Spring Autowiring by Name

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

Spring Autowiring by Name

For example, if a "triangle" bean exposes an "pointA, pointB & pointC" properties, Spring will find these point bean("pointA, pointB & pointC") in current container and wire it automatically. And if no matching found, just do nothing.

You can enable this feature via autowire="byName" like below :

Normally, you wire the bean explicitly, via ref attribute like this :
<bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Triangle" id="triangle">
   <property name="pointA" ref="pointA"></property>
   <property name="pointB" ref="pointB"></property>
   <property name="pointC" ref="pointC"></property>
</bean>
<bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="pointA">
   <property name="x" value="0"></property>
   <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="pointB">
   <property name="x" value="-20"></property>
   <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="pointC">
   <property name="x" value="20"></property>
   <property name="y" value="0"></property>
</bean>

With autowire by name enabled, you do not need to declares the property tag anymore. As long as the "pointA, pointB & pointC" beans are same name as the property of "triangle" bean, which is "pointA, pointB & pointC", Spring will wire it automatically.

Lets see Exaple
Triangle.java
package com.dineshonjava.sdnext.autoWiring.tutorial;

public class Triangle 
{
 private Point pointA;
 private Point pointB;
 private Point pointC;
 
 /**
  * @param pointA the pointA to set
  */
 public void setPointA(Point pointA) {
  this.pointA = pointA;
 }

 /**
  * @param pointB the pointB to set
  */
 public void setPointB(Point pointB) {
  this.pointB = pointB;
 }

 /**
  * @param pointC the pointC to set
  */
 public void setPointC(Point pointC) {
  this.pointC = pointC;
 }

 public void draw()
 {
  System.out.println("PointA is ("+pointA.getX()+", "+pointA.getY()+")");
  System.out.println("PointB is ("+pointB.getX()+", "+pointB.getY()+")");
  System.out.println("PointC is ("+pointC.getX()+", "+pointC.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="byName" class="com.dineshonjava.sdnext.autoWiring.tutorial.Triangle" id="triangle">
  </bean>
 <bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="pointA">
  <property name="x" value="0"></property>
  <property name="y" value="0"></property>
 </bean>
  
 <bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="pointB">
  <property name="x" value="-20"></property>
  <property name="y" value="0"></property>
 </bean>
  
 <bean class="com.dineshonjava.sdnext.autoWiring.tutorial.Point" id="pointC">
  <property name="x" value="20"></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");
  Triangle triangle = (Triangle) context.getBean("triangle");
  triangle.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 [triangle,pointA,pointB,pointC]; root of factory hierarchy
PointA is (0, 0)
PointB is (-20, 0)
PointC is (20, 0)






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