public String getPrincipal() {
        return this.principal;
    }
<p>
The principal.
</p>
<p>
Valid principals are CertificateArn (arn:aws:iot:<i>region</i>:<i>accountId</i>:cert/<i>certificateId</i>),
thingGroupArn (arn:aws:iot:<i>region</i>:<i>accountId</i>:thinggroup/<i>groupName</i>) and CognitoId
(<i>region</i>:<i>id</i>).
</p>

@return The principal.</p>
        <p>
        Valid principals are CertificateArn
        (arn:aws:iot:<i>region</i>:<i>accountId</i>:cert/<i>certificateId</i>), thingGroupArn
        (arn:aws:iot:<i>region</i>:<i>accountId</i>:thinggroup/<i>groupName</i>) and CognitoId
        (<i>region</i>:<i>id</i>).
aws-java-sdk-iot/src/main/java/com/amazonaws/services/iot/model/DetachPrincipalPolicyRequest.java