Updating property value in properties file without deleting other values [duplicate]

Question

Content of First.properties:

name=elango
country=india
phone=12345

I want change country from india to america. This is my code:

import java.io.*;
public class UpdateProperty 
{
    public static void main(String args[]) throws Exception 
    {   
        FileOutputStream out = new FileOutputStream("First.properties");
        FileInputStream in = new FileInputStream("First.properties");
        Properties props = new Properties();
        props.load(in);
        in.close();
        props.setProperty("country", "america");
        props.store(out, null);
        out.close();
    } 
}

Output content of First.properties:

country=america

The other properties are deleted. I want update a particular property value, without deleting the other properties.

Appledorf

Similar: #7462401 and #566432 – God

Answer 1

Open the output stream and store properties after you have closed the input stream.

try (FileInputStream in = new FileInputStream("First.properties")) {
    Properties props = new Properties();
    props.load(in);
}
        
try (FileOutputStream out = new FileOutputStream("First.properties"))
    props.setProperty("country", "america");
    props.store(out, null);
}

Sitzmark

Thanks Vasyl Keretsman i change code. Is it correct? Properties props = new Properties(); props.load(in); props.setProperty("country", "america"); props.store(out, null); out.close(); in.close(); but answer is same. I didn't get the expected answer – Appledorf

Not correct. I have added the code to my answer – Sitzmark

Thank You Vasyl Keretsman. It is working .. – Appledorf

@VasylKeretsman it is removed all existing comments in the file – Lazurite

Closing streams should be done in a finally block/ try-with-resources statement. – Edwyna

Maybe you are also interested in this Property Library. It can preserve order and comments. #566432 – X

Yes gr8 it solved ......... but why ????? – Poeticize

How did this become the accepted answer ? It removes all previously set properties. – Chenee

This answer should state that you have to rewrite all properties again. Check this answer #7462401 – Chenee

Those for which the code is not working. Please verify the sequence of lines with the code provided. Sequence of lines does matter here. – Bezonian

It removes all the previous properties. And aslo adds the timestamp in the first line of the property file. – Abroach

Answer 2

You can use Apache Commons Configuration library. The best part of this is, it won't even mess up the properties file and keeps it intact (even comments).

Javadoc

PropertiesConfiguration conf = new PropertiesConfiguration("propFile.properties");
conf.setProperty("key", "value");
conf.save();    

Kollwitz

This is much better answer than the accepted one – Ethnography

@José Mª I downloaded commons.apache.org/proper/commons-configuration/index.html ApacheCommons Configurator 2.1.1 and it seems that save() method and some others doesn't exists . Is there any alternative ? – Valued

@Valued Please check this website: commons.apache.org/proper/commons-configuration/userguide_v1.10/… There is a "Saving" section where its explained. – Ethnography

@José Mª Thanks for the link . It seems to be only for the version 1.10 , not for the version 2.1.1 which is the latest :) . I am searching inside commons.apache.org/proper/commons-configuration/userguide/… to find something similar . – Valued

@Valued Sorry I can't test it right now, but I thought it should work because there is a annotation at the header of the website where you can see: "Last Published: 08 February 2017|Version: 2.1.1" It's quite confusing, but you can still use older versions. Unfortunately, I cannot help you any more with this :( – Ethnography

@JoséMª I had used the 1.1 version. Also, the 2.1 version has the save() method in it. commons.apache.org/proper/commons-configuration/apidocs/org/… – Kollwitz

@Kollwitz Thank you for the info, but how can that link demonstrate it? There are only 1 match with "save()" in the whole page and doesn't correspond to the method description. Where is save() hidden? – Ethnography

Okay you are using the apache-commons thats causing the issue. Use the commons-configuration one. Use this: mvnrepository.com/artifact/commons-configuration/… – Kollwitz

I am using commons configuration2 but getting an error when using above code `PropertiesConfiguration() in PropertiesConfiguration can not be applied to (java.lang.String) – Pullet

Hi @J.Doem: You can use the Older 1.10 version which has a String args constructor to pass the file name directly. Else, for V2, you can use the PropertyConfiguration class's loadIncludeFile(String fileName) method to pass the File name. – Kollwitz

This solution solved my 2 issues. 1. Saving the file without losing other data and also 2. Keys positions are not swapped (By using other solutions i.e., with FileInput & Output streams, positions of keys are getting swapped to random positions and also comments are getting removed). – Hypothec

Answer 3

Properties prop = new Properties();
prop.load(...); // FileInputStream 
prop.setProperty("key", "value");
prop.store(...); // FileOutputStream 

Harrelson