T</td> 
   <td align="center">entity</td> 
   <td align="center">实体对象</td> 
  </tr> 
  <tr> 
   <td align="center">Wrapper</td> 
   <td align="center">updateWrapper</td> 
   <td align="center">实体对象封装操作类 UpdateWrapper</td> 
  </tr> 
  <tr> 
   <td align="center">Collection</td> 
   <td align="center">entityList</td> 
   <td align="center">实体对象集合</td> 
  </tr> 
  <tr> 
   <td align="center">int</td> 
   <td align="center">batchSize</td> 
   <td align="center">插入批次数量</td> 
  </tr> 
 </tbody> 
</table>

案例：

## 4、 Remove ##

// 根据 entity 条件，删除记录
    boolean remove(Wrapper<T> queryWrapper);
    // 根据 ID 删除
    boolean removeById(Serializable id);
    // 根据 columnMap 条件，删除记录
    boolean removeByMap(Map<String, Object> columnMap);
    // 删除（根据ID 批量删除）
    boolean removeByIds(Collection<? extends Serializable> idList);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">Wrapper</td> 
   <td align="center">queryWrapper</td> 
   <td align="center">实体包装类 QueryWrapper</td> 
  </tr> 
  <tr> 
   <td align="center">Serializable</td> 
   <td align="center">id</td> 
   <td align="center">主键 ID</td> 
  </tr> 
  <tr> 
   <td align="center">Map&lt;String, Object&gt;</td> 
   <td align="center">columnMap</td> 
   <td align="center">表字段 map 对象</td> 
  </tr> 
  <tr> 
   <td align="center">Collection&lt;? extends Serializable&gt;</td> 
   <td align="center">idList</td> 
   <td align="center">主键 ID 列表</td> 
  </tr> 
 </tbody> 
</table>

案例：

MyUser user01 = MyUser.builder().name("张三").age(12).address("北京").build();
    MyUser user02 = MyUser.builder().name("李四").age(26).address("上海").build();
    ArrayList<MyUser> myUsers = new ArrayList<>();
    myUsers.add(user01);
    myUsers.add(user02);
    
    LambdaQueryWrapper<MyUser> eq = new QueryWrapper<MyUser>().lambda().eq(MyUser::getAge, 1);
    boolean remove = myUserService.remove(eq);
    boolean b = myUserService.removeById(1);
    HashMap<String, Object> removeMap = new HashMap<>();
    removeMap.put("age", 1);
    
    boolean b1 = myUserService.removeByMap(removeMap);
    ArrayList<Integer> ids = new ArrayList<>();
    ids.add(1);
    ids.add(2);
    boolean b2 = myUserService.removeByIds(ids);

## 5、 Update ##

// 根据 UpdateWrapper 条件，更新记录 需要设置sqlset
    boolean update(Wrapper<T> updateWrapper);
    // 根据 whereWrapper 条件，更新记录
    boolean update(T updateEntity, Wrapper<T> whereWrapper);
    // 根据 ID 选择修改
    boolean updateById(T entity);
    // 根据ID 批量更新
    boolean updateBatchById(Collection<T> entityList);
    // 根据ID 批量更新
    boolean updateBatchById(Collection<T> entityList, int batchSize);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">Wrapper</td> 
   <td align="center">updateWrapper</td> 
   <td align="center">实体对象封装操作类 UpdateWrapper</td> 
  </tr> 
  <tr> 
   <td align="center">T</td> 
   <td align="center">entity</td> 
   <td align="center">实体对象</td> 
  </tr> 
  <tr> 
   <td align="center">Collection</td> 
   <td align="center">entityList</td> 
   <td align="center">实体对象集合</td> 
  </tr> 
  <tr> 
   <td align="center">int</td> 
   <td align="center">batchSize</td> 
   <td align="center">更新批次数量</td> 
  </tr> 
 </tbody> 
</table>

案例：

LambdaUpdateWrapper<MyUser> eq = new UpdateWrapper<MyUser>().lambda().eq(MyUser::getAge, 1);
    MyUser myUser = MyUser.builder().id(18L).name("李四").age(12).build();
    // 根据 UpdateWrapper 条件，更新记录 需要设置sqlset
    boolean update = myUserService.update(eq);
    boolean update1 = myUserService.update(myUser, eq);
    
