java - 这是类加载器的错误使用还是不好的做法？

Question

我的程序设计为从可运行的 jar 文件启动，根据需要设置所有内容，然后加载另一个 jar 文件中的类以启动程序。这允许 self 更新、重新启动等。好吧，我的类加载代码对我来说似乎有点时髦。下面是我用来加载程序的代码。这是不正确的使用还是不好的做法？

    try {
        Preferences.userRoot().put("clientPath", Run.class.getProtectionDomain().getCodeSource().getLocation().toURI().toString()); //Original client location; helps with restarts
    } catch (URISyntaxException e1) {
        e1.printStackTrace();
    }

    try {
        Preferences.userRoot().flush();
    } catch (BackingStoreException e1) {
        e1.printStackTrace();
    }


    File file = new File(path); // path of the jar we will be launching to initiate the program outside of the Run class
    URL url = null;
    try {
        url = file.toURI().toURL(); // converts the file path to a url
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }
    URL[] urls = new URL[] { url };
    ClassLoader cl = new URLClassLoader(urls);

    Class cls = null;
    try {
        cls = cl.loadClass("com.hexbit.EditorJ.Load"); // the class we are loading to initiate the program
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }

    try {
        cls.newInstance();  // starts the class that has been loaded and the program is on its way
    } catch (InstantiationException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }

Answer 1

您遇到的最大问题是，当您收到异常时，您假装记录该异常可以继续，就好像什么也没发生一样。

如果您聚合 try/catch block ，您的代码将更短且更易于阅读，并且不会认为异常并不重要。

试试这个例子

public static Object load(String path, String className) {
    try {
        URL url = new File(path).toURI().toURL();
        ClassLoader cl = new URLClassLoader(new URL[] { url });
        return cl.loadClass(className).newInstance();
    } catch (Exception e) {
        throw new IllegalStateException("Unable to load "+className+" " + e);
    }
}