Properties file are often used in Java applications in the aim to store configuration parameters, internationalization and various informations. A properties file have « .properties » as extension where each line is a key/value entry. The key and the value are separated by the equal symbol « = ». Properties can also be stored in a XML file (see last chapter).
In this tutorial, we will see how to read a properties file in Java. Consider the following properties file named config.properties :
database . url = localhost
database . login = roufid
database . password = password
1- Load properties file Since JDK 1.0
Java offers the Properties class from the java.util package to read properties file. Below an example :
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
public class PropertiesExample {
public static void main ( String [ ] args ) {
// Properties file path.
String filePath = "c:/files/config.properties" ;
Properties prop = new Properties ( ) ;
try ( InputStream inputStream = new FileInputStream ( filePath ) ) {
// Loading the properties.
prop . load ( inputStream ) ;
// Getting properties
String url = prop . getProperty ( "database.url" ) ;
String login = prop . getProperty ( "database.login" ) ;
String password = prop . getProperty ( "database.password" ) ;
System . out . println ( "URL = " + url ) ;
System . out . println ( "login = " + login ) ;
System . out . println ( "password = " + password ) ;
} catch ( IOException ex ) {
System . out . println ( "Problem occurs when reading file !" ) ;
ex . printStackTrace ( ) ;
}
}
}
Note that we used the With a try with resources , so no need to close the inputStream.
Output :
URL = localhost
login = roufid
password = password
2- Load properties from a file located in classpath The access to a properties file located in application classpath depends of whether your are on a static method or not.
In a static method, you can access a file in your classpath by using the following code :
<YOUR_CLASS_NAME> . class . getClassLoader ( ) . getResourceAsStream ( <YOUR_FILE_NAME> )
Full example :
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
public class PropertiesExample {
public static void main ( String [ ] args ) {
// Properties file path.
String filePath = "config.properties" ;
Properties prop = new Properties ( ) ;
try ( InputStream inputStream = PropertiesExample . class . getClassLoader ( ) . getResourceAsStream ( filePath ) ) {
// Loading the properties.
prop . load ( inputStream ) ;
// Getting properties
String url = prop . getProperty ( "database.url" ) ;
String login = prop . getProperty ( "database.login" ) ;
String password = prop . getProperty ( "database.password" ) ;
System . out . println ( "URL = " + url ) ;
System . out . println ( "login = " + login ) ;
System . out . println ( "password = " + password ) ;
} catch ( IOException ex ) {
System . out . println ( "Problem occurs when reading file !" ) ;
ex . printStackTrace ( ) ;
}
}
}
In a non-static method, you can access a file in the classpath by using the following code :
getClass ( ) . getClassLoader ( ) . getResourceAsStream ( <YOUR_FILE_NAME> ) ;
3- XML properties file Properties can also be stored in a XML file respecting the properties dtd . Below an example :
<? xml version = "1.0" encoding = "UTF-8" standalone = "no" ?>
< ! DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd" >
< properties >
< entry key = "database.password" > password < / entry >
< entry key = "database.login" > roufid < / entry >
< entry key = "database.url" > localhost < / entry >
< / properties >
However, reading the properties file remains the same. Replace just
by
prop . loadFromXML ( inputStream ) ;
Related
