【Java学习笔记】操作JAR文件

作者：gnuhpc
出处：http://www.cnblogs.com/gnuhpc/

JAR文件是一种具有特定构造的zip文件

1.JAR文件的创建：

import java.util.jar.JarEntry;
import java.util.jar.JarOutputStream;
import java.util.jar.Manifest;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class JarCreate {
    public static void main(String arg[]) {
        JarCreate zc = new JarCreate();
        zc.create("testfile.jar",arg);
    }
    public void create(String jarfilename,String filename[]) {
        byte block[] = new byte[256];
        int length;
        try {

            //FileInputStream->Manifest->JarOutputStream

     //                                                                ^

     //                                                                 |

     //                                                    FileOutputStream

            FileInputStream fis = new FileInputStream("manifest");
            Manifest man = new Manifest(fis);//创建manifest文件
            FileOutputStream fos = new FileOutputStream(jarfilename);
            JarOutputStream out = new JarOutputStream(fos,man);
            for(int i=0; i<filename.length; i++) {
                FileInputStream in = new FileInputStream(filename[i]);
                String name = filename[i].replace(File.separatorChar,'/');

                JarEntry jarentry = new JarEntry(name);
                out.putNextEntry(jarentry);

                //FileInputStream->FileOutputStream
                while((length = in.read(block)) > 0)
                    out.write(block,0,length);

                out.closeEntry();
                in.close();
            }
            out.close();
        } catch(IOException e) {
            System.out.println(e);
        }
    }
}

2.JAR文件的读取

import java.util.jar.JarFile;
import java.util.jar.JarEntry;
import java.util.Enumeration;
import java.io.IOException;
public class JarList {
    public static void main(String arg[]) {
        JarList zl = new JarList();
        zl.list("testfile.jar");
    }
    public void list(String filename) {
        try {
            JarFile jarfile = new JarFile(filename);
Enumeration entrylist = jarfile.entries();
            while(entrylist.hasMoreElements()) {
                JarEntry jarentry = (JarEntry)entrylist.nextElement();
                System.out.println(jarentry.getName());
            }
            jarfile.close();
        } catch(IOException e) {
            System.out.println(e);
        }
    }
}

3.JAR文件的解压

import java.util.jar.JarFile;
import java.util.jar.JarEntry;
import java.util.Enumeration;
import java.io.InputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class JarExtract {
    public static void main(String arg[]) {
        JarExtract ze = new JarExtract();
        ze.extract("testfile.jar");
    }
    public void extract(String jarfilename) {
        byte block[] = new byte[256];
        int length;
        try {
            JarFile jarfile = new JarFile(jarfilename);
            Enumeration entrylist = jarfile.entries();
            while(entrylist.hasMoreElements()) {
                JarEntry jarentry = (JarEntry)entrylist.nextElement();
                InputStream in = jarfile.getInputStream(jarentry);
                String newfilename = jarentry.getName();
                FileOutputStream out = new FileOutputStream(newfilename);
                while((length = in.read(block)) > 0)
                    out.write(block,0,length);
                in.close();
                out.close();
            }
        } catch(IOException e) {
            System.out.println(e);
        }
    }
}

作者：gnuhpc
出处：http://www.cnblogs.com/gnuhpc/