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。

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。

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

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:mongo="http://www.springframework.org/schema/data/mongo"
xsi:schemaLocation="http://www.springframework.org/schema/data/mongo http://www.springframework.org/schema/data/mongo/spring-mongo.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 
<mongo:db-factory id="mongoDbFactory" dbname="yourdb" />
<mongo:mapping-converter id="converter" />

<bean name="gridFsTemplate"
class="org.springframework.data.mongodb.gridfs.GridFsTemplate">
<constructor-arg ref="mongoDbFactory" />
<constructor-arg ref="converter" />
</bean>
</beans>

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<GridFSDBFile> 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");
}
}