Spring Autowiring by AutoDetect

In Spring "Autowiring by AutoDetect means" If a default constructor is found, uses "constructor"; Otherwise, uses "byType". In this case, since there is a default constructor in "Circle" class, so, Spring auto wired it via constructor method – "public Circle(Point center)".

For example, if "autowiring by autodetect". Auto wiring the "center" bean into "circle", via constructor or  by type, Its based on the implementation of Circle bean. Spring will find the "center" in current container and wire it automatically one of constructor or  by type.

You can enable this feature via autowire="autodetect" like below :
With autowire by autodetectenabled, you do not need to declares the property tag anymore.
<bean autowire="autodetect" 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>

1.See AutoDetect – by Constructor Example
If a default constructor is supplied, auto detect will chooses wire by constructor.
Circle.java
package com.dineshonjava.sdnext.autoWiring.tutorial;

public class Circle
{
 private Point center;
  
 /**
  * USING CONSTRUCTOR
  * @param center the center to set
  * autowiring by constructor
  */
 public Center(Point center) {
  this.center = center;
 }

/**
  * USING SETTER
  * @param center the center to set
  * autowiring by type
  */
 public setCenter(Point center) {
  this.center = center;
 }
 
public void draw()
 {
  System.out.println("Center of circle is ("+center.getX()+", "+center.getY()+")");
 }
}

2.See AutoDetect – by Type Example
If a default constructor is not found, auto detect will chooses wire by type.
Circle.java
package com.dineshonjava.sdnext.autoWiring.tutorial;

public class Circle
{
 private Point center;
  
 /**
  * USING SETTER ONLY
  * @param center the center to set
  * autowiring by type
  */
 public 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="constructor" 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)




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