Spring Data MongoDB : 保存二进制文件, GridFS例程

原文

在MongoDB中，可以使用GridFS来存储二进制文件。本教程将向你展示如何使用Spring Data GridFsTemplate来存储/读取MongoDB中的图像。

1. GridFS – 保存示例（Spring配置文件采用注解方式）
   加一个图像文件并将其保存到MongoDB中。
   SpringMongoConfig.java:

   package com.mkyong.config;
   
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.data.mongodb.config.AbstractMongoConfiguration;
   import org.springframework.data.mongodb.gridfs.GridFsTemplate;
   
   import com.mongodb.Mongo;
   import com.mongodb.MongoClient;
   /**
    * Spring MongoDB configuration file
    *
    */
   @Configuration
   public class SpringMongoConfig extends AbstractMongoConfiguration{
   
       @Bean
       public GridFsTemplate gridFsTemplate() throws Exception {
           return new GridFsTemplate(mongoDbFactory(), mappingMongoConverter());
       }
   
       @Override
       protected String getDatabaseName() {
           return "yourdb";
       }
   
       @Override
       @Bean
       public Mongo mongo() throws Exception {
           return new MongoClient("127.0.0.1");
       }
   }
   

   GridFsAppStore.java

   package com.mkyong.core;
   
   import java.io.FileInputStream;
   import java.io.FileNotFoundException;
   import java.io.IOException;
   import java.io.InputStream;
   
   import org.springframework.context.ApplicationContext;
   import org.springframework.context.annotation.AnnotationConfigApplicationContext;
   import org.springframework.data.mongodb.gridfs.GridFsOperations;
   
   import com.mkyong.config.SpringMongoConfig;
   import com.mongodb.BasicDBObject;
   import com.mongodb.DBObject;
   
   /**
   * GridFs example
   *
   * @author mkyong
   *
   */
   
   public class GridFsAppStore {
   
       public static void main(String[] args) {
   
           ApplicationContext ctx =
                new AnnotationConfigApplicationContext(SpringMongoConfig.class);
           GridFsOperations gridOperations =
                 (GridFsOperations) ctx.getBean("gridFsTemplate");
   
           DBObject metaData = new BasicDBObject();
           metaData.put("extra1", "anything 1");
           metaData.put("extra2", "anything 2");
   
           InputStream inputStream = null;
           try {
               inputStream = new FileInputStream("/Users/mkyong/Downloads/testing.png");
               gridOperations.store(inputStream, "testing.png", "image/png", metaData);
           } catch (FileNotFoundException e) {
               e.printStackTrace();
           } finally {
               if (inputStream != null) {
                   try {
                       inputStream.close();
                   } catch (IOException e) {
                       e.printStackTrace();
                   }
               }
           }
           System.out.println("Done");
       }
   }
   

   查看MongoDB控制台，看看保存的内容。

   > show dbs
   yourdb  0.203125GB
   
   > use yourdb
   switched to db yourdb
   
   > show collections
   fs.chunks
   fs.files
   system.indexes
   
   > db.fs.files.find()
   { "_id" : ObjectId("51641c5630045c9b3db35afc"), "chunkSize" : NumberLong(262144),
   "length" : NumberLong(4238), "md5" : "9969527cd95a5a573f15e953f0036800", "filename" : "testing.png",
   "contentType" : "image/png", "uploadDate" : ISODate("2013-04-09T13:49:10.104Z"),
   "aliases" : null, "metadata" : { "extra1" : "anything 1", "extra2" : "anything 2" } }
   >
   
   > db.fs.chunks.find()
   { "_id" : ObjectId("51641c5630045c9b3db35afd"),
   "files_id" : ObjectId("51641c5630045c9b3db35afc"), "n" : 0,
   "data" : BinData(0,"/9j/4AAQSkZJRgABAgAAZ......EQH/9k=") }
   

   图像的信息保存在fs.files中，图像的具体内容（采用二进制编码）存储在fs.chunks中，并将_id和files_id进行关联。

2. GridFS – 读取示例 (Spring配置文件采用XML方式)
   从MongoDB读取上述图像文件，并将其另存为另一个图像。
   SpringConfig.xml

   GridFsAppStore.java

   package com.mkyong.core;
   
   import java.io.IOException;
   import java.util.List;
   
   import org.springframework.context.ApplicationContext;
   import org.springframework.context.support.GenericXmlApplicationContext;
   import org.springframework.data.mongodb.core.query.Criteria;
   import org.springframework.data.mongodb.core.query.Query;
   import org.springframework.data.mongodb.gridfs.GridFsOperations;
   
   import com.mongodb.BasicDBObject;
   import com.mongodb.DBObject;
   import com.mongodb.gridfs.GridFSDBFile;
   
   /**
    * GridFs example
    *
    * @author mkyong
    *
    */
   
   public class GridFsAppRead {
   
       public static void main(String[] args) {
           ApplicationContext ctx =
               new GenericXmlApplicationContext("SpringConfig.xml");
           GridFsOperations gridOperations =
               (GridFsOperations) ctx.getBean("gridFsTemplate");
   
           List result = gridOperations.find(
                new Query().addCriteria(Criteria.where("filename").is("testing.png")));
   
           for (GridFSDBFile file : result) {
               try {
                   System.out.println(file.getFilename());
                   System.out.println(file.getContentType());
                   //save as another image
                   file.writeTo("/Users/mkyong/Downloads/new-testing.png");
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
           System.out.println("Done");
       }
   }