public String getIdentifier() {
        return this.identifier;
    }
<p>
An immutable identifier for a data source that is unique for an Amazon Web Services Region. Performance Insights
gathers metrics from this data source. In the console, the identifier is shown as <i>ResourceID</i>. When you
call <code>DescribeDBInstances</code>, the identifier is returned as <code>DbiResourceId</code>.
</p>

@return An immutable identifier for a data source that is unique for an Amazon Web Services Region. Performance
        Insights gathers metrics from this data source. In the console, the identifier is shown as
        <i>ResourceID</i>. When you call <code>DescribeDBInstances</code>, the identifier is returned as
        <code>DbiResourceId</code>.
aws-java-sdk-pi/src/main/java/com/amazonaws/services/pi/model/GetResourceMetricsResult.java