public void setIdentifier(String identifier) {
        this.identifier = 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>
<p>
To use a DB instance as a data source, specify its <code>DbiResourceId</code> value. For example, specify
<code>db-ABCDEFGHIJKLMNOPQRSTU1VW2X</code>.
</p>

@param identifier
       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>
       <p>
       To use a DB instance as a data source, specify its <code>DbiResourceId</code> value. For example, specify
       <code>db-ABCDEFGHIJKLMNOPQRSTU1VW2X</code>.
aws-java-sdk-pi/src/main/java/com/amazonaws/services/pi/model/GetResourceMetricsRequest.java