Revert "If jmx-reporter isn't provided with a metrics registry, use t…

…he default."

This reverts commit 6191e22.
It turns out a JmxReporter is always created for the default metrics registry.

metrics-spring/src/main/java/com/yammer/metrics/spring/config/JmxReporterBeanDefinitionParser.java

@@ -2,10 +2,8 @@
 
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
-import org.springframework.util.StringUtils;
 import org.w3c.dom.Element;
 
-import com.yammer.metrics.Metrics;
 import com.yammer.metrics.spring.JmxReporterFactory;
 
 public class JmxReporterBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
@@ -23,12 +21,7 @@ protected boolean shouldGenerateIdAsFallback() {
     @Override
     protected void doParse(Element element, BeanDefinitionBuilder builder) {
         builder.setFactoryMethod("createInstance");
-        String registry = element.getAttribute("metrics-registry");
-        if (StringUtils.hasText(registry)) {
-        	builder.addConstructorArgReference(registry);
-        } else {
-        	builder.addConstructorArgValue(Metrics.defaultRegistry());
-        }
+        builder.addConstructorArgReference(element.getAttribute("metrics-registry"));
     }
 
 }

metrics-spring/src/main/resources/com/yammer/metrics/spring/config/metrics.xsd

@@ -32,7 +32,7 @@
     <xsd:element name="jmx-reporter">
         <xsd:complexType>
             <xsd:attribute name="id" type="xsd:string" use="optional"/>
-            <xsd:attribute name="metrics-registry" type="xsd:string" use="optional"/>
+            <xsd:attribute name="metrics-registry" type="xsd:string" use="required"/>
         </xsd:complexType>
     </xsd:element>