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列举对象 V2（Java SDK）

最近更新时间：2024.02.04 18:31:02

首次发布时间：2023.01.19 14:37:15

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本文介绍如何通过 TOS Java SDK 的 listObjectsType2 接口简单列举指定桶中的对象、列举所有对象、列举包含指定前缀的对象、列举指定目录下的对象和子目录等。

注意事项

要列举对象，您的账号必须具备 tos:ListBucket 权限，具体操作请参见 IAM 策略概述。

参数说明

listObjectsType2 接口支持的参数如下。

参数

描述

prefix

本次查询结果的前缀。

delimiter

对对象名称进行分组的字符。

startAfter

此次列举对象的起点。

continuationToken

指定列举操作需要从此 token 开始。可从上次列举结果中的 nextContinuationToken 中获取。

maxKeys

返回列举对象的最大数。一次最多返回 1000 条结果，若不设置则默认返回 1000 条。

encodingType

对返回的内容进行编码并指定编码的类型。

示例代码

简单列举

以下代码展示如何列举桶 bucket-example 中最多 10 个对象。

import com.volcengine.tos.TOSV2;
import com.volcengine.tos.TOSV2ClientBuilder;
import com.volcengine.tos.TosClientException;
import com.volcengine.tos.TosServerException;
import com.volcengine.tos.model.object.*;

public class ListObjectsType2BasicExample {
    public static void main(String[] args) {
        String endpoint = "your endpoint";
        String region = "your region";
        String accessKey = System.getenv("TOS_ACCESS_KEY");
        String secretKey = System.getenv("TOS_SECRET_KEY");

        String bucketName = "bucket-example";
        int maxKeys = 10;

        TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey);
        try{
            ListObjectsType2Input input = new ListObjectsType2Input()
                    // 必须设置 bucket name
                    .setBucket(bucketName).setMaxKeys(maxKeys);
            ListObjectsType2Output output = tos.listObjectsType2(input);
            System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                    output.isTruncated(), output.getNextContinuationToken());
            if (output.getContents() != null) {
                for (int i = 0; i < output.getContents().size(); i++) {
                    ListedObjectV2 object = output.getContents().get(i);
                    System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                                object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                }
            }
            if (output.getCommonPrefixes() != null) {
                for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                    ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                    System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                }
            }
        } catch (TosClientException e) {
            // 操作失败，捕获客户端异常，一般情况是请求参数错误，此时请求并未发送
            System.out.println("listObjectsType2 failed");
            System.out.println("Message: " + e.getMessage());
            if (e.getCause() != null) {
                e.getCause().printStackTrace();
            }
        } catch (TosServerException e) {
            // 操作失败，捕获服务端异常，可以获取到从服务端返回的详细错误信息
            System.out.println("listObjectsType2 failed");
            System.out.println("StatusCode: " + e.getStatusCode());
            System.out.println("Code: " + e.getCode());
            System.out.println("Message: " + e.getMessage());
            System.out.println("RequestID: " + e.getRequestID());
        } catch (Throwable t) {
            // 作为兜底捕获其他异常，一般不会执行到这里
            System.out.println("listObjectsType2 failed");
            System.out.println("unexpected exception, message: " + t.getMessage());
        }
    }
}

分页列举

以下代码展示如何分页列举桶 bucket-example 中的对象。

import com.volcengine.tos.TOSV2;
import com.volcengine.tos.TOSV2ClientBuilder;
import com.volcengine.tos.TosClientException;
import com.volcengine.tos.TosServerException;
import com.volcengine.tos.model.object.ListObjectsType2Input;
import com.volcengine.tos.model.object.ListObjectsType2Output;
import com.volcengine.tos.model.object.ListedCommonPrefix;
import com.volcengine.tos.model.object.ListedObjectV2;

public class ListObjectsType2ByPageExample {
    public static void main(String[] args) {
        String endpoint = "your endpoint";
        String region = "your region";
        String accessKey = System.getenv("TOS_ACCESS_KEY");
        String secretKey = System.getenv("TOS_SECRET_KEY");

        String bucketName = "bucket-example";
        int maxKeys = 10;

        TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey);
        try{
            ListObjectsType2Input input = new ListObjectsType2Input()
                    .setBucket(bucketName).setMaxKeys(maxKeys);
            ListObjectsType2Output output = tos.listObjectsType2(input);
            System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                    output.isTruncated(), output.getNextContinuationToken());
            if (output.getContents() != null) {
                for (int i = 0; i < output.getContents().size(); i++) {
                    ListedObjectV2 object = output.getContents().get(i);
                    System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                                object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                }
            }
            if (output.getCommonPrefixes() != null) {
                for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                    ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                    System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                }
            }
            if (output.isTruncated()) {
                // isTruncated 为 true 说明接下来还有数据，可以继续列举
                // 下一页的列举需要设置上一次列举返回的 NextContinuationToken
                input.setContinuationToken(output.getNextContinuationToken());
                output = tos.listObjectsType2(input);
                System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                        output.isTruncated(), output.getNextContinuationToken());
                if (output.getContents() != null) {
                    for (int i = 0; i < output.getContents().size(); i++) {
                        ListedObjectV2 object = output.getContents().get(i);
                        System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                                object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                    }
                    if (output.getCommonPrefixes() != null) {
                        for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                            ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                            System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                        }
                    }
                }
            }
        } catch (TosClientException e) {
            // 操作失败，捕获客户端异常，一般情况是请求参数错误，此时请求并未发送
            System.out.println("listObjectsType2 failed");
            System.out.println("Message: " + e.getMessage());
            if (e.getCause() != null) {
                e.getCause().printStackTrace();
            }
        } catch (TosServerException e) {
            // 操作失败，捕获服务端异常，可以获取到从服务端返回的详细错误信息
            System.out.println("listObjectsType2 failed");
            System.out.println("StatusCode: " + e.getStatusCode());
            System.out.println("Code: " + e.getCode());
            System.out.println("Message: " + e.getMessage());
            System.out.println("RequestID: " + e.getRequestID());
        } catch (Throwable t) {
            // 作为兜底捕获其他异常，一般不会执行到这里
            System.out.println("listObjectsType2 failed");
            System.out.println("unexpected exception, message: " + t.getMessage());
        }
    }
}

列举指定前缀的所有对象

以下代码展示如何列举桶 bucket-example 中指定前缀的所有对象。

import com.volcengine.tos.TOSV2;
import com.volcengine.tos.TOSV2ClientBuilder;
import com.volcengine.tos.TosClientException;
import com.volcengine.tos.TosServerException;
import com.volcengine.tos.model.object.ListObjectsType2Input;
import com.volcengine.tos.model.object.ListObjectsType2Output;
import com.volcengine.tos.model.object.ListedCommonPrefix;
import com.volcengine.tos.model.object.ListedObjectV2;

public class ListObjectsType2ByPrefixExample {
    public static void main(String[] args) {
        String endpoint = "your endpoint";
        String region = "your region";
        String accessKey = System.getenv("TOS_ACCESS_KEY");
        String secretKey = System.getenv("TOS_SECRET_KEY");

        String bucketName = "bucket-example";
        int maxKeys = 10;
        String prefix = "example_dir/";

        TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey);
        try{
            boolean isTruncated = true;
            String continuationToken = null;
            while (isTruncated) {
                ListObjectsType2Input input = new ListObjectsType2Input().setBucket(bucketName)
                        .setMaxKeys(maxKeys).setPrefix(prefix).setContinuationToken(continuationToken);
                ListObjectsType2Output output = tos.listObjectsType2(input);
                System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                        output.isTruncated(), output.getNextContinuationToken());
                if (output.getContents() != null) {
                    for (int i = 0; i < output.getContents().size(); i++) {
                        ListedObjectV2 object = output.getContents().get(i);
                        System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                    "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                                    object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                    }
                }
                if (output.getCommonPrefixes() != null) {
                    for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                        ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                        System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                    }
                }
                isTruncated = output.isTruncated();
                continuationToken = output.getNextContinuationToken();
            }
        } catch (TosClientException e) {
            // 操作失败，捕获客户端异常，一般情况是请求参数错误，此时请求并未发送
            System.out.println("listObjectsType2 failed");
            System.out.println("Message: " + e.getMessage());
            if (e.getCause() != null) {
                e.getCause().printStackTrace();
            }
        } catch (TosServerException e) {
            // 操作失败，捕获服务端异常，可以获取到从服务端返回的详细错误信息
            System.out.println("listObjectsType2 failed");
            System.out.println("StatusCode: " + e.getStatusCode());
            System.out.println("Code: " + e.getCode());
            System.out.println("Message: " + e.getMessage());
            System.out.println("RequestID: " + e.getRequestID());
        } catch (Throwable t) {
            // 作为兜底捕获其他异常，一般不会执行到这里
            System.out.println("listObjectsType2 failed");
            System.out.println("unexpected exception, message: " + t.getMessage());
        }
    }
}

