Spring @PropertySource Example : Spring is a powerful framework, having almost everything a developer need to develop an application. Today we are going to talk about the @PropertySource annotation. Suppose we have a property file and we want to load and use the values in our Java class without using any IO method. So the question is how we can use property file values inside our Java class?

The Spring Framework already has the answer of this question. @PropertySource annotation is used to load the property file inside the Java class. @PropertySource is mostly used with the conjunction of @Configuration. After passing the property file name in @PropertySource annotation we can use property file's values using org.springframework.core.env.Environment interface or @Value annotation.

Example of @PropertySource annotation :

application.properties

# database configuration
db.driverClassName=com.mysql.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/testdb
db.username=root
db.password=root

Configuration.java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;

@Configuration
@PropertySource("classpath:application.properties")
public class Configuration {
    @Autowired
    Environment env;
    @Value("${db.url}")
    private String url;
    @Value("${db.driverClassName}")
    private String driverClassName

    @Bean
    public DatabaseConfig dbCon() {
        DatabaseConfig dbCon= new DatabaseConfig();
        dbCon.setDriverClassName(driverClassName);
        dbCon.setUrl(url);
        dbCon.setUsername(env.getProperty("db.username"));
        dbCon.setPassword(env.getProperty("db.password")); 
        return dbCon;
    }
}

In the above example we are getting passing the property file name application.properties in @PropertySource, and after loading this file all properties can be accessed using the env.getProperty(key) or using the @Value(${key}) annotation.