上篇文章讲到了如何基于MongoTemplate封装通用Repository，只是解决了数据存储层的代码冗余，但是没有解决业务层的冗余，为了解决业务层的代码冗余，封装一个类似Mybatis plus的通用Service，相信使用过Mybstis plus的同学都知道。

1. 添加依赖，使用的Springboot 2.7.10

<!-- Mongodb 依赖 MongoTemplate -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
<!-- web -->
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>
<!-- hutool-->
<dependency>
  <groupId>cn.hutool</groupId>
  <artifactId>hutool-all</artifactId>
  <version>5.8.16</version>
</dependency>

2. 构建通用Service

构建通用Service，BaseService.java，内容如下：

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;

import java.util.List;
import java.util.Optional;

public interface BaseService<T,ID> {
    //查询所有
    List<T> findAll();
    //查询所有，根据条件
    List<T> findAll(T example);
    //根据ID查询
    Optional<T> findById(ID id);
    //根据ID集合查询
    Iterable<T> findAllById(Iterable<ID> ids);
    //保存
    T save(T entity);
    //批量保存
    <S extends T> List<S> saveAll(Iterable<S> entities);
    //根据ID删除
    void deleteById(ID id);
    //根据ID批量删除
    void deleteAllById(Iterable<? extends ID> ids);
    //分页信息查询，可以自定义分页对象，也可以使用Mybatis plus分页对象
    Page<T> findByPage(T entity, Pageable pageable);
}

3. 构建通用Service的实现

构建通用Service的实现，此处基于MongoRepository实现，当然也可以使用之前文档自定义通过Repository实现，BaseServiceImpl，内容如下：

import com.learning.mongodb.crud.service.BaseService;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.ExampleMatcher;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.mongodb.repository.MongoRepository;

import java.util.List;
import java.util.Optional;

public abstract class BaseServiceImpl<T, ID> implements BaseService<T, ID> {
   
    protected final MongoRepository<T, ID> mongoRepository;

    public BaseServiceImpl(MongoRepository<T, ID> mongoRepository) {
        this.mongoRepository = mongoRepository;
    }
    
    @Override
    public List<T> findAll() {
        return mongoRepository.findAll();
    }
    
    @Override
    public List<T> findAll(T entity) {
        ExampleMatcher matcher = ExampleMatcher.matching()
                .withNullHandler(ExampleMatcher.NullHandler.IGNORE)
                .withIgnoreCase()
                .withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING);
        Example<T> query = Example.of(entity, matcher);
        return mongoRepository.findAll(query);
    }

    @Override
    public Optional<T> findById(ID id) {
        return this.mongoRepository.findById(id);
    }

    @Override
    public Iterable<T> findAllById(Iterable<ID> ids) {
        return this.mongoRepository.findAllById(ids);
    }

    @Override
    public T save(T entity) {
        return this.mongoRepository.save(entity);
    }

    @Override
    public <S extends T> List<S> saveAll(Iterable<S> entities) {
        return this.mongoRepository.saveAll(entities);
    }

    @Override
    public void deleteById(ID id) {
        this.mongoRepository.deleteById(id);
    }

    @Override
    public void deleteAllById(Iterable<? extends ID> ids) {
        this.mongoRepository.deleteAllById(ids);
    }

    @Override
    public Page<T> findByPage(T entity, Pageable pageable) {
        ExampleMatcher matcher = ExampleMatcher.matching()
                .withNullHandler(ExampleMatcher.NullHandler.IGNORE)
                .withIgnoreCase()
                .withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING);
        Example<T> query = Example.of(entity, matcher);
        return this.mongoRepository.findAll(query, pageable);
    }
}

4. 使用

定义BookMongoRepository.java

public interface BookMongoRepository extends MongoRepository<Book, ObjectId> {}

定义BookService.java接口

public interface BookService extends BaseService<Book, ObjectId> {}

定义BookServiceImpl.java实现类

@Service
public class BookServiceImpl extends BaseServiceImpl<Book, ObjectId> implements BookService {

    private final BookMongoRepository bookMongoRepository;

    public BookServiceImpl(BookMongoRepository bookMongoRepository) {
        super(bookMongoRepository);
        this.bookMongoRepository = bookMongoRepository;
    }
}

定义Book2Controller.java

@RestController
@RequestMapping(value = "/book2")
public class Book2Controller {
    @Resource
    private BookService bookService;

    @PostMapping
    public Book add(@RequestBody Book book) {
        return this.bookService.save(book);
    }

    @GetMapping
    public List<Book> books() {
        return bookService.findAll();
    }

    @GetMapping(value = "/{id}")
    public Book book(@PathVariable(name = "id") String id) {
        return bookService.findById(new ObjectId(id)).orElseThrow(() -> new RuntimeException("未知的书籍:" + id));
    }
}

测试

curl --location 'http://localhost:8080/book2' \
--header 'Content-Type: application/json' \
--data '{
    "name":"Go语言入门",
    "price":39.9
}'

总结

​ 以上就是基于MongoRepository封装的通用Service，也可以使用之前文章自定义Repository来实现，如果同学们有更好的方案欢迎讨论。