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Bucket Policy
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Last updated: 2025-10-09 11:10:59
Bucket Policy
Last updated: 2025-10-09 11:10:59
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Overview

This document provides an API overview of bucket policies and SDK example code.
API
Operation Name
Operation Description
PUT Bucket policy
Set the permission policy for the specified bucket.
GET Bucket policy
Query the permission policy for the specified bucket.
Deleting a Bucket Policy
Delete the permission policy for the specified bucket.

PUT Bucket policy

Overview

The PUT Bucket policy API is used to write a permission policy for a bucket. If the bucket already has a permission policy, the policy passed in this request will overwrite the existing one.

Method Prototype

public void setBucketPolicy(String bucketName, String policyText)

Request sample

import com.qcloud.cos.COSClient;
import com.qcloud.cos.ClientConfig;
import com.qcloud.cos.auth.BasicCOSCredentials;
import com.qcloud.cos.auth.COSCredentials;
import com.qcloud.cos.region.Region;

public class BucketPolicyDemo {
    public static void SetBucketPolicy() {
        // 1 Initialize user identity information (Recommended to use temporary key)
        String tmpSecretId = "SECRETID";
        String tmpSecretKey = "SECRETKEY";
        String sessionToken = "TOKEN";
        BasicSessionCredentials cred = new BasicSessionCredentials(tmpSecretId, tmpSecretKey, sessionToken);
        // 2 Set the region of the bucket
        Region region = new Region("COS_REGION"); //COS_REGION parameter: Configure it to the real region of the bucket, for example ap-beijing. For more abbreviations of COS regions, please see https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1
        ClientConfig clientConfig = new ClientConfig(region);
        // 3 Generating a COS client
        COSClient cosclient = new COSClient(cred, clientConfig);
        // The bucket name must contain appid
        String bucketName = "examplebucket-1250000000";
        String bucketPolicyStr = "{" +
                "    \\"Statement\\": [" +
                "      {" +
                "        \\"Principal\\": {" +
                "          \\"qcs\\": [" +
                "            \\"qcs::cam::uin/100000000001:uin/100000000011\\"" + // Replace with the UIN of the account to be granted the permission
                "          ]" +
                "        }," +
                "        \\"Effect\\": \\"allow\\"," +
                "        \\"Action\\": [" +
                "          \\"cos:PutObject\\"" +
                "        ]," +
                "        \\"Resource\\": [" + // Change to allowed path prefixes, can be determined based on the user login status of your website to judge the specific paths that allow uploads, for example: a.jpg or a/* or * (using wildcard * poses significant security risks, please evaluate usage cautiously)
                "          \\"qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/exampleobject\\"" +
                "        ]," +
                "        \\"Condition\\": {" +
                "          \\"string_equal\\": {" +
                "            \\"cos:x-cos-mime-limit\\": \\"image/jpeg\\"" +
                "          }" +
                "        }" +
                "      }" +
                "    ]," +
                "    \\"Version\\": \\"2.0\\"" +
                "  }";

        cosclient.setBucketPolicy(bucketName, bucketPolicyStr);
        cosclient.shutdown();
    }
    public static void main(String[] args) {
        SetBucketPolicy();
    }
}

Parameter Description

Parameter Name
Description
Required
Statement
Describe the detailed information of one or more permissions
Yes
Version
Syntax version of a policy, which is 2.0 by default.
Yes
Principal
Describe the entity authorized by the policy. For details, see Accessing Policy Language Overview
Yes
Action
Here refers to the COS API. Specify a single operation, a sequence of operations, or all operations (*) as required. For example, the action is name/cos:GetService. Note that the case is sensitive.
Yes
Effect
The options include allow (permission) and deny (explicit deny).
Yes
Resource
Authorized data to be operated, which can be any resources, resources with a specified path prefix, resources with a specified absolute path, or resources with combinations of the above conditions.
Yes
Condition
Constraint conditions, which can be left blank. For details, see condition description.
No

GET Bucket policy

Overview

The GET Bucket policy API is used to read the permission policy of a bucket.

