Java上传文件到MongoDB GirdFS

上传有两种方式，一种是使用UploadFromStream，另外一种是OpenUploadStream方式，这里使用的是第二种方式：

    public ObjectId save(){
        GridFSBucket gfsbk = GridFSBuckets.create(db, "user_photo");
        byte[] data = "Data to upload into GridFS".getBytes(StandardCharsets.UTF_8);
        GridFSUploadStream uploadStream = gfsbk .openUploadStream("user_09734");
        uploadStream.write(data);
        ObjectId id = uploadStream.getFileId();
        uploadStream.close();
        return id;
    }

解析:
1. GridFSBucket gfsbk = GridFSBuckets.create(db, “user_photo”);

创建一个容器，传入一个`MongoDatabase`类实例db，和容器名称"user_photo"作为参数   

2. GridFSUploadStream uploadStream = gfsbk .openUploadStream(“user_09734”);

打开上传流，传入一个String参数作为GirdFS文件的文件名

3. ObjectId id = uploadStream.getFileId();

得到刚刚上传的文件的id

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Mongo Java驱动GirdFS上传参考资料
下面是我编写的上传帮助类：

package com.huanle.utils.db;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import org.bson.types.ObjectId;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.huanle.utils.model.FileEntity;
import com.mongodb.Block;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.gridfs.GridFSBucket;
import com.mongodb.client.gridfs.GridFSBuckets;
import com.mongodb.client.gridfs.GridFSUploadStream;
import com.mongodb.client.gridfs.model.GridFSFile;
import com.mongodb.gridfs.GridFS;

@Component
public class GirdFSHelper {

    private GridFSBucket gfsbk;
    private MongoDatabase db;

    @Autowired
    public GirdFSHelper(MongoDBHelper mongoManager){
        this.db = mongoManager.getDB("huanle");
    }

    /**保存文件到GirdFS,通过openUploadStream方式
     * @param bucket 容器名称
     * @param file 文件实体
     * @return 返回FileEntity
     */
    public FileEntity save(String bucket,FileEntity file){
        gfsbk = GridFSBuckets.create(db, bucket);
        GridFSUploadStream uploadStream = gfsbk.openUploadStream(file.getFileName());
        uploadStream.write(file.getContent());
        ObjectId id = uploadStream.getFileId();
        uploadStream.flush();
        uploadStream.close();
        FileEntity filter = new FileEntity();
        filter.setId(id);
        filter = find(bucket,filter);
        return filter;
    }


    public FileEntity download(String bucket,FileEntity filter) throws IOException{
        filter = find(bucket,filter);
        if(filter==null){
            return null;
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        gfsbk = GridFSBuckets.create(db, bucket);
        gfsbk.downloadToStream(filter.getId(), out);
        filter.setContent(out.toByteArray());
        out.close();
        return filter;
    }


    public FileEntity find(String bucket,FileEntity filter){
        gfsbk = GridFSBuckets.create(db, bucket);
        System.out.println(filter.toBson());
        GridFSFile result = gfsbk.find(filter.toBson()).first();
        if(result==null){ 
            return null;
        }
        filter.setId(result.getObjectId());
        filter.setSize(result.getLength());
        filter.setFileName(result.getFilename());
        filter.setUploadTime(result.getUploadDate());
        return filter;
    }

}


package com.huanle.utils.model;

import java.util.Date;

import javax.validation.constraints.Past;

import org.bson.Document;
import org.bson.types.ObjectId;
import org.hibernate.validator.constraints.Range;

import com.huanle.utils.annotation.FileContent;
import com.huanle.utils.annotation.FileName;
import com.huanle.utils.annotation.PlainString;

/**文件辅助实体类
 * @author luchu
 *
 */
public class FileEntity {

    public static String ID="_id",FILE_NAME="fileName",SIZE="size",UPLOAD_TIME="uploadTime",CONTENT="content";

    private ObjectId id;
    @PlainString
    @FileName
    private String fileName;
    @Range(max=41943040)
    private long size;
    @Past
    private Date uploadTime;
    @FileContent
    private byte[] content;


    public Document toBson(){
        Document doc = new Document();
        if(this.id!=null){
            doc.append(ID, this.id);
        }
        if(this.fileName!=null){
            doc.append(FILE_NAME, this.fileName);
        }
        if(this.size!=0){
            doc.append(SIZE, this.size);
        }
        if(this.uploadTime!=null){
            doc.append(UPLOAD_TIME, this.uploadTime);
        }
        return doc;
    }


}