Respect jaeger.service-name property (#57)

* Respect jaeger.service-name property

JAEGER_SERVICE_NAME is an environment variable set by e.g. the
jaeger-operator when it injects environment variables into containers.

This change means that Spring apps can use the auto-container inject
feature of the operator and be identified correctly by default.

See https://www.jaegertracing.io/docs/1.13/client-features/

See #56

opentracing-spring-jaeger-starter/src/main/java/io/opentracing/contrib/java/spring/jaeger/starter/JaegerConfigurationProperties.java

@@ -40,10 +40,9 @@ public class JaegerConfigurationProperties {
 
   /**
    * Service name to be used
-   * By default it will be the value of the 'spring.application.name' property name
-   * and if that is not set, it falls back to 'unknown-spring-boot'
+   * Expect certain properties in order, falling back to 'unknown-spring-boot'.
    */
-  @Value("${spring.application.name:unknown-spring-boot}")
+  @Value("${jaeger.service-name:${spring.application.name:unknown-spring-boot}}")
   private String serviceName;
 
   /**

opentracing-spring-jaeger-starter/src/test/java/io/opentracing/contrib/java/spring/jaeger/starter/basic/JaegerTracerServiceNameSetExplicitWithPropsTest.java

@@ -26,6 +26,7 @@
         "opentracing.jaeger.enabled=true",
         "spring.application.name=foo",
         "app.env=stage",
+        "jaeger.service-name=please-override",
         "opentracing.jaeger.service-name=${spring.application.name}-${app.env}"
     }
 )

opentracing-spring-jaeger-starter/src/test/java/io/opentracing/contrib/java/spring/jaeger/starter/basic/JaegerTracerServiceNameSetWithoutOpentracingPrefixTest.java

@@ -0,0 +1,41 @@
+/**
+ * Copyright 2018-2019 The OpenTracing Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package io.opentracing.contrib.java.spring.jaeger.starter.basic;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+import io.opentracing.contrib.java.spring.jaeger.starter.AbstractTracerSpringTest;
+import org.junit.Test;
+import org.springframework.test.context.TestPropertySource;
+
+@TestPropertySource(
+    properties = {
+        "spring.main.banner-mode=off",
+        "opentracing.jaeger.enabled=true",
+        "jaeger.service-name=foo",
+        "spring.application.name=bar"
+    }
+)
+public class JaegerTracerServiceNameSetWithoutOpentracingPrefixTest extends AbstractTracerSpringTest {
+
+  @Test
+  public void testNameIsAsExpected() {
+    assertThat(tracer).isNotNull();
+    assertThat(tracer).isInstanceOf(io.jaegertracing.internal.JaegerTracer.class);
+
+    // 'jaeger.service-name' should take priority over 'spring.application.name'
+    assertThat((getTracer()).getServiceName()).isEqualTo("foo");
+  }
+}