protected Bson buildMetadataDocumentFilter(final String entityId) {
        return eq("entityId", entityId);
    }
<p>buildMetadataDocumentFilter.</p>

@param entityId a {@link String} object
@return a {@link Bson} object
pac4j-saml/src/main/java/org/pac4j/saml/metadata/mongo/SAML2MongoMetadataGenerator.java