Ability to set the configuration file from the classpath of runtime a…

…ttachment (#2581)

Fix #2576

Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>

agent/runtime-attach/src/main/java/com/microsoft/applicationinsights/attach/ApplicationInsights.java

@@ -17,6 +17,13 @@
 /** This class allows you to attach the Application Insights agent for Java at runtime. */
 public final class ApplicationInsights {
 
+  /**
+   * This property allows configuring an Application Insights json file. It can be helpful to get an
+   * Application Insights json file by Spring profile.
+   */
+  public static final String APPLICATIONINSIGHTS_RUNTIME_ATTACH_CONFIGURATION_FILE =
+      "applicationinsights.runtime-attach.configuration.classpath.file";
+
   private static final Logger logger = Logger.getLogger(ApplicationInsights.class.getName());
 
   private static final String RUNTIME_ATTACHED_ENABLED_PROPERTY =
@@ -30,6 +37,9 @@ private ApplicationInsights() {}
   /**
    * Attach the Application Insights agent for Java to the current JVM. The attachment must be
    * requested at the beginning of the main method.
+   *
+   * @throws ConfigurationException If the file given by the
+   *     applicationinsights.runtime-attach.configuration.classpath.file property was not found
    */
   public static void attach() {
 
@@ -53,22 +63,55 @@ public static void attach() {
 
   private static Optional<String> findJsonConfig() {
 
-    InputStream configContentAsInputStream =
-        ApplicationInsights.class.getResourceAsStream("/applicationinsights.json");
+    String fileName = findJsonConfigFile();
+
+    InputStream configContentAsInputStream = findResourceAsStream(fileName);
+
     if (configContentAsInputStream == null) {
       return Optional.empty();
     }
+
+    String json = findJson(configContentAsInputStream);
+    return Optional.of(json);
+  }
+
+  private static String findJson(InputStream configContentAsInputStream) {
     try (InputStreamReader inputStreamReader =
             new InputStreamReader(configContentAsInputStream, StandardCharsets.UTF_8);
         BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {
-      String json = bufferedReader.lines().collect(Collectors.joining(""));
-      return Optional.of(json);
+      return bufferedReader.lines().collect(Collectors.joining(""));
     } catch (IOException e) {
       throw new IllegalStateException(
           "Unexpected issue during loading of JSON configuration file: " + e.getMessage());
     }
   }
 
+  private static InputStream findResourceAsStream(String fileName) {
+    InputStream configContentAsInputStream =
+        ApplicationInsights.class.getResourceAsStream("/" + fileName);
+    if (configContentAsInputStream == null && isJsonFileConfiguredWithProperty()) {
+      throw new ConfigurationException(fileName + " not found on the class path");
+    }
+    return configContentAsInputStream;
+  }
+
+  public static class ConfigurationException extends IllegalArgumentException {
+    ConfigurationException(String message) {
+      super(message);
+    }
+  }
+
+  private static String findJsonConfigFile() {
+    if (isJsonFileConfiguredWithProperty()) {
+      return System.getProperty(APPLICATIONINSIGHTS_RUNTIME_ATTACH_CONFIGURATION_FILE);
+    }
+    return "applicationinsights.json";
+  }
+
+  private static boolean isJsonFileConfiguredWithProperty() {
+    return System.getProperty(APPLICATIONINSIGHTS_RUNTIME_ATTACH_CONFIGURATION_FILE) != null;
+  }
+
   private static boolean agentIsAttached() {
     try {
       Class.forName("io.opentelemetry.javaagent.OpenTelemetryAgent", false, null);

smoke-tests/apps/SpringBootAttachInMain/src/main/java/com/microsoft/applicationinsights/smoketestapp/SpringBootApp.java

@@ -4,7 +4,6 @@
 package com.microsoft.applicationinsights.smoketestapp;
 
 import com.microsoft.applicationinsights.attach.ApplicationInsights;
-import java.io.IOException;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.builder.SpringApplicationBuilder;
@@ -13,7 +12,7 @@
 @SpringBootApplication
 public class SpringBootApp extends SpringBootServletInitializer {
 
-  public static void main(String[] args) throws IOException {
+  public static void main(String[] args) {
     ApplicationInsights.attach();
     SpringApplication.run(SpringBootApp.class, args);
   }