# Attach a policy to an DynamoDB existing table
You can attach a resource-based policy to an existing table or modify an existing policy by using the DynamoDB console, [PutResourcePolicy](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_PutResourcePolicy.html) API, the AWS CLI, AWS SDK, or an [CloudFormation template](rbac-create-table.md#rbac-create-table-cfn).
## AWS CLI example to attach a new policy
The following IAM policy example uses the `put-resource-policy` AWS CLI command to attach a resource-based policy to an existing table. This example allows the user *John* to perform the [GetItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_GetItem.html), [PutItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_PutItem.html), [UpdateItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html), and [UpdateTable](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateTable.html) API actions on an existing table named *MusicCollection*.
Remember to replace the *italicized* text with your resource-specific information.
```
aws dynamodb put-resource-policy \
--resource-arn arn:aws:dynamodb:us-west-2:123456789012:table/MusicCollection \
--policy \
"{
\"Version\": \"2012-10-17\",
\"Statement\": [
{
\"Effect\": \"Allow\",
\"Principal\": {
\"AWS\": \"arn:aws:iam::111122223333:user/John\"
},
\"Action\": [
\"dynamodb:GetItem\",
\"dynamodb:PutItem\",
\"dynamodb:UpdateItem\",
\"dynamodb:UpdateTable\"
],
\"Resource\": \"arn:aws:dynamodb:us-west-2:123456789012:table/MusicCollection\"
}
]
}"
```
## AWS CLI example to conditionally update an existing policy
To conditionally update an existing resource-based policy of a table, you can use the optional `expected-revision-id` parameter. The following example will only update the policy if it exists in DynamoDB and its current revision ID matches the provided `expected-revision-id` parameter.
```
aws dynamodb put-resource-policy \
--resource-arn arn:aws:dynamodb:us-west-2:123456789012:table/MusicCollection \
--expected-revision-id 1709841168699 \
--policy \
"{
\"Version\": \"2012-10-17\",
\"Statement\": [
{
\"Effect\": \"Allow\",
\"Principal\": {
\"AWS\": \"arn:aws:iam::111122223333:user/John\"
},
\"Action\": [
\"dynamodb:GetItem\",
\"dynamodb:UpdateItem\",
\"dynamodb:UpdateTable\"
],
\"Resource\": \"arn:aws:dynamodb:us-west-2:123456789012:table/MusicCollection\"
}
]
}"
```
## AWS Management Console
1. Sign in to the AWS Management Console and open the DynamoDB console at [https://console.aws.amazon.com/dynamodb/](https://console.aws.amazon.com/dynamodb/).
1. From the dashboard, choose an existing table.
1. Navigate to the **Permissions** tab, and choose **Create table policy**.
1. In the resource-based policy editor, add the policy you would like to attach and choose **Create policy**.
The following IAM policy example allows the user *John* to perform the [GetItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_GetItem.html), [PutItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_PutItem.html), [UpdateItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html), and [UpdateTable](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateTable.html) API actions on an existing table named *MusicCollection*.
Remember to replace the *italicized* text with your resource-specific information.
------
#### [ JSON ]
****
```
{
"Version":"2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::111122223333:user/username"
},
"Action": [
"dynamodb:GetItem",
"dynamodb:PutItem",
"dynamodb:UpdateItem",
"dynamodb:UpdateTable"
],
"Resource": "arn:aws:dynamodb:us-east-1:123456789012:table/MusicCollection"
}
]
}
```
------
## AWS SDK for Java 2.x
The following IAM policy example uses the `putResourcePolicy` method to attach a resource-based policy to an existing table. This policy allows a user to perform the [GetItem](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_GetItem.html) API action on an existing table.
```
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
import software.amazon.awssdk.services.dynamodb.model.PutResourcePolicyRequest;
/**
* Before running this Java V2 code example, set up your development
* environment, including your credentials.
*
* For more information, see the following documentation topic:
*
* [Get started with the AWS SDK for Java 2.x](https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html)
*/
public class PutResourcePolicy {
public static void main(String[] args) {
final String usage = """
Usage:
Where:
tableArn - The Amazon DynamoDB table ARN to attach the policy to. For example, arn:aws:dynamodb:us-west-2:123456789012:table/MusicCollection.
allowedAWSPrincipal - Allowed AWS principal ARN that the example policy will give access to. For example, arn:aws:iam::123456789012:user/John.
""";
if (args.length != 2) {
System.out.println(usage);
System.exit(1);
}
String tableArn = args[0];
String allowedAWSPrincipal = args[1];
System.out.println("Attaching a resource-based policy to the Amazon DynamoDB table with ARN " +
tableArn);
Region region = Region.US_WEST_2;
DynamoDbClient ddb = DynamoDbClient.builder()
.region(region)
.build();
String result = putResourcePolicy(ddb, tableArn, allowedAWSPrincipal);
System.out.println("Revision ID for the attached policy is " + result);
ddb.close();
}
public static String putResourcePolicy(DynamoDbClient ddb, String tableArn, String allowedAWSPrincipal) {
String policy = generatePolicy(tableArn, allowedAWSPrincipal);
PutResourcePolicyRequest request = PutResourcePolicyRequest.builder()
.policy(policy)
.resourceArn(tableArn)
.build();
try {
return ddb.putResourcePolicy(request).revisionId();
} catch (DynamoDbException e) {
System.err.println(e.getMessage());
System.exit(1);
}
return "";
}
private static String generatePolicy(String tableArn, String allowedAWSPrincipal) {
return "{\n" +
" \"Version\": \"2012-10-17\",\n" +,
" \"Statement\": [\n" +
" {\n" +
" \"Effect\": \"Allow\",\n" +
" \"Principal\": {\"AWS\":\"" + allowedAWSPrincipal + "\"},\n" +
" \"Action\": [\n" +
" \"dynamodb:GetItem\"\n" +
" ],\n" +
" \"Resource\": \"" + tableArn + "\"\n" +
" }\n" +
" ]\n" +
"}";
}
}
```