1 files changed, 89 insertions, 0 deletions
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/util/ThreadLocalRequestScopePropagator.java b/gerrit-server/src/main/java/com/google/gerrit/server/util/ThreadLocalRequestScopePropagator.java
new file mode 100644
index 0000000000..581ccc1483
--- /dev/null
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/util/ThreadLocalRequestScopePropagator.java
@@ -0,0 +1,89 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.util;
+
+import com.google.inject.OutOfScopeException;
+import com.google.inject.Scope;
+
+import java.util.concurrent.Callable;
+
+/**
+ * {@link RequestScopePropagator} implementation for request scopes based on
+ * a {@link ThreadLocal} context.
+ *
+ * @param <C> "context" type stored in the {@link ThreadLocal}.
+ */
+public abstract class ThreadLocalRequestScopePropagator<C>
+    extends RequestScopePropagator {
+
+  private final ThreadLocal<C> threadLocal;
+
+  protected ThreadLocalRequestScopePropagator(Scope scope,
+      ThreadLocal<C> threadLocal) {
+    super(scope);
+    this.threadLocal = threadLocal;
+  }
+
+  /**
+   * @see RequestScopePropagator#wrap(Callable)
+   */
+  @Override
+  protected final <T> Callable<T> wrapImpl(final Callable<T> callable) {
+    final C ctx = continuingContext(requireContext());
+    return new Callable<T>() {
+      @Override
+      public T call() throws Exception {
+        if (threadLocal.get() != null) {
+          // This is consistent with the Guice ServletScopes.continueRequest()
+          // behavior.
+          throw new IllegalStateException("Cannot continue request, "
+              + "thread already has request in progress. A new thread must "
+              + "be used to propagate the request scope context.");
+        }
+
+        threadLocal.set(ctx);
+        try {
+          return callable.call();
+        } finally {
+          threadLocal.remove();
+        }
+      }
+    };
+  }
+
+  private C requireContext() {
+    C context = threadLocal.get();
+    if (context == null) {
+      throw new OutOfScopeException("Cannot access scoped object");
+    }
+    return context;
+  }
+
+  /**
+   * Returns a new context object based on the passed in context that has no
+   * request scoped objects initialized.
+   * <p>
+   * Note that some code paths expect request-scoped objects like
+   * {@code CurrentUser} to be constructible starting from just the context
+   * object returned by this method. For example, in the SSH scope, the context
+   * includes the {@code SshSession}, which is used by
+   * {@code SshCurrentUserProvider} to construct a new {@code CurrentUser} in
+   * the new thread.
+   *
+   * @param ctx the context to continue.
+   * @return a new context.
+   */
+  protected abstract C continuingContext(C ctx);
+}