列举桶内所有对象

以下代码展示如何列举桶 bucket-example 中所有对象。

import com.volcengine.tos.TOSV2;
import com.volcengine.tos.TOSV2ClientBuilder;
import com.volcengine.tos.TosClientException;
import com.volcengine.tos.TosServerException;
import com.volcengine.tos.model.object.*;

public class ListObjectsType2AllObjectExample {
    public static void main(String[] args) {
        String endpoint = "your endpoint";
        String region = "your region";
        String accessKey = System.getenv("TOS_ACCESS_KEY");
        String secretKey = System.getenv("TOS_SECRET_KEY");

        String bucketName = "bucket-example";
        int maxKeys = 10;

        TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey);
        try{
            boolean isTruncated = true;
            String continuationToken = null;
            while (isTruncated) {
                ListObjectsType2Input input = new ListObjectsType2Input().setBucket(bucketName).setMaxKeys(maxKeys)
                        .setContinuationToken(continuationToken);
                ListObjectsType2Output output = tos.listObjectsType2(input);
                System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                        output.isTruncated(), output.getNextContinuationToken());
                if (output.getContents() != null) {
                    for (int i = 0; i < output.getContents().size(); i++) {
                        ListedObjectV2 object = output.getContents().get(i);
                        System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                                object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                    }
                }
                if (output.getCommonPrefixes() != null) {
                    for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                        ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                        System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                    }
                }
                isTruncated = output.isTruncated();
                continuationToken = output.getNextContinuationToken();
            }
        } catch (TosClientException e) {
            // 操作失败，捕获客户端异常，一般情况是请求参数错误，此时请求并未发送
            System.out.println("listObjectsType2 failed");
            System.out.println("Message: " + e.getMessage());
            if (e.getCause() != null) {
                e.getCause().printStackTrace();
            }
        } catch (TosServerException e) {
            // 操作失败，捕获服务端异常，可以获取到从服务端返回的详细错误信息
            System.out.println("listObjectsType2 failed");
            System.out.println("StatusCode: " + e.getStatusCode());
            System.out.println("Code: " + e.getCode());
            System.out.println("Message: " + e.getMessage());
            System.out.println("RequestID: " + e.getRequestID());
        } catch (Throwable t) {
            // 作为兜底捕获其他异常，一般不会执行到这里
            System.out.println("listObjectsType2 failed");
            System.out.println("unexpected exception, message: " + t.getMessage());
        }
    }
}

列举指定目录下的文件和子目录

TOS 只有对象的概念, 可通过创建一个大小为 0 并且以斜线 / 结尾的对象, 模拟目录的功能。
通过 Delimiter 和 Prefix 两个参数可以模拟目录的功能:

  • 首先设置 Delimiter 为 / 同时设置 Prefix 为空, 可返回根目录下的对象和子目录信息。
  • 在设置 Delimiter 为 / 同时设置 Prefix 为子目录(commonPrefixes), 可返回子目录的对象和次级目录。

