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

作者：盐析白兔 | 2024-03-07 22:26:50

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iservice

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：

get 查询单行
remove 删除
list 查询集合
page 分页
save新增
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> {
}
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@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}
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3.2.1、新增

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);
}
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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);
}
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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);
}
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3.2.2、查询

1、单行查询

根据id查询

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

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);
}
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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);
}
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3.2.3、删除

根据id删除

@Test
public void testServcie(){
    boolean b = userService.removeById(21);
}
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根据实体的id删除

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

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

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);
}
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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);
}
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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 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();
    }
    ..........
}
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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>
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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;
}
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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);
}
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3.2.7、查询记录数

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