在Java中将属性文件中的属性作为静态常量使用

Question

如何使用属性文件存储应用程序中的全局变量，并使用公共静态常量变量将它们注入到应用程序中？

查看this question，我希望找到一种方法，可以从属性文件中将我的静态常量变量注入到应用程序中。但是我最终找到了一种方法，既能拥有蛋糕，又能吃掉它。

我在下面发布这个解决方案，以补充SO的文集...

- coderatchet

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请先在您的问题中添加更多细节，不要只是链接另一个问题。 - Sotirios Delimanolis

谢谢，我已经编辑了帖子，使其更具问题性 :) - coderatchet

Answer 1

我的解决方案涉及全局变量的概念（这似乎是不好的），所以如果你有胆量，请继续阅读。

我相信，尽管我们希望遵循函数式编程的潮流，并从我们的函数中删除所有“拉动”依赖的概念，但有些真理需要绝对的基础，因此一些形式的全局变量作为源头是有帮助的。在运行时应用中，但我不想引发争论...

解决方案

1. Start with a public class named Globals (or something obvious like this)

2. To Inject a property from a property file you need to establish the basename (or location) of the properties file, e.g. "com.example.myapp.core.configuration" may represent a configuration file in your core module with a physical url of jar:file:C:/jars/myapp.ear/core.jar!/com/example/myapp/core/configuration.properties. make this basename a static final variable:

   public static final String CORE_CONFIGURATION_BASENAME = "com.example.myapp.core.configuration";
   

3. then define the property keys as private variables (for encapsulation), e.g.

   private static final String DOMAIN_PACKAGE_KEY = "myapp.domain.package.name";
   

4. then define the property themself as a public final static variable, like so:

   public static final String DOMAIN_PACKAGE; //we leave it uninitialized on purpose.
   

5. the above code will throw a compiler error when built, so we need to initialize it using the static block. to do this, we must first retrieve the resource bundle using the basename we defined:

   static {
       ResourceBundle bundle = PropertyResourceBundle(CORE_CONFIGURATION_BASENAME);
       ...
   }
   

6. then we assign the final properties using the keys we define:"

   static {
       ResourceBundle bundle = PropertyResourceBundle(CORE_CONFIGURATION_BASENAME);
       DOMAIN_PACKAGE = bundle.getString(DOMAIN_PACKAGE_KEY);
   }
   

就是这样。这将在加载Globals类时初始化，因此如果您更改配置属性的值并希望它们反映在应用程序中，您需要重新启动应用程序以强制类加载器重新加载类。

总之：

package com.example.myapp.core.util;

import java.util.PropertyResourceBundle;
import java.util.ResourceBundle;

public class Globals {
    public static final String CORE_CONFIGURATION_BASENAME = "com.example.myapp.core.configuration";
    private static final String DOMAIN_PACKAGE_KEY = "myapp.domain.package.name";
    public static final String DOMAIN_PACKAGE; //we leave it uninitialized on purpose.

    static {
        ResourceBundle bundle = PropertyResourceBundle(CORE_CONFIGURATION_BASENAME);
        DOMAIN_PACKAGE = bundle.getString(DOMAIN_PACKAGE_KEY);
    }
}

- coderatchet