从Jar Java外的配置文件中读取

Question

Currently I am trying to read my config file from root of project directory, in order to make this actual configuration I want to move this to external location and then read from there.

Adding a complete path in following code throws out error :

package CopyEJ;

import java.util.Properties;

public class Config
{
   Properties configFile;
   public Config()
   {
    configFile = new java.util.Properties();
    try {
     // configFile.load(this.getClass().getClassLoader().getResourceAsStream("CopyEJ/config.properties"));
      Error Statement ** configFile.load(this.getClass().getClassLoader().getResourceAsStream("C://EJ_Service//config.properties"));
    }catch(Exception eta){
        eta.printStackTrace();
    }
   }

   public String getProperty(String key)
   {
    String value = this.configFile.getProperty(key);
    return value;
   }
}

Here's the error:

java.lang.NullPointerException
    at java.util.Properties$LineReader.readLine(Properties.java:365)
    at java.util.Properties.load(Properties.java:293)
    at CopyEJ.Config.<init>(Config.java:13)
    at CopyEJ.CopyEJ.main(CopyEJ.java:22)
Exception in thread "main" java.lang.NullPointerException
    at java.io.File.<init>(File.java:194)
    at CopyEJ.CopyEJ.main(CopyEJ.java:48)

How can I fix this ?

Answer 1

The purpose of method getResourceAsStream is to open stream on some file, which exists inside your jar. If you know exact location of particular file, just open new FileInputStream .

Ie your code should look like:

try (FileInputStream fis = new FileInputStream("C://EJ_Service//config.properties")) {
     configFile.load(fis);
} catch(Exception eta){
     eta.printStackTrace();
}

Answer 2

This line requires your config.properties to be in the java CLASSPATH

this.getClass().getClassLoader().getResourceAsStream("C://EJ_Service//config.properties")

When it is not, config.properties won't be accessible.

You can try some other alternative and use the configFile.load() function to read from.

One example would be:

InputStream inputStream = new FileInputStream(new File("C:/EJ_Service/config.properties"));

configFile.load(inputStream);