Java 如何在 Web 应用程序中读取属性文件？
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How to read properties file in web application?
提问by Roman
Properties file location is WEB-INF/classes/auth.properties.
属性文件位置是WEB-INF/classes/auth.properties.
I cannot use JSF-specific ways (with ExternalContext) because I need properties file in a service module which doesn't have a dependency on a web-module.
我不能使用 JSF 特定的方式（使用 ExternalContext），因为我需要在不依赖于 web 模块的服务模块中的属性文件。
I've already tried
我已经试过了
MyService.class.getClassLoader().getResourceAsStream("/WEB-INF/classes/auth.properties");
but it returns null.
但它返回null。
I've also tried to read it with FileInputStreambut it requires the full path what is unacceptable.
我也试过用FileInputStream它来阅读它，但它需要完整的路径，这是不可接受的。
Any ideas?
有任何想法吗？
采纳答案by BalusC
Several notes:
几个注意事项：
You should prefer the
ClassLoaderas returned byThread#getContextClassLoader().ClassLoader classLoader = Thread.currentThread().getContextClassLoader();This returns the parentmost classloader which has access to allresources. The
Class#getClassLoader()will only return the (child) classloader of the class in question which may not per se have access to the desired resource. It will always work in environments with a single classloader, but not always in environments with a complex hierarchy of classloaders like webapps.The
/WEB-INFfolder is not in the root of the classpath. The/WEB-INF/classesfolder is. So you need to load the properties files relative to that.classLoader.getResourceAsStream("/auth.properties");If you opt for using the
Thread#getContextClassLoader(), remove the leading/.
你应该更喜欢
ClassLoader通过返回的Thread#getContextClassLoader()。ClassLoader classLoader = Thread.currentThread().getContextClassLoader();这将返回可以访问所有资源的最父类加载器。该
Class#getClassLoader()会只返回类的（子）类加载器中可能本身并不访问所需的资源问题。它始终适用于具有单个类加载器的环境，但并不总是适用于具有复杂类加载器层次结构（如 webapps）的环境。该
/WEB-INF文件夹不在类路径的根目录中。该/WEB-INF/classes文件夹。因此，您需要加载与此相关的属性文件。classLoader.getResourceAsStream("/auth.properties");如果您选择使用
Thread#getContextClassLoader()，请删除前导/.
The JSF-specific ExternalContext#getResourceAsStream()which uses ServletContext#getResourceAsStream()"under the hoods" only returns resources from the webcontent (there where the /WEB-INFfolder is sitting), not from the classpath.
特定于 JSF 的ExternalContext#getResourceAsStream()使用ServletContext#getResourceAsStream()“幕后”仅从 web 内容（/WEB-INF文件夹所在的位置）返回资源，而不是从类路径。
回答by Jesper
Try this:
尝试这个：
MyService.class.getClassLoader().getResourceAsStream("/auth.properties");
Reading files with getResourceAsStreamlooks on the classpath to find the resource to load. Since the classesdirectory is in the classpath for your webapp, referring to the file as /auth.propertiesshould work.
getResourceAsStream在类路径上读取文件以查找要加载的资源。由于该classes目录位于您的 web 应用程序的类路径中，因此引用该文件/auth.properties应该可以工作。
回答by Gelvis
ResourceBundle (http://download.oracle.com/javase/6/docs/api/java/util/ResourceBundle.html) resolve most of the problems with a relative/absotule path for Properties Files.
ResourceBundle ( http://download.oracle.com/javase/6/docs/api/java/util/ResourceBundle.html) 通过属性文件的相对/绝对路径解决了大多数问题。
It uses the the Resource class and point it to a Dummy Class to make reference to a properties file.
它使用 Resource 类并将其指向一个虚拟类以引用属性文件。
For example:
例如：
- You a have file called MAINProperties.properties and inside it there is a property: mail.host=foo.example.com
- Create a Dummy Class called MAINProperties without nothing.
Use the following code:
ResourceBundle.getBundle("com.example.com.MAINProperties").getProperty("mail.host")
- 你有一个名为 MAINProperties.properties 的文件，里面有一个属性：mail.host=foo.example.com
- 创建一个名为 MAINProperties 的虚拟类，没有任何内容。
使用以下代码：
ResourceBundle.getBundle("com.example.com.MAINProperties").getProperty("mail.host")
And That's it. No InputStreams Required.
就是这样。不需要输入流。
P.D. Apache Commons has a Library Called Apache Commons Configuration that has a lot of capabilities (reloadable files, multiple domain types) that could be used in combination of the above.
PD Apache Commons 有一个名为 Apache Commons Configuration 的库，它具有许多功能（可重新加载的文件、多个域类型），可以结合上述功能使用。
