摘要：一般來說，可以被加入到中的東西，除了文件夾，就只有包了但有的時候，我們可能希望將一個已經存在的包里面的所有文件加入，這包括下的所有文件和下的所有包直接將該包加入中是不能達到上述目的的，那么就可以使用下面這個工具達到此目的用法

一般來說，可以被加入到java classpath中的東西，除了文件夾，就只有jar包了；
但有的時候，我們可能希望將一個已經存在的war包里面的所有class文件加入classpath，這包括/WEB-INF/classes下的所有class文件和/WEB-INF/lib下的所有jar包；
直接將該war包加入classpath中是不能達到上述目的的，那么就可以使用下面這個工具達到此目的：

package kilim.tools;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * classloader which allows user to set a war archive path to be included in the
 * classpath dynamically.
 * 
 * @author pf_miles
 * 
 */
public class WarPathClassLoader extends URLClassLoader {

    private boolean warPathSet;
    private String explodedWarPath;

    public WarPathClassLoader(ClassLoader parent) {
        super(new URL[0], parent);
    }

    public void setWarPath(String path) {
        if (this.warPathSet)
            throw new RuntimeException("War archive path already set. Kilim-fiber tools cannot weave multiple war archives at the same time.");
        File w = new File(path);
        if (w.exists()) {
            final File dir;
            try {
                warPathSet = true;
                // 0.create a temp dir
                dir = createTempDirectory(w.getName());
                // 1.extract the war to the temp dir
                extractTo(w, dir);
                // 2.add /WEB-INF/classes to cp
                File clses = locateFile(dir, "WEB-INF", "classes");
                super.addURL(clses.toURI().toURL());
                // 3.add all jars under /WEB-INF/lib/ to cp
                File lib = locateFile(dir, "WEB-INF", "lib");
                File[] jars = lib.listFiles();
                for (File j : jars)
                    super.addURL(j.toURI().toURL());
            } catch (MalformedURLException e) {
                throw new RuntimeException(e);
            }
            // delete temp dir when exit
            Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
                public void run() {
                    if (dir != null) {
                        delRecur(dir);
                    }
                }
            }));
            this.explodedWarPath = dir.getAbsolutePath();
        } else {
            throw new RuntimeException("File not exists: " + path);
        }
    }

    private static void delRecur(File file) {
        if (!file.exists())
            return;
        if (file.isDirectory()) {
            // 1.del sub files first
            for (File s : file.listFiles())
                delRecur(s);
            // 2.del the dir
            file.delete();
        } else {
            file.delete();
        }
    }

    private static File locateFile(File dir, String... paths) {
        File cur = dir;
        outter: for (String p : paths) {
            File[] all = cur.listFiles();
            for (File f : all) {
                if (p.equals(f.getName())) {
                    cur = f;
                    continue outter;
                }
            }
            throw new RuntimeException("No path named "" + p + "" found in file: " + cur.getAbsolutePath());
        }
        return cur;
    }

    // extract content of "w" to dir
    private static void extractTo(File w, File dir) {
        String dirPath = dir.getAbsolutePath();
        if (!dirPath.endsWith("/"))
            dirPath += "/";
        try {
            JarFile jar = new JarFile(w);
            Enumeration e = jar.entries();
            byte[] buf = new byte[4096];

            while (e.hasMoreElements()) {
                JarEntry file = (JarEntry) e.nextElement();
                File f = new File(dirPath + file.getName());

                if (file.isDirectory()) { // if its a directory, create it
                    f.mkdirs();
                    continue;
                }

                InputStream is = jar.getInputStream(file);
                FileOutputStream fos = ensureOpen(f);

                // write contents of "is" to "fos"
                for (int avai = is.read(buf); avai != -1; avai = is.read(buf)) {
                    fos.write(buf, 0, avai);
                }
                fos.close();
                is.close();
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    // if does not exist, create one, and ensure all parent dirs exist
    private static FileOutputStream ensureOpen(File f) throws IOException {
        if (!f.exists()) {
            File p = f.getParentFile();
            if (p != null && !p.exists())
                p.mkdirs();
            f.createNewFile();
        }
        return new FileOutputStream(f);
    }

    private static File createTempDirectory(String dirName) {
        final File temp;

        try {
            temp = File.createTempFile(dirName, Long.toString(System.currentTimeMillis()));
            temp.deleteOnExit();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        if (!(temp.delete())) {
            throw new RuntimeException("Could not delete temp file: " + temp.getAbsolutePath());
        }

        if (!(temp.mkdir())) {
            throw new RuntimeException("Could not create temp directory: " + temp.getAbsolutePath());
        }

        return (temp);
    }

    /**
     * get the temporary directory path which contains the exploded war files
     */
    public String getExplodedWarPath() {
        if (this.explodedWarPath == null)
            throw new RuntimeException(""explodedWarPath" is null, maybe the war path is not set.");
        return this.explodedWarPath;
    }

}

用法：new一個WarPathClassLoader實例，然后調用setWarPath指定war包所在位置即可

gist地址：https://gist.github.com/pfmiles/2002fdace1caa247618b