SpringBoot 使用Mongo的GridFs实现分布式文件存储操作

1. 准备工作
2. 在pom.xml文件中引入相应依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-mongodb</artifactId>
</dependency>
<dependency>
    <groupId>com.mongodb</groupId>
    <artifactId>mongodb-driver</artifactId>
    <version>3.4.3</version>
</dependency>
<dependency>
    <groupId>com.mongodb</groupId>
    <artifactId>mongodb-driver-core</artifactId>
    <version>3.4.3</version>
</dependency>
<dependency>
    <groupId>com.mongodb</groupId>
    <artifactId>mongo-java-driver</artifactId>
    <version>3.4.3</version>
</dependency>

• 创建MongoDB配置类，并在application.properties文件中配置MongoDB相关的配置项：

MongoDB配置类：

@Configuration
public class MongoDBConfig {

    @Bean
    public MongoTemplate mongoTemplate(MongoDbFactory mongoDbFactory){
        return new MongoTemplate(mongoDbFactory);
    }
}

application.properties文件中的配置项：

# MongoDB配置
spring.data.mongodb.uri=mongodb://127.0.0.1:27017/test

1. 使用GridFs存储文件
2. 在controller类中注入mongoTemplate，并使用mongoTemplate操作GridFs。
   GridFs操作分为两步：先将文件存储到GridFs数据库，再将文件的ObjectId存储到普通MongoDB数据库中（这里是book数据库的book_image集合）。下面是一个示例：

@RestController
public class GridFsController {

    @Autowired
    private MongoTemplate mongoTemplate;

    @RequestMapping(value = "/gridfs", method = RequestMethod.POST)
    public String uploadGridFs(@RequestParam("file") MultipartFile file) throws IOException{

        DB db = mongoTemplate.getDb();
        GridFS gridFS = new GridFS(db, "book_image");// 获取GridFS对象
        GridFSInputFile gridFSInputFile = gridFS.createFile(file.getInputStream());// 创建GridFS文件
        gridFSInputFile.setFilename(file.getOriginalFilename());// 设置文件名称
        gridFSInputFile.setContentType(file.getContentType());// 设置文件类型
        gridFSInputFile.save();// 保存文件到GridFS库
        String fileId = gridFSInputFile.getId().toString();// 获取文件ID
        DBObject query = new BasicDBObject("bookId", "123456");// 将文件ID存储到book_image集合中（以bookId为条件）
        DBObject update = new BasicDBObject("$set", new BasicDBObject("imageId", fileId));
        mongoTemplate.getCollection("book_image").update(query, update, true, false);
        return "success";
    }
}

1. 使用GridFs查询文件
2. 同样，在controller类中使用mongoTemplate查询数据。根据普通MongoDB集合book_image中的ObjectId，从GridFs中查询文件并返回。

@RestController
public class GridFsController {

    @Autowired
    private MongoTemplate mongoTemplate;

    @RequestMapping(value = "/gridfs", method = RequestMethod.GET)
    public ResponseEntity<byte[]> getGridFsImage() throws IOException{
        String bookId = "123456";// 可根据业务需要修改查询条件
        BasicDBObject query = new BasicDBObject();
        query.put("bookId", bookId);
        String imageId = "";
        DBCursor cursor = mongoTemplate.getCollection("book_image").find(query);
        while(cursor.hasNext()){
            BasicDBObject obj = (BasicDBObject) cursor.next();
            imageId = obj.getString("imageId");
        }
        GridFS gridFS = new GridFS(mongoTemplate.getDb(), "book_image");
        GridFSDBFile gridFSDBFile = gridFS.findOne(imageId);
        byte[] bytes = IOUtils.toByteArray(gridFSDBFile.getInputStream());
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.IMAGE_PNG);
        return new ResponseEntity<byte[]>(bytes, headers, HttpStatus.OK);
    }
}

以上就是使用SpringBoot和MongoDB的GridFs操作分布式文件存储的完整攻略，包括文件存储和文件查询两方面的实现示例。