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What this is

This file is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

 * Copyright (C) The Apache Software Foundation. All rights reserved.
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.txt file.  */

// WARNING This class MUST not have references to the Category or
// WARNING RootCategory classes in its static initiliazation neither
// WARNING directly nor indirectly.

// Contributors:
//                Luke Blanshard 
//                Mario Schomburg - IBM Global Services/Germany
//                Anders Kristensen
//                Igor Poteryaev

package org.apache.log4j;

import java.util.Hashtable;
import java.util.Enumeration;
import java.util.Vector;

import org.apache.log4j.spi.LoggerFactory;
import org.apache.log4j.spi.HierarchyEventListener;
import org.apache.log4j.spi.LoggerRepository;
import org.apache.log4j.spi.RendererSupport;
import org.apache.log4j.Appender;
import org.apache.log4j.or.RendererMap;
import org.apache.log4j.or.ObjectRenderer;
import org.apache.log4j.helpers.LogLog;

   This class is specialized in retrieving loggers by name and also
   maintaining the logger hierarchy.


The casual user does not have to deal with this class directly.

The structure of the logger hierarchy is maintained by the {@link #getLogger} method. The hierarchy is such that children link to their parent but parents do not have any pointers to their children. Moreover, loggers can be instantiated in any order, in particular descendant before ancestor.

In case a descendant is created before a particular ancestor, then it creates a provision node for the ancestor and adds itself to the provision node. Other descendants of the same ancestor add themselves to the previously created provision node. @author Ceki Gülcü */ public class Hierarchy implements LoggerRepository, RendererSupport { private LoggerFactory defaultFactory; private Vector listeners; Hashtable ht; Logger root; RendererMap rendererMap; int thresholdInt; Level threshold; boolean emittedNoAppenderWarning = false; boolean emittedNoResourceBundleWarning = false; /** Create a new logger hierarchy. @param root The root of the new hierarchy. */ public Hierarchy(Logger root) { ht = new Hashtable(); listeners = new Vector(1); this.root = root; // Enable all level levels by default. setThreshold(Level.ALL); this.root.setHierarchy(this); rendererMap = new RendererMap(); defaultFactory = new DefaultCategoryFactory(); } /** Add an object renderer for a specific class. */ public void addRenderer(Class classToRender, ObjectRenderer or) { rendererMap.put(classToRender, or); } public void addHierarchyEventListener(HierarchyEventListener listener) { if(listeners.contains(listener)) { LogLog.warn("Ignoring attempt to add an existent listener."); } else { listeners.addElement(listener); } } /** This call will clear all logger definitions from the internal hashtable. Invoking this method will irrevocably mess up the logger hierarchy.

You should really know what you are doing before invoking this method. @since 0.9.0 */ public void clear() { //System.out.println("\n\nAbout to clear internal hash table."); ht.clear(); } public void emitNoAppenderWarning(Category cat) { // No appenders in hierarchy, warn user only once. if(!this.emittedNoAppenderWarning) { LogLog.warn("No appenders could be found for logger (" + cat.getName() + ")."); LogLog.warn("Please initialize the log4j system properly."); this.emittedNoAppenderWarning = true; } } /** Check if the named logger exists in the hierarchy. If so return its reference, otherwise returns null. @param name The name of the logger to search for. */ public Logger exists(String name) { Object o = ht.get(new CategoryKey(name)); if(o instanceof Logger) { return (Logger) o; } else { return null; } } /** The string form of {@link #setThreshold(Level)}. */ public void setThreshold(String levelStr) { Level l = (Level) Level.toLevel(levelStr, null); if(l != null) { setThreshold(l); } else { LogLog.warn("Could not convert ["+levelStr+"] to Level."); } } /** Enable logging for logging requests with level l or higher. By default all levels are enabled. @param l The minimum level for which logging requests are sent to their appenders. */ public void setThreshold(Level l) { if(l != null) { thresholdInt = l.level; threshold = l; } } public void fireAddAppenderEvent(Category logger, Appender appender) { if(listeners != null) { int size = listeners.size(); HierarchyEventListener listener; for(int i = 0; i < size; i++) { listener = (HierarchyEventListener) listeners.elementAt(i); listener.addAppenderEvent(logger, appender); } } } void fireRemoveAppenderEvent(Category logger, Appender appender) { if(listeners != null) { int size = listeners.size(); HierarchyEventListener listener; for(int i = 0; i < size; i++) { listener = (HierarchyEventListener) listeners.elementAt(i); listener.removeAppenderEvent(logger, appender); } } } /** Returns a {@link Level} representation of the enable state. @since 1.2 */ public Level getThreshold() { return threshold; } /** Returns an integer representation of the this repository's threshold. @since 1.2 */ //public //int getThresholdInt() { // return thresholdInt; //} /** Return a new logger instance named as the first parameter using the default factory.

