minor refactor: make constructor private

Author: SylvainJuge

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

@@ -8,6 +8,7 @@
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 
+import io.opentelemetry.instrumentation.jmx.yaml.StateMapping;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.logging.Level;
@@ -103,7 +104,7 @@ private static void verifyAndAddNameSegment(List<String> segments, StringBuilder
     segments.add(newSegment);
   }
 
-  public BeanAttributeExtractor(String baseName, String... nameChain) {
+  private BeanAttributeExtractor(String baseName, String... nameChain) {
     if (baseName == null || nameChain == null) {
       throw new IllegalArgumentException("null argument for BeanAttributeExtractor");
     }
@@ -289,10 +290,11 @@ private String extractStringAttribute(MBeanServerConnection connection, ObjectNa
   }
 
   /**
-   * Wraps provided extractor to filter-out negative values by replacing them with {@literal null}.
+   * Provides a bean attribute extractor to filter-out negative values by replacing them with
+   * {@literal null}.
    *
-   * @param extractor extractor to wrap
-   * @return extractor filtering-out negative values
+   * @param extractor original extractor
+   * @return equivalent extractor filtering-out negative values
    */
   public static BeanAttributeExtractor filterNegativeValues(BeanAttributeExtractor extractor) {
     return new BeanAttributeExtractor(extractor.baseName, extractor.nameChain) {
@@ -310,4 +312,25 @@ protected Number extractNumericalAttribute(
       }
     };
   }
+
+  public static BeanAttributeExtractor forStateMetric(
+      BeanAttributeExtractor extractor, String key, StateMapping stateMapping) {
+    return new BeanAttributeExtractor(extractor.baseName, extractor.nameChain) {
+      @Override
+      protected Object getSampleValue(MBeanServerConnection connection, ObjectName objectName) {
+        // metric actual type is sampled in the discovery process, so we have to
+        // make this extractor as extracting integers.
+        return 0;
+      }
+
+      @Nullable
+      @Override
+      protected Number extractNumericalAttribute(
+          MBeanServerConnection connection, ObjectName objectName) {
+        String rawStateValue = extractor.extractValue(connection, objectName);
+        String mappedStateValue = stateMapping.getStateValue(rawStateValue);
+        return key.equals(mappedStateValue) ? 1 : 0;
+      }
+    };
+  }
 }

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

@@ -19,7 +19,6 @@
 import java.util.Map;
 import java.util.Set;
 import javax.annotation.Nullable;
-import javax.management.MBeanServerConnection;
 import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 
@@ -214,25 +213,8 @@ private static List<MetricExtractor> createStateMappingExtractors(
         }
       }
 
-      BeanAttributeExtractor stateMetricExtractor =
-          new BeanAttributeExtractor(attrExtractor.getAttributeName()) {
-
-            @Override
-            protected Object getSampleValue(
-                MBeanServerConnection connection, ObjectName objectName) {
-              // metric actual type is sampled in the discovery process, so we have to
-              // make this extractor as extracting integers.
-              return 0;
-            }
-
-            @Override
-            protected Number extractNumericalAttribute(
-                MBeanServerConnection connection, ObjectName objectName) {
-              String rawStateValue = attrExtractor.extractValue(connection, objectName);
-              String mappedStateValue = stateMapping.getStateValue(rawStateValue);
-              return key.equals(mappedStateValue) ? 1 : 0;
-            }
-          };
+      BeanAttributeExtractor extractor =
+          BeanAttributeExtractor.forStateMetric(attrExtractor, key, stateMapping);
 
       // state metric are always up/down counters
       MetricInfo stateMetricInfo =
@@ -243,8 +225,7 @@ protected Number extractNumericalAttribute(
               metricInfo.getUnit(),
               MetricInfo.Type.UPDOWNCOUNTER);
 
-      extractors.add(
-          new MetricExtractor(stateMetricExtractor, stateMetricInfo, stateMetricAttributes));
+      extractors.add(new MetricExtractor(extractor, stateMetricInfo, stateMetricAttributes));
     }
     return extractors;
   }