log4j2自定义Appender 实现输出日志到 JTextArea控件

一、Main类定义输出控件，实例化窗口后赋值为JTextArea控件

public class Main {
    public static JTextArea text = null;//输出日志的控件

    public static void main(String[] args) {
        JFrame frame = new JFrame("窗口");
        App app = new App();
        frame.setContentPane(app.panel1);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        Main.text = app.txtConsoleMsg;
        app.Init();
    }
}

二、自定义Appender

package com.test.util;

import com.test.Main;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
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.layout.PatternLayout;

import javax.swing.*;
import java.io.Serializable;

@Plugin(name = "JTextArea", category = "Core", elementType = "appender", printObject = true)
public class JTextAreaAppender extends AbstractAppender {


    protected JTextAreaAppender(String name, Filter filter, Layout<? extends Serializable> layout, boolean ignoreExceptions) {
        super(name, filter, layout, ignoreExceptions);
    }

    @Override
    public void append(LogEvent logEvent) {

        String msg = logEvent.getMessage().getFormattedMessage();
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                if (Main.text != null) {
                    Main.text.append(msg + "\n");//输出日志到窗口控件
                }
            }
        });
    }

    // 下面这个方法可以接收配置文件中的参数信息
    @PluginFactory
    public static JTextAreaAppender createAppender(@PluginAttribute("name") String name,
                                            @PluginElement("Filter") final Filter filter,
                                            @PluginElement("Layout") Layout<? extends Serializable> layout,
                                            @PluginAttribute("ignoreExceptions") boolean ignoreExceptions) {
        if (name == null) {
            LOGGER.error("No name provided for MyCustomAppenderImpl");
            return null;
        }
        if (layout == null) {
            layout = PatternLayout.createDefaultLayout();
        }
        return new JTextAreaAppender(name, filter, layout, ignoreExceptions);
    }
}

二、配置log4j2.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="ON" packages="com.test.util">
    <appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
        <JTextArea name="JTextArea"/>
    </appenders>
    <loggers>
        <root level="INFO">
            <appender-ref ref="Console"/>
            <Appender-Ref ref="JTextArea"/>
        </root>
    </loggers>
</configuration>