如何设置pageToken通过Java SDK从Google Cloud Storage获取项目列表? [英] How can I set pageToken to get item lists from Google Cloud Storage via Java SDK?

问题描述

我想设置pageToken来获取存储在Google Cloud Storage中的项目.我正在使用Java API v1.19.x的Google API客户端库.

I want to set pageToken to get items stored at Google Cloud Storage. I'm using Google API Client Library for Java v1.19.x.

我不知道从文件路径(或文件名)生成pageToken.

I have no idea to generate pageToken from file path(or file name).

存储在存储桶中的2个文件.

2 files stored in bucket.

• 我的桶
  • /test.csv
  • /test2.csv
  • my-bucket
    • /test.csv
    • /test2.csv

    当我尝试使用以下参数 Google API浏览器时，我可以得到nextPageToken Cgh0ZXN0LmNzdg==.

    When I tried Google APIs Explorer with following parameters, I could get nextPageToken Cgh0ZXN0LmNzdg==.

    我发现我可以通过使用base64解码nextPageToken来获得test.csv字符串.

    And I found out that I can get test.csv string by decoding nextPageToken with base64.

    • 存储桶:我的存储桶
    • pageToken:
    • 前缀:测试
    • maxResults:1

    {"kind": "storage#objects", "nextPageToken": "Cgh0ZXN0LmNzdg==", ...}

    但是如何从test.csv获取Cgh0ZXN0LmNzdg==?

    尽管我尝试了Base64编码，但结果不匹配.

    Although I tried Base64 encoding, result didn't match.

    import com.google.api.client.repackaged.org.apache.commons.codec.binary.Base64;
    
    String lastFile = "test.csv"
    String token = Base64.encodeBase64String(lastFile.getBytes());
    
    String bucket = "my-bucket"
    String prefix = "test"
    
    Storage.Objects.List listObjects = client.objects().list(bucket);
    listObjects.setPrefix(prefix);
    listObjects.setPageToken(token);
    long maxResults = 1;
    listObjects.setMaxResults(maxResults);
    do {
        Objects objects = listObjects.execute();
        List<StorageObject> items = objects.getItems();
    
        token = objects.getNextPageToken();
        listObjects.setPageToken(token);
    } while (token != null);
    

    推荐答案

    我可以自己使用以下代码从文件路径字符串中获取下一个标记.

    I could get next token from file path string using following codes by myself.

    如何从路径字符串获取nextToken

    字符串nextToken = base64encode(0x0a + asciiCode + pathString)

    String nextToken = base64encode(0x0a + asciiCode + pathString)

    asciiCode可以在0x01(SOH)和0x7f(DEL)之间使用.它似乎取决于路径长度.

    asciiCode can be taken between 0x01(SOH) and 0x7f(DEL). It seems to depend on path length.

    • 我的水桶/
      • a/a(3byte)0x03
      • a/ab(4byte)0x04
      • test.txt(8byte)0x08
      • my-bucket/
        • a/a(3byte) 0x03
        • a/ab(4byte) 0x04
        • test.txt(8byte) 0x08

        通知

        如果路径长度大于1024字节，则似乎适用另一条规则.但是我找不到规则.

        If path length is longer than 1024 byte, another rule seems to apply. But I couldn't found out rules.

        另请参见对象名称要求

        import com.google.common.io.BaseEncoding;
        
        String lastFile = "test.csv"
        String token = base64Encode(lastFile);
        
        String bucket = "my-bucket"
        String prefix = "test"
        
        Storage.Objects.List listObjects = client.objects().list(bucket);
        listObjects.setPrefix(prefix);
        listObjects.setPageToken(token);
        long maxResults = 1;
        listObjects.setMaxResults(maxResults);
        do {
            Objects objects = listObjects.execute();
            List<StorageObject> items = objects.getItems();
        
            token = objects.getNextPageToken();
            listObjects.setPageToken(token);
        } while (token != null);
        
        private String base64Encode(String path) {
            byte[] encoding;
            byte[] utf8 = path.getBytes(Charsets.UTF_8);
            encoding = new byte[utf8.length + 2];
            encoding[0] = 0x0a;
            encoding[1] = new Byte(String.valueOf(path.length()));
            String s = BaseEncoding.base64().encode(encoding);
            return s;
        }
        

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