    MyUser myUser01 = MyUser.builder().id(18L).name("李四").age(12).build();
    MyUser myUser02 = MyUser.builder().id(18L).name("李四").age(12).build();
    ArrayList<MyUser> myUsers = new ArrayList<>();
    myUsers.add(myUser01);
    myUsers.add(myUser02);
    // 根据 ID 选择修改
    boolean b = myUserService.updateById(myUser01);
    // 根据ID 批量更新
    boolean b1 = myUserService.updateBatchById(myUsers);
    boolean b2 = myUserService.updateBatchById(myUsers,1);

## 6、 Get ##

// 根据 ID 查询
    T getById(Serializable id);
    // 根据 Wrapper，查询一条记录。结果集，如果是多个会抛出异常，随机取一条加上限制条件 wrapper.last("LIMIT 1")
    T getOne(Wrapper<T> queryWrapper);
    // 根据 Wrapper，查询一条记录
    T getOne(Wrapper<T> queryWrapper, boolean throwEx);
    // 根据 Wrapper，查询一条记录
    Map<String, Object> getMap(Wrapper<T> queryWrapper);
    // 根据 Wrapper，查询一条记录
    <V> V getObj(Wrapper<T> queryWrapper, Function<? super Object, V> mapper);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">Serializable</td> 
   <td align="center">id</td> 
   <td align="center">主键 ID</td> 
  </tr> 
  <tr> 
   <td align="center">Wrapper</td> 
   <td align="center">queryWrapper</td> 
   <td align="center">实体对象封装操作类 QueryWrapper</td> 
  </tr> 
  <tr> 
   <td align="center">boolean</td> 
   <td align="center">throwEx</td> 
   <td align="center">有多个 result 是否抛出异常</td> 
  </tr> 
  <tr> 
   <td align="center">T</td> 
   <td align="center">entity</td> 
   <td align="center">实体对象</td> 
  </tr> 
  <tr> 
   <td align="center">Function&lt;? super Object, V&gt;</td> 
   <td align="center">mapper</td> 
   <td align="center">转换函数</td> 
  </tr> 
 </tbody> 
</table>

案例：

MyUser byId = myUserService.getById(1);
    LambdaQueryWrapper<MyUser> eq = new QueryWrapper<MyUser>().lambda().eq(MyUser::getAge, 1);
    MyUser one = myUserService.getOne(eq);
    MyUser one1 = myUserService.getOne(eq, false);
    
    Map<String, Object> map = myUserService.getMap(eq);
    String obj1 = myUserService.getObj(eq, Object::toString);

## 7、 List ##

// 查询所有
    List<T> list();
    // 查询列表
    List<T> list(Wrapper<T> queryWrapper);
    // 查询（根据ID 批量查询）
    Collection<T> listByIds(Collection<? extends Serializable> idList);
    
    // 查询（根据 columnMap 条件）
    Collection<T> listByMap(Map<String, Object> columnMap);
    // 查询所有列表
    List<Map<String, Object>> listMaps();
    // 查询列表
    List<Map<String, Object>> listMaps(Wrapper<T> queryWrapper);
    
    // 查询全部记录
    List<Object> listObjs();
    // 查询全部记录
    <V> List<V> listObjs(Function<? super Object, V> mapper);
    // 根据 Wrapper 条件，查询全部记录
    List<Object> listObjs(Wrapper<T> queryWrapper);
    // 根据 Wrapper 条件，查询全部记录
    <V> List<V> listObjs(Wrapper<T> queryWrapper, Function<? super Object, V> mapper);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">Wrapper</td> 
   <td align="center">queryWrapper</td> 
   <td align="center">实体对象封装操作类 QueryWrapper</td> 
  </tr> 
  <tr> 
   <td align="center">Collection&lt;? extends Serializable&gt;</td> 
   <td align="center">idList</td> 
   <td align="center">主键 ID 列表</td> 
  </tr> 
  <tr> 
   <td align="center">Map&lt;String, Object&gt;</td> 
   <td align="center">columnMap</td> 
   <td align="center">表字段 map 对象</td> 
  </tr> 
  <tr> 
   <td align="center">Function&lt;? super Object, V&gt;</td> 
   <td align="center">mapper</td> 
   <td align="center">转换函数</td> 
  </tr> 
 </tbody> 
</table>

