怎么打印当前ClassLoader 加载了哪些Jar

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发布于 2022-11-28 08:27:30

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代码可运行

文章被收录于专栏：Java升级打怪进阶之路Java升级打怪进阶之路

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代码可运行

具体代码如下：

public static void main(String[] args) {
        URL[] urLs = Launcher.getBootstrapClassPath().getURLs();
        System.out.println("启动类加载器加载的jar：");
        for (URL urL : urLs) {
            System.out.println("==> " + urL.toExternalForm());
        }
        printClassLoader("扩展类加载器和其加载的jar:",ClassLoaderJarPrint.class.getClassLoader().getParent());
        printClassLoader("应用类加载器和其加载的jar:",ClassLoaderJarPrint.class.getClassLoader());
    }

    public static void printClassLoader(String name, ClassLoader CL) {
        if (CL != null) {
            System.out.println(name + " ClassLoader -> " + CL.toString());
            printURLForClassLoader(CL);
        } else {
            System.out.println(name + " ClassLoader -> null");
        }
    }

    public static void printURLForClassLoader(ClassLoader CL) {
        Object ucp = insightField(CL, "ucp");
        Object path = insightField(ucp, "path");
        ArrayList ps = (ArrayList) path;
        for (Object p : ps) {
            System.out.println(" -=>" + p.toString());
        }
    }

    private static Object insightField(Object obj, String fName) {
        try {
            Field f = null;
            if (obj instanceof URLClassLoader) {
                f = URLClassLoader.class.getDeclaredField(fName);
            } else {
                f = obj.getClass().getDeclaredField(fName);
            }
            f.setAccessible(true);
            return f.get(obj);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }