Dependency Injection by setter method in Spring

The Spring IoC container also supports setter injection, which is the preferred method of dependency injection in Spring. Setter injection uses the set* methods in a class file to garner property names that are configurable in the spring XML config.

We can inject the dependency by setter method also. The <property> subelement of <bean> is used for setter injection. Here we are going to inject

  1. primitive and String-based values
  2. Dependent object (contained object)
  3. Collection values etc.

Injecting primitive and string-based values by setter method

Let's see the simple example to inject primitive and string-based values by setter method. We have created three files here:

  • Employee.java
  • applicationContext.xml
  • Test.java
Employee.java

It is a simple class containing three fields id, name and city with its setters and getters and a method to display these informations.

package com.javatportal;

public class Employee {
private int id;
private String name;
private String city;

public int getId() {
	return id;
}
public void setId(int id) {
	this.id = id;
}
public String getName() {
	return name;
}
public void setName(String name) {
	this.name = name;
}

public String getCity() {
	return city;
}
public void setCity(String city) {
	this.city = city;
}
void display(){
	System.out.println(id+" "+name+" "+city);
}

}

applicationContext.xml

We are providing the information into the bean by this file. The property element invokes the setter method. The value subelement of property will assign the specified value.

<?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:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
                http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<bean id="obj" class="com.javatportal.Employee">
<property name="id">
<value>20</value>
</property>
<property name="name">
<value>Arun</value>
</property>
<property name="city">
<value>ghaziabad</value>
</property>

</bean>

</beans>
Test.java

This class gets the bean from the applicationContext.xml file and calls the display method.

package com.javatportal;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.*;

public class Test {
	public static void main(String[] args) {
		
		Resource r=new ClassPathResource("applicationContext.xml");
		BeanFactory factory=new XmlBeanFactory(r);
		
		Employee e=(Employee)factory.getBean("obj");
		s.display();
		
	}
}

Output:20 Mithilesh NewDelhi