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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  package org.apache.logging.log4j.message;
18  
19  import org.apache.logging.log4j.status.StatusLogger;
20  
21  /**
22   * Creates {@link FormattedMessage} instances for {@link MessageFactory2} methods (and {@link MessageFactory} by
23   * extension.)
24   * <p>
25   * Creates {@link SimpleMessage} objects that do not retain a reference to the parameter object.
26   * </p>
27   * <p>
28   * Intended for use by the {@link StatusLogger}: this logger retains a queue of recently logged messages in memory,
29   * causing memory leaks in web applications. (LOG4J2-1176)
30   * </p>
31   * <p>
32   * This class is immutable.
33   * </p>
34   * <h4>Note to implementors</h4>
35   * <p>
36   * This class does <em>not</em> implement any {@link MessageFactory2} methods and lets the superclass funnel those calls
37   * through {@link #newMessage(String, Object...)}.
38   * </p>
39   */
40  public final class ParameterizedNoReferenceMessageFactory extends AbstractMessageFactory {
41      private static final long serialVersionUID = 5027639245636870500L;
42  
43      /**
44       * Message implementation that only keeps a reference to the error text and the error (if any), not to the
45       * message parameters, in order to avoid memory leaks. This addresses LOG4J2-1368.
46       * @since 2.6
47       */
48      static class StatusMessage implements Message {
49          private static final long serialVersionUID = 4199272162767841280L;
50          private final String formattedMessage;
51          private final Throwable throwable;
52  
53          public StatusMessage(final String formattedMessage, final Throwable throwable) {
54              this.formattedMessage = formattedMessage;
55              this.throwable = throwable;
56          }
57  
58          @Override
59          public String getFormattedMessage() {
60              return formattedMessage;
61          }
62  
63          @Override
64          public String getFormat() {
65              return formattedMessage;
66          }
67  
68          @Override
69          public Object[] getParameters() {
70              return null;
71          }
72  
73          @Override
74          public Throwable getThrowable() {
75              return throwable;
76          }
77      }
78  
79      /**
80       * Constructs a message factory with default flow strings.
81       */
82      public ParameterizedNoReferenceMessageFactory() {
83          super();
84      }
85  
86      /**
87       * Instance of ParameterizedStatusMessageFactory.
88       */
89      public static final ParameterizedNoReferenceMessageFactory INSTANCE = new ParameterizedNoReferenceMessageFactory();
90  
91      /**
92       * Creates {@link SimpleMessage} instances containing the formatted parameterized message string.
93       *
94       * @param message The message pattern.
95       * @param params The message parameters.
96       * @return The Message.
97       *
98       * @see MessageFactory#newMessage(String, Object...)
99       */
100     @Override
101     public Message newMessage(final String message, final Object... params) {
102         if (params == null) {
103             return new SimpleMessage(message);
104         }
105         final ParameterizedMessage msg = new ParameterizedMessage(message, params);
106         return new StatusMessage(msg.getFormattedMessage(), msg.getThrowable());
107     }
108 }