service层接口怎么写_java中service层的作用

Java知识点总结：想看的可以从这里进入

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

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); } 

   

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); } 

   

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

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

   

2、多行查询

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); } 

   

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); } 

   

3.2.3、删除

1. 根据id删除

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

   

2. 根据实体的id删除

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

   

3. 批量删除

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

   

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); } 

   

3.2.4、修改

1. 根据ID修改

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

   

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); } 

   

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 = L; //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

    <!-- 配置mybatis-plus的分页拦截器--> <bean id="paginationInnerInterceptor" class="com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor"/> <!-- 配置mybatis-plus的分页拦截器插件 --> <bean id="mybatisPlusInterceptor" class="com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor"> <property name="interceptors" > <list> <ref bean="paginationInnerInterceptor"/> </list> </property> </bean> <!-- 将插件加入到MybatisSqlSessionFactoryBean 中--> <bean class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean"> <!--加载连接池--> <property name="dataSource" ref="dataSource"/> <!-- 设置MyBatis配置文件的路径（可以不设置） --> <property name="configLocation" value="classpath:mybatis-config.xml"/> <!--加载映射文件路径--> <property name="mapperLocations" value="classpath:mapping/*.xml"/> <!--分页插件生效 --> <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); } 

  

3.2.7、查询记录数

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

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