Read a property file

1/12/2016


Source: http://crunchify.com/java-properties-file-how-to-read-config-properties-values-in-java/

.properties is a file extension for files mainly used in Java related technologies to store the configurable parameters of an application. They can also be used for storing strings for Internationalization and localization; these are known as Property Resource Bundles.

Each parameter is stored as a pair of strings, one storing the name of the parameter (called the key/map), and the other storing the value.

source: http://www.avajava.com/tutorials/lessons/how-do-i-read-a-properties-file.html

How do I read a properties file?

Author: Deron Eriksson

Description: This Java tutorial describes how to read properties from a file.

Tutorial created using: Windows XP || JDK 1.5.0_09 || Eclipse Web Tools Platform 1.5.1

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The JavaSW Properties class offers a very convenient method of storing data for your application. It consists of various String values and String keys that you use to look up these values. It is basically a hashtable. The load method of the Properties class offers a very convenient mechanism for loading key/value String pairs from a properties file in the file system.

Let's create a ReadPropertiesFile class. This class reads in properties from a 'test.properties' file at the root level of our project.

The ReadPropertiesFile class creates an input stream from the test.properties file. It creates a Properties object and loads the properties (key/value pairs) from the input stream. It then enumerates over the keys of the Properties object, and retrieves the value for each key. The key/value pairs are displayed via standard output.

ReadPropertiesFile.java

package test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;

public class ReadPropertiesFile {
 public static void main(String[] args) {
  try {
   File file = new File("test.properties");
   FileInputStream fileInput = new FileInputStream(file);
   Properties properties = new Properties();
   properties.load(fileInput);
   fileInput.close();

   Enumeration enuKeys = properties.keys();
   while (enuKeys.hasMoreElements()) {
    String key = (String) enuKeys.nextElement();
    String value = properties.getProperty(key);
    System.out.println(key + ": " + value);
   }
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
}

The contents of the test.properties file are displayed below. Each key is represented on the left side of the = sign, and each value is on the right side of the = sign. Comments are designated by lines starting with # signs.

test.properties

# This is my test.properties file
favoriteFood=kun pao chicken
favoriteVegetable=artichoke
favoriteSoda=Dr Pepper

The ReadPropertiesFile class is executed below. We can see the results of the execution at the bottom of the screen capture.

In the console, the three key/value pairs are displayed. Notice that they are not displayed in the order that they are entered in the properties file. This is because the Properties object is a hashtable, which is a data structure that is optimal for quick storage and retrieval of individual data values, but it does not really have a sense of order to the returned results.