001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.log4j; 019 020import java.io.IOException; 021import java.io.OutputStream; 022import org.apache.log4j.helpers.LogLog; 023 024/** 025 * ConsoleAppender appends log events to <code>System.out</code> or 026 * <code>System.err</code> using a layout specified by the user. The 027 * default target is <code>System.out</code>. 028 * 029 * @author Ceki Gülcü 030 * @author Curt Arnold 031 * @since 1.1 */ 032public class ConsoleAppender extends WriterAppender { 033 034 public static final String SYSTEM_OUT = "System.out"; 035 public static final String SYSTEM_ERR = "System.err"; 036 037 protected String target = SYSTEM_OUT; 038 039 /** 040 * Determines if the appender honors reassignments of System.out 041 * or System.err made after configuration. 042 */ 043 private boolean follow = false; 044 045 /** 046 * Constructs an unconfigured appender. 047 */ 048 public ConsoleAppender() { 049 } 050 051 /** 052 * Creates a configured appender. 053 * 054 * @param layout layout, may not be null. 055 */ 056 public ConsoleAppender(Layout layout) { 057 this(layout, SYSTEM_OUT); 058 } 059 060 /** 061 * Creates a configured appender. 062 * @param layout layout, may not be null. 063 * @param target target, either "System.err" or "System.out". 064 */ 065 public ConsoleAppender(Layout layout, String target) { 066 setLayout(layout); 067 setTarget(target); 068 activateOptions(); 069 } 070 071 /** 072 * Sets the value of the <b>Target</b> option. Recognized values 073 * are "System.out" and "System.err". Any other value will be 074 * ignored. 075 * */ 076 public 077 void setTarget(String value) { 078 String v = value.trim(); 079 080 if (SYSTEM_OUT.equalsIgnoreCase(v)) { 081 target = SYSTEM_OUT; 082 } else if (SYSTEM_ERR.equalsIgnoreCase(v)) { 083 target = SYSTEM_ERR; 084 } else { 085 targetWarn(value); 086 } 087 } 088 089 /** 090 * Returns the current value of the <b>Target</b> property. The 091 * default value of the option is "System.out". 092 * 093 * See also {@link #setTarget}. 094 * */ 095 public 096 String getTarget() { 097 return target; 098 } 099 100 /** 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}