Java Properties File Examples

The below link is about "Java Properties File Examples".

http://www.mkyong.com/java/java-properties-file-examples/

The examples are quite easy to understand. Property file should name as "xxx.properties" in Java project.

1. Write to properties file

Set the property value, and write it into a properties file named “config.properties“.

package com.mkyong.common;
 
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;
 
public class App 
{
    public static void main( String[] args )
    {
     Properties prop = new Properties();
 
     try {
      //set the properties value
      prop.setProperty("database", "localhost");
      prop.setProperty("dbuser", "mkyong");
      prop.setProperty("dbpassword", "password");
 
      //save properties to project root folder
      prop.store(new FileOutputStream("config.properties"), null);
 
     } catch (IOException ex) {
      ex.printStackTrace();
        }
    }
}

Output

config.properties

#Mon Jan 11 18:54:40 MYT 2010
dbpassword=password
database=localhost
dbuser=mkyong

P.S If file path is not specified, then this properties file will be stored in your project root folder.

2. Load a properties file

Load a properties file from the file system and retrieved the property value.

package com.mkyong.common;
 
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;
 
public class App 
{
    public static void main( String[] args )
    {
     Properties prop = new Properties();
 
     try {
               //load a properties file
      prop.load(new FileInputStream("config.properties"));
 
               //get the property value and print it out
                System.out.println(prop.getProperty("database"));
      System.out.println(prop.getProperty("dbuser"));
      System.out.println(prop.getProperty("dbpassword"));
 
     } catch (IOException ex) {
      ex.printStackTrace();
        }
 
    }
}

Output

localhost
mkyong
password

3. Load a properties file from classpath

Load a properties file named “config.properties” from project classpath, and retrieved the property value.

package com.mkyong.common;
 
import java.io.FileInputStream;
import java.io.IOException;
import java.utilutil.Properties;
 
public class App 
{
    public static void main( String[] args )
    {
     Properties prop = new Properties();
 
     try {
               //load a properties file from class path, inside static method
      prop.load(App.class.getClassLoader().getResourceAsStream("config.properties");));
 
               //get the property value and print it out
                System.out.println(prop.getProperty("database"));
      System.out.println(prop.getProperty("dbuser"));
      System.out.println(prop.getProperty("dbpassword"));
 
     } catch (IOException ex) {
      ex.printStackTrace();
        }
 
    }
}

For non-static method, use this :

prop.load(getClass().getClassLoader().getResourceAsStream("config.properties");));