Use Implementation-Title as default service name if it is available

CHANGELOG.asciidoc

@@ -29,6 +29,8 @@ endif::[]
 * Replaced `authorization` in the default value of `sanitize_field_names` with `*auth*` - {pull}2326[#2326]
 * Unsampled transactions are dropped and not sent to the APM-Server if the APM-Server version is 8.0+ - {pull}2329[#2329]
 * Adding agent logging capabilities to our SDK, making it available for external plugins - {pull}2390[#2390]
+* When the `MANIFEST.MF` of the main jar contains the `Implementation-Title` attribute, it is used as the default service name - {pull}1921[#1921]
+  Note: this may change your service names if you relied on the auto-discovery that uses the name of the jar file. If that jar file also contains an `Implementation-Title` attribute in the `MANIFEST.MF` file, the latter will take precedence.
 
 [float]
 ===== Bug fixes

apm-agent-core/src/main/java/co/elastic/apm/agent/configuration/ServiceNameUtil.java

@@ -20,6 +20,8 @@
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+import java.util.jar.Attributes;
+import java.util.jar.JarFile;
 
 public class ServiceNameUtil {
     private static final String JAR_VERSION_SUFFIX = "-(\\d+\\.)+(\\d+)(.*)?$";
@@ -91,7 +93,14 @@ private static String parseJarCommand(String command) {
         String result = null;
         for (String commandPart : commandParts) {
             if (commandPart.endsWith(".jar")) {
-                result = removeVersionFromJar(removePath(removeJarExtension(commandPart)));
+                try (JarFile jarFile = new JarFile(commandPart)) {
+                    result = jarFile.getManifest().getMainAttributes().getValue(Attributes.Name.IMPLEMENTATION_TITLE);
+                } catch (Exception ignored) {
+                }
+
+                if (result == null || result.isEmpty()) {
+                    result = removeVersionFromJar(removePath(removeJarExtension(commandPart)));
+                }
                 break;
             }
         }

apm-agent/src/test/resources/configuration.asciidoc.ftl

@@ -83,6 +83,7 @@ ELASTIC_APM_SERVER_URL=http://localhost:8200
 For Spring-based application, uses the `spring.application.name` property, if set.
 For Servlet-based applications, uses the `display-name` of the `web.xml`, if available.
 Falls back to the servlet context path the application is mapped to (unless mapped to the root context).
+Falls back to the `Implementation-Title` in the `MANIFEST.MF` file.
 Falls back to the name of the main class or jar file.
 If the service name is set explicitly, it overrides all of the above.
 </#assign>

docs/configuration.asciidoc

@@ -497,6 +497,7 @@ NOTE: Service name auto discovery mechanisms require APM Server 7.0+.
 | For Spring-based application, uses the `spring.application.name` property, if set.
 For Servlet-based applications, uses the `display-name` of the `web.xml`, if available.
 Falls back to the servlet context path the application is mapped to (unless mapped to the root context).
+Falls back to the `Implementation-Title` in the `MANIFEST.MF` file.
 Falls back to the name of the main class or jar file.
 If the service name is set explicitly, it overrides all of the above.
  | String | false
@@ -2891,6 +2892,7 @@ The default unit for this option is `ms`.
 # Default value: For Spring-based application, uses the `spring.application.name` property, if set.
 # For Servlet-based applications, uses the `display-name` of the `web.xml`, if available.
 # Falls back to the servlet context path the application is mapped to (unless mapped to the root context).
+# Falls back to the `Implementation-Title` in the `MANIFEST.MF` file.
 # Falls back to the name of the main class or jar file.
 # If the service name is set explicitly, it overrides all of the above.
 #