IService接口和ServiceImpl实现类（Mybatis-Plus对service层的封装）

Java知识点总结：想看的可以从这里进入

目录

• • • 3.2、IService接口
    • • 3.2.1、新增
      • 3.2.2、查询
      • • 1、单行查询
        • 2、多行查询
      • 3.2.3、删除
      • 3.2.4、修改
      • 3.2.5、修改或更新
      • 3.2.6、分页
      • 3.2.7、查询记录数

3.2、IService接口

BaseMapper 是用在Mapper中，而IService是在Service层使用的封装接口，它进一步封装 CRUD 。为了和BaseMapper 中方法进行区分，它采用了不同的前缀：

1. get 查询单行
2. remove 删除
3. list 查询集合
4. page 分页
5. save新增
6. update修改

IService还有一个实现的类ServiceImpl，在使用使用时分别对应service接口和impl实现类。

public interface UserService extends IService<User> {}

@Servicepublic class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {}

3.2.1、新增

1. 新增一条记录

   @Resourceprivate UserService userService;@Testpublic void testServcie(){User user= new User();user.setUsername("service增加");user.setPassword("12321");boolean save = userService.save(user);System.out.println("是否成功："+save);}

   

2. 批量操作

   @Resourceprivate UserService userService;@Testpublic void testServcie(){List<User> users = new ArrayList<>();User user1 = new User("批量增加1","123");users.add(user1);User user2 = new User("批量增加2","123");users.add(user2);User user3 = new User("批量增加3","123");users.add(user3);User user4 = new User("批量增加4","123");users.add(user4);User user5 = new User("批量增加5","123");users.add(user5);boolean save = userService.saveBatch(users);System.out.println("是否成功："+save);}

   

3. 设置批次数量

   public void testServcie(){List<User> users = new ArrayList<>();User user1 = new User("指定数量批量增加6","123");users.add(user1);User user2 = new User("指定数量批量增加7","123");users.add(user2);User user3 = new User("指定数量批量增加8","123");users.add(user3);User user4 = new User("指定数量批量增加9","123");users.add(user4);User user5 = new User("指定数量批量增加10","123");users.add(user5);boolean save = userService.saveBatch(users,2);System.out.println("是否成功："+save);}

   

3.2.2、查询

1、单行查询

1. 根据id查询

   @Testpublic void testServcie(){User user = userService.getById(1);System.out.println(user);}

   

2、多行查询

1. 根据ID批量查询

   @Testpublic void testServcie(){List<Integer> list = Arrays.asList(1, 2, 3);List<User> users = userService.listByIds(list);users.forEach(System.out::println);}

   

2. 查询所有

   @Testpublic void testServcie(){//返回list List<User> list = userService.list();System.out.println(list);//返回mapList<Map<String, Object>> maps = userService.listMaps();System.out.println(maps);List<Object> objects = userService.listObjs();System.out.println(objects);}

   

3.2.3、删除

1. 根据id删除

   @Testpublic void testServcie(){boolean b = userService.removeById(21);}

   

2. 根据实体的id删除

   @Testpublic void testServcie(){User user = userService.getById(22);boolean b = userService.removeById(user);}

   

3. 批量删除

   @Testpublic void testServcie(){List<Integer> list = Arrays.asList(23, 24, 25);boolean b = userService.removeByIds(list);}

   

4. 根据Map条件删除

   @Testpublic void testServcie(){Map<String ,Object> map = new HashMap<>();map.put("username","批量增加5");map.put("password","123");boolean b = userService.removeByMap(map);}

   

3.2.4、修改

1. 根据ID修改

   @Testpublic void testServcie(){User user = userService.getById(27);user.setUsername("修改1");user.setPassword("213123");boolean b = userService.updateById(user);}

   

2. 批量修改

   @Testpublic void testServcie(){List<Integer> list = Arrays.asList(28, 29, 30);List<User> users = userService.listByIds(list);users.forEach(user -> {user.setUsername("批量修改");});boolean b = userService.updateBatchById(users);}

   

3.2.5、修改或更新

3.2.6、分页

在Mybatis-plus中提供了有关分页的接口和实现类 IPage 和 Page

public class Page<T> implements IPage<T> {private static final long serialVersionUID = 8545996863226528798L;//用来存放查询出来的数据protected List<T> records = Collections.emptyList();//返回的数据总数protected long total = 0;// 每页显示条数，默认 10protected long size = 10;//当前页，默认1protected long current = 1;// 排序字段信息@Setterprotected List<OrderItem> orders = new ArrayList<>();//自动优化 COUNT SQLprotected boolean optimizeCountSql = true;// 是否进行 count 查询protected boolean searchCount = true;public Page() {}/** * 有参构造函数 * @param current 当前页 * @param size每页显示条数 */public Page(long current, long size) {this(current, size, 0);}public Page(long current, long size, long total) {this(current, size, total, true);}public Page(long current, long size, boolean searchCount) {this(current, size, 0, searchCount);}public Page(long current, long size, long total, boolean searchCount) {if (current > 1) {this.current = current;}this.size = size;this.total = total;this.searchCount = searchCount;}//是否存在上一页public boolean hasPrevious() {return this.current > 1;}//是否存在下一页public boolean hasNext() {return this.current < this.getPages();}..........}

• 配置

  • 使用Spring时，在Spring的配置文件中先配置mybatis-plus内置的分页插件

    <bean id="paginationInnerInterceptor" class="com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor"/><bean id="mybatisPlusInterceptor" class="com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor"><property name="interceptors" ><list><ref bean="paginationInnerInterceptor"/></list></property></bean><bean class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean"><property name="dataSource" ref="dataSource"/><property name="configLocation" value="classpath:mybatis-config.xml"/><property name="mapperLocations" value="classpath:mapping/*.xml"/><property name="plugins"><array><ref bean="mybatisPlusInterceptor"/></array></property></bean>

  • 使用SpringBoot时配置时，在配置类中配置

    @Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor() {MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));return interceptor;}

• 分页查询数据

  @Testpublic void testServcie(){Page<User> page = userService.page(new Page<>(1,5));System.out.println("总数据："+page.getTotal());List<User> users = page.getRecords();users.forEach(System.out::println);}

  

3.2.7、查询记录数

@Testpublic void testServcie(){long count = userService.count();System.out.println(count);}