Line data    Source code

       1             : // Copyright (C) 2012 The Android Open Source Project
       2             : //
       3             : // Licensed under the Apache License, Version 2.0 (the "License");
       4             : // you may not use this file except in compliance with the License.
       5             : // You may obtain a copy of the License at
       6             : //
       7             : // http://www.apache.org/licenses/LICENSE-2.0
       8             : //
       9             : // Unless required by applicable law or agreed to in writing, software
      10             : // distributed under the License is distributed on an "AS IS" BASIS,
      11             : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      12             : // See the License for the specific language governing permissions and
      13             : // limitations under the License.
      14             : 
      15             : package com.google.gerrit.server.util;
      16             : 
      17             : import com.google.inject.OutOfScopeException;
      18             : import com.google.inject.Scope;
      19             : import java.util.concurrent.Callable;
      20             : 
      21             : /**
      22             :  * {@link RequestScopePropagator} implementation for request scopes based on a {@link ThreadLocal}
      23             :  * context.
      24             :  *
      25             :  * @param <C> "context" type stored in the {@link ThreadLocal}.
      26             :  */
      27             : public abstract class ThreadLocalRequestScopePropagator<C> extends RequestScopePropagator {
      28             : 
      29             :   private final ThreadLocal<C> threadLocal;
      30             : 
      31             :   protected ThreadLocalRequestScopePropagator(
      32             :       Scope scope, ThreadLocal<C> threadLocal, ThreadLocalRequestContext local) {
      33          92 :     super(scope, local);
      34          92 :     this.threadLocal = threadLocal;
      35          92 :   }
      36             : 
      37             :   /** @see RequestScopePropagator#wrap(Callable) */
      38             :   @Override
      39             :   protected final <T> Callable<T> wrapImpl(Callable<T> callable) {
      40          91 :     C ctx = continuingContext(requireContext());
      41          91 :     return () -> {
      42          91 :       C old = threadLocal.get();
      43          91 :       threadLocal.set(ctx);
      44             :       try {
      45          91 :         return callable.call();
      46             :       } finally {
      47          91 :         if (old != null) {
      48           0 :           threadLocal.set(old);
      49             :         } else {
      50          91 :           threadLocal.remove();
      51             :         }
      52             :       }
      53             :     };
      54             :   }
      55             : 
      56             :   private C requireContext() {
      57          91 :     C context = threadLocal.get();
      58          91 :     if (context == null) {
      59           0 :       throw new OutOfScopeException("Cannot access scoped object");
      60             :     }
      61          91 :     return context;
      62             :   }
      63             : 
      64             :   /**
      65             :    * Returns a new context object based on the passed in context that has no request scoped objects
      66             :    * initialized.
      67             :    *
      68             :    * <p>Note that some code paths expect request-scoped objects like {@code CurrentUser} to be
      69             :    * constructible starting from just the context object returned by this method. For example, in
      70             :    * the SSH scope, the context includes the {@code SshSession}, which is used by {@code
      71             :    * SshCurrentUserProvider} to construct a new {@code CurrentUser} in the new thread.
      72             :    *
      73             :    * @param ctx the context to continue.
      74             :    * @return a new context.
      75             :    */
      76             :   protected abstract C continuingContext(C ctx);
      77             : }