Struts2没有直接使用Log4j、JCL(Apache Java Commons Logger)或slf4j。
它编写了自己的LoggerFactory(com.opensymphony.xwork2.util.logging.LoggerFactory),然后让其选择使用何种LoggerFactory,然后再进行日志处理。
在action中使用,可以按照以下的方式编码:
private Logger logger = LoggerFactory.getLogger(FooAction.class);
String msg="debug level logger Info";
logger.debug(msg);
struts2中日志源码涉及的有:
在org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter类中init方法中,初始化日志对象,如下:
public void init(FilterConfig filterConfig) throws ServletException {
InitOperations init = new InitOperations();
Dispatcher dispatcher = null;
try {
FilterHostConfig config = new FilterHostConfig(filterConfig);
init.initLogging(config);
dispatcher = init.initDispatcher(config);
init.initStaticContentLoader(config, dispatcher);
prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher);
execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);
this.excludedPatterns = init.buildExcludedPatternsList(dispatcher);
postInit(dispatcher, filterConfig);
} finally {
if (dispatcher != null) {
dispatcher.cleanUpAfterInit();
}
init.cleanup();
}
}
在org.apache.struts2.dispatcher.ng.InitOperations类中的initLogging方法,
public void initLogging( HostConfig filterConfig ) { String factoryName = filterConfig.getInitParameter("loggerFactory"); if (factoryName != null) { try { Class cls = ClassLoaderUtil.loadClass(factoryName, this.getClass()); LoggerFactory fac = (LoggerFactory) cls.newInstance(); LoggerFactory.setLoggerFactory(fac); } catch ( InstantiationException e ) { System.err.println("Unable to instantiate logger factory: " + factoryName + ", using default"); e.printStackTrace(); } catch ( IllegalAccessException e ) { System.err.println("Unable to access logger factory: " + factoryName + ", using default"); e.printStackTrace(); } catch ( ClassNotFoundException e ) { System.err.println("Unable to locate logger factory class: " + factoryName + ", using default"); e.printStackTrace(); } } }
以下代码显示,Struts会通过名为loggerFactory的参数加载LoggerFactory,
则可以通过在web.xml中设置
<filter>
<filter-name>strut2</filter-name>
<filter-class>
org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
</filter-class>
<init-param>
<param-name>loggerFactory</param-name>
<param-value>
com.opensymphony.xwork2.util.logging.commons.CommonsLoggerFactory
</param-value>
</init-param>
</filter>
以下看看LoggerFactory.getLogger();方法的实现
见com.opensymphony.xwork2.util.logging.LoggerFactory类。
public static void setLoggerFactory(LoggerFactory factory) { lock.writeLock().lock(); try { LoggerFactory.factory = factory; } finally { lock.writeLock().unlock(); } }
设置日志处理类,此处用到了写锁处理。
public static Logger getLogger(String name) { return getLoggerFactory().getLoggerImpl(name); }
protected static LoggerFactory getLoggerFactory() { lock.readLock().lock(); try { if (factory != null) { return factory; } } finally { lock.readLock().unlock(); } lock.writeLock().lock(); try { if (factory == null) { String userLoggerFactory = System.getProperty(XWorkConstants.XWORK_LOGGER_FACTORY); if (userLoggerFactory != null) { try { Class clazz = Class.forName(userLoggerFactory); factory = (LoggerFactory) clazz.newInstance(); } catch (Exception e) { throw new XWorkException("System property [" + XWorkConstants.XWORK_LOGGER_FACTORY + "] was defined as [" + userLoggerFactory + "] but there is a problem to use that LoggerFactory!", e); } } else { try { Class.forName("org.apache.commons.logging.LogFactory"); factory = new com.opensymphony.xwork2.util.logging.commons.CommonsLoggerFactory(); } catch (ClassNotFoundException ex) { //commons-logging not found try slf4j LogFactory try { Class.forName("org.slf4j.LoggerFactory"); factory = new Slf4jLoggerFactory(); } catch (ClassNotFoundException cnfex) { // slf4j not found, falling back to jdk logging factory = new JdkLoggerFactory(); } } } } return factory; } finally { lock.writeLock().unlock(); } }
日志获取类共取了四次,
1,webwork的配置文件读取
2,org.apache.commons.logging.LogFactory
3,org.slf4j.LoggerFactory
4,JdkLoggerFactory