# Create IAM policies with the AWS SDK for Java 2.x
The [IAM Policy Builder API](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/policybuilder/iam/package-summary.html) is a library that you can use to build [IAM policies](https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies.html) in Java and upload them to AWS Identity and Access Management (IAM).
Instead of building an IAM policy by manually assembling a JSON string or by reading a file, the API provides a client-side, object-oriented approach to generate the JSON string. When you read an existing IAM policy in JSON format, the API converts it to an [IamPolicy](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/policybuilder/iam/IamPolicy.html) instance for handling.
The IAM Policy Builder API became available with version 2.20.105 of the SDK, so use that version or a later one in your Maven build file. The latest version number of the SDK is [listed on Maven central](https://central.sonatype.com/artifact/software.amazon.awssdk/iam-policy-builder).
The following snippet shows an example dependency block for a Maven `pom.xml` file. This allows you to use the IAM Policy Builder API in your project.
```
software.amazon.awssdk
iam-policy-builder
2.27.21
```
## Create an `IamPolicy`
This section shows several examples of how to build policies by using the IAM Policy Builder API.
In each of the following examples, start with the `[IamPolicy.Builder](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/policybuilder/iam/IamPolicy.Builder.html)` and add one or more statements by using the `addStatement` method. Following this pattern, the [IamStatement.Builder](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/policybuilder/iam/IamStatement.Builder.html) has methods to add the effect, actions, resources, and conditions to the statement.
### Example: Create a time-based policy
The following example creates an identity-based policy that permits the Amazon DynamoDB `GetItem` action between two points in time.
```
public String timeBasedPolicyExample() {
IamPolicy policy = IamPolicy.builder()
.addStatement(b -> b
.effect(IamEffect.ALLOW)
.addAction("dynamodb:GetItem")
.addResource(IamResource.ALL)
.addCondition(b1 -> b1
.operator(IamConditionOperator.DATE_GREATER_THAN)
.key("aws:CurrentTime")
.value("2020-04-01T00:00:00Z"))
.addCondition(b1 -> b1
.operator(IamConditionOperator.DATE_LESS_THAN)
.key("aws:CurrentTime")
.value("2020-06-30T23:59:59Z")))
.build();
// Use an IamPolicyWriter to write out the JSON string to a more readable format.
return policy.toJson(IamPolicyWriter.builder()
.prettyPrint(true)
.build());
}
```
#### JSON output
The last statement in the previous example returns the following JSON string.
Read more about this [example](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_examples_aws-dates.html) in the *AWS Identity and Access Management User Guide*.
------
#### [ JSON ]
****
```
{
"Version":"2012-10-17",
"Statement": {
"Effect": "Allow",
"Action": "dynamodb:GetItem",
"Resource": "*",
"Condition": {
"DateGreaterThan": {
"aws:CurrentTime": "2020-04-01T00:00:00Z"
},
"DateLessThan": {
"aws:CurrentTime": "2020-06-30T23:59:59Z"
}
}
}
}
```
------
### Example: Specify multiple conditions
The following example shows how you can create an identity-based policy that allows access to specific DynamoDB attributes. The policy contains two conditions.
```
public String multipleConditionsExample() {
IamPolicy policy = IamPolicy.builder()
.addStatement(b -> b
.effect(IamEffect.ALLOW)
.addAction("dynamodb:GetItem")
.addAction("dynamodb:BatchGetItem")
.addAction("dynamodb:Query")
.addAction("dynamodb:PutItem")
.addAction("dynamodb:UpdateItem")
.addAction("dynamodb:DeleteItem")
.addAction("dynamodb:BatchWriteItem")
.addResource("arn:aws:dynamodb:*:*:table/table-name")
.addConditions(IamConditionOperator.STRING_EQUALS.addPrefix("ForAllValues:"),
"dynamodb:Attributes",
List.of("column-name1", "column-name2", "column-name3"))
.addCondition(b1 -> b1.operator(IamConditionOperator.STRING_EQUALS.addSuffix("IfExists"))
.key("dynamodb:Select")
.value("SPECIFIC_ATTRIBUTES")))
.build();
return policy.toJson(IamPolicyWriter.builder()
.prettyPrint(true).build());
}
```
#### JSON output
The last statement in the previous example returns the following JSON string.
