path: root/src/main/java/org/apache/logging/log4j/core/appender/ConsoleAppender.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */
package org.apache.logging.log4j.core.appender;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Constructor;
import java.nio.charset.Charset;

import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.helpers.Booleans;
import org.apache.logging.log4j.core.helpers.Loader;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.util.PropertiesUtil;

/**
 * ConsoleAppender appends log events to <code>System.out</code> or
 * <code>System.err</code> using a layout specified by the user. The
 * default target is <code>System.out</code>.
 * @doubt accessing System.out or .err as a byte stream instead of a writer
 *    bypasses the JVM's knowledge of the proper encoding. (RG) Encoding
 * is handled within the Layout. Typically, a Layout will generate a String
 * and then call getBytes which may use a configured encoding or the system
 * default. OTOH, a Writer cannot print byte streams.
 */
@Plugin(name = "Console", category = "Core", elementType = "appender", printObject = true)
public final class ConsoleAppender extends AbstractOutputStreamAppender {

    private static final String JANSI_CLASS = "org.fusesource.jansi.WindowsAnsiOutputStream";
    private static ConsoleManagerFactory factory = new ConsoleManagerFactory();

    /**
     * Enumeration of console destinations.
     */
    public enum Target {
        /** Standard output. */
        SYSTEM_OUT,
        /** Standard error output. */
        SYSTEM_ERR
    }

    private ConsoleAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
                            final OutputStreamManager manager,
                            final boolean ignoreExceptions) {
        super(name, layout, filter, ignoreExceptions, true, manager);
    }

    /**
     * Create a Console Appender.
     * @param layout The layout to use (required).
     * @param filter The Filter or null.
     * @param t The target ("SYSTEM_OUT" or "SYSTEM_ERR"). The default is "SYSTEM_OUT".
     * @param follow If true will follow changes to the underlying output stream.
     * @param name The name of the Appender (required).
     * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
     *               they are propagated to the caller.
     * @return The ConsoleAppender.
     */
    @PluginFactory
    public static ConsoleAppender createAppender(
            @PluginElement("Layout") Layout<? extends Serializable> layout,
            @PluginElement("Filters") final Filter filter,
            @PluginAttribute("target") final String t,
            @PluginAttribute("name") final String name,
            @PluginAttribute("follow") final String follow,
            @PluginAttribute("ignoreExceptions") final String ignore) {
        if (name == null) {
            LOGGER.error("No name provided for ConsoleAppender");
            return null;
        }
        if (layout == null) {
            layout = PatternLayout.createLayout(null, null, null, null, null);
        }
        final boolean isFollow = Boolean.parseBoolean(follow);
        final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
        final Target target = t == null ? Target.SYSTEM_OUT : Target.valueOf(t);
        return new ConsoleAppender(name, layout, filter, getManager(isFollow, target, layout), ignoreExceptions);
    }

    private static OutputStreamManager getManager(final boolean follow, final Target target, final Layout<? extends Serializable> layout) {
        final String type = target.name();
        final OutputStream os = getOutputStream(follow, target);
        return OutputStreamManager.getManager(target.name() + "." + follow, new FactoryData(os, type, layout), factory);
    }

    private static OutputStream getOutputStream(final boolean follow, final Target target) {
        final String enc = Charset.defaultCharset().name();
        PrintStream printStream = null;
        try {
            printStream = target == Target.SYSTEM_OUT ?
                    follow ? new PrintStream(new SystemOutStream(), true, enc) : System.out :
                    follow ? new PrintStream(new SystemErrStream(), true, enc) : System.err;
        } catch (final UnsupportedEncodingException ex) { // should never happen
            throw new IllegalStateException("Unsupported default encoding " + enc, ex);
        }
        final PropertiesUtil propsUtil = PropertiesUtil.getProperties();
        if (!propsUtil.getStringProperty("os.name").startsWith("Windows") ||
                propsUtil.getBooleanProperty("log4j.skipJansi")) {
            return printStream;
        }
        try {
            final ClassLoader loader = Loader.getClassLoader();
            // We type the parameter as a wildcard to avoid a hard reference to Jansi.
            final Class<?> clazz = loader.loadClass(JANSI_CLASS);
            final Constructor<?> constructor = clazz.getConstructor(OutputStream.class);
            return (OutputStream) constructor.newInstance(printStream);
        } catch (final ClassNotFoundException cnfe) {
            LOGGER.debug("Jansi is not installed, cannot find {}", JANSI_CLASS);
        } catch (final NoSuchMethodException nsme) {
            LOGGER.warn("{} is missing the proper constructor", JANSI_CLASS);
        } catch (final Throwable ex) { // CraftBukkit - Exception -> Throwable
            LOGGER.warn("Unable to instantiate {}", JANSI_CLASS);
        }
        return printStream;
    }

    /**
     * An implementation of OutputStream that redirects to the current System.err.
     */
    private static class SystemErrStream extends OutputStream {
        public SystemErrStream() {
        }

        @Override
        public void close() {
            // do not close sys err!
        }

        @Override
        public void flush() {
            System.err.flush();
        }

        @Override
        public void write(final byte[] b) throws IOException {
            System.err.write(b);
        }

        @Override
        public void write(final byte[] b, final int off, final int len)
                throws IOException {
            System.err.write(b, off, len);
        }

        @Override
        public void write(final int b) {
            System.err.write(b);
        }
    }

    /**
     * An implementation of OutputStream that redirects to the current System.out.
     */
    private static class SystemOutStream extends OutputStream {
        public SystemOutStream() {
        }

        @Override
        public void close() {
            // do not close sys out!
        }

        @Override
        public void flush() {
            System.out.flush();
        }

        @Override
        public void write(final byte[] b) throws IOException {
            System.out.write(b);
        }

        @Override
        public void write(final byte[] b, final int off, final int len)
                throws IOException {
            System.out.write(b, off, len);
        }

        @Override
        public void write(final int b) throws IOException {
            System.out.write(b);
        }
    }

    /**
     * Data to pass to factory method.
     */
    private static class FactoryData {
        private final OutputStream os;
        private final String type;
        private final Layout<? extends Serializable> layout;

        /**
         * Constructor.
         * @param os The OutputStream.
         * @param type The name of the target.
         * @param layout A Serializable layout
         */
        public FactoryData(final OutputStream os, final String type, final Layout<? extends Serializable> layout) {
            this.os = os;
            this.type = type;
            this.layout = layout;
        }
    }

    /**
     * Factory to create the Appender.
     */
    private static class ConsoleManagerFactory implements ManagerFactory<OutputStreamManager, FactoryData> {

        /**
         * Create an OutputStreamManager.
         * @param name The name of the entity to manage.
         * @param data The data required to create the entity.
         * @return The OutputStreamManager
         */
        @Override
        public OutputStreamManager createManager(final String name, final FactoryData data) {
            return new OutputStreamManager(data.os, data.type, data.layout);
        }
    }

}