static void initLogger()
{System.out.println("configurating log4j with log4j xml");DOMConfigurator.configure("log4j.xml");logger = Logger.getLogger("name");
}

/**
A static version of {@link #doConfigure(String, LoggerRepository)}.
*/
static
public
void configure(String filename) throws FactoryConfigurationError
{new DOMConfigurator().doConfigure(filename, LogManager.getLoggerRepository());
}public
void doConfigure(final String filename, LoggerRepository repository)
{ParseAction action = new ParseAction() {public Document parse(final DocumentBuilder parser) throws SAXException, IOException {return parser.parse(new File(filename));}public String toString() { return "file [" + filename + "]"; }};doConfigure(action, repository);}private final void doConfigure(final ParseAction action,final LoggerRepository repository)throws FactoryConfigurationError
{DocumentBuilderFactory dbf = null;this.repository = repository;try { LogLog.debug("System property is :"+OptionConverter.getSystemProperty(dbfKey, null)); dbf = DocumentBuilderFactory.newInstance();LogLog.debug("Standard DocumentBuilderFactory search succeded.");LogLog.debug("DocumentBuilderFactory is: "+dbf.getClass().getName());} catch(FactoryConfigurationError fce) {Exception e = fce.getException();LogLog.debug("Could not instantiate a DocumentBuilderFactory.", e);throw fce;}try {dbf.setValidating(true);DocumentBuilder docBuilder = dbf.newDocumentBuilder();docBuilder.setErrorHandler(new SAXErrorHandler());      docBuilder.setEntityResolver(new Log4jEntityResolver());Document doc = action.parse(docBuilder);     parse(doc.getDocumentElement());} catch (Exception e) {if (e instanceof InterruptedException || e instanceof InterruptedIOException){Thread.currentThread().interrupt();}// I know this is miserable...LogLog.error("Could not parse "+ action.toString() + ".", e);}}  

 package org.apache.log4j.spi;import java.util.Enumeration;import org.apache.log4j.Appender;
import org.apache.log4j.Category;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;/**A <code>LoggerRepository</code> is used to create and retrieve<code>Loggers</code>. The relation between loggers in a repositorydepends on the repository but typically loggers are arranged in anamed hierarchy.<p>In addition to the creational methods, a<code>LoggerRepository</code> can be queried for existing loggers,can act as a point of registry for events related to loggers. @author Ceki G&uuml;lc&uuml;@since 1.2 */
public interface LoggerRepository {/**Add a {@link HierarchyEventListener} event to the repository.*/publicvoid addHierarchyEventListener(HierarchyEventListener listener);/**Returns whether this repository is disabled for a givenlevel. The answer depends on the repository threshold and the<code>level</code> parameter. See also {@link #setThreshold}method.  */boolean isDisabled(int level);/**Set the repository-wide threshold. All logging requests below thethreshold are immediately dropped. By default, the threshold isset to <code>Level.ALL</code> which has the lowest possible rank.  */publicvoid setThreshold(Level level);/**Another form of {@link #setThreshold(Level)} accepting a stringparameter instead of a <code>Level</code>. */publicvoid setThreshold(String val);publicvoid emitNoAppenderWarning(Category cat);/**Get the repository-wide threshold. See {@link#setThreshold(Level)} for an explanation. */publicLevel getThreshold();publicLogger getLogger(String name);publicLogger getLogger(String name, LoggerFactory factory);publicLogger getRootLogger();publicabstractLogger exists(String name);publicabstractvoid shutdown();publicEnumeration getCurrentLoggers();/**Deprecated. Please use {@link #getCurrentLoggers} instead.  */publicEnumeration getCurrentCategories();publicabstractvoid fireAddAppenderEvent(Category logger, Appender appender);publicabstractvoid resetConfiguration();}

 static public  LoggerRepository getLoggerRepository()
{if (repositorySelector == null) {repositorySelector = new DefaultRepositorySelector(new NOPLoggerRepository());guard = null;Exception ex = new IllegalStateException("Class invariant violation");String msg ="log4j called after unloading, see http://logging.apache.org/log4j/1.2/faq.html#unload.";if (isLikelySafeScenario(ex)) {LogLog.debug(msg, ex);} else {LogLog.error(msg, ex);}}return repositorySelector.getLoggerRepository();
}

static public final String DEFAULT_CONFIGURATION_FILE = "log4j.properties";static final String DEFAULT_XML_CONFIGURATION_FILE = "log4j.xml";public static final String DEFAULT_INIT_OVERRIDEE_KEY="log4j.defaultInitOverride" 