Read more about this [example](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_examples_dynamodb_attributes.html) in the *AWS Identity and Access Management User Guide*.
------
#### [ JSON ]
****
```
{
"Version":"2012-10-17",
"Statement": {
"Effect": "Allow",
"Action": [
"dynamodb:GetItem",
"dynamodb:BatchGetItem",
"dynamodb:Query",
"dynamodb:PutItem",
"dynamodb:UpdateItem",
"dynamodb:DeleteItem",
"dynamodb:BatchWriteItem"
],
"Resource": "arn:aws:dynamodb:*:*:table/table-name",
"Condition": {
"ForAllValues:StringEquals": {
"dynamodb:Attributes": [
"column-name1",
"column-name2",
"column-name3"
]
},
"StringEqualsIfExists": {
"dynamodb:Select": "SPECIFIC_ATTRIBUTES"
}
}
}
}
```
------
### Example: Specify principals
The following example shows how to create a resource-based policy that denies access to a bucket for all principals except for those specified in the condition.
```
public String specifyPrincipalsExample() {
IamPolicy policy = IamPolicy.builder()
.addStatement(b -> b
.effect(IamEffect.DENY)
.addAction("s3:*")
.addPrincipal(IamPrincipal.ALL)
.addResource("arn:aws:s3:::BUCKETNAME/*")
.addResource("arn:aws:s3:::BUCKETNAME")
.addCondition(b1 -> b1
.operator(IamConditionOperator.ARN_NOT_EQUALS)
.key("aws:PrincipalArn")
.value("arn:aws:iam::444455556666:user/user-name")))
.build();
return policy.toJson(IamPolicyWriter.builder()
.prettyPrint(true).build());
}
```
#### JSON output
The last statement in the previous example returns the following JSON string.
Read more about this [example](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_principal.html#principal-anonymous) in the *AWS Identity and Access Management User Guide*.
------
#### [ JSON ]
****
```
{
"Version":"2012-10-17",
"Statement" : {
"Effect" : "Deny",
"Principal" : "*",
"Action" : "s3:*",
"Resource" : [ "arn:aws:s3:::BUCKETNAME/*", "arn:aws:s3:::BUCKETNAME" ],
"Condition" : {
"ArnNotEquals" : {
"aws:PrincipalArn" : "arn:aws:iam::444455556666:user/user-name"
}
}
}
}
```
------
### Example: Allow cross-account access
The following example shows how to allow another AWS account to upload objects to your bucket while retaining full owner control of the uploaded objects.
```
public String allowCrossAccountAccessExample() {
IamPolicy policy = IamPolicy.builder()
.addStatement(b -> b
.effect(IamEffect.ALLOW)
.addPrincipal(IamPrincipalType.AWS, "111122223333")
.addAction("s3:PutObject")
.addResource("arn:aws:s3:::amzn-s3-demo-bucket/*")
.addCondition(b1 -> b1
.operator(IamConditionOperator.STRING_EQUALS)
.key("s3:x-amz-acl")
.value("bucket-owner-full-control")))
.build();
return policy.toJson(IamPolicyWriter.builder()
.prettyPrint(true).build());
}
```
#### JSON output
The last statement in the previous example returns the following JSON string.
Read more about this [example](https://docs.aws.amazon.com/AmazonS3/latest/userguide/example-bucket-policies.html#example-bucket-policies-acl-2) in the *Amazon Simple Storage Service User Guide*.
