Java MongoDB 保存图片

本文介绍如何使用GridFS API把图片文件保存到MongoDB。GridFS API也能保存其他二进制文件，如视频和音乐文件。

1. 保存图片

下面代码使用photo命名空间，新的filename保存图片到MongoDB。

String newFileName = "mkyong-java-image";File imageFile = new File("mongodb.png");GridFS gfsPhoto = new GridFS(db, "photo");GridFSInputFile gfsFile = gfsPhoto.createFile(imageFile);gfsFile.setFilename(newFileName);gfsFile.save();

2. 获取图片

String newFileName = "mkyong-java-image";GridFS gfsPhoto = new GridFS(db, "photo");GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);System.out.println(imageForOutput);

输出，图片以如下的JSON格式被保存：

{    "_id" :    {        "$oid" : "4dc9511a14a7d017fee35746"    } ,    "chunkSize" : 262144 ,    "length" : 22672 ,    "md5" : "1462a6cfa27669af1d8d21c2d7dd1f8b" ,    "filename" : "mkyong-java-image" ,    "contentType" :  null  ,    "uploadDate" :    {        "$date" : "2011-05-10T14:52:10Z"    } ,    "aliases" :  null}

3. 打印所有图片

使用DBCursor遍历所有图片。

GridFS gfsPhoto = new GridFS(db, "photo");DBCursor cursor = gfsPhoto.getFileList();while (cursor.hasNext()) {    System.out.println(cursor.next());}

4. 保存为另一张图片

从MongoDB中获取图片并把它保存为另一张图片。

String newFileName = "mkyong-java-image";GridFS gfsPhoto = new GridFS(db, "photo");GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);imageForOutput.writeTo("mongodbNew.png"); //output to new file

5. 删除图片

String newFileName = "mkyong-java-image";GridFS gfsPhoto = new GridFS(db, "photo");gfsPhoto.remove(gfsPhoto.findOne(newFileName));

完整实例

import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.MongoClient;import com.mongodb.MongoException;import com.mongodb.gridfs.GridFS;import com.mongodb.gridfs.GridFSDBFile;import com.mongodb.gridfs.GridFSInputFile;import java.io.File;import java.io.IOException;import java.net.UnknownHostException;public class SaveImage {    public static void main(String[] args) {        try {            MongoClient mongoClient = new MongoClient("localhost", 27017);            DB db = mongoClient.getDB("imagedb");            DBCollection collection = db.getCollection("dummyColl");            String newFileName = "mkyong-java-image";            File imageFile = new File("mongodb.png");            // create a "photo" namespace            GridFS gfsPhoto = new GridFS(db, "photo");            // get image file from local drive            GridFSInputFile gfsFile = gfsPhoto.createFile(imageFile);            // set a new filename for identify purpose            gfsFile.setFilename(newFileName);            // save the image file into mongoDB            gfsFile.save();            // print the result            DBCursor cursor = gfsPhoto.getFileList();            while (cursor.hasNext()) {                System.out.println(cursor.next());            }            // get image file by it's filename            GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);            // save it into a new image file            imageForOutput.writeTo("mongodbNew.png");            // remove the image file from mongoDB            gfsPhoto.remove(gfsPhoto.findOne(newFileName));            System.out.println("Done");        } catch (UnknownHostException e) {            e.printStackTrace();        } catch (MongoException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }}