java编程实现jar的解包和打包

Java编程可以利用`java.util.jar`包下的`JarFile`和`JarEntry`类来实现jar的解包和打包。

1. 解包jar文件：

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class JarUnpacker {
    public static void unpack(String jarPath, String destPath) throws Exception {
        JarFile jarFile = new JarFile(jarPath);
        Enumeration<JarEntry> entries = jarFile.entries();

        while (entries.hasMoreElements()) {
            JarEntry jarEntry = entries.nextElement();
            String fileName = jarEntry.getName();
            File destFile = new File(destPath + File.separator + fileName);

            if (jarEntry.isDirectory()) {
                destFile.mkdirs();
            } else {
                InputStream in = jarFile.getInputStream(jarEntry);
                OutputStream out = new FileOutputStream(destFile);
                byte[] buffer = new byte[1024];
                int len;
                while ((len = in.read(buffer)) > 0) {
                    out.write(buffer, 0, len);
                }
                in.close();
                out.close();
            }
        }

        jarFile.close();
    }
}

以上代码会将`jarPath`指定的jar文件解压到`destPath`指定的目录中。

2. 打包jar文件：

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.jar.JarEntry;
import java.util.jar.JarOutputStream;

public class JarPacker {
    public static void pack(String sourcePath, String jarPath) throws Exception {
        JarOutputStream jarOut = new JarOutputStream(new FileOutputStream(jarPath));

        File sourceFile = new File(sourcePath);
        if (sourceFile.isDirectory()) {
            packDir(sourceFile, "", jarOut);
        } else {
            packFile(sourceFile, "", jarOut);
        }

        jarOut.close();
    }

    private static void packDir(File dir, String parentPath, JarOutputStream jarOut) throws IOException {
        String dirPath = parentPath + dir.getName() + "/";
        JarEntry jarEntry = new JarEntry(dirPath);
        jarOut.putNextEntry(jarEntry);

        File[] files = dir.listFiles();
        if (files != null) {
            for (File file : files) {
                if (file.isDirectory()) {
                    packDir(file, dirPath, jarOut);
                } else {
                    packFile(file, dirPath, jarOut);
                }
            }
        }
    }

    private static void packFile(File file, String parentPath, JarOutputStream jarOut) throws IOException {
        JarEntry jarEntry = new JarEntry(parentPath + file.getName());
        jarOut.putNextEntry(jarEntry);

        byte[] buffer = new byte[1024];
        int len;
        FileInputStream in = new FileInputStream(file);
        while ((len = in.read(buffer)) > 0) {
            jarOut.write(buffer, 0, len);
        }
        in.close();
    }
}

以上代码会将`sourcePath`指定的文件或目录打包成`jarPath`指定的jar文件。