refactored logging so that log4j is no longer a runtime depedency

updates to documentation to come


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/logging/trunk@138807 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/logging/LogSource.java

@@ -0,0 +1,95 @@
+/*
+ * 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 file.
+ */
+
+package org.apache.commons.httpclient.log;
+
+import java.util.HashMap;
+import java.lang.reflect.Constructor;
+
+/**
+ * @author Rod Waldhoff
+ * @version $Id: LogSource.java,v 1.1 2001/08/02 16:27:06 rwaldhoff Exp $
+ */
+public class LogSource {
+    static protected HashMap _logs = new HashMap();
+    static protected boolean _log4jIsAvailable = false;
+    static {
+        try {
+            if(null != Class.forName("org.apache.log4j.Category")) {
+                _log4jIsAvailable = true;
+            } else {
+                _log4jIsAvailable = false;
+            }
+        } catch(ClassNotFoundException e) {
+            _log4jIsAvailable = false;
+        }
+    }
+
+    private LogSource() {
+    }
+
+    static public Log getInstance(String name) {
+        Log log = (Log)(_logs.get(name));
+        if(null == log) {
+            log = makeNewLogInstance(name);
+            _logs.put(name,log);
+        }
+        return log;
+    }
+
+    static public Log getInstance(Class clazz) {
+        return getInstance(clazz.getName());
+    }
+
+    /**
+     * Create a new {@link Log} implementation, based
+     * on the given <i>name</i>
+     * <p>
+     * The specific {@link Log} implementation returned
+     * is determined by the value of the
+     * <tt>httpclient.log</tt> property.
+     * The value of <tt>httpclient.log</tt> may be set to
+     * the fully specified name of a class that implements
+     * the {@link Log} interface.  This class must also
+     * have a public constructor that takes a single
+     * {@link String} argument (containing the <i>name</i>
+     * of the {@link Log} to be constructed.
+     * <p>
+     * When <tt>httpclient.log</tt> is not set,
+     * or when no corresponding class can be found,
+     * this method will return a {@link Log4JCategoryLog}
+     * if the log4j {@link org.apache.log4j.Category} class is
+     * available in the {@link LogSource}'s classpath, or
+     * a {@link NoOpLog} if it is not.
+     *
+     * @param name the log name (or category)
+     */
+    static public Log makeNewLogInstance(String name) {
+        Log log = null;
+        String logclassname = System.getProperty("httpclient.log","org.apache.commons.httpclient.log.NoOpLog");
+        try {
+            Class logclass = Class.forName(logclassname);
+            Class[] argtypes = new Class[1];
+            argtypes[0] = "".getClass();
+            Constructor ctor = logclass.getConstructor(argtypes);
+            Object[] args = new Object[1];
+            args[0] = name;
+            log = (Log)(ctor.newInstance(args));
+        } catch(Exception e) {
+            log = null;
+        }
+        if(null == log) {
+            if(_log4jIsAvailable) {
+                return new Log4JCategoryLog(name);
+            } else {
+                log = new NoOpLog(name);
+            }
+        }
+        return log;
+    }
+}