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一、简述
Maven项目通过package打成jar包后，jar包中包含所有依赖lib文件。本文介绍了两种方式解析嵌套jar中的class文件，一种是通过spring-boot-loader包JarFileArchive，另一种是util包中JarFile。
二、JarFileArchive方式
1.spring-boot-loader依赖引入
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-loader</artifactId><version>2.2.4.RELEASE</version>
</dependency>2.demo案例
public static void main(String args[]) throws Exception {String jarPath = "C:\\Users\\root\\Desktop\\make-test.jar";// 方案一：spring-boot-loaderlong start1 = System.currentTimeMillis();getClassInfoByJarLib(jarPath);long end1 = System.currentTimeMillis();log.info("收集所有lib类ClassInfo,花费时间={}",(end1-start1));} public static void getClassInfoByJarLib(String jarPath) {String filePath = "file:/"+ URLDecoder.decode(jarPath, StandardCharsets.UTF_8).replaceAll("\\\\","/")+"!/";String rootJarPath = "jar:"+ filePath;try {JarFileArchive jarFileArchive = new JarFileArchive(new Handler().getRootJarFileFromUrl(new URL(rootJarPath)));//getNestedArchives获取嵌套的jar等文件，参数是个EntryFilter，过滤条件jarFileArchive.getNestedArchives(entry -> entry.getName().startsWith("BOOT-INF/lib/") && entry.getName().endsWith(".jar")).forEach(archive -> {archive.iterator().forEachRemaining(entry -> {String entryName = entry.getName();// 过滤嵌套jar包中字节码文件if (entryName.endsWith(".class")) {String className = entryName.replace('/', '.').replace(".class", "");log.info("className:{}",className);}});});} catch (IOException e) {log.error("解析嵌套jarLib中ClassInfo异常，jarPath={}",jarPath,e);throw new RuntimeException(e);}}三、JarFile方式
1.demo案例
public static void main(String args[]) throws Exception {String jarPath = "C:\\Users\\root\\Desktop\\make-test.jar";// 方案二：JarFilelong start2 = System.currentTimeMillis();processJar(jarPath);long end2 = System.currentTimeMillis();log.info("收集所有lib类ClassInfo,花费时间={}",(end2-start2));} private static void processJar(String jarPath){try (JarFile jarFile = new JarFile(new File(jarPath))) {jarFile.stream().parallel()// 过滤出所有符合要求的jar包.filter(entry -> !entry.isDirectory() && entry.getName().startsWith("BOOT-INF/lib/") && entry.getName().endsWith(".jar")).forEach(entry -> processNestedJar(jarFile, entry.getName()));} catch (IOException e) {log.error("解析嵌套jarLib中ClassInfo异常，jarPath={}",jarPath,e);throw new RuntimeException(e);}}private static void processNestedJar(JarFile jarFile, String entryName){// 处理嵌套jar文件try (InputStream nestedJarStream = jarFile.getInputStream(jarFile.getJarEntry(entryName));JarInputStream jarInputStream = new JarInputStream(nestedJarStream)) {JarEntry nestedEntry;while ((nestedEntry = jarInputStream.getNextJarEntry()) != null) {if (nestedEntry.isDirectory()) {continue;}String nestedEntryName = nestedEntry.getName();if (!nestedEntryName.endsWith(".class")) {continue;}try {String className = nestedEntryName.replace('/', '.').replace(".class", "");log.info("className:{}",className);} catch (Exception e) {log.error("目标类={}查找失败",nestedEntryName,e);throw new RuntimeException(e);}}} catch (IOException e) {log.error("目标类={}查找失败",entryName,e);throw new RuntimeException(e);}}四、两种方式对比
实测项目make-test.jar中所有依赖lib约200个，其中所有class字节码文件约7万多个。方案JarFileArchive约1.5s全部解析，方案JarFile约6s全部解析。