案例：

LambdaQueryWrapper<MyUser> eq = new QueryWrapper<MyUser>().lambda().eq(MyUser::getAge, 1);
    ArrayList<Integer> ids = new ArrayList<>();
    ids.add(1);
    List<MyUser> list = myUserService.list();
    List<MyUser> list1 = myUserService.list(eq);
    Collection<MyUser> myUsers = myUserService.listByIds(ids);
    
    HashMap<String, Object> eqMap = new HashMap<>();
    eqMap.put("age", 1);
    Collection<MyUser> myUsers1 = myUserService.listByMap(eqMap);
    List<Map<String, Object>> maps = myUserService.listMaps();
    List<Map<String, Object>> maps1 = myUserService.listMaps(eq);
    
    List<Object> objects = myUserService.listObjs();
    List<Object> objects1 = myUserService.listObjs(eq);
    List<String> strings1 = myUserService.listObjs(Objects::toString);
    List<String> strings = myUserService.listObjs(eq, Object::toString);

## 8、 Page ##

// 无条件分页查询
    IPage<T> page(IPage<T> page);
    // 条件分页查询
    IPage<T> page(IPage<T> page, Wrapper<T> queryWrapper);
    // 无条件分页查询
    IPage<Map<String, Object>> pageMaps(IPage<T> page);
    // 条件分页查询
    IPage<Map<String, Object>> pageMaps(IPage<T> page, Wrapper<T> queryWrapper);

参数说明

<table> 
 <thead> 
  <tr> 
   <th align="center">类型</th> 
   <th align="center">参数名</th> 
   <th align="center">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">IPage</td> 
   <td align="center">page</td> 
   <td align="center">翻页对象</td> 
  </tr> 
  <tr> 
   <td align="center">Wrapper</td> 
   <td align="center">queryWrapper</td> 
   <td align="center">实体对象封装操作类 QueryWrapper</td> 
  </tr> 
 </tbody> 
</table>

案例：

Page<MyUser> page = new Page<>(1, 2);
    LambdaQueryWrapper<MyUser> eq = new QueryWrapper<MyUser>().lambda().eq(MyUser::getAge, 1);
    // 无条件分页查询
    IPage<MyUser> userIPagepage = myUserService.page(page);
    // 条件分页查询
    IPage<MyUser> page1 = myUserService.page(page, eq);
    // 无条件分页查询
    IPage<Map<String, Object>> mapIPage = myUserService.pageMaps(page);
    // 条件分页查询
    IPage<Map<String, Object>> mapIPage1 = myUserService.pageMaps(page, eq);

## 9、 Count ##

// 查询总记录数
    int count();
    // 根据 Wrapper 条件，查询总记录数
    int count(Wrapper<T> queryWrapper);

参数说明

案例：

int count = myUserService.count();
    LambdaQueryWrapper<MyUser> eq = new LambdaQueryWrapper<MyUser>().eq(MyUser::getAge, 1);
    int count1 = myUserService.count(eq);

## 10、 Chain ##

### 10.1 查询 ###

// 链式查询 普通
    QueryChainWrapper<T> query();
    // 链式查询 lambda 式。注意：不支持 Kotlin
    LambdaQueryChainWrapper<T> lambdaQuery();
    
    // 示例：
    query().eq("column", value).one();
    lambdaQuery().eq(Entity::getId, value).list();

案例(在server中)：

MyUser age = query().eq("age", 1).one();
    List<MyUser> list = lambdaQuery().eq(MyUser::getAge, 1).list();

### 10.2 更新 ###

// 链式更改 普通
    UpdateChainWrapper<T> update();
    // 链式更改 lambda 式。注意：不支持 Kotlin
    LambdaUpdateChainWrapper<T> lambdaUpdate();
    
    // 示例：
    update().eq("column", value).remove();
    lambdaUpdate().eq(Entity::getId, value).update(entity);

案例:

update().eq("age", 1).remove();
    
    MyUser myUser = new MyUser();
    boolean update2 = lambdaUpdate().eq(MyUser::getAge, 12).update(myUser);

[Link 1]: https://baomidou.com/pages/49cc81/#service-crud-%E6%8E%A5%E5%8F%A3