这篇文章从本教程的第1部分继续。

嗨，在我的前一篇文章中，我解释了如何通过Spring设置JMX服务器以及如何通过身份验证和授权保护对它的访问。

在本文中，我将展示如何实现一个简单的MBean，该MBean允许用户在运行时更改Log4j记录器的级别，而无需重新启动应用程序。

为了方便测试，Spring配置与我的前一篇文章仅作了些许更改。 实质保持不变。

Spring配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"xmlns:util="http://www.springframework.org/schema/util"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd"><bean id="propertyConfigurer"class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"><property name="locations"><list><value>classpath:jemos-jmx.properties</value><value>file:///${user.home}/.secure/jmxconnector-credentials.properties</value></list></property></bean><!-- In order to automatically detect MBeans we need to recognise Spring beans --><context:component-scan base-package="uk.co.jemos.experiments.jmx.mbeans" /><!-- This causes MBeans annotations to be recognised and MBeans to be registered with the JMX server --><context:mbean-export default-domain="jemos.mbeans"/><bean id="jemosJmxServer" class="org.springframework.jmx.support.ConnectorServerFactoryBean"depends-on="rmiRegistry"><property name="objectName" value="connector:name=rmi" /><property name="serviceUrl"value="service:jmx:rmi://localhost/jndi/rmi://localhost:${jemos.jmx.rmi.port}/jemosJmxConnector" /><property name="environment"><!-- the following is only valid when the sun jmx implementation is used --><map><entry key="jmx.remote.x.password.file" value="${user.home}/.secure/jmxremote.password" /><entry key="jmx.remote.x.access.file" value="${user.home}/.secure/jmxremote.access" /></map></property></bean><bean id="rmiRegistry" class="org.springframework.remoting.rmi.RmiRegistryFactoryBean"><property name="port" value="${jemos.jmx.rmi.port}" /></bean><!-- Used for testing --><bean id="clientConnector" class="org.springframework.jmx.support.MBeanServerConnectionFactoryBean"depends-on="jemosJmxServer"><property name="serviceUrl" value="service:jmx:rmi://localhost/jndi/rmi://localhost:${jemos.jmx.rmi.port}/jemosJmxConnector"/><property name="environment"><map><entry key="jmx.remote.credentials"><bean factory-method="commaDelimitedListToStringArray"><constructor-arg value="${jmx.username},${jmx.password}" /></bean></entry></map></property></bean></beans>

我们唯一感兴趣的配置部分是扫描Spring组件和MBean导出器的声明（这也会导致MBean注释被识别，Spring Bean作为MBeans向JMX服务器注册）

LoggerConfigurator MBean

package uk.co.jemos.experiments.jmx.mbeans;import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.springframework.jmx.export.annotation.ManagedOperation;
import org.springframework.jmx.export.annotation.ManagedOperationParameter;
import org.springframework.jmx.export.annotation.ManagedOperationParameters;
import org.springframework.jmx.export.annotation.ManagedResource;
import org.springframework.stereotype.Component;/*** MBean which allows clients to change or retrieve the logging level for a* Log4j Logger at runtime.* * @author mtedone* */
@Component
@ManagedResource(objectName = LoggerConfigurator.MBEAN_NAME, //
description = "Allows clients to set the Log4j Logger level at runtime")
public class LoggerConfigurator {public static final String MBEAN_NAME = "jemos.mbeans:type=config,name=LoggingConfiguration";@ManagedOperation(description = "Returns the Logger LEVEL for the given logger name")@ManagedOperationParameters({ @ManagedOperationParameter(description = "The Logger Name", name = "loggerName"), })public String getLoggerLevel(String loggerName) {Logger logger = Logger.getLogger(loggerName);Level loggerLevel = logger.getLevel();return loggerLevel == null ? "The logger " + loggerName+ " has not level" : loggerLevel.toString();}@ManagedOperation(description = "Set Logger Level")@ManagedOperationParameters({@ManagedOperationParameter(description = "The Logger Name", name = "loggerName"),@ManagedOperationParameter(description = "The Level to which the Logger must be set", name = "loggerLevel") })public void setLoggerLevel(String loggerName, String loggerLevel) {Logger thisLogger = Logger.getLogger(this.getClass());thisLogger.setLevel(Level.INFO);Logger logger = Logger.getLogger(loggerName);logger.setLevel(Level.toLevel(loggerLevel, Level.INFO));thisLogger.info("Set logger " + loggerName + " to level "+ logger.getLevel());}}

除了Spring JMX注释（以粗体显示）之外，这是一个普通的Spring bean。 但是，使用这些注释，我们制作了一个MBean，并且该bean将在启动时向JMX服务器注册。

@ManagedOperation和@ManagedOperationParameters批注确定在jconsole上显示的内容。 可以省略这些注释，但是在不提供任何有关参数类型的信息的情况下，参数名称将不会变成p1和p2之类的东西。

例如，使用值foo.bar.baz和INFO调用该函数将导致以下输出：

...snip2011-08-11 21:33:36 LoggerConfigurator [INFO] Set logger foo.bar.baz to level INFO

在本系列的下一篇和最后一篇文章中，我将展示如何设置MBean，以在达到HEAP内存阈值时向侦听器发出警报，如我以前的一篇文章中所述

继续第3部分 。

参考： JMX和Spring –我们的JCG合作伙伴 Marco Tedone的第2部分 ，位于Marco Tedone的博客博客中。