The listObjects interface enables the enumeration of object information within a bucket based on a specified prefix, returning up to 1,000 objects per request. By default, the results return the owner information of the bucket.

Parameters

Parameter	Description
prefix	The prefix of the current query results.
delimiter	The character used for grouping object names; the default value is /.
marker	The starting point of the subjects listed here.
encodingType	Returns the key encoding type.
maxKeys	Maximum return count, with an upper limit of 1,000; that is, up to 1,000 objects can be returned in a single listing operation.

List all objects

The following code demonstrates how to list all objects in a specified bucket.

import android.os.Bundle;​
import android.util.Log;​
​
import androidx.appcompat.app.AppCompatActivity;​
​
import com.volcengine.tos.TOSV2;​
import com.volcengine.tos.TOSV2ClientBuilder;​
import com.volcengine.tos.TosException;​
import com.volcengine.tos.model.object.ListObjectsV2Input;​
import com.volcengine.tos.model.object.ListObjectsV2Output;​
import com.volcengine.tos.model.object.ListedObjectV2;​
​
public class ListObjectLoopExample extends AppCompatActivity {​
​
    @Override​
    protected void onCreate(Bundle savedInstanceState) {​
        String endpoint = "your endpoint";​
        String region = "your region";​
        String accessKey = "your access key";​
        String secretKey = "your secret key";​
        String securityToken = "your security token";​
​
        String bucketName = "your bucket name";​
        int maxKeys = 1000;​
​
        super.onCreate(savedInstanceState);​
        setContentView(R.layout.activity_display_message);​
        TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey, securityToken);​
​
        Thread tosThread = new Thread(new Runnable() {​
            @Override​
            public void run() {​
                try{​
                    boolean isTruncated = true;​
                    String marker = "";​
                    int total = 0;​
                    while (isTruncated) {​
                        ListObjectsV2Input input = new ListObjectsV2Input()​
                                ​
                                .setBucket(bucketName).setMaxKeys(maxKeys).setMarker(marker);​
                        ListObjectsV2Output output = tos.listObjects(input);​
                        Log.i("listObjects", "listObjects succeed, is truncated? " + output.isTruncated() + "next marker is " + output.getNextMarker());​
                        if (output.getContents() != null) {​
                            for (int i = 0; i < output.getContents().size(); i++) {​
                                ListedObjectV2 object = output.getContents().get(i);​
                                Log.i("listObjects", "No." + (i+1+total) + " listed object is " + object);​
                            }​
                            total += output.getContents().size();​
                        }​
                        isTruncated = output.isTruncated();​
                        marker = output.getNextMarker();​
                    }​
                } catch (TosException e) {​
                    Log.e("TosException", "listObjects failed");​
                    e.printStackTrace();​
                }​
            }​
        });​
​
        tosThread.start();​
    }​
}​

List all objects with the specified prefix

The following code demonstrates how to list all objects with a specified prefix.

List objects following the specified position

Setting the marker parameter specifies the starting position for listing. The TOS service will return all objects whose string values follow marker in lexicographical order.

The following code demonstrates how to list objects after a specified starting position.

List objects and subdirectories in the specified directory

TOS provides file semantics only and does not support folder semantics. To simulate directory functionality, create a zero-byte object that ends with a forward slash (/).

The functionality of a directory can be simulated using the delimiter and prefix parameters:

First, set the delimiter to /. By simultaneously setting prefix to an empty value, objects and subdirectory information in the root directory can be returned.

When setting the delimiter to /. Simultaneously, when prefix is set as a subdirectory, objects and subdirectories within that subdirectory can be returned.

The following code is used to list objects and subdirectories within the specified directory.

Relevant documentation

For API documentation on listing objects, refer to ListObjects.

Torch Object Storage