static {// By default we use a DefaultRepositorySelector which always returns 'h'.Hierarchy h = new Hierarchy(new RootLogger((Level) Level.DEBUG));repositorySelector = new DefaultRepositorySelector(h);/** Search for the properties file log4j.properties in the CLASSPATH. */String override =OptionConverter.getSystemProperty(DEFAULT_INIT_OVERRIDE_KEY,null);// if there is no default init override, then get the resource// specified by the user or the default config file.if(override == null || "false".equalsIgnoreCase(override)) {String configurationOptionStr = OptionConverter.getSystemProperty(DEFAULT_CONFIGURATION_KEY, null);String configuratorClassName = OptionConverter.getSystemProperty(CONFIGURATOR_CLASS_KEY, null);   URL url = null;// if the user has not specified the log4j.configuration// property, we search first for the file "log4j.xml" and then// "log4j.properties"if(configurationOptionStr == null) {   url = Loader.getResource(DEFAULT_XML_CONFIGURATION_FILE);if(url == null) {url = Loader.getResource(DEFAULT_CONFIGURATION_FILE);}} else {try {url = new URL(configurationOptionStr);} catch (MalformedURLException ex) {// so, resource is not a URL:// attempt to get the resource from the class pathurl = Loader.getResource(configurationOptionStr); } }// If we have a non-null url, then delegate the rest of the// configuration to the OptionConverter.selectAndConfigure// method.if(url != null) {LogLog.debug("Using URL ["+url+"] for automatic log4j configuration.");try {OptionConverter.selectAndConfigure(url, configuratorClassName,LogManager.getLoggerRepository());} catch (NoClassDefFoundError e) {LogLog.warn("Error during default initialization", e);}} else {LogLog.debug("Could not find resource: ["+configurationOptionStr+"].");}} else {LogLog.debug("Default initialization of overridden by " + DEFAULT_INIT_OVERRIDE_KEY + "property."); }
} 

// By default we use a DefaultRepositorySelector which always returns 'h'.
Hierarchy h =newHierarchy(new RootLogger((Level) Level.DEBUG));
repositorySelector = new DefaultRepositorySelector(h);

 /**Very similar to <code>System.getProperty</code> exceptthat the {@link SecurityException} is hidden.@param key The key to search for.@param def The default value to return.@return the string value of the system property, or the defaultvalue if there is no property with that key.@since 1.1 */publicstaticString getSystemProperty(String key, String def) {try {return System.getProperty(key, def);} catch(Throwable e) { // MS-Java throws com.ms.security.SecurityExceptionExLogLog.debug("Was not allowed to read system property ""+key+"".");return def;}}

  if(override == null || "false".equalsIgnoreCase(override)) 

  if(configurationOptionStr == null) 

  if(configurationOptionStr == null) {    url = Loader.getResource(DEFAULT_XML_CONFIGURATION_FILE);if(url == null) {url = Loader.getResource(DEFAULT_CONFIGURATION_FILE);}
} 

static public URL getResource(String resource) {ClassLoader classLoader = null;URL url = null;try {if(!java1 && !ignoreTCL) {classLoader = getTCL();if(classLoader != null) {LogLog.debug("Trying to find ["+resource+"] using context classloader "+classLoader+".");url = classLoader.getResource(resource);      if(url != null) {return url;}}}// We could not find resource. Ler us now try with the// classloader that loaded this class.classLoader = Loader.class.getClassLoader(); if(classLoader != null) {LogLog.debug("Trying to find ["+resource+"] using "+classLoader+" class loader.");url = classLoader.getResource(resource);if(url != null) {return url;}}} catch(IllegalAccessException t) {LogLog.warn(TSTR, t);} catch(InvocationTargetException t) {if (t.getTargetException() instanceof InterruptedException|| t.getTargetException() instanceof InterruptedIOException) {Thread.currentThread().interrupt();}LogLog.warn(TSTR, t);} catch(Throwable t) {////  can't be InterruptedException or InterruptedIOException//    since not declared, must be error or RuntimeError.LogLog.warn(TSTR, t);}// Last ditch attempt: get the resource from the class path. It// may be the case that clazz was loaded by the Extentsion class// loader which the parent of the system class loader. Hence the// code below.LogLog.debug("Trying to find ["+resource+"] using ClassLoader.getSystemResource().");return ClassLoader.getSystemResource(resource);}