Dependency Injection via Setter method in spring

This is 6 of 16 parts of tutorial series

Tutorial Content: Spring tutorial for beginners

    Introduction to spring framework Spring interview questions Dependency injection(ioc) in spring Spring hello world example in eclipse Spring java based configuaration Dependency injection via setter method in spring Dependency injection via constructor in spring Spring Bean scopes with examples Initializing collections in spring Beans Autowiring in spring Inheritance in Spring Spring ApplicationContext Spring lifetime callbacks BeanPostProcessors in Spring Annotation based Configuration in spring Spring AOP tutorial
As the name implies, using setter method spring container will inject the dependencies.This technique is considered as the best approach for dependency injection.
For configuring spring in your eclipse ide please refer  hello world example

1.Country.java:

This is simple pojo class having some attributes so here country has name and object of Capital class.
Create Country.java under package org.arpit.javapostsforlearning.Copy following content into Country.java.
package org.arpit.javapostsforlearning;

public class Country {

    String countryName;
    Capital capital;
    public String getCountryName() {
        return countryName;
    }
    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }
    public Capital getCapital() {
        return capital;
    }
    public void setCapital(Capital capital) {
        this.capital = capital;
    }
}

2.Capital.java

This is also simple pojo class having one attribute called "capitalName".
Create Capital.java under package org.arpit.javapostsforlearning.java.Above Country class contains object of this class.Copy following content into Capital.java
package org.arpit.javapostsforlearning;

public class Capital {

    String capitalName;

    public String getCapitalName() {
        return capitalName;
    }

    public void setCapitalName(String capitalName) {
        this.capitalName = capitalName;
    }
}

3.SetterMehtodMain.java

This class contains main function.Create SetterMethodMain.java under package org.arpit.javapostsforlearning.Copy following content into SetterMethodMain.java
 package org.arpit.javapostsforlearning;

import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;

public class SetterInjectionMain {

    public static void main(String[] args) {
        ApplicationContext appContext = new ClassPathXmlApplicationContext("ApplicationContext.xml");

        Country countryObj = (Country) appContext.getBean("CountryBean");
        String countryName=countryObj.getCountryName();
        String capitalName=countryObj.getCapital().getCapitalName();
        System.out.println(capitalName+" is capital of "+countryName);
       
    }
}
You can note here that we have used ClassPathXmlApplicationContext for getting bean here.There are various ways for getting beans.In hello world example we have used XmlBeanFactory for getting beans.

4.ApplicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

  <bean id="CountryBean" class="org.arpit.javapostsforlearning.Country">
      <property name="countryName" value="India"/>
      <property name="capital" ref="CapitalBean"/>
  </bean>
  <bean id="CapitalBean" class="org.arpit.javapostsforlearning.Capital">
      <property name="capitalName" value="Delhi"/>
  </bean>
</beans>
Here We have declared two beans with corresponding ids.
1.Class Country with id as "CountryBean"
2.Class Capital with id as "CapitalBean"
Property's value tag is for assigning value to corresponding attribute. so In above xml file,we have assigned countryName attribute of Country class with value as india
<property name="Name Of Attribute" value="Value Of attribute to be assigned"/>
Property's ref tag is for assigning reference to corresponding attribute. so In above xml file,we have assigned reference of Capital class to capital attribute of Country class.
<property name="Name Of Attribute" ref="id of referencing bean"/>

5.Run it

When you will run above application,you will get following as output.

Delhi is capital of India

Source code:

In next post,we will see dependency injection via constructor

Written by Arpit:

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