minor rename + enhance tests

Author: SylvainJuge

instrumentation/jmx-metrics/javaagent/src/main/java/io/opentelemetry/instrumentation/javaagent/jmx/JmxMetricInsightInstaller.java

@@ -35,7 +35,7 @@ public void afterAgent(AutoConfiguredOpenTelemetrySdk autoConfiguredSdk) {
 
       try {
         config.getList("otel.jmx.config").stream().map(Paths::get).forEach(jmx::addCustomRules);
-        config.getList("otel.jmx.target.system").forEach(jmx::addClasspathRules);
+        config.getList("otel.jmx.target.system").forEach(jmx::addClassPathRules);
       } catch (IllegalArgumentException e) {
         // for now only log JMX errors as they do not prevent agent startup
         logger.log(Level.SEVERE, "Error while loading JMX configuration", e);

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

@@ -54,10 +54,9 @@ public JmxTelemetryBuilder beanDiscoveryDelay(long delayMs) {
    * @throws IllegalArgumentException when classpath resource does not exist or can't be parsed
    */
   @CanIgnoreReturnValue
-  public JmxTelemetryBuilder addClasspathRules(String target) {
+  public JmxTelemetryBuilder addClassPathRules(String target) {
     String yamlResource = String.format("/jmx/rules/%s.yaml", target);
-    ClassLoader classLoader = JmxTelemetryBuilder.class.getClassLoader();
-    try (InputStream inputStream = classLoader.getResourceAsStream(yamlResource)) {
+    try (InputStream inputStream = JmxTelemetryBuilder.class.getResourceAsStream(yamlResource)) {
       if (inputStream == null) {
         throw new IllegalArgumentException("JMX rules not found in classpath: " + yamlResource);
       }

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

@@ -9,6 +9,7 @@
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import io.opentelemetry.api.OpenTelemetry;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import org.junit.jupiter.api.Test;
@@ -25,13 +26,26 @@ void createDefault() {
   @Test
   void missingClasspathTarget() {
     JmxTelemetryBuilder builder = JmxTelemetry.builder(OpenTelemetry.noop());
-    assertThatThrownBy(() -> builder.addClasspathRules("should-not-exist"))
+    assertThatThrownBy(() -> builder.addClassPathRules("should-not-exist"))
         .isInstanceOf(IllegalArgumentException.class);
   }
 
+  @Test
+  void invalidClasspathTarget() {
+    JmxTelemetryBuilder builder = JmxTelemetry.builder(OpenTelemetry.noop());
+    assertThatThrownBy(() -> builder.addClassPathRules("invalid"))
+        .isInstanceOf(IllegalArgumentException.class);
+  }
+
+  @Test
+  void knownClassPathTarget() {
+    JmxTelemetry.builder(OpenTelemetry.noop()).addClassPathRules("jvm").build();
+  }
+
   @Test
   void invalidExternalYaml(@TempDir Path dir) throws Exception {
     Path invalid = Files.createTempFile(dir, "invalid", ".yaml");
+    Files.write(invalid, ":this !is /not YAML".getBytes(StandardCharsets.UTF_8));
     JmxTelemetryBuilder builder = JmxTelemetry.builder(OpenTelemetry.noop());
     assertThatThrownBy(() -> builder.addCustomRules(invalid))
         .isInstanceOf(IllegalArgumentException.class);

instrumentation/jmx-metrics/library/src/test/resources/jmx/rules/invalid.yaml

@@ -0,0 +1 @@
+:this !is /not YAML