在本教程中，我将解释如何使用Amazon的S3存储和Amazon提供的javaapi。这个例子展示了如何创建一个bucket，列出它的内容，在bucket中创建一个文件夹，上传一个文件，给这个文件一个公共访问权限，最后如何删除所有这些项目。

建立你的项目

我们需要awssdkforjava才能使这个示例正常工作。如果我们现在还没有下载SDK，请在此处下载。我们还需要将归档文件中的.JAR文件集成到项目中。或者，我们可以使用具有以下依赖项的Maven

<dependency>
  <groupId>com.amazonaws</groupId>
  <artifactId>aws-java-sdk</artifactId>
  <version>1.9.2</version>
</dependency>

在Amazon IAM中创建用户(https://console.aws.amazon.com/iam)如果你没有的话。在这里我们将得到一个“访问密钥”和“秘密访问密钥”。我们需要此凭据才能连接到S3.

向新用户添加IAM中的“AWSConnector”和“AmazonS3FullAccess”权限。如果没有这个，我们希望能够通过服务器进行身份验证。

通过Amazon S3认证

有4种不同的方法可以根据amazons3验证请求

1. 使用默认的凭证配置文件——这是Amazon推荐的方法。创建具有以下结构的文件并填写访问密钥：

# Move this credentials file to (~/.aws/credentials)
# after you fill in your access and secret keys in the default profile

# WARNING: To avoid accidental leakage of your credentials,
#          DO NOT keep this file in your source directory.
[default]
aws_access_key_id=
aws_secret_access_key=

默认情况下，将此文件保存在.aws文件夹中的文件名“credentials”下，对于Windows用户，保存在C:\Users\user.aws\credentials中，或者在Linux中保存在主目录下

如果使用此方法，则可以在代码中创建凭据对象，如下所示：

AWSCredentials credentials = new ProfileCredentialsProvider().getCredentials();

2. 使用环境变量–设置系统中下列环境变量的值

AWS_ACCESS_KEY_ID

和

AWS_SECRET_ACCESS_KEY

3. Java系统属性

aws.accessKeyId

和

aws.secretKey

. 使用

SystemPropertiesCredentialsProvider

加载程序中的变量

4. 以编程方式设置凭证——在这个例子中，我将使用这个方法，因为它更容易理解

在代码中使用以下内容：

AWSCredentials credentials = new BasicAWSCredentials("YourAccessKeyID", "YourSecretAccessKey");

创建S3客户端

为了能够与S3通信，我们必须使用

AmazonS3

. 我们将使用实例向服务器发送请求

AmazonS3 s3client = new AmazonS3Client(credentials);

创建Bucket

bucket在整个S3领域中必须具有唯一的名称

String bucketName = "theitroad-net-example-bucket";
s3client.createBucket(bucketName);

列出bucket

你可以像这样把单子从所有的桶里拿出来

for (Bucket bucket : s3client.listBuckets()) {
	System.out.println(" - " + bucket.getName());
}

在S3 Bucket中创建文件夹

使用此代码在bucket中创建一个空文件夹

public static void createFolder(String bucketName, String folderName, AmazonS3 client) {
	//create meta-data for your folder and set content-length to 0
	ObjectMetadata metadata = new ObjectMetadata();
	metadata.setContentLength(0);

	//create empty content
	InputStream emptyContent = new ByteArrayInputStream(new byte[0]);

	//create a PutObjectRequest passing the folder name suffixed by /
	PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName,
				folderName + SUFFIX, emptyContent, metadata);

	//send request to S3 to create folder
	client.putObject(putObjectRequest);
}

S3上传文件

如果你想上传一个文件到一个文件夹使用这个

String fileName = folderName + SUFFIX + "testvideo.mp4";
s3client.putObject(new PutObjectRequest(bucketName, fileName, 
		new File("C:\Users\user\Desktop\testvideo.mp4")));

只需删除文件夹和文件名中的后缀即可直接上传到bucket中。如果你想让你的文件公开(文件在amazons3中默认是私有的)，将其设置为PutObjectRequest(更多细节请参见下面的完整示例)

.withCannedAcl(CannedAccessControlList.PublicRead)

删除文件、文件夹、bucket

要删除存储桶，请使用此选项。存储桶必须为空，否则无法删除它们

s3client.deleteBucket(bucketName);

要删除文件，请使用：

s3client.deleteObject(bucketName, fileName);

要删除文件夹，必须先删除其中的所有文件。请看下面完整的例子了解更多信息。

完整示例

在这里你可以在一个工作程序中找到上面所有的代码片段。异常处理排除在可读性之外，请不要忘记在代码中添加它

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.InputStream;
import java.util.List;

import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3Client;
import com.amazonaws.services.s3.model.Bucket;
import com.amazonaws.services.s3.model.CannedAccessControlList;
import com.amazonaws.services.s3.model.ObjectMetadata;
import com.amazonaws.services.s3.model.PutObjectRequest;
import com.amazonaws.services.s3.model.S3ObjectSummary;

public class AmazonS3Example {

	private static final String SUFFIX = "/";

	public static void main(String[] args) {
		//credentials object identifying user for authentication
		//user must have AWSConnector and AmazonS3FullAccess for 
		//this example to work
		AWSCredentials credentials = new BasicAWSCredentials(
				"YourAccessKeyID", 
				"YourSecretAccessKey");

		//create a client connection based on credentials
		AmazonS3 s3client = new AmazonS3Client(credentials);

		//create bucket - name must be unique for all S3 users
		String bucketName = "theitroad-net-example-bucket";
		s3client.createBucket(bucketName);

		//list buckets
		for (Bucket bucket : s3client.listBuckets()) {
			System.out.println(" - " + bucket.getName());
		}

		//create folder into bucket
		String folderName = "testfolder";
		createFolder(bucketName, folderName, s3client);

		//upload file to folder and set it to public
		String fileName = folderName + SUFFIX + "testvideo.mp4";
		s3client.putObject(new PutObjectRequest(bucketName, fileName, 
				new File("C:\Users\user\Desktop\testvideo.mp4"))
				.withCannedAcl(CannedAccessControlList.PublicRead));

		deleteFolder(bucketName, folderName, s3client);

		//deletes bucket
		s3client.deleteBucket(bucketName);
	}

	public static void createFolder(String bucketName, String folderName, AmazonS3 client) {
		//create meta-data for your folder and set content-length to 0
		ObjectMetadata metadata = new ObjectMetadata();
		metadata.setContentLength(0);

		//create empty content
		InputStream emptyContent = new ByteArrayInputStream(new byte[0]);

		//create a PutObjectRequest passing the folder name suffixed by /
		PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName,
				folderName + SUFFIX, emptyContent, metadata);

		//send request to S3 to create folder
		client.putObject(putObjectRequest);
	}

	/**
	 * This method first deletes all the files in given folder and than the
	 * folder itself
	 */
	public static void deleteFolder(String bucketName, String folderName, AmazonS3 client) {
		List fileList = 
				client.listObjects(bucketName, folderName).getObjectSummaries();
		for (S3ObjectSummary file : fileList) {
			client.deleteObject(bucketName, file.getKey());
		}
		client.deleteObject(bucketName, folderName);
	}
}