guava

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/*
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 * Copyright (C) 2008 The Guava Authors
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 * http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.google.common.testing;
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import com.google.common.annotations.GwtCompatible;
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import com.google.errorprone.annotations.concurrent.GuardedBy;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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import java.util.logging.Handler;
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import java.util.logging.LogRecord;
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import org.checkerframework.checker.nullness.qual.Nullable;
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/**
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 * Tests may use this to intercept messages that are logged by the code under test. Example:
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 *
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 * <pre>
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 *   TestLogHandler handler;
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 *
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 *   protected void setUp() throws Exception {
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 *     super.setUp();
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 *     handler = new TestLogHandler();
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 *     SomeClass.logger.addHandler(handler);
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 *     addTearDown(new TearDown() {
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 *       public void tearDown() throws Exception {
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 *         SomeClass.logger.removeHandler(handler);
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 *       }
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 *     });
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 *   }
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 *
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 *   public void test() {
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 *     SomeClass.foo();
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 *     LogRecord firstRecord = handler.getStoredLogRecords().get(0);
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 *     assertEquals("some message", firstRecord.getMessage());
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 *   }
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 * </pre>
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 *
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 * @author Kevin Bourrillion
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 * @since 10.0
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 */
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@GwtCompatible
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@ElementTypesAreNonnullByDefault
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public class TestLogHandler extends Handler {
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  private final Object lock = new Object();
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  /** We will keep a private list of all logged records */
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  @GuardedBy("lock")
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  private final List<LogRecord> list = new ArrayList<>();
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  /** Adds the most recently logged record to our list. */
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  @Override
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  public void publish(@Nullable LogRecord record) {
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    synchronized (lock) {
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      if (record != null) {
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        list.add(record);
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      }
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    }
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  }
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  @Override
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  public void flush() {}
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  @Override
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  public void close() {}
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  public void clear() {
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    synchronized (lock) {
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      list.clear();
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    }
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  }
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  /** Returns a snapshot of the logged records. */
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  /*
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   * TODO(cpovirk): consider higher-level APIs here (say, assertNoRecordsLogged(),
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   * getOnlyRecordLogged(), getAndClearLogRecords()...)
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   *
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   * TODO(cpovirk): consider renaming this method to reflect that it takes a snapshot (and/or return
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   * an ImmutableList)
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   */
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  public List<LogRecord> getStoredLogRecords() {
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    synchronized (lock) {
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      List<LogRecord> result = new ArrayList<>(list);
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      return Collections.unmodifiableList(result);
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    }
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  }
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}
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