Method Prototype

public BucketPolicy getBucketPolicy(String bucketName)

Request sample:

import com.qcloud.cos.COSClient;
import com.qcloud.cos.ClientConfig;
import com.qcloud.cos.auth.BasicCOSCredentials;
import com.qcloud.cos.auth.COSCredentials;
import com.qcloud.cos.region.Region;
import com.qcloud.cos.model.BucketPolicy;

public class BucketPolicyDemo {
    public static void GetBucketPolicy() {
        // 1 Initialize user identity information (Recommended to use temporary key)
        String tmpSecretId = "SECRETID";
        String tmpSecretKey = "SECRETKEY";
        String sessionToken = "TOKEN";
        BasicSessionCredentials cred = new BasicSessionCredentials(tmpSecretId, tmpSecretKey, sessionToken);
        // 2 Set the region of the bucket
        Region region = new Region("COS_REGION"); //COS_REGION parameter: Configure it to the real region of the bucket, for example ap-beijing. For more abbreviations of COS regions, please see https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1
        ClientConfig clientConfig = new ClientConfig(region);
        // 3 Generating a COS client
        COSClient cosclient = new COSClient(cred, clientConfig);
        // The bucket name must contain appid
        String bucketName = "examplebucket-1250000000";
        BucketPolicy bucketPolicy = cosclient.getBucketPolicy(bucketName);
        System.out.println(bucketPolicy.getPolicyText());
          cosclient.shutdown();
    }
    public static void main(String[] args) {
        GetBucketPolicy();
    }
}

Return Result Description

public class BucketPolicy implements Serializable {
    private static final long serialVersionUID = 1L;
    /** The raw, policy JSON text, as returned by COS */
    private String policyText;

    /**
     * Gets the raw policy JSON text as returned by COS. If no policy has been applied to the
     * specified bucket, the policy text will be null.
     * 
     * @return The raw policy JSON text as returned by COS. If no policy has been applied to the
     *         specified bucket, this method returns null policy text.
     * 
     * @see BucketPolicy#setPolicyText(String)
     */
    public String getPolicyText() {
        return policyText;
    }

    /**
     * Sets the raw policy JSON text. A bucket will have no policy text unless the policy text is
     * explicitly provided through this method.
     *
     * @param policyText The raw policy JSON text.
     * 
     * @see BucketPolicy#getPolicyText()
     */
    public void setPolicyText(String policyText) {
        this.policyText = policyText;
    }
}

Deleting a Bucket Policy

Overview

The DELETE Bucket policy request can be used to delete the permission policy for a bucket.

Method Prototype

public void deleteBucketPolicy(String bucketName)

Request sample:

import com.qcloud.cos.COSClient;
import com.qcloud.cos.ClientConfig;
import com.qcloud.cos.auth.BasicCOSCredentials;
import com.qcloud.cos.auth.COSCredentials;
import com.qcloud.cos.region.Region;
import com.qcloud.cos.model.BucketPolicy;

public class BucketPolicyDemo {
    public static void DelBucketPolicy() {
        // 1 Initialize user identity information (Recommended to use temporary key)
        String tmpSecretId = "SECRETID";
        String tmpSecretKey = "SECRETKEY";
        String sessionToken = "TOKEN";
        BasicSessionCredentials cred = new BasicSessionCredentials(tmpSecretId, tmpSecretKey, sessionToken);
        // 2 Set the region of the bucket
        Region region = new Region("COS_REGION"); //COS_REGION parameter: Configure it to the real region of the bucket, for example ap-beijing. For more abbreviations of COS regions, please see https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1
        ClientConfig clientConfig = new ClientConfig(region);
        // 3 Generating a COS client
        COSClient cosclient = new COSClient(cred, clientConfig);
        // The bucket name must contain appid
        String bucketName = "examplebucket-1250000000";
        cosclient.deleteBucketPolicy(bucketName);
          cosclient.shutdown();
    }
    public static void main(String[] args) {
        DelBucketPolicy();
    }
}

Related Example

Complete example of bucket policy, please visit GitHub to view.

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