Make servlet context path key private

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/servlet/ServletContextPath.java

@@ -7,6 +7,7 @@
 
 import io.opentelemetry.context.Context;
 import io.opentelemetry.context.ContextKey;
+import java.util.function.Supplier;
 
 /**
  * The context key here is used to propagate the servlet context path throughout the request, so
@@ -22,18 +23,41 @@ public final class ServletContextPath {
 
   // Keeps track of the servlet context path that needs to be prepended to the route when updating
   // the span name
-  public static final ContextKey<String> CONTEXT_KEY =
+  private static final ContextKey<ServletContextPath> CONTEXT_KEY =
       ContextKey.named("opentelemetry-servlet-context-path-key");
 
-  public static String prepend(Context context, String spanName) {
-    String value = context.get(CONTEXT_KEY);
-    // checking isEmpty just to avoid unnecessary string concat / allocation
-    if (value != null && !value.isEmpty()) {
-      return value + spanName;
-    } else {
-      return spanName;
+  public static Context init(Context context, Supplier<String> contextPathSupplier) {
+    ServletContextPath servletContextPath = context.get(CONTEXT_KEY);
+    if (servletContextPath != null) {
+      return context;
+    }
+    String contextPath = contextPathSupplier.get();
+    if (contextPath == null) {
+      // context path isn't know yet
+      return context;
+    }
+    if (contextPath.isEmpty() || contextPath.equals("/")) {
+      // normalize empty context path to null
+      contextPath = null;
     }
+    return context.with(CONTEXT_KEY, new ServletContextPath(contextPath));
+  }
+
+  private final String contextPath;
+
+  private ServletContextPath(String contextPath) {
+    this.contextPath = contextPath;
   }
 
-  private ServletContextPath() {}
+  public static String prepend(Context context, String spanName) {
+    ServletContextPath servletContextPath = context.get(CONTEXT_KEY);
+    if (servletContextPath != null) {
+      String value = servletContextPath.contextPath;
+      if (value != null) {
+        return value + spanName;
+      }
+    }
+
+    return spanName;
+  }
 }

instrumentation/servlet/servlet-2.2/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/servlet/v2_2/Servlet2Helper.java

@@ -43,4 +43,8 @@ public void stopSpan(
 
     instrumenter.end(context, requestContext, responseContext, throwable);
   }
+
+  public Context updateContext(Context context, HttpServletRequest request) {
+    return addServletContextPath(context, request);
+  }
 }

instrumentation/servlet/servlet-3.0/library/src/main/java/io/opentelemetry/instrumentation/servlet/v3_0/Servlet3HttpServerTracer.java

@@ -44,7 +44,7 @@ public Context updateContext(
         context,
         servlet ? SERVLET : FILTER,
         () -> SPAN_NAME_PROVIDER.getSpanNameOrNull(mappingResolver, request));
-    return updateContext(context, request);
+    return addServletContextPath(context, request);
   }
 
   @Override

instrumentation/servlet/servlet-common/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/servlet/BaseServletHelper.java

@@ -67,12 +67,8 @@ protected Context customizeContext(Context context, REQUEST request) {
     return context;
   }
 
-  private Context addServletContextPath(Context context, REQUEST request) {
-    String contextPath = accessor.getRequestContextPath(request);
-    if (contextPath != null && !contextPath.isEmpty() && !contextPath.equals("/")) {
-      return context.with(ServletContextPath.CONTEXT_KEY, contextPath);
-    }
-    return context;
+  protected Context addServletContextPath(Context context, REQUEST request) {
+    return ServletContextPath.init(context, () -> accessor.getRequestContextPath(request));
   }
 
   public Context getServerContext(REQUEST request) {
@@ -88,27 +84,13 @@ public void recordException(Context context, Throwable throwable) {
     AppServerBridge.recordException(context, throwable);
   }
 
-  /**
-   * When server spans are managed by app server instrumentation we need to add context path of
-   * current request to context if it isn't already added. Servlet instrumentation adds it when it
-   * starts server span.
-   */
-  public Context updateContext(Context context, REQUEST request) {
-    String contextPath = context.get(ServletContextPath.CONTEXT_KEY);
-    if (contextPath == null) {
-      context = addServletContextPath(context, request);
-    }
-
-    return context;
-  }
-
   public Context updateContext(
       Context context, REQUEST request, MappingResolver mappingResolver, boolean servlet) {
     ServerSpanNaming.updateServerSpanName(
         context,
         servlet ? SERVLET : FILTER,
         () -> spanNameProvider.getSpanNameOrNull(mappingResolver, request));
-    return updateContext(context, request);
+    return addServletContextPath(context, request);
   }
 
   /*

instrumentation/servlet/servlet-common/library/src/main/java/io/opentelemetry/instrumentation/servlet/ServletHttpServerTracer.java

@@ -70,12 +70,8 @@ protected Context customizeContext(Context context, REQUEST request) {
     return addServletContextPath(context, request);
   }
 
-  private Context addServletContextPath(Context context, REQUEST request) {
-    String contextPath = accessor.getRequestContextPath(request);
-    if (contextPath != null && !contextPath.isEmpty() && !contextPath.equals("/")) {
-      return context.with(ServletContextPath.CONTEXT_KEY, contextPath);
-    }
-    return context;
+  protected Context addServletContextPath(Context context, REQUEST request) {
+    return ServletContextPath.init(context, () -> accessor.getRequestContextPath(request));
   }
 
   @Override
@@ -224,20 +220,6 @@ public String getSpanName(REQUEST request) {
     return contextPath + servletPath;
   }
 
-  /**
-   * When server spans are managed by app server instrumentation we need to add context path of
-   * current request to context if it isn't already added. Servlet instrumentation adds it when it
-   * starts server span.
-   */
-  public Context updateContext(Context context, REQUEST request) {
-    String contextPath = context.get(ServletContextPath.CONTEXT_KEY);
-    if (contextPath == null) {
-      context = addServletContextPath(context, request);
-    }
-
-    return context;
-  }
-
   public void onTimeout(Context context, long timeout) {
     Span span = Span.fromContext(context);
     span.setStatus(StatusCode.ERROR);