Java load properties file correctly

问题

I have the following project structure:

ProjectName/src/java/com/main/Main.java

And I have a properties file in the following folder:

ProjectName/config/settings.properties

Now I tried to load the properties file in the Main.java with:

InputStream input = Main.class.getResourceAsStream("/config/settings.properties");
Properties prop = System.getProperties();
prop.load(input);

But this does not work. How is it the right way to do it?

Edit: I got the following error:

Exception in thread "main" java.lang.NullPointerException
    at java.util.Properties$LineReader.readLine(Unknown Source)
    at java.util.Properties.load0(Unknown Source)
    at java.util.Properties.load(Unknown Source)

Edit2: Now it works with eclipse. I did the following (adapted from getResourceAsStream() is returning null. Properties file is not loading)

1) This directory [config] must be put into the "build path". Right-click the directory in the Package Explorer or Project Explorer view, select "Build Path", then "Use as Source Folder". Note: This build path will be the class path for the project, when you run it.

2) As the config directory now is part of your class path and contains your properties file, you can simply load it with InputStream input = Server.class.getClassLoader().getResourceAsStream("settings.properties");

This works well for eclipse but not yet for a jar. I think I also have to add the build path somehow to the ant script.

How can I do that?

Edit3: If I take the settings.properties out of the config folder in the jar, then it works. Why? I want it in the config folder in the jar too.

回答1:

Use following :

InputStream input = Main.class.getResourceAsStream("../../../../config/settings.properties");
Properties prop = System.getProperties();
prop.load(input);

By adding ../ I am getting 1 step backward in your filesystem. In your code you were using /config....., which means C:/config..... (if it is in C drive).

The following will also work in your case. (but not in zipped file)

InputStream input = new FileInputStream("config/settings.properties");
Properties prop = System.getProperties();
prop.load(input);

回答2:

getResourceAsStream find files relatively compiled (class) files on in jar file. Example: Your compiled files are in bin directory than you should put properties file to bin/config/settings.properties for give access to it.

回答3:

You are using maven. So follow the maven structure and keep your resources like prop, xml etc files in resource folder and then call.

So folder structure would be like this

src/main/resource|
                 |
                  config|
                        |
                        settings.properties

InputStream input = Main.class.getClass().getResourceAsStream("/config/settings.properties");

回答4:

Three things

You need add the settings.properties to a jar (can be the same jar as your Main)
Your classpath should include this jar
You need to use the context Class Loader to load the properties file in you Main.

Classloader cl = Thread.currentThread().getContextClassLoader();

cl.getResourceAsStream("settings.properties");

来源：https://stackoverflow.com/questions/26358139/java-load-properties-file-correctly

标签

java

classloader

properties-file