001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.testing;
018
019import com.google.common.annotations.GwtCompatible;
020import com.google.errorprone.annotations.concurrent.GuardedBy;
021import java.util.ArrayList;
022import java.util.Collections;
023import java.util.List;
024import java.util.logging.Handler;
025import java.util.logging.LogRecord;
026import org.jspecify.annotations.NullMarked;
027import org.checkerframework.checker.nullness.qual.Nullable;
028
029/**
030 * Tests may use this to intercept messages that are logged by the code under test. Example:
031 *
032 * <pre>
033 *   TestLogHandler handler;
034 *
035 *   protected void setUp() throws Exception {
036 *     super.setUp();
037 *     handler = new TestLogHandler();
038 *     SomeClass.logger.addHandler(handler);
039 *     addTearDown(new TearDown() {
040 *       public void tearDown() throws Exception {
041 *         SomeClass.logger.removeHandler(handler);
042 *       }
043 *     });
044 *   }
045 *
046 *   public void test() {
047 *     SomeClass.foo();
048 *     LogRecord firstRecord = handler.getStoredLogRecords().get(0);
049 *     assertEquals("some message", firstRecord.getMessage());
050 *   }
051 * </pre>
052 *
053 * @author Kevin Bourrillion
054 * @since 10.0
055 */
056@GwtCompatible
057@NullMarked
058public class TestLogHandler extends Handler {
059  private final Object lock = new Object();
060
061  /** We will keep a private list of all logged records */
062  @GuardedBy("lock")
063  private final List<LogRecord> list = new ArrayList<>();
064
065  /** Adds the most recently logged record to our list. */
066  @Override
067  public void publish(@Nullable LogRecord record) {
068    synchronized (lock) {
069      if (record != null) {
070        list.add(record);
071      }
072    }
073  }
074
075  @Override
076  public void flush() {}
077
078  @Override
079  public void close() {}
080
081  public void clear() {
082    synchronized (lock) {
083      list.clear();
084    }
085  }
086
087  /** Returns a snapshot of the logged records. */
088  /*
089   * TODO(cpovirk): consider higher-level APIs here (say, assertNoRecordsLogged(),
090   * getOnlyRecordLogged(), getAndClearLogRecords()...)
091   *
092   * TODO(cpovirk): consider renaming this method to reflect that it takes a snapshot (and/or return
093   * an ImmutableList)
094   */
095  public List<LogRecord> getStoredLogRecords() {
096    synchronized (lock) {
097      List<LogRecord> result = new ArrayList<>(list);
098      return Collections.unmodifiableList(result);
099    }
100  }
101}