以下代码展示如何列举桶 bucket-example 根目录下的对象和子目录。

import com.volcengine.tos.TOSV2;
import com.volcengine.tos.TOSV2ClientBuilder;
import com.volcengine.tos.TosClientException;
import com.volcengine.tos.TosServerException;
import com.volcengine.tos.model.object.ListObjectsType2Input;
import com.volcengine.tos.model.object.ListObjectsType2Output;
import com.volcengine.tos.model.object.ListedCommonPrefix;
import com.volcengine.tos.model.object.ListedObjectV2;

public class ListObjectsType2ByDelimiterExample {
    public static void main(String[] args) {
        String endpoint = "your endpoint";
        String region = "your region";
        String accessKey = System.getenv("TOS_ACCESS_KEY");
        String secretKey = System.getenv("TOS_SECRET_KEY");

        String bucketName = "bucket-example";
        int maxKeys = 10;
        String delimiter = "/";

        TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey);
        try{
            boolean isTruncated = true;
            String continuationToken = null;
            while (isTruncated) {
                ListObjectsType2Input input = new ListObjectsType2Input().setBucket(bucketName)
                        .setMaxKeys(maxKeys).setDelimiter(delimiter).setContinuationToken(continuationToken);
                ListObjectsType2Output output = tos.listObjectsType2(input);
                System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                        output.isTruncated(), output.getNextContinuationToken());
                if (output.getContents() != null) {
                    for (int i = 0; i < output.getContents().size(); i++) {
                        ListedObjectV2 object = output.getContents().get(i);
                        System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                        "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                                object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                    }
                }
                if (output.getCommonPrefixes() != null) {
                    for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                        ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                        System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                        // commonPrefix 为子目录，可用其作为 prefix 参数继续往下列举
                        listCommonPrefix(bucketName, maxKeys, delimiter, commonPrefix.getPrefix(), tos);
                    }
                }
                isTruncated = output.isTruncated();
                continuationToken = output.getNextContinuationToken();
            }
        } catch (TosClientException e) {
            // 操作失败，捕获客户端异常，一般情况是请求参数错误，此时请求并未发送
            System.out.println("listObjectsType2 failed");
            System.out.println("Message: " + e.getMessage());
            if (e.getCause() != null) {
                e.getCause().printStackTrace();
            }
        } catch (TosServerException e) {
            // 操作失败，捕获服务端异常，可以获取到从服务端返回的详细错误信息
            System.out.println("listObjectsType2 failed");
            System.out.println("StatusCode: " + e.getStatusCode());
            System.out.println("Code: " + e.getCode());
            System.out.println("Message: " + e.getMessage());
            System.out.println("RequestID: " + e.getRequestID());
        } catch (Throwable t) {
            // 作为兜底捕获其他异常，一般不会执行到这里
            System.out.println("listObjectsType2 failed");
            System.out.println("unexpected exception, message: " + t.getMessage());
        }
    }

    private static void listCommonPrefix(String bucketName, int maxKeys, String delimiter, String prefix, TOSV2 tos) {
        boolean isTruncated = true;
        String continuationToken = null;
        while (isTruncated) {
            ListObjectsType2Input input = new ListObjectsType2Input().setBucket(bucketName).setMaxKeys(maxKeys)
                    .setDelimiter(delimiter).setContinuationToken(continuationToken).setPrefix(prefix);
            ListObjectsType2Output output = tos.listObjectsType2(input);
            System.out.printf("listObjectsType2 succeed, is truncated? %b, next continuation token is %s.\n",
                    output.isTruncated(), output.getNextContinuationToken());
            if (output.getContents() != null) {
                for (int i = 0; i < output.getContents().size(); i++) {
                    ListedObjectV2 object = output.getContents().get(i);
                    System.out.printf("Listed object, key is %s, size is %d, storageClass is %s, ETag is %s, " +
                                    "last modified is %s, crc64 value is %s.\n", object.getKey(), object.getSize(),
                            object.getStorageClass(), object.getEtag(), object.getLastModified().toString(), object.getHashCrc64ecma());
                }
            }
            if (output.getCommonPrefixes() != null) {
                for (int i = 0; i < output.getCommonPrefixes().size(); i++) {
                    ListedCommonPrefix commonPrefix = output.getCommonPrefixes().get(i);
                    System.out.println("Listed commonPrefix is " + commonPrefix.getPrefix());
                }
            }
            isTruncated = output.isTruncated();
            continuationToken = output.getNextContinuationToken();
        }
    }
}