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
18 package org.apache.log4j;
19
20 import java.io.IOException;
21 import java.io.OutputStream;
22 import org.apache.log4j.helpers.LogLog;
23
24 /**
25 * ConsoleAppender appends log events to <code>System.out</code> or
26 * <code>System.err</code> using a layout specified by the user. The
27 * default target is <code>System.out</code>.
28 *
29 * @author Ceki Gülcü
30 * @author Curt Arnold
31 * @since 1.1 */
32 public class ConsoleAppender extends WriterAppender {
33
34 public static final String SYSTEM_OUT = "System.out";
35 public static final String SYSTEM_ERR = "System.err";
36
37 protected String target = SYSTEM_OUT;
38
39 /**
40 * Determines if the appender honors reassignments of System.out
41 * or System.err made after configuration.
42 */
43 private boolean follow = false;
44
45 /**
46 * Constructs an unconfigured appender.
47 */
48 public ConsoleAppender() {
49 }
50
51 /**
52 * Creates a configured appender.
53 *
54 * @param layout layout, may not be null.
55 */
56 public ConsoleAppender(Layout layout) {
57 this(layout, SYSTEM_OUT);
58 }
59
60 /**
61 * Creates a configured appender.
62 * @param layout layout, may not be null.
63 * @param target target, either "System.err" or "System.out".
64 */
65 public ConsoleAppender(Layout layout, String target) {
66 setLayout(layout);
67 setTarget(target);
68 activateOptions();
69 }
70
71 /**
72 * Sets the value of the <b>Target</b> option. Recognized values
73 * are "System.out" and "System.err". Any other value will be
74 * ignored.
75 * */
76 public
77 void setTarget(String value) {
78 String v = value.trim();
79
80 if (SYSTEM_OUT.equalsIgnoreCase(v)) {
81 target = SYSTEM_OUT;
82 } else if (SYSTEM_ERR.equalsIgnoreCase(v)) {
83 target = SYSTEM_ERR;
84 } else {
85 targetWarn(value);
86 }
87 }
88
89 /**
90 * Returns the current value of the <b>Target</b> property. The
91 * default value of the option is "System.out".
92 *
93 * See also {@link #setTarget}.
94 * */
95 public
96 String getTarget() {
97 return target;
98 }
99
100 /**
101 * Sets whether the appender honors reassignments of System.out
102 * or System.err made after configuration.
103 * @param newValue if true, appender will use value of System.out or
104 * System.err in force at the time when logging events are appended.
105 * @since 1.2.13
106 */
107 public final void setFollow(final boolean newValue) {
108 follow = newValue;
109 }
110
111 /**
112 * Gets whether the appender honors reassignments of System.out
113 * or System.err made after configuration.
114 * @return true if appender will use value of System.out or
115 * System.err in force at the time when logging events are appended.
116 * @since 1.2.13
117 */
118 public final boolean getFollow() {
119 return follow;
120 }
121
122 void targetWarn(String val) {
123 LogLog.warn("["+val+"] should be System.out or System.err.");
124 LogLog.warn("Using previously set target, System.out by default.");
125 }
126
127 /**
128 * Prepares the appender for use.
129 */
130 public void activateOptions() {
131 if (follow) {
132 if (target.equals(SYSTEM_ERR)) {
133 setWriter(createWriter(new SystemErrStream()));
134 } else {
135 setWriter(createWriter(new SystemOutStream()));
136 }
137 } else {
138 if (target.equals(SYSTEM_ERR)) {
139 setWriter(createWriter(System.err));
140 } else {
141 setWriter(createWriter(System.out));
142 }
143 }
144
145 super.activateOptions();
146 }
147
148 /**
149 * {@inheritDoc}
150 */
151 protected
152 final
153 void closeWriter() {
154 if (follow) {
155 super.closeWriter();
156 }
157 }
158
159
160 /**
161 * An implementation of OutputStream that redirects to the
162 * current System.err.
163 *
164 */
165 private static class SystemErrStream extends OutputStream {
166 public SystemErrStream() {
167 }
168
169 public void close() {
170 }
171
172 public void flush() {
173 System.err.flush();
174 }
175
176 public void write(final byte[] b) throws IOException {
177 System.err.write(b);
178 }
179
180 public void write(final byte[] b, final int off, final int len)
181 throws IOException {
182 System.err.write(b, off, len);
183 }
184
185 public void write(final int b) throws IOException {
186 System.err.write(b);
187 }
188 }
189
190 /**
191 * An implementation of OutputStream that redirects to the
192 * current System.out.
193 *
194 */
195 private static class SystemOutStream extends OutputStream {
196 public SystemOutStream() {
197 }
198
199 public void close() {
200 }
201
202 public void flush() {
203 System.out.flush();
204 }
205
206 public void write(final byte[] b) throws IOException {
207 System.out.write(b);
208 }
209
210 public void write(final byte[] b, final int off, final int len)
211 throws IOException {
212 System.out.write(b, off, len);
213 }
214
215 public void write(final int b) throws IOException {
216 System.out.write(b);
217 }
218 }
219
220 }
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