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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. 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, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.util.internal.logging;
17  
18  
19  import org.slf4j.LoggerFactory;
20  import org.slf4j.helpers.NOPLoggerFactory;
21  
22  import java.io.OutputStream;
23  import java.io.PrintStream;
24  import java.io.UnsupportedEncodingException;
25  
26  /**
27   * Logger factory which creates a <a href="http://www.slf4j.org/">SLF4J</a>
28   * logger.
29   */
30  public class Slf4JLoggerFactory extends InternalLoggerFactory {
31  
32      public Slf4JLoggerFactory() {
33      }
34  
35      Slf4JLoggerFactory(boolean failIfNOP) {
36          assert failIfNOP; // Should be always called with true.
37  
38          // SFL4J writes it error messages to System.err. Capture them so that the user does not see such a message on
39          // the console during automatic detection.
40          final StringBuffer buf = new StringBuffer();
41          final PrintStream err = System.err;
42          try {
43              System.setErr(new PrintStream(new OutputStream() {
44                  @Override
45                  public void write(int b) {
46                      buf.append((char) b);
47                  }
48              }, true, "US-ASCII"));
49          } catch (UnsupportedEncodingException e) {
50              throw new Error(e);
51          }
52  
53          try {
54              if (LoggerFactory.getILoggerFactory() instanceof NOPLoggerFactory) {
55                  throw new NoClassDefFoundError(buf.toString());
56              } else {
57                  err.print(buf);
58                  err.flush();
59              }
60          } finally {
61              System.setErr(err);
62          }
63      }
64  
65      @Override
66      public InternalLogger newInstance(String name) {
67          return new Slf4JLogger(LoggerFactory.getLogger(name));
68      }
69  }