Inversion of Control (IoC)

Spring Framework is built on the Inversion of Control principle. Dependency injection is the technique to implement IoC in applications.

About this example

In this very sample project i try to use bean control from context file. Let's say you have to use special databases on your project. And you want to use them only changing one string variable. On the App.java file you just have to change variable value to use database bean.

About context file

<bean id="Oracle" class="dao.OracleSqlApplicationDao"/>

<bean id="MsSql" class="dao.MsSqlApplicationDao"/>

<bean id="MySql" class="dao.MySqlApplicationDao"/>

Main method

String database = "MySql"; //Oracle, MySql or MsSql

//Read appContext file
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("appContext.xml");
//Get database bean from context.
ApplicationManager app = new ApplicationManager(context.getBean(database, IApplicationDao.class));

app.create();

Using Constuctor Injection

In the branch constructorInjection i use Constructor Injection (Setter Injection)

Context File

<bean id="database" class="dao.OracleSqlApplicationDao"/>


<bean id="service" class="service.ApplicationManager">
  <property name="database" ref="database"></property>
</bean>

App.java

//Read appContext file
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("appContext.xml");
//Get database bean from context.
IApplicationService app = context.getBean("service", IApplicationService.class);

app.create();

ApplicationManager.java

private IApplicationDao database;

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

@Override
public void create() {
  System.out.println("New App creating...");
  database.add();	
}

Using Annotation

You can also do same thing using annotations Click here to see Using Annotation barnch

cagritrk / springIoC