可以在不重写整个文件的情况下以编程方式更新 Jar 文件吗?

问题描述

可以使用 jar 命令更新 JAR 文件中的单个文件，如下所示:

It is possible to update individual files in a JAR file using the jar command as follows:

jar uf TicTacToe.jar images/new.gif

有没有办法以编程方式做到这一点?

Is there a way to do this programmatically?

如果我使用 JarOutputStream，我必须重写整个 jar 文件，所以我想知道是否有类似的随机访问"方式来做到这一点.鉴于它可以使用 jar 工具完成，我原以为会有类似的方式以编程方式完成.

I have to rewrite the entire jar file if I use JarOutputStream, so I was wondering if there was a similar "random access" way to do this. Given that it can be done using the jar tool, I had expected there to be a similar way to do it programmatically.

推荐答案

可以使用 Zip 文件系统提供程序在 Java 7 中可用:

It is possible to update just parts of the JAR file using Zip File System Provider available in Java 7:

import java.net.URI;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.util.HashMap;
import java.util.Map;

public class ZipFSPUser {
    public static void main(String [] args) throws Throwable {
        Map<String, String> env = new HashMap<>();
        env.put("create", "true");
        // locate file system by using the syntax
        // defined in java.net.JarURLConnection
        URI uri = URI.create("jar:file:/codeSamples/zipfs/zipfstest.zip");

       try (FileSystem zipfs = FileSystems.newFileSystem(uri, env)) {
            Path externalTxtFile = Paths.get("/codeSamples/zipfs/SomeTextFile.txt");
            Path pathInZipfile = zipfs.getPath("/SomeTextFile.txt");
            // copy a file into the zip file
            Files.copy( externalTxtFile,pathInZipfile,
                    StandardCopyOption.REPLACE_EXISTING );
        }
    }
}

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