11/26/2013

java.util.Properties, trim, null, whitespace, and escaping

This is the simple test to show the values of properties when loading from a properties file. It tries to answer some common questions about properties value:

Do I need to trim whitespaces from a property value loaded from a properties file?

Yes. Leading whitespaces in a property value are automatically trimmed by Java, but trailing whitespaces are preserved. So if whitespaces are not significant, then property values need to be trimmed val.trim()


Do I need to check null when operating on a property value loaded from a properties file?

Yes. If a property does not exit in the properties file, then calling props.getProperty(key) will return null.


Do I need to check isEmpty when operating on a property value loaded from a properties file?

Yes. If only the key exits in the properties file without assigning any value, then calling props.getProperty(key) will return an empty string. If the value line contains only multiple whitespaces, they will be trimmed away and its value is still empty string.


Do I need to escape = or : characters in property file?

No need to escape = or : in property value, but if the = or : is part of the property key, then you need to escape them. Java treats the first occurrence of = or : or whitespace as the key-value delimiter. So after the delimiter is identified, any use of them no longer needs escaping.

import java.util.*;
import java.io.*;

public class PropertiesTest {
    public static void main(String args[]) throws Exception {
        Properties props = new Properties();
        props.load(new FileInputStream(new File("a.properties")));
        for(String key : props.stringPropertyNames()) {
            System.out.printf("'%s' --> '%s'%n", key, props.getProperty(key));
        }

        System.out.printf("property.not.defined = %s%n", props.getProperty("adsfadsfdjsakfads"));
    }
}
The properties file a.properties:
no.value =
no.value.with.trailing.spaces =
prop.with.leading.trailing.spaces =      value              
prop.with.leading.spaces =      value
equal.sign.in.value = user=admin
colon.in.value = user:password
equal.sign.colon.in.value = user=admin:password=secrete
equal.sign.in.value.escaped = user\=admin
equal.sign.colon.in.value.escaped = user\=admin\:password\=secrete
\=\:in.key.escaped = value for =:in.key.escaped
=:in.key.not.escaped = value for =:in.key.not.escaped
To compile and run this program:
javac PropertiesTest.java
java PropertiesTest

'equal.sign.in.value' --> 'user=admin'
'equal.sign.colon.in.value' --> 'user=admin:password=secrete'
'no.value' --> ''
'prop.with.leading.spaces' --> 'value'
'equal.sign.in.value.escaped' --> 'user=admin'
'=:in.key.escaped' --> 'value for =:in.key.escaped'
'prop.with.leading.trailing.spaces' --> 'value     '
'colon.in.value' --> 'user:password'
'no.value.with.trailing.spaces' --> ''
'equal.sign.colon.in.value.escaped' --> 'user=admin:password=secrete'
'' --> ':in.key.not.escaped = value for =:in.key.not.escaped'
property.not.defined = null
For complete description, see java.util.Properties javadoc.

7 comments:

xproph said...

Hi there!
Nice blog you have with some interesting articles. Keep up it up!

Thanks.
devmain blogspot

Dex Banner said...

Good writing and even a decent writer you are...great blog!

Anna said...

Great and Useful Article.

Online Java Training

Java Online Training India

Java Online Course

Java EE course

Java EE training

Best Recommended books for Spring framework

Java Interview Questions








Java Course in Chennai

Java Online Training India

Bala Subramaniam Chandrasekar said...
This comment has been removed by the author.
Jeffy said...

Thank you for sharing such a nice and interesting blog with us. I have seen that all will say the same thing repeatedly. But in your blog, I had a chance to get some useful and unique information. I would like to suggest your blog in my dude circle. please keep on updates. hope it might be much useful for us. keep on updating...
seo company in chennai
Digital Marketing company in chennai

Jeffy said...

Thank you for sharing such a nice and interesting blog with us. Hope it might be much useful for us. keep on updating...!!
seo company in india
digital marketing company in india
seo company in chennai
digital marketing company in chennai

Aasha said...

Thanks for this blog. provided great information. All the details are explained clearly with the great explanation. Thanks for this wonderful blog. Step by step processes execution are given clearly.Know the details about different thing.
Digital Marketing Company in Chennai