minor code refactor to use lists instead of arrays

Author: SylvainJuge

instrumentation/jmx-metrics/library/src/main/java/io/opentelemetry/instrumentation/jmx/engine/BeanGroup.java

@@ -5,7 +5,11 @@
 
 package io.opentelemetry.instrumentation.jmx.engine;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
 import javax.annotation.Nullable;
+import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 import javax.management.QueryExp;
 
@@ -16,7 +20,7 @@
 public class BeanGroup {
   // How to specify the MBean(s)
   @Nullable private final QueryExp queryExp;
-  private final ObjectName[] namePatterns;
+  private final List<ObjectName> namePatterns;
 
   /**
    * Constructor for BeanGroup.
@@ -25,17 +29,29 @@ public class BeanGroup {
    * @param namePatterns an array of ObjectNames used to look for MBeans; usually they will be
    *     patterns. If multiple patterns are provided, they work as logical OR.
    */
-  public BeanGroup(@Nullable QueryExp queryExp, ObjectName... namePatterns) {
+  private BeanGroup(@Nullable QueryExp queryExp, List<ObjectName> namePatterns) {
     this.queryExp = queryExp;
     this.namePatterns = namePatterns;
   }
 
+  public static BeanGroup forSingleBean(String bean) throws MalformedObjectNameException {
+    return new BeanGroup(null, Collections.singletonList(new ObjectName(bean)));
+  }
+
+  public static BeanGroup forBeans(List<String> beans) throws MalformedObjectNameException {
+    List<ObjectName> list = new ArrayList<>();
+    for (String name : beans) {
+      list.add(new ObjectName(name));
+    }
+    return new BeanGroup(null, list);
+  }
+
   @Nullable
   QueryExp getQueryExp() {
     return queryExp;
   }
 
-  ObjectName[] getNamePatterns() {
+  List<ObjectName> getNamePatterns() {
     return namePatterns;
   }
 }

instrumentation/jmx-metrics/library/src/main/java/io/opentelemetry/instrumentation/jmx/engine/MetricDef.java

@@ -5,6 +5,8 @@
 
 package io.opentelemetry.instrumentation.jmx.engine;
 
+import java.util.List;
+
 /**
  * A class providing a complete definition on how to create an Open Telemetry metric out of the JMX
  * system: how to extract values from MBeans and how to model, name and decorate them with
@@ -74,7 +76,7 @@ public class MetricDef {
   private final BeanGroup beans;
 
   // Describes how to get the metric values and their attributes, and how to report them
-  private final MetricExtractor[] metricExtractors;
+  private final List<MetricExtractor> metricExtractors;
 
   /**
    * Constructor for MetricDef.
@@ -84,7 +86,7 @@ public class MetricDef {
    *     MetricExtractor is provided, they should use unique metric names or unique metric
    *     attributes
    */
-  public MetricDef(BeanGroup beans, MetricExtractor... metricExtractors) {
+  public MetricDef(BeanGroup beans, List<MetricExtractor> metricExtractors) {
     this.beans = beans;
     this.metricExtractors = metricExtractors;
   }
@@ -93,7 +95,7 @@ BeanGroup getBeanGroup() {
     return beans;
   }
 
-  MetricExtractor[] getMetricExtractors() {
+  List<MetricExtractor> getMetricExtractors() {
     return metricExtractors;
   }
 }

instrumentation/jmx-metrics/library/src/main/java/io/opentelemetry/instrumentation/jmx/engine/MetricExtractor.java

@@ -5,6 +5,7 @@
 
 package io.opentelemetry.instrumentation.jmx.engine;
 
+import java.util.List;
 import javax.annotation.Nullable;
 
 /**
@@ -22,14 +23,14 @@ public class MetricExtractor {
   private final BeanAttributeExtractor attributeExtractor;
 
   // Defines the Measurement attributes to be used when reporting the metric value.
-  private final MetricAttribute[] attributes;
+  private final List<MetricAttribute> attributes;
 
   @Nullable private volatile DetectionStatus status;
 
   public MetricExtractor(
       BeanAttributeExtractor attributeExtractor,
       MetricInfo metricInfo,
-      MetricAttribute... attributes) {
+      List<MetricAttribute> attributes) {
     this.attributeExtractor = attributeExtractor;
     this.metricInfo = metricInfo;
     this.attributes = attributes;
@@ -43,7 +44,7 @@ BeanAttributeExtractor getMetricValueExtractor() {
     return attributeExtractor;
   }
 
-  MetricAttribute[] getAttributes() {
+  List<MetricAttribute> getAttributes() {
     return attributes;
   }
 

instrumentation/jmx-metrics/library/src/main/java/io/opentelemetry/instrumentation/jmx/engine/MetricRegistrar.java

@@ -180,9 +180,8 @@ static Consumer<ObservableLongMeasurement> longTypeCallback(MetricExtractor extr
    */
   static Attributes createMetricAttributes(
       MBeanServerConnection connection, ObjectName objectName, MetricExtractor extractor) {
-    MetricAttribute[] metricAttributes = extractor.getAttributes();
     AttributesBuilder attrBuilder = Attributes.builder();
-    for (MetricAttribute metricAttribute : metricAttributes) {
+    for (MetricAttribute metricAttribute : extractor.getAttributes()) {
       String attributeValue = metricAttribute.acquireAttributeValue(connection, objectName);
       if (attributeValue != null) {
         attrBuilder = attrBuilder.put(metricAttribute.getAttributeName(), attributeValue);

instrumentation/jmx-metrics/library/src/main/java/io/opentelemetry/instrumentation/jmx/yaml/JmxRule.java

