Add possibility to specify serviceName with 'fromEnv'

Signed-off-by: Juraci Paixão Kröhling <juraci@kroehling.de>

jaeger-core/src/main/java/io/jaegertracing/Configuration.java

@@ -186,11 +186,15 @@ public Configuration(String serviceName) {
    * @return Configuration object from environmental variables
    */
   public static Configuration fromEnv() {
-    return new Configuration(getProperty(JAEGER_SERVICE_NAME))
-        .withTracerTags(tracerTagsFromEnv())
-        .withReporter(ReporterConfiguration.fromEnv())
-        .withSampler(SamplerConfiguration.fromEnv())
-        .withCodec(CodecConfiguration.fromEnv());
+    return Configuration.fromEnv(getProperty(JAEGER_SERVICE_NAME));
+  }
+
+  public static Configuration fromEnv(String serviceName) {
+    return new Configuration(serviceName)
+            .withTracerTags(tracerTagsFromEnv())
+            .withReporter(ReporterConfiguration.fromEnv())
+            .withSampler(SamplerConfiguration.fromEnv())
+            .withCodec(CodecConfiguration.fromEnv());
   }
 
   public JaegerTracer.Builder getTracerBuilder() {

jaeger-core/src/test/java/io/jaegertracing/ConfigurationTest.java

@@ -33,14 +33,11 @@
 import io.jaegertracing.internal.samplers.RateLimitingSampler;
 import io.jaegertracing.spi.Codec;
 import io.jaegertracing.spi.Sampler;
-import io.opentracing.noop.NoopTracerFactory;
 import io.opentracing.propagation.Format;
 import io.opentracing.propagation.Format.Builtin;
 import io.opentracing.propagation.TextMap;
 import io.opentracing.propagation.TextMapExtractAdapter;
 import io.opentracing.propagation.TextMapInjectAdapter;
-import io.opentracing.util.GlobalTracer;
-import java.lang.reflect.Field;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
@@ -74,18 +71,25 @@ public void clearProperties() throws NoSuchFieldException, IllegalAccessExceptio
     System.clearProperty(Configuration.JAEGER_PROPAGATION);
 
     System.clearProperty(TEST_PROPERTY);
-
-    // Reset opentracing's global tracer
-    Field field = GlobalTracer.class.getDeclaredField("tracer");
-    field.setAccessible(true);
-    field.set(null, NoopTracerFactory.create());
   }
 
   @Test
   public void testFromEnv() {
     System.setProperty(Configuration.JAEGER_SERVICE_NAME, "Test");
     assertNotNull(Configuration.fromEnv().getTracer());
-    assertFalse(GlobalTracer.isRegistered());
+  }
+
+  @Test
+  public void testFromEnvWithExplicitServiceName() {
+    // prepare
+    String serviceName = "testFromEnvWithExplicitServiceName";
+    System.setProperty(Configuration.JAEGER_SERVICE_NAME, "not" + serviceName);
+
+    // test
+    JaegerTracer tracer = Configuration.fromEnv(serviceName).getTracer();
+
+    // check
+    assertEquals(serviceName, tracer.getServiceName());
   }
 
   @Test