------
#### [ JSON ]
****
```
{
"Version":"2012-10-17",
"Statement" : {
"Effect" : "Allow",
"Principal" : {
"AWS" : "111122223333"
},
"Action" : "s3:PutObject",
"Resource" : "arn:aws:s3:::amzn-s3-demo-bucket/*",
"Condition" : {
"StringEquals" : {
"s3:x-amz-acl" : "bucket-owner-full-control"
}
}
}
}
```
------
## Use an `IamPolicy` with IAM
After you have created a `IamPolicy` instance, you use an [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/iam/IamClient.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/iam/IamClient.html) to work with the IAM service.
The following example builds a policy that allows an [IAM identity](https://docs.aws.amazon.com/IAM/latest/UserGuide/id.html) to write items to a DynamoDB table in the account that is specified with the `accountID` parameter. The policy is then uploaded to IAM as a JSON string.
```
public String createAndUploadPolicyExample(IamClient iam, String accountID, String policyName) {
// Build the policy.
IamPolicy policy =
IamPolicy.builder() // 'version' defaults to "2012-10-17".
.addStatement(IamStatement.builder()
.effect(IamEffect.ALLOW)
.addAction("dynamodb:PutItem")
.addResource("arn:aws:dynamodb:us-east-1:" + accountID + ":table/exampleTableName")
.build())
.build();
// Upload the policy.
iam.createPolicy(r -> r.policyName(policyName).policyDocument(policy.toJson()));
return policy.toJson(IamPolicyWriter.builder().prettyPrint(true).build());
}
```
The next example builds on the previous example. The code downloads the policy and uses it as the basis for a new policy by copying and altering the statement. The new policy is then uploaded.
```
public String createNewBasedOnExistingPolicyExample(IamClient iam, String accountID, String policyName, String newPolicyName) {
String policyArn = "arn:aws:iam::" + accountID + ":policy/" + policyName;
GetPolicyResponse getPolicyResponse = iam.getPolicy(r -> r.policyArn(policyArn));
String policyVersion = getPolicyResponse.policy().defaultVersionId();
GetPolicyVersionResponse getPolicyVersionResponse =
iam.getPolicyVersion(r -> r.policyArn(policyArn).versionId(policyVersion));
// Create an IamPolicy instance from the JSON string returned from IAM.
String decodedPolicy = URLDecoder.decode(getPolicyVersionResponse.policyVersion().document(), StandardCharsets.UTF_8);
IamPolicy policy = IamPolicy.fromJson(decodedPolicy);
/*
All IamPolicy components are immutable, so use the copy method that creates a new instance that
can be altered in the same method call.
Add the ability to get an item from DynamoDB as an additional action.
*/
IamStatement newStatement = policy.statements().get(0).copy(s -> s.addAction("dynamodb:GetItem"));
// Create a new statement that replaces the original statement.
IamPolicy newPolicy = policy.copy(p -> p.statements(Arrays.asList(newStatement)));
// Upload the new policy. IAM now has both policies.
iam.createPolicy(r -> r.policyName(newPolicyName)
.policyDocument(newPolicy.toJson()));
return newPolicy.toJson(IamPolicyWriter.builder().prettyPrint(true).build());
}
```
### IamClient
The previous examples use an `IamClient` argument that is created as shown in the following snippet.
```
IamClient iam = IamClient.builder().region(Region.AWS_GLOBAL).build();
```
### Policies in JSON
The examples return the following JSON strings.
```
First example
{
"Version": "2012-10-17",
"Statement" : {
"Effect" : "Allow",
"Action" : "dynamodb:PutItem",
"Resource" : "arn:aws:dynamodb:us-east-1:111122223333:table/exampleTableName"
}
}
Second example
{
"Version": "2012-10-17",
"Statement" : {
"Effect" : "Allow",
"Action" : [ "dynamodb:PutItem", "dynamodb:GetItem" ],
"Resource" : "arn:aws:dynamodb:us-east-1:111122223333:table/exampleTableName"
}
}
```