Function Compute:背景

コンテキストとは何ですか?

Function Computeが関数を実行すると、関数の実行に使用されるメソッドにコンテキストオブジェクトが渡されます。 コンテキストオブジェクトには、呼び出し、サービス、関数、、実行環境に関する情報が含まれます。 次の表に、コンテキストに含まれるパラメーターを示します。

定義は下記の通りです。

package com.aliyun.fc.runtime;

public interface Context {

    public String getRequestId();

    public Credentials getExecutionCredentials();

    public FunctionParam getFunctionParam();

    public FunctionComputeLogger getLogger();

    public Service getService();

    # public OpenTracing getTracing();

    public int getRetryCount();
}

例: 一時キーを使用してOSSにアクセスする

次のサンプルプログラムでは、コンテキストで一時キーを使用してファイルをObject Storage Service (OSS) にアップロードする方法の例を示します。 詳細なコードについては、「java11-oss」をご参照ください。

package example;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import com.aliyun.fc.runtime.Context;
import com.aliyun.fc.runtime.Credentials;
import com.aliyun.fc.runtime.StreamRequestHandler;
import com.aliyun.oss.OSS;
import com.aliyun.oss.OSSClientBuilder;

public class App implements StreamRequestHandler {

    @Override
    public void handleRequest(
            InputStream inputStream, OutputStream outputStream, Context context) throws IOException {

        // The name of the bucket, which must be created in advance. 
        String bucketName = "my-bucket";
        // Specify the endpoint of the region where the bucket resides. We recommend that you use an internal endpoint. In this example, the internal endpoint https://oss-cn-hangzhou-internal.aliyuncs.com of the China (Hangzhou) region is used. 
        String endpoint = "https://oss-cn-hangzhou-internal.aliyuncs.com";

        // Obtain the key information. Before you execute the function, make sure that the service to which the function belongs is configured with a role that is attached with the AliyunOSSFullAccess policy. 
        // We recommend that you use the AliyunFCDefaultRole role. 
        Credentials creds = context.getExecutionCredentials();

        // Create an OSSClient instance. 
        /*
        The AccessKey pair of an Alibaba Cloud account has permissions on all API operations. Using these credentials to perform operations in Function Compute is a high-risk operation. We recommend that you use a RAM user to call API operations or perform routine O&M. 
        We recommend that you do not save the AccessKey ID and AccessKey secret to your project code. Otherwise, the AccessKey pair may be leaked and the security of all resources in your account may be compromised. 
        In this example, the Access Key pair is obtained from the context. 
        */
        OSS ossClient = new OSSClientBuilder().build(endpoint, creds.getAccessKeyId(), creds.getAccessKeySecret(), creds.getSecurityToken());

        // Specify a byte array. 
        byte[] content = "Hello FC".getBytes();
        // Specify the name of the bucket and the full path of the object. In this example, the bucket name is examplebucket and the full path of the object is exampledir/exampleobject.txt. Do not include the bucket name in the full path of the object. 
        ossClient.putObject(bucketName, "exampledir/exampleobject.txt", new ByteArrayInputStream(content));

        // Close your OSSClient. 
        ossClient.shutdown();

        outputStream.write(new String("done").getBytes());
    }
}