轉自：http://www.huihoo.org/apache/tomcat/heavyz/ClassLoaderFactory.java.html
package org.apache.catalina.startup;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import org.apache.catalina.loader.StandardClassLoader;
/**
* Utility class for building class loaders for Catalina. The factory
* method requires the following parameters in order to build a new class
* loader (with suitable defaults in all cases):
- A set of directories containing unpacked classes (and resources)
that should be included in the class loader's
repositories.
- A set of directories containing classes and resources in JAR files.
Each readable JAR file discovered in these directories will be
added to the class loader's repositories.
ClassLoader instance that should become the parent of
the new class loader.
*
* @author Craig R. McClanahan
* @version $Revision: 1.8 $ $Date: 2002/02/17 08:26:02 $
*/
public final class ClassLoaderFactory {
/**
* Debugging detail level for processing the startup.
*/
private static int debug = 0;
/**
* Return the debugging detail level.
*/
public static int getDebug() {
return (debug);
}
/**
* 設置DEBUG級別
*/
public static void setDebug(int newDebug) {
debug = newDebug;
}
/**
* 該類是一個靜態類，用來創建和返回ClassLoader對象（實際上是StandardClassLoader對象）
* 它將根據設置和參數返回apache定置的ClassLoader對象，以完成自己的類載入
*
* @param unpacked 類路徑CLASSPATH的數組
* @param packed 含有JAR文件的類路徑
* @param parent 父ClassLoader對象。當一個ClassLoader對象無法完成類載入時，它將請求父對象幫助
*
* @exception Exception if an error occurs constructing the class loader
*/
public static ClassLoader createClassLoader(File unpacked[],
File packed[],
ClassLoader parent)
throws Exception {
if (debug >= 1)
log("Creating new class loader");
// list裏將被填入所有需要附加到CLASSPATH上去的文件名
ArrayList list = new ArrayList();
// Add unpacked directories
if (unpacked != null) {
for (int i = 0; i < unpacked.length; i++) {
File file = unpacked[i];
if (!file.isDirectory() || !file.exists() || !file.canRead())
continue;
if (debug >= 1)
log(" Including directory " + file.getAbsolutePath());
URL url = new URL("file", null,
file.getCanonicalPath() + File.separator);
list.add(url.toString());
}
}
// Add packed directory JAR files
if (packed != null) {
for (int i = 0; i < packed.length; i++) {
File directory = packed[i];
if (!directory.isDirectory() || !directory.exists() ||
!directory.canRead())
continue;
String filenames[] = directory.list();
for (int j = 0; j < filenames.length; j++) {
String filename = filenames[j].toLowerCase();
if (!filename.endsWith(".jar"))
continue;
File file = new File(directory, filenames[j]);
if (debug >= 1)
log(" Including jar file " + file.getAbsolutePath());
URL url = new URL("file", null,
file.getCanonicalPath());
list.add(url.toString());
}
}
}
// 填好了list
// 創建StandardClassLoader對象，並返回
String array[] = (String[]) list.toArray(new String[list.size()]);
StandardClassLoader classLoader = null;
if (parent == null)
classLoader = new StandardClassLoader(array);
else
classLoader = new StandardClassLoader(array, parent);
classLoader.setDelegate(true);
return (classLoader);
}
/**
* 輸出日誌
*/
private static void log(String message) {
System.out.print("ClassLoaderFactory: ");
System.out.println(message);
}
/**
* 輸出日誌和異常信息
*/
private static void log(String message, Throwable exception) {
log(message);
exception.printStackTrace(System.out);
}
}
