在Java中初始化复杂静态成员的最佳方法是什么？ [英] What is the best way to initialize a complex static member in Java?

问题描述

我的目标是在我的类中拥有一个私有静态属性对象，在创建其他属性我的应用程序所需的对象。当前的实现如下所示：

My objective is to have a private static Properties object in my class, to act as defaults when creating other Properties objects needed by my application. The current implementation looks like this:

public class MyClass {
    private static Properties DEFAULT_PROPERTIES = new Properties();

    static {
        try {
           DEFAULT_PROPERTIES.load(
               MyClass.class.getResourceAsStream("myclass.properties"));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
 }

看着它，它有效，但感觉不对。

Looking at it, it works, but it doesn't feel right.

你会怎么做？

推荐答案

基本上有两种方式。第一种方法是使用你所显示的静态块（但随后使用 ExceptionInInitializerError 而不是 RuntimeException ）。第二种方法是使用静态方法，您可以在声明时立即调用：

There are basically two ways. First way is using the static block as you have shown (but then with an ExceptionInInitializerError instead of the RuntimeException). Second way is using a static method which you call immediately on declaration:

private static Properties DEFAULT_PROPERTIES = getDefaultProperties();

private static Properties getDefaultProperties() {
    Properties properties = new Properties();
    try {
        properties.load(MyClass.class.getResourceAsStream("myclass.properties"));
    } catch (IOException e) {
        throw new ConfigurationException("Cannot load properties file", e);
    }
    return properties;
}

ConfigurationException 可以只是你的自定义类扩展 RuntimeException 。

The ConfigurationException can just be your custom class extending RuntimeException.

我个人更喜欢 static 阻止，因为拥有一个在其生命中只执行一次的方法是没有意义的。但是如果你重构方法以便它采用文件名并且可以全局重用，那么这将是更优选的。

I personally prefer the static block because it doesn't make sense having a method which is executed only once ever in its life. But if you refactor the method so that it takes a filename and can be reused globally, then that would be more preferred.

private static Properties DEFAULT_PROPERTIES = SomeUtil.getProperties("myclass.properties");

// Put this in a SomeUtil class.
public static Properties getProperties(String filename) {
    Properties properties = new Properties();
    try {
        properties.load(Thread.currentThread().getContextClassLoader().getResourceAsStream(filename));
    } catch (IOException e) {
        throw new ConfigurationException("Cannot load " + filename, e);
    }
    return properties;
}

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