错误：使用 Java => java.net.UnknownHostException 连接 Google Cloud Storage 时：oauth2.googleapis.com

Question

While connecting to Google Cloud Storage using Java libraries, We are getting below exception :

1. Caused by: java.net.UnknownHostException: oauth2.googleapis.com
2. Caused by: java.io.IOException: Error getting access token for service account: oauth2.googleapis.com

We have created the Google Cloud Storage service account, Project and downloaded JSON file also.

Below is the code snippet :

GoogleCredentials googleCredentails = 
            ServiceAccountCredentials.fromStream(new FileInputStream("D:\\Naresh\\Projects\\GoogleCloudStorage\\delta-trees-236311-ae7c1cfcda68.json"));

Storage googleStorageService = StorageOptions.newBuilder().setCredentials(googleCredentails)
            .setProjectId("delta-trees-236311")
            .build().getService();

String googleBucketName = "ewf-ocr-poc";
File f = new File("D:\\Naresh\\Projects\\GoogleCloudStorage\\EWFDocumentThroughJava.txt");
byte[] readFileToByteArray = readFileToByteArray(f);
String fileName = f.getName();
InputStream fis = new FileInputStream(f);        
googleStorageService.create(BlobInfo.newBuilder(googleBucketName, fileName).build(),
            readFileToByteArray);

Answer 1

It could be the internet pemission.

try: Android studio: <uses-permission android:name="android.permission.INTERNET" /> On Android Manifest

Xamarin:

<uses-permission android:name="android.permission.INTERNET"></uses-permission>
         <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

On Android Manifest

Answer 2

Looks like you need to add your https proxy in the java app to make your connection to gcp host work. You can add is using below system properties:

    System.setProperty("https.proxyHost", yourProxyHost);
    System.setProperty("https.proxyPort", yourProxyPort);