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

悠悠 2024-03-25 21:19 40阅读 0赞

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#### 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> {
        
    }

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

##### 3.2.1、新增 #####

![image-20230306112657281][]

1.  新增一条记录
    
        @Resource
        private UserService userService;
        @Test
        public 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);
        }
    
    ![image-20230306113912564][]
2.  批量操作
    
        @Resource
        private UserService userService;
        @Test
        public 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);
        }
    
    ![image-20230306114731705][]
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);
        }
    
    ![image-20230306114954565][]

##### 3.2.2、查询 #####

###### 1、单行查询 ######

![image-20230306123815377][]

1.  根据id查询
    
        @Test
        public void testServcie(){
              
            User user = userService.getById(1);
            System.out.println(user);
        }
    
    ![image-20230306124359229][]

###### 2、多行查询 ######

![image-20230306125349084][]

1.  根据ID批量查询
    
        @Test
        public void testServcie(){
              
            List<Integer> list = Arrays.asList(1, 2, 3);
            List<User> users = userService.listByIds(list);
            users.forEach(System.out::println);
        }
    
    ![image-20230306124647126][]
2.  查询所有
    
        @Test
        public void testServcie(){
              
            //返回list
         	List<User> list = userService.list();
            System.out.println(list);
            //返回map
            List<Map<String, Object>> maps = userService.listMaps();
            System.out.println(maps);
        
            List<Object> objects = userService.listObjs();
            System.out.println(objects);
        }
    
    ![image-20230306125554522][]

##### 3.2.3、删除 #####

![image-20230306115936178][]

1.  根据id删除
    
        @Test
        public void testServcie(){
              
            boolean b = userService.removeById(21);
        }
    
    ![image-20230306120252382][]
2.  根据实体的id删除
    
        @Test
        public void testServcie(){
              
            User user = userService.getById(22);
            boolean b = userService.removeById(user);
        }
    
    ![image-20230306120455791][]
3.  批量删除
    
        @Test
        public void testServcie(){
              
            List<Integer> list = Arrays.asList(23, 24, 25);
            boolean b = userService.removeByIds(list);
        }
    
    ![image-20230306120634151][]
4.  根据Map条件删除
    
        @Test
        public 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);
        }
    
    ![image-20230306120900709][]

##### 3.2.4、修改 #####

![image-20230306121504141][]

1.  根据ID修改
    
        @Test
        public void testServcie(){
              
            User user = userService.getById(27);
            user.setUsername("修改1");
            user.setPassword("213123");
            boolean b = userService.updateById(user);
        }
    
    ![image-20230306121740680][]
2.  批量修改
    
        @Test
        public 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);
        }
    
    ![image-20230306122251212][]

##### 3.2.5、修改或更新 #####

![image-20230306115225586][]

##### 3.2.6、分页 #####

![image-20230306125813443][]

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 10
        protected long size = 10;
        //当前页，默认1
        protected long current = 1;
        // 排序字段信息
        @Setter
        protected List<OrderItem> orders = new ArrayList<>();
        //自动优化 COUNT SQL
        protected 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
        
            @Bean
            public MybatisPlusInterceptor mybatisPlusInterceptor() {
                    
                MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
                interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
                return interceptor;
            }
 *  分页查询数据
    
        @Test
        public 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);
        }
    
    ![image-20230306133721050][]

##### 3.2.7、查询记录数 #####

![image-20230306133903188][]

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

![image-20230306134002194][]

[Java]: https://blog.csdn.net/yuandfeng/article/details/114333525
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