Java解析嵌套jar中class文件

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-loader
        long 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：JarFile
        long 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。