Spring Autowiring by Type - Dinesh on Java

In Spring “Autowire byType means” autowiring is done by property data type. Spring container looks at the properties of the beans on which autowire attribute is set to byType in the XML configuration file. It then tries to match and wire its properties with the beans defined by the same data type in the configuration file.

For example, if a “circle” bean exposes an “center” property of Point data type, Spring will find these “center” in current container and wire it automatically. And if no matching found, just do nothing.

Popular Tutorials

You can enable this feature via autowire=”byType” like below :

Normally, you wire the bean explicitly, via ref attribute like this :

<bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Circle" id="circle">
   <property name="center" ref="center"></property>
</bean>
<bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="center">
   <property name="x" value="0"></property>
   <property name="y" value="0"></property>
</bean>

With autowire by type enabled, you do not need to declares the property tag anymore. As long as the “center” beans are same data type as the property of “circle” bean, which is “center“, Spring will wire it automatically.

Lets see Exaple
Circle.java

package com.dineshonjava.sdnext.autoWiring.tutorial;

public class Circle
{
 private Point center;
  
 /**
  * @param center the center to set
  */
 public void setCenter(Point center) {
  this.center = center;
 }

 public void draw()
 {
  System.out.println("Center of circle is ("+center.getX()+", "+center.getY()+")");
 }
}

Point.java

package com.dineshonjava.sdnext.autoWiring.tutorial;

public class Point
{
 private int x;
 private int y;
 /**
  * @return the x
  */
 public int getX() {
  return x;
 }
 /**
  * @param x the x to set
  */
 public void setX(int x) {
  this.x = x;
 }
 /**
  * @return the y
  */
 public int getY() {
  return y;
 }
 /**
  * @param y the y to set
  */
 public void setY(int y) {
  this.y = y;
 }
}

spring.xml

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemalocation="http://www.springframework.org/schema/beans  
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<bean autowire="byType" class="com.dineshonjava.sdnext.autoWiring.tutorial.Circle" id="circle">
  </bean>
 <bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="center">
  <property name="x" value="0"></property>
  <property name="y" value="0"></property>
 </bean>
</beans>

DrawingApp.java

package com.dineshonjava.sdnext.autoWiring.tutorial;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


/**
 * @author Dinesh Rajput
 *
 */
public class DrawingApp 
{
 /**
  * @param args
  */
 public static void main(String[] args) 
 {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
  Circle circle = (Circle) context.getBean("circle");
  circle.draw();
 }
}

Now run this application and get following output on the console.

Output:

Jun 25, 2012 7:55:23 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [spring.xml]

Jun 25, 2012 7:55:24 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons

INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1592174: defining beans [circle ,center]; root of factory hierarchy

Center of Circle is (0, 0)

Spring Related Topics you may like

Understanding Bean Scopes |index| Using ApplicationContextAware in Spring

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Dinesh Rajput