log4j2动态修改日志级别及拓展性使用

一、供参考的完整日志配置

    
    
        ${sys:vmparam}
        ${basePath}/app.log
    

    
    
        
            
        

        
        
            
                
                
                
            
            
            

            
            
                
                    
                    
                    
                    
                
            
        
    

    
    
        
        
            
            
        
 
        
            
         
        
        
            
            
        
        
        
        
            
        
        
        
        
        
        
    

二、动态修改日志级别

Collection current = LoggerContext.getContext(false).getLoggers();
Collection notcurrent = LoggerContext.getContext().getLoggers();
Collection allConfig = current;
allConfig.addAll(notcurrent);
for (org.apache.logging.log4j.core.Logger log:allConfig){
    log.setLevel(Level.DEBUG);
}

三、自定义appender

以上介绍，均依赖于log4j2提供的官方配置，当对日志的业务逻辑复杂时，光靠配置也许满足不了需要，此时我们会想自己能操控打印的日志，做日志的路由，或保存等操作，这个时候就需要有自定义的appender，可以配置的就靠配置完成，不能的就自己写代码干预，而log4j2刚好提供了这样的拓展性。

如下代码即是自定义的Appender，通过实现AbstractAppender接口，配置@Plugin注解对应的信息并在eppend方法中写自己的业务逻辑，从而实现了对日志更大自由度的控制，如下展示的log4j配置文件中的配置节点名称要和注解中配置的name属性一致，并在Configuration节点配置好自定义Appender所在的包路径即可。
　　Appender的自定义，可以参考log4j-core源码中org.apache.logging.log4j.core.appender.mom包中其它的扩展appender的实现。主要是实现AbstractAppender和AbstractManager。

package com.jyk.log4j2.log4j2_test;

import java.io.Serializable;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
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.appender.AppenderLoggingException;
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;
 
@Plugin(name = "MyAppender", category = "Core", elementType = "appender", printObject = true)
public class MyAppender extends AbstractAppender {
 
    /**
     * @fields serialVersionUID
     */
    private static final long serialVersionUID = -830237775522429777L;
    private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
    private final Lock readLock = rwLock.readLock();
 
    //需要实现的构造方法，直接使用父类就行
    protected MyAppender(final String name, final Filter filter, final Layout layout,
            final boolean ignoreExceptions) {
        super(name, filter, layout, ignoreExceptions);
    }
 
    @Override
    public void append(LogEvent event) {
        readLock.lock();
        try {
            final byte[] bytes = getLayout().toByteArray(event);//日志二进制文件，输出到指定位置就行
            
            //拿到每次打印的日志，写自己的业务逻辑
            System.out.println("enter my append...");
        } catch (Exception ex) {
            if (!ignoreExceptions()) {
                throw new AppenderLoggingException(ex);
            }
        } finally {
            readLock.unlock();
        }
    }
 
    // 下面这个方法可以接收配置文件中的参数信息
    @PluginFactory
    public static MyAppender createAppender(@PluginAttribute("name") String name,
            @PluginElement("Filter") final Filter filter,
            @PluginElement("Layout") Layout 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 MyAppender(name, filter, layout, ignoreExceptions);
    }
}

自定义appender配置