通过java向jar写入新文件

原始需求

有网友提问： 我想在程序中动态地向同一个jar包中添加文件，比如，我的可执行jar包是test.jar,我要在它运行时生成一些xml文件并将这些文件添加到test.jar中,请问如何实现？

分析

test.jar在运行过程中是无法改变自身内容的，但是可以创建内容与test.jar一致的test2.jar
问题就转换成了：

1. 如何复制已有的test.jar重命名为test2.jar
2. 如何继续向test2.jar添加新的文件

实施步骤

引入依赖

        <dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.12.0</version></dependency><dependency><groupId>commons-io</groupId><artifactId>commons-io</artifactId><version>2.5</version></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-compress</artifactId><version>1.23.0</version></dependency>

核心编码

借助 commons-compress 来操作Jar

    public void test()throws IOException{String src = getClass().getResource("/apache-jstl.jar").getPath();String add1 = getClass().getResource("/servlet-api.jar").getPath();String add2 = getClass().getResource("/log4j2.xml").getPath();String newJar = src.replace(".jar", DateFormatUtils.format(System.currentTimeMillis(), "_HHmmssSSS") + ".jar");log.info("源文件: {}", src);log.info("++新增: {}", add1);log.info("++新增: {}", add2);log.info("新文件: {}", newJar);try (ArchiveOutputStream outputStream = new JarArchiveOutputStream(new FileOutputStream(newJar));JarArchiveInputStream jarInput = new JarArchiveInputStream(new FileInputStream(src))){JarArchiveEntry jarEntry;while ((jarEntry = jarInput.getNextJarEntry()) != null){if (!jarEntry.isDirectory()){outputStream.putArchiveEntry(jarEntry);IOUtils.copy(jarInput, outputStream);}}outputStream.flush();// 追加addFilesFile[] addFiles = {new File(add1), new File(add2)};for (File addFile : addFiles){JarArchiveEntry addEntry = new JarArchiveEntry("add/" + addFile.getName());outputStream.putArchiveEntry(addEntry);try (InputStream entryInputStream = new FileInputStream(addFile)){IOUtils.copy(entryInputStream, outputStream);}}// 追加add/001.txtJarArchiveEntry entry = new JarArchiveEntry("add/001.txt");outputStream.putArchiveEntry(entry);outputStream.write("org.apache.commons.compress.archivers.jar.JarArchiveOutputStream;".getBytes(StandardCharsets.UTF_8));outputStream.closeArchiveEntry();outputStream.finish();}}

使用JDK API实现

public void test2(){try{String src = getClass().getResource("/apache-jstl.jar").getPath();String add1 = getClass().getResource("/servlet-api.jar").getPath();String add2 = getClass().getResource("/log4j2.xml").getPath();String newJar = src.replace(".jar", DateFormatUtils.format(System.currentTimeMillis(), "_HHmmssSSS") + ".jar");log.info("源文件: {}", src);log.info("++新增: {}", add1);log.info("++新增: {}", add2);log.info("新文件: {}", newJar);addFilesToJar(new File(src), newJar, new File(add1), new File(add2));}catch (IOException e){log.error(e.getMessage(), e);}}/*** JDK-API实现-将addFiles添加到srcJar并重命名为newJar* * @param srcJar* @param newJar* @param addFiles* @throws IOException*/private void addFilesToJar(File srcJar, String newJar, File... addFiles)throws IOException{try (JarOutputStream jarOutputStream = new JarOutputStream(new FileOutputStream(newJar)); JarFile jarFile = new JarFile(srcJar)){// 遍历jar文件数据写入新jarEnumeration<JarEntry> entrys = jarFile.entries();while (entrys.hasMoreElements()){JarEntry jarEntry = entrys.nextElement();if (!jarEntry.isDirectory()){jarOutputStream.putNextEntry(jarEntry);try (InputStream entryInputStream = jarFile.getInputStream(jarEntry)){IOUtils.copy(entryInputStream, jarOutputStream);}}}// 追加写入for (File addFile : addFiles){JarEntry jarEntry = new JarEntry("add/" + addFile.getName());jarOutputStream.putNextEntry(jarEntry);try (InputStream entryInputStream = new FileInputStream(addFile)){IOUtils.copy(entryInputStream, jarOutputStream);}}}}

运行效果

原始文件

运行后：



大功告成！！！

有任何问题和建议，都可以向我提问讨论,大家一起进步，谢谢!

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