@@ -128,14 +128,9 @@ private static Map<String, Metric> validateAttributeMapping(Map<String, Metric>
   public MetricDef buildMetricDef() throws Exception {
     BeanGroup group;
     if (bean != null) {
-      group = new BeanGroup(null, new ObjectName(bean));
+      group = BeanGroup.forSingleBean(bean);
     } else if (beans != null && !beans.isEmpty()) {
-      ObjectName[] objectNames = new ObjectName[beans.size()];
-      int k = 0;
-      for (String oneBean : beans) {
-        objectNames[k++] = new ObjectName(oneBean);
-      }
-      group = new BeanGroup(null, objectNames);
+      group = BeanGroup.forBeans(beans);
     } else {
       throw new IllegalStateException("No ObjectName specified");
     }
@@ -172,9 +167,7 @@ public MetricDef buildMetricDef() throws Exception {
       StateMapping stateMapping = getEffectiveStateMapping(m, this);
 
       if (stateMapping.isEmpty()) {
-        metricExtractors.add(
-            new MetricExtractor(
-                attrExtractor, metricInfo, attributeList.toArray(new MetricAttribute[0])));
+        metricExtractors.add(new MetricExtractor(attrExtractor, metricInfo, attributeList));
       } else {
 
         // generate one metric extractor per state metric key
@@ -184,7 +177,7 @@ public MetricDef buildMetricDef() throws Exception {
       }
     }
 
-    return new MetricDef(group, metricExtractors.toArray(new MetricExtractor[0]));
+    return new MetricDef(group, metricExtractors);
   }
 
   private static List<MetricExtractor> createStateMappingExtractors(
@@ -237,10 +230,7 @@ protected Number extractNumericalAttribute(
               MetricInfo.Type.UPDOWNCOUNTER);
 
       extractors.add(
-          new MetricExtractor(
-              stateMetricExtractor,
-              stateMetricInfo,
-              stateMetricAttributes.toArray(new MetricAttribute[0])));
+          new MetricExtractor(stateMetricExtractor, stateMetricInfo, stateMetricAttributes));
     }
     return extractors;
   }

instrumentation/jmx-metrics/library/src/test/java/io/opentelemetry/instrumentation/jmx/engine/RuleParserTest.java

@@ -254,7 +254,7 @@ void testConf5() throws Exception {
     assertThat(metricDef).isNotNull();
     assertThat(metricDef.getMetricExtractors()).hasSize(1);
 
-    MetricExtractor m1 = metricDef.getMetricExtractors()[0];
+    MetricExtractor m1 = metricDef.getMetricExtractors().get(0);
     assertThat(m1.getMetricValueExtractor().getAttributeName()).isEqualTo("ATTRIBUTE");
     assertThat(m1.getAttributes()).isEmpty();
 
@@ -286,7 +286,7 @@ void testConf6() throws Exception {
     assertThat(metricDef).isNotNull();
     assertThat(metricDef.getMetricExtractors()).hasSize(1);
 
-    MetricExtractor m1 = metricDef.getMetricExtractors()[0];
+    MetricExtractor m1 = metricDef.getMetricExtractors().get(0);
     assertThat(m1.getMetricValueExtractor().getAttributeName()).isEqualTo("ATTRIBUTE");
     // MetricAttribute set at the metric level should override the one set at the definition level
     assertThat(m1.getAttributes())
@@ -321,7 +321,7 @@ void testConf7() throws Exception {
     assertThat(metricDef.getMetricExtractors()).hasSize(1);
 
     // Test that the MBean attribute is correctly parsed
-    MetricExtractor m1 = metricDef.getMetricExtractors()[0];
+    MetricExtractor m1 = metricDef.getMetricExtractors().get(0);
     assertThat(m1.getMetricValueExtractor().getAttributeName()).isEqualTo("ATTRIBUTE");
     assertThat(m1.getInfo().getMetricName()).isEqualTo("ATTRIBUTE");
     assertThat(m1.getAttributes())
@@ -350,7 +350,7 @@ void testConf8() throws Exception {
     assertThat(metricDef).isNotNull();
     assertThat(metricDef.getMetricExtractors()).hasSize(1);
 
-    MetricExtractor m1 = metricDef.getMetricExtractors()[0];
+    MetricExtractor m1 = metricDef.getMetricExtractors().get(0);
     assertThat(m1.getMetricValueExtractor().getAttributeName()).isEqualTo("Attr.with.dot");
     assertThat(m1.getAttributes()).isEmpty();
 
@@ -426,7 +426,7 @@ void testStateMetricConf() throws Exception {
               assertThat(me.getInfo().getType()).isEqualTo(MetricInfo.Type.UPDOWNCOUNTER);
 
               assertThat(me.getAttributes()).hasSize(1);
-              MetricAttribute stateAttribute = me.getAttributes()[0];
+              MetricAttribute stateAttribute = me.getAttributes().get(0);
               assertThat(stateAttribute.getAttributeName()).isEqualTo("state_attribute");
               String stateAttributeValue =
                   stateAttribute.acquireAttributeValue(mockConnection, objectName);