How to Read Config File in Java – With Actual Class Example rovided

Pavan July 11, 2009 Java 22 Comments

In my last post I mentioned “Config Class”couple of times.. here you will see actual class and its usage. The class is very simple. We just need to provide proper path to config file we going to use.

The Config File Class

import java.util.*;
import java.util.Properties;

public class Config
{
   Properties configFile;
   public Config()
   {
	configFile = new java.util.Properties();
	try {
	  configFile.load(this.getClass().getClassLoader().
	  getResourceAsStream("myapp/config.cfg"));
	}catch(Exception eta){
	    eta.printStackTrace();
	}
   }

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

You can get any property/settings from config with method ‘getProperty’

Here is my config sample file

#This is comment
mDbUser = myuser
mDbHost = myserver
mDbPwds = mypwd
mDbName = mydb

#This is comment

mDbUser = myuser

mDbHost = myserver

mDbPwds = mypwd

mDbName = mydb

Usage:

cfg = new Config();
dbname   = cfg.getProperty("mDbUser");

I hope you find this useful. If you wish to read more Java articles from our site visit this.

Tags:config, Java

22 Comments

himanshi
April 12, 2021 | Reply

how to read multiple .cfg file
Adil
July 19, 2018 | Reply

very helpful and clean. Maybe few comment can add more value

usage
Config cfg = new Config();
String dbname = cfg.getProperty(“mDbUser”);

Pavan
July 27, 2018 | Reply

Thanks Adil.
I will try and improve the quality of the articles.

Vlad
January 29, 2019 | Reply

Hey i have a question about the .conf iles in java, could u email me=

kouki

February 21, 2014 | Reply

hello, i need to develop a component java/j2ee that will serve to compare 2 configurations of two projects and then do the impact.
Someone help me please to identify my classes and do my class Diagram.

Jerome

April 22, 2013 | Reply

And here is the Singleton version:
import java.util.Properties;

public class Config {

private Properties configFile;

private static Config instance;

private Config() {
configFile = new java.util.Properties();
try {
configFile.load(this.getClass().getClassLoader().getResourceAsStream(“config.cfg”));
} catch (Exception eta) {
eta.printStackTrace();
}
}

private String getValue(String key) {
return configFile.getProperty(key);
}

public static String getProperty(String key) {
if (instance == null) instance = new Config();
return instance.getValue(key);
}
}

Usage:
$value = Config.getProperty(key);

Pavan
April 23, 2013 | Reply

Thanks @Jerome

downdrown
July 26, 2013 | Reply

Is it possible to load the config file from a file on the file system?

Like System.getProperty(“user.homer”)+”/myconfig.cfg” ??

Hope for reply, thanks!

Pavan
July 26, 2013 | Reply

Yes, you can load config from a file on the file system. here it is how you can do it
Properties prop = new Properties(); prop.load(new FileInputStream("c://config.properties")); System.out.println(prop.getProperty("name_of_variable_in_config"));
You can also refer our article Write Config File in Java

Thanks for stopping by. See you around!

downdrown
July 29, 2013 |

Thank you! helped me a lot!
Aisha
December 21, 2017 |

Thanks 😉

Do you know how to user variables on selection step installation ?
Pavan
December 26, 2017 |

I think I did not get your question. Can you elaborate some more please.

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January 19, 2013 | Reply

Everyone loves what you guys tend to be up too. This type of clever work and coverage!
Keep up the terrific works guys I’ve included you guys to our blogroll.

Johnnyhurley1994

January 16, 2013 | Reply

Hello do you by any change have one of these formats to write to a cfg file in one of the field

cfg = new WriteConfig();
cfg.setProperty(“mDbUser”) = myuser

Pavan
January 17, 2013 | Reply

Not at the moment.
I did not understand how you going to use this functionality, just to prepare properties file? OR you want to load the updated properties file runtime?

Sarang

December 12, 2012 | Reply

It Works, my file path was wrong so i was getting error.

Sarang

December 12, 2012 | Reply

I have past the same code as above, only thing i have changed is the name of the config file but am getting the following error.
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)

mayank99

September 1, 2012 | Reply

Suppose my code requires to store multiple user name???
I did normally i.e.
db.user=user1
db.user=user2
.
.
.
.

but it is extracting the last user only

Plz suggest me some alternative

Pavan
December 13, 2012 | Reply

@mayank99
Properties file is simply a set of key value pair. If you assign multiple values to same key the latest assignment is going to override previous one. You can assign users as comma separated list and then fetch and process it to give you list of users.
e.g.
db.user=user1,user2

August 9, 2012 | Reply

Awesome, thanks!

Sachid

April 20, 2012 | Reply

Thanks it helped me a lot !

yem

November 13, 2010 | Reply

help full, thanks

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