compare more than two war files and repackage them excluding common jars

Some times you need to deploy more than one war files under same servlet container. In those war files there might have some common jars across them, which you want to deploy directly to servlet containers class path. So that container won't load those jars separately in the context of each war application. Which in turn will reduce the utilisation of permgen memory space. Following code snippet will help you to compare more than two war files, extract common shared libraries inside separate folder and repackage those wars excluding common jar files. This will generate two folders "shared" and "repackaged" inside given path where you have kept war files. "shared" folder will contain all extracted shared jar files and "repackaged" folder contains all war repackaged excluding shared jar files. 

import java.io.File;
import java.io.FileFilter;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.JarOutputStream;

/**
 * @author Pandurang Patil 02-Mar-2014
 * 
 */
public class RepackProcessor {

 private String    source;

 private Boolean    verbose    = false;

 private static final String sharedLocateion  = "shared";
 private static final String outPutLocation  = "repackaged";
 private Set<String>   commonLibs   = new HashSet<String>();
 private Set<String>   allLibs    = new HashSet<String>();
 private Set<String>   commonCopiedLibs = new HashSet<String>();

 public void process() throws Exception {
  File f = new File(source);
  if (f.isDirectory()) {
   File[] files = f.listFiles(new FileFilter() {

    public boolean accept(File pathname) {
     if (pathname.isFile() && pathname.getName().endsWith(".war")) {
      return true;
     }
     return false;
    }
   });
   if (files == null || files.length < 2) {
    System.out.println("You need to have at least have two war files in your source directory");
    return;
   }
   System.out.println("Scanning existing war files...");
   for (File file : files) {
    scan(file);
   }
   System.out.println("Scan complete...");

   if (commonLibs.size() == 0) {
    System.out.println("There are no common libraries found, so there is no need to repackage the wars, you can use them as is");
   } else {
    java.io.File mainDir = new java.io.File(source + java.io.File.separator + sharedLocateion);
    mainDir.mkdir();
    mainDir = new java.io.File(source + java.io.File.separator + outPutLocation);
    mainDir.mkdir();
    System.out.println("Repackaging...");
    for (File file : files) {
     repackage(file);
    }
   }
  } else {
   System.out.println("You need to specify directory which contains all war files that needs to be repackaged.");
  }
 }

 /**
  * Repackage war files by excluding common jar files.
  * 
  * @param warFile
  * @throws IOException
  */
 public void repackage(File warFile) throws IOException {
  FileOutputStream fos = new FileOutputStream(new File(source + java.io.File.separator + outPutLocation + java.io.File.separator + warFile.getName()));
  System.out.print("\nRepackaging war =>" + warFile.getName());
  JarOutputStream target = new JarOutputStream(fos);
  JarFile war = new JarFile(warFile);
  Enumeration<JarEntry> files = war.entries();
  while (files.hasMoreElements()) {
   java.util.jar.JarEntry file = files.nextElement();
   extractAndAdd(war, file, target);
  }
  System.out.println();
  target.close();
  war.close();
 }

 /**
  * Scan war file contents to identify shared libraries.
  * 
  * @param warFile
  * @throws Exception
  */
 public void scan(File warFile) throws Exception {
  JarFile war = new JarFile(warFile);
  Enumeration<JarEntry> files = war.entries();
  while (files.hasMoreElements()) {
   JarEntry file = files.nextElement();
   String fileName = file.getName();
   if (!file.isDirectory() && fileName.startsWith("WEB-INF/lib/") && fileName.endsWith(".jar")) {
    // file is jar file.
    if (!commonLibs.contains(fileName)) {
     if (allLibs.contains(fileName)) {
      // If given file is there in all libs that means it been added while scanning previous war file.
      // That means its common file between two wars.
      commonLibs.add(fileName);
     } else {
      // other wise add it in all libs list.
      allLibs.add(fileName);
     }
    }
   }
  }
  war.close();
 }

 /**
  * Extract given file from source war file and add it to destination war file. While doing that it will exclude
  * common jar files and copy to shared folder.
  * 
  * @param sourceWarFile
  *            Source war file.
  * @param source
  *            source file from source war file.
  * @param target
  *            Target war file output stream.
  * @throws IOException
  */
 private void extractAndAdd(JarFile sourceWarFile, JarEntry source, JarOutputStream target) throws IOException {
  String fileName = source.getName();
  if (!source.isDirectory() && commonLibs.contains(fileName)) {
   if (commonCopiedLibs.contains(fileName)) {
    return;
   } else {
    if (verbose)
     System.out.println("copying to shared Lib => " + fileName);
    else
     System.out.print(" .");
    java.io.File newFile = new java.io.File(this.source + java.io.File.separator + sharedLocateion + java.io.File.separator
      + fileName.substring(fileName.lastIndexOf("/") + 1, fileName.length()));
    java.io.InputStream is = sourceWarFile.getInputStream(source); // get the input stream
    java.io.FileOutputStream fos = new java.io.FileOutputStream(newFile);
    while (is.available() > 0) { // write contents of 'is' to 'fos'
     fos.write(is.read());
    }
    fos.close();
    is.close();
    commonCopiedLibs.add(fileName);
   }
  } else {
   if (verbose)
    System.out.println("adding to war =>" + fileName);
   else
    System.out.print(" .");
   target.putNextEntry(source);
   if (!source.isDirectory()) {

    java.io.InputStream is = sourceWarFile.getInputStream(source); // get the input stream
    while (is.available() > 0) { // write contents of 'is' to 'target war'
     target.write(is.read());
    }
   }
   target.closeEntry();
  }
 }

 public static void main(String[] args) throws Exception {
  RepackProcessor rp = new RepackProcessor();
  // Copy all war files at one location and provide absolute path to the location which contains all those war
  // files.
  rp.source = "<location of folder where all war files are placed.";
  rp.process();
 }
}