If a logger of that name already exists, then it will be returned. Otherwise, a new logger will be instantiated and then linked with its existing ancestors as well as children. @param name The name of the logger to retrieve. */ public Logger getLogger(String name) { return getLogger(name, defaultFactory); } /** Return a new logger instance named as the first parameter using factory.

If a logger of that name already exists, then it will be returned. Otherwise, a new logger will be instantiated by the factory parameter and linked with its existing ancestors as well as children. @param name The name of the logger to retrieve. @param factory The factory that will make the new logger instance. */ public Logger getLogger(String name, LoggerFactory factory) { //System.out.println("getInstance("+name+") called."); CategoryKey key = new CategoryKey(name); // Synchronize to prevent write conflicts. Read conflicts (in // getChainedLevel method) are possible only if variable // assignments are non-atomic. Logger logger; synchronized(ht) { Object o = ht.get(key); if(o == null) { logger = factory.makeNewLoggerInstance(name); logger.setHierarchy(this); ht.put(key, logger); updateParents(logger); return logger; } else if(o instanceof Logger) { return (Logger) o; } else if (o instanceof ProvisionNode) { //System.out.println("("+name+") ht.get(this) returned ProvisionNode"); logger = factory.makeNewLoggerInstance(name); logger.setHierarchy(this); ht.put(key, logger); updateChildren((ProvisionNode) o, logger); updateParents(logger); return logger; } else { // It should be impossible to arrive here return null; // but let's keep the compiler happy. } } } /** Returns all the currently defined categories in this hierarchy as an {@link java.util.Enumeration Enumeration}.

The root logger is not included in the returned {@link Enumeration}. */ public Enumeration getCurrentLoggers() { // The accumlation in v is necessary because not all elements in // ht are Logger objects as there might be some ProvisionNodes // as well. Vector v = new Vector(ht.size()); Enumeration elems = ht.elements(); while(elems.hasMoreElements()) { Object o = elems.nextElement(); if(o instanceof Logger) { v.addElement(o); } } return v.elements(); } /** @deprecated Please use {@link #getCurrentLoggers} instead. */ public Enumeration getCurrentCategories() { return getCurrentLoggers(); } /** Get the renderer map for this hierarchy. */ public RendererMap getRendererMap() { return rendererMap; } /** Get the root of this hierarchy. @since 0.9.0 */ public Logger getRootLogger() { return root; } /** This method will return true if this repository is disabled for level object passed as parameter and false otherwise. See also the {@link #setThreshold(Level) threshold} emthod. */ public boolean isDisabled(int level) { return thresholdInt > level; } /** @deprecated Deprecated with no replacement. */ public void overrideAsNeeded(String override) { LogLog.warn("The Hiearchy.overrideAsNeeded method has been deprecated."); } /** Reset all values contained in this hierarchy instance to their default. This removes all appenders from all categories, sets the level of all non-root categories to null, sets their additivity flag to true and sets the level of the root logger to {@link Level#DEBUG DEBUG}. Moreover, message disabling is set its default "off" value.

Existing categories are not removed. They are just reset.

This method should be used sparingly and with care as it will block all logging until it is completed.

