在Java中初始化一个复杂静态成员的最佳方法是什么？(What is the best way to initialize a complex static member in Java?)

我的目标是在我的类中创建一个私有静态Properties对象，以在创建我的应用程序所需的其他Properties对象时充当默认值。目前的实现如下所示：

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，但它感觉不对。

你会怎么做？

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); } } }

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

How would you do it?

最满意答案

基本上有两种方法。第一种方法是使用静态块（如前所示）（但是使用ExceptionInInitializerError而不是RuntimeException ）。第二种方法是使用你在声明中立即调用的静态方法：

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可以只是您的自定义类扩展RuntimeException 。

我个人更喜欢static块，因为它没有任何意义，它只能在其生命中执行过一次 。但是，如果您重构该方法以使其具有文件名并且可以在全局范围内重用，那么这将更受欢迎。

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; }

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; }

The ConfigurationException can just be your custom class extending RuntimeException.

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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