如何从Class文件夹外部读取java中的属性文件？

Question

I have the following path structure to the main class:

D:/java/myapp/src/manClass.java

and i want to put the properties file in

D:/java/myapp/config.properties

which will contain a file name and some other configurations. I'll set the file name in properties file like this: file=file_to_read.txt

this file_to_read.txt will be located in D:/java/myapp/folder_of_file/

The main class will read the file name from the properties file first and then get the contents form the file.

I can do this if both config.properties and file_to_read.txt are in src/ with the mainClass.java . But could not succeed with the way I want to do it.

Can anybody help me with this? I need your suggestion about what can I do if I want to put the myapp folder anywhere in my drive with the same internal structure in it I described above and the program will do the job correctly.

I also need your suggestion that if I want to do the job from the jar created after building the project then can I do that without any problem?

I've tried as the following just to read the properties file:

        URL location = myClass.class.getProtectionDomain().getCodeSource().getLocation();

        String filePath = location.getPath().substring(1,location.getPath().length());

        InputStream in = myClass.class.getResourceAsStream(filePath + "config.properties");
        prop.load(in);

        in.close();

        System.out.println(prop.getProperty("file"));

But this gives err when tried to getProperty from the properties file. Thanks!

Answer 1

How to read a properties file in java from outside the Class folder ?

Use FileInputStream with a fixed disk file system path.

InputStream input = new FileInputStream("D:/java/myapp/config.properties");

Much better is to just move it to one of the existing paths covered by the classpath instead, or to add its original path D:/java/myapp/ to the classpath. Then you can get it as follows:

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

or

InputStream input = Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties");

Answer 2

Thanks everybody for your suggestions. I've done the job by this way:

        Properties prop = new Properties();
        String dir = System.getProperty("user.dir");
        InputStream in = new FileInputStream(dir + "/myapp/config.properties");
        prop.load(in);
        in.close();
        String filePath = dir + "/myapp/folder_of_file/" + prop.getProperty("file"); /*file contains the file name to read*/

Answer 3

Properties property=new Properties();
property.load(new FileInputStream("C:/java/myapp/config.properties"));

Answer 4

You need to specify absolute path but you shouldn't hard-code it as that will make it harder for switching between development and production environment etc..

You may get the base path of the file(s) from a System property which you can access using System.getProperty("basePath") in your code and which should be prepended to your file name to create an absolute path.

While running your application you can specify the path in java command line as follows:

java -DbasePath="/a/b/c" ...

... signifies the current arguments to your Java command to run your program.