@since 0.8.5 */ public void resetConfiguration() { getRootLogger().setLevel((Level) Level.DEBUG); root.setResourceBundle(null); setThreshold(Level.ALL); // the synchronization is needed to prevent JDK 1.2.x hashtable // surprises synchronized(ht) { shutdown(); // nested locks are OK Enumeration cats = getCurrentLoggers(); while(cats.hasMoreElements()) { Logger c = (Logger) cats.nextElement(); c.setLevel(null); c.setAdditivity(true); c.setResourceBundle(null); } } rendererMap.clear(); } /** Does mothing. @deprecated Deprecated with no replacement. */ public void setDisableOverride(String override) { LogLog.warn("The Hiearchy.setDisableOverride method has been deprecated."); } /** Used by subclasses to add a renderer to the hierarchy passed as parameter. */ public void setRenderer(Class renderedClass, ObjectRenderer renderer) { rendererMap.put(renderedClass, renderer); } /** Shutting down a hierarchy will safely close and remove all appenders in all categories including the root logger.

Some appenders such as {@link} and {@link AsyncAppender} need to be closed before the application exists. Otherwise, pending logging events might be lost.

The shutdown method is careful to close nested appenders before closing regular appenders. This is allows configurations where a regular appender is attached to a logger and again to a nested appender. @since 1.0 */ public void shutdown() { Logger root = getRootLogger(); // begin by closing nested appenders root.closeNestedAppenders(); synchronized(ht) { Enumeration cats = this.getCurrentLoggers(); while(cats.hasMoreElements()) { Logger c = (Logger) cats.nextElement(); c.closeNestedAppenders(); } // then, remove all appenders root.removeAllAppenders(); cats = this.getCurrentLoggers(); while(cats.hasMoreElements()) { Logger c = (Logger) cats.nextElement(); c.removeAllAppenders(); } } } /** This method loops through all the *potential* parents of 'cat'. There 3 possible cases: 1) No entry for the potential parent of 'cat' exists We create a ProvisionNode for this potential parent and insert 'cat' in that provision node. 2) There entry is of type Logger for the potential parent. The entry is 'cat's nearest existing parent. We update cat's parent field with this entry. We also break from the loop because updating our parent's parent is our parent's responsibility. 3) There entry is of type ProvisionNode for this potential parent. We add 'cat' to the list of children for this potential parent. */ final private void updateParents(Logger cat) { String name =; int length = name.length(); boolean parentFound = false; //System.out.println("UpdateParents called for " + name); // if name = "w.x.y.z", loop thourgh "w.x.y", "w.x" and "w", but not "w.x.y.z" for(int i = name.lastIndexOf('.', length-1); i >= 0; i = name.lastIndexOf('.', i-1)) { String substr = name.substring(0, i); //System.out.println("Updating parent : " + substr); CategoryKey key = new CategoryKey(substr); // simple constructor Object o = ht.get(key); // Create a provision node for a future parent. if(o == null) { //System.out.println("No parent "+substr+" found. Creating ProvisionNode."); ProvisionNode pn = new ProvisionNode(cat); ht.put(key, pn); } else if(o instanceof Category) { parentFound = true; cat.parent = (Category) o; //System.out.println("Linking " + + " -> " + ((Category) o).name); break; // no need to update the ancestors of the closest ancestor } else if(o instanceof ProvisionNode) { ((ProvisionNode) o).addElement(cat); } else { Exception e = new IllegalStateException("unexpected object type " + o.getClass() + " in ht."); e.printStackTrace(); } } // If we could not find any existing parents, then link with root. if(!parentFound) cat.parent = root; } /** We update the links for all the children that placed themselves in the provision node 'pn'. The second argument 'cat' is a reference for the newly created Logger, parent of all the children in 'pn' We loop on all the children 'c' in 'pn': If the child 'c' has been already linked to a child of 'cat' then there is no need to update 'c'. Otherwise, we set cat's parent field to c's parent and set c's parent field to cat. */ final private void updateChildren(ProvisionNode pn, Logger logger) { //System.out.println("updateChildren called for " +; final int last = pn.size(); for(int i = 0; i < last; i++) { Logger l = (Logger) pn.elementAt(i); //System.out.println("Updating child "; // Unless this child already points to a correct (lower) parent, // make cat.parent point to l.parent and l.parent to cat. if(! { logger.parent = l.parent; l.parent = logger; } } } }

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