Question

我的程序设计用于从可运行的jar文件启动，如果需要设置所有内容，然后在另一个jar文件中加载一个类来启动程序。这允许自我更新，重新启动等等。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。这是不正确的用法还是不好的做法？

    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

你遇到的最大问题是当你得到一个Exception时，你假装记录异常就可以继续，好像什么也没发生一样。

如果你聚合try / catch块，你的代码会更短更容易阅读，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);
    }
}

这是不正确的使用或类加载器的不良做法？

1 个答案: