Java 访问 .jar 之外的属性文件？
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Accessing properties files outside the .jar?
提问by Jason S
I have a .jar file I'm putting together. I want to create a really really simple .properties file with configurable things like the user's name & other stuff, so that they can hand-edit rather than my having to include a GUI editor.
我有一个 .jar 文件要放在一起。我想创建一个非常简单的 .properties 文件，其中包含可配置的内容，例如用户名和其他内容，以便他们可以手动编辑，而不必包含 GUI 编辑器。
What I'd like to do is to be able to search, in this order:
我想要做的是能够按以下顺序进行搜索：
- a specified properties file (
args[0]) - MyApp.properties in the current directory (the directory from which Java was called)
- MyApp.properties in the user's directory (the user.homesystem property?)
- MyApp.properties in the directory where the application .jar is stored
- 指定的属性文件 (
args[0]) - 当前目录中的 MyApp.properties（调用 Java 的目录）
- 用户目录中的 MyApp.properties（user.home系统属性？）
- MyApp.properties 在应用程序.jar 的存放目录中
I know how to access #1 and #3 (I think), but how can I determine at runtime #2 and #4?
我知道如何访问 #1 和 #3（我认为），但是如何在运行时确定 #2 和 #4？
采纳答案by erickson
#2 is the "user.dir"system property. #3 is the "user.home" property.
#2 是“user.dir”系统属性。#3 是“user.home”属性。
#4 is a bit of a kludge no matter how you approach it. Here's an alternate technique that works if you have a class loaded from a JAR not on the system classpath.
无论你如何接近它，#4 都有些杂乱无章。如果您从不在系统类路径上的 JAR 加载了一个类，这里有一个替代技术。
CodeSource src = MyClass.class.getProtectionDomain().getCodeSource();
if (src != null) {
URL url = new URL(src.getLocation(), "MyApp.properties");
...
}
else {
/* Fail... */
}
回答by Steve Reed
For the current working directory:
对于当前工作目录：
new File(".");
For a file named MyApp.properties in the current directory:
对于当前目录中名为 MyApp.properties 的文件：
new File(new File("."), "MyApp.properties");
回答by Chris Thornhill
For 4, you could try this. Get the classpath:
对于 4，你可以试试这个。获取类路径：
String classpath = System.getProperty("java.class.path");
Then search it for the name of your application jar:
然后搜索您的应用程序 jar 的名称：
int jarPos = classpath.indexOf("application.jar");
Parse out the path leading up to it:
解析出通向它的路径：
int jarPathPos = classpath.lastIndexOf(File.pathSeparatorChar, jarPos) + 1;
String path = classpath.substring(jarPathPos, jarPos);
Then append MyApp.properties. Make sure to check for jarPos == -1, meaning the jar isn't found if the classpath (perhaps when running in your dev environment).
然后附加MyApp.properties. 确保检查jarPos == -1，这意味着如果类路径（可能在您的开发环境中运行时），则找不到 jar。
