mongodb作為nosql資料庫的一種，在javaee開發中也越來越受到重視，這裡介紹springboot+jpa+mongodb開發過程。

1、新建maven工程，引入springboot和mongodb依賴。

pom.xml

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId
 
>
            <version>2.0.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
            <version>2.0.4.RELEASE</
 
version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <version>2.0.4.RELEASE</version>
        </dependency>
        <
 
dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.22</version>
        </dependency>
    </dependencies>

2、編寫application.yml配置檔案，配置mongodb資料庫

application.yml

spring:
  data:
    mongodb:
      uri: mongodb://localhost:27017/webserver

3、編寫實體類並做對映配置

User.java

package com.xxx.entity;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.ToString;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
@Document(collection = "xx_user")
@Data
@AllArgsConstructor
@ToString
public class User {
    @Id
    private Long id;
    private String username;
    private String password;
    private int age;
}

4、編寫Repository介面，訪問資料庫。

UserRepository.java

package com.xxx.dao;
import com.xxx.entity.User;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface UserRepository extends MongoRepository<User,Long>{
}

5、編寫Service介面，並新建測試。

UserService.java

package com.xxx.service;
import com.xxx.dao.UserRepository;
import com.xxx.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
    public User findOne(Long id){
        return userRepository.findById(id).get();
    }

    public User save(User user){
        return userRepository.save(user);
    }

    public List<User> queryAll(){
        return userRepository.findAll();
    }
}

UserServiceTest.java

package com.xxx.service;
import com.xxx.entity.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
import static org.junit.Assert.*;
@SpringBootTest
@RunWith(SpringRunner.class)
public class UserServiceTest {
    @Autowired
    private UserService userService;
    @Test
    public void findOne() throws Exception {
        User user = userService.findOne(3L);
        System.out.println(user);
        assertEquals("null",user.getPassword());
    }

    @Test
    public void save() throws Exception {
        User user = new User(3L,"convertor","null",0);
        assertEquals("convertor",userService.save(user).getUsername());
    }

    @Test
    public void queryAll() throws Exception {
        List<User> list = userService.queryAll();
        assertEquals(3,list.size());
    }

}

單元測試用的是SpringBootTest，這裡條件設定的合理，測試結果基本就都是綠的。

6、補充：如何讓mongodb中的collection去掉屬性_class

新增bean配置

package com.xxx.config;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.convert.CustomConversions;
import org.springframework.data.mongodb.MongoDbFactory;
import org.springframework.data.mongodb.core.convert.DbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;

@Configuration
public class MongoMappingConfig {
    @Bean
    public MappingMongoConverter mappingMongoConverter(MongoDbFactory factory, 
    MongoMappingContext context, BeanFactory beanFactory){
        DbRefResolver dbRefResolver = new DefaultDbRefResolver(factory);
        MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver,context);
        try{
            converter.setCustomConversions(beanFactory.getBean(CustomConversions.class));
        }catch (Exception e){
            e.printStackTrace();
        }
        //don't save column _class to mongo collection
        converter.setTypeMapper(new DefaultMongoTypeMapper(null));
        return converter;
    }
}

再次單元測試，發現數據庫中的結果如下：

> db.xx_user.find()
{ "_id" : NumberLong(1), "username" : "windows", "password" : "win7", "age" : 7, "_class" : "com
.xxx.entity.User" }
{ "_id" : NumberLong(2), "username" : "mongodb", "password" : "mongo", "age" : 3, "_class" : "co
m.xxx.entity.User" }
{ "_id" : NumberLong(3), "username" : "convertor", "password" : "null", "age" : 0 }
>

前面兩條資料是沒有配置mongodb的TypeMapper生成的，帶有_class屬性欄位，_id為3的資料是配置了TypeMapper之後生成的，去掉了_class屬性。