Using Spring Expression Language with value

Using SpEL is easy for externalise the value. This simple example demonstrate how to use spring expression language.

Create a POJO MySetting 

@Component("mySetting")
public class MySetting {

	private String username = "admin";
	
	private String password = "p@ssword1";
	
	private String database = "test";
	
	private String driver = "com.mysql.driver";

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public String getDatabase() {
		return database;
	}

	public void setDatabase(String database) {
		this.database = database;
	}

	public String getDriver() {
		return driver;
	}

	public void setDriver(String driver) {
		this.driver = driver;
	}
	
}

Create a service class – MyDatabase

@Service("myDatabase")
public class MyDatabase {
	
	@Value("#{mySetting.username}")
	private String username;
	@Value("#{mySetting.password}")
	private String password;
	@Value("#{mySetting.database}")
	private String database;
	@Value("#{mySetting.driver}")
	private String driver;
	
	private void print(){ 
		System.out.println(this.username);
		System.out.println(this.password);
		System.out.println(this.database);
		System.out.println(this.driver);
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public String getDatabase() {
		return database;
	}

	public void setDatabase(String database) {
		this.database = database;
	}

	public String getDriver() {
		return driver;
	}

	public void setDriver(String driver) {
		this.driver = driver;
	}

Create a client file to run

package com.eweol.example;

import org.springframework.context.support.GenericXmlApplicationContext;

public class MyClient {

   public static void main(String[] args) {
		
     GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
     ctx.load("classpath:/applicationcontext.xml");
     ctx.refresh();
		
     MyDatabase db = ctx.getBean(MyDatabase.class);
     db.print();
   }
}

applicationContext.xml
First scan codebase for dependency requirement, then scan the code for injectable bean under the package.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<beans xmlns="http://www.springframework.org/schema/beans" 
xmlns:context="http://www.springframework.org/schema/context" 
xmlns:mvc="http://www.springframework.org/schema/mvc" 
xmlns:p="http://www.springframework.org/schema/p" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">

  
  <context:annotation-config />

  <context:component-scan base-package="com.eweol.example"/>
         
</beans>