這篇文章從本教程的第1部分繼續。

嗨，在我的前一篇文章中，我解釋了如何通過Spring設置JMX服務器以及如何通過身份驗證和授權保護對它的訪問。

在本文中，我將展示如何實現一個簡單的MBean，該MBean允許用戶在運行時更改Log4j記錄器的級別，而無需重新啟動應用程序。

為了方便測試，Spring配置與我的前一篇文章僅作了些許更改。 實質保持不變。

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>

我們唯一感興趣的配置部分是掃描Spring組件和MBean導出器的聲明（這也會導致MBean注釋被識別，Spring Bean作為MBeans向JMX服務器注冊）

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注釋（以粗體顯示）之外，這是一個普通的Spring bean。 但是，使用這些注釋，我們制作了一個MBean，并且該bean將在啟動時向JMX服務器注冊。

@ManagedOperation和@ManagedOperationParameters批注確定在jconsole上顯示的內容。 可以省略這些注釋，但是在不提供任何有關參數類型的信息的情況下，參數名稱將不會變成p1和p2之類的東西。

例如，使用值foo.bar.baz和INFO調用該函數將導致以下輸出：

...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，我將展示如何設置MBean，以在達到HEAP內存閾值時向偵聽器發出警報，如我以前的一篇文章中所述

繼續第3部分 。

參考： JMX和Spring –我們的JCG合作伙伴 Marco Tedone的第2部分 ，位于Marco Tedone的博客博客中。