1 /*
2  * Copyright (C) 2008 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.google.common.testing;
18 
19 import com.google.common.annotations.Beta;
20 import com.google.common.annotations.GwtCompatible;
21 import java.util.ArrayList;
22 import java.util.Collections;
23 import java.util.List;
24 import java.util.logging.Handler;
25 import java.util.logging.LogRecord;
26 import org.checkerframework.checker.nullness.compatqual.NullableDecl;
27 
28 /**
29  * Tests may use this to intercept messages that are logged by the code under test. Example:
30  *
31  * <pre>
32  *   TestLogHandler handler;
33  *
34  *   protected void setUp() throws Exception {
35  *     super.setUp();
36  *     handler = new TestLogHandler();
37  *     SomeClass.logger.addHandler(handler);
38  *     addTearDown(new TearDown() {
39  *       public void tearDown() throws Exception {
40  *         SomeClass.logger.removeHandler(handler);
41  *       }
42  *     });
43  *   }
44  *
45  *   public void test() {
46  *     SomeClass.foo();
47  *     LogRecord firstRecord = handler.getStoredLogRecords().get(0);
48  *     assertEquals("some message", firstRecord.getMessage());
49  *   }
50  * </pre>
51  *
52  * @author Kevin Bourrillion
53  * @since 10.0
54  */
55 @Beta
56 @GwtCompatible
57 public class TestLogHandler extends Handler {
58   /** We will keep a private list of all logged records */
59   private final List<LogRecord> list = new ArrayList<>();
60 
61   /** Adds the most recently logged record to our list. */
62   @Override
publish(@ullableDecl LogRecord record)63   public synchronized void publish(@NullableDecl LogRecord record) {
64     list.add(record);
65   }
66 
67   @Override
flush()68   public void flush() {}
69 
70   @Override
close()71   public void close() {}
72 
clear()73   public synchronized void clear() {
74     list.clear();
75   }
76 
77   /** Returns a snapshot of the logged records. */
78   /*
79    * TODO(cpovirk): consider higher-level APIs here (say, assertNoRecordsLogged(),
80    * getOnlyRecordLogged(), getAndClearLogRecords()...)
81    *
82    * TODO(cpovirk): consider renaming this method to reflect that it takes a snapshot (and/or return
83    * an ImmutableList)
84    */
getStoredLogRecords()85   public synchronized List<LogRecord> getStoredLogRecords() {
86     List<LogRecord> result = new ArrayList<>(list);
87     return Collections.unmodifiableList(result);
88   }
89 }
90