public String getSourceIdentifier() {
        return this.sourceIdentifier;
    }
<p>
The identifier of the event source for which events are returned. If not specified, then all sources are included
in the response.
</p>
<p>
Constraints:
</p>
<ul>
<li>
<p>
If <code>SourceIdentifier</code> is provided, <code>SourceType</code> must also be provided.
</p>
</li>
<li>
<p>
If the source type is <code>DBInstance</code>, a <code>DBInstanceIdentifier</code> must be provided.
</p>
</li>
<li>
<p>
If the source type is <code>DBSecurityGroup</code>, a <code>DBSecurityGroupName</code> must be provided.
</p>
</li>
<li>
<p>
If the source type is <code>DBParameterGroup</code>, a <code>DBParameterGroupName</code> must be provided.
</p>
</li>
<li>
<p>
If the source type is <code>DBSnapshot</code>, a <code>DBSnapshotIdentifier</code> must be provided.
</p>
</li>
<li>
<p>
Cannot end with a hyphen or contain two consecutive hyphens.
</p>
</li>
</ul>

@return The identifier of the event source for which events are returned. If not specified, then all sources are
        included in the response.</p>
        <p>
        Constraints:
        </p>
        <ul>
        <li>
        <p>
        If <code>SourceIdentifier</code> is provided, <code>SourceType</code> must also be provided.
        </p>
        </li>
        <li>
        <p>
        If the source type is <code>DBInstance</code>, a <code>DBInstanceIdentifier</code> must be provided.
        </p>
        </li>
        <li>
        <p>
        If the source type is <code>DBSecurityGroup</code>, a <code>DBSecurityGroupName</code> must be provided.
        </p>
        </li>
        <li>
        <p>
        If the source type is <code>DBParameterGroup</code>, a <code>DBParameterGroupName</code> must be
        provided.
        </p>
        </li>
        <li>
        <p>
        If the source type is <code>DBSnapshot</code>, a <code>DBSnapshotIdentifier</code> must be provided.
        </p>
        </li>
        <li>
        <p>
        Cannot end with a hyphen or contain two consecutive hyphens.
        </p>
        </li>
aws-java-sdk-docdb/src/main/java/com/amazonaws/services/docdb/model/DescribeEventsRequest.java