In Spring, you can use @Autowired annotation to auto wire bean on the setter method, constructor or a field. Moreover, it can autowired property in a particular bean.
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Note:
The @Autowired annotation is auto wire the bean by matching data type if spring container find more than one beans same data type then it find by name.
You can use @Autowired annotation on setter methods to get ref id of the <property> element in XML configuration file(spring.xml). When Spring finds an @Autowired annotation used with setter methods, it tries to perform byType autowiring on the method.
See following full example to demonstrate the use of @Autowired.
Circle.java
package com.dineshonjava.sdnext.autowiredannotation.tutorial; import org.springframework.beans.factory.annotation.Autowired; public class Circle { private Point center; //using autowired annotation with setter method @Autowired public void setCenter(Point center) { this.center = center; } public void draw() { System.out.println("Circle is drawn of center ("+center.getX()+", "+center.getY()+")"); } }
Point.java
package com.dineshonjava.sdnext.autowiredannotation.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; } }
DrawingApp.java
package com.dineshonjava.sdnext.autowiredannotation.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(); } }
spring.xml
<beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p" xmlns:> Once you are done with creating source and bean configuration files, let us run the application. If everything is fine with your application, this will print the following message:Output:Jul 10, 2012 7:41:44 PM org.springframework.context.support.AbstractApplicationContext prepareRefreshINFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@ab50cd: startup date [Tue Jul 10 19:41:44 IST 2012]; root of context hierarchyJul 10, 2012 7:41:44 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitionsINFO: Loading XML bean definitions from class path resource [spring.xml]Jul 10, 2012 7:41:44 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletonsINFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1d80e6d: defining beans [circle,pointA,pointB,pointC,center,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchyCircle is drawn of center (10, 10)
package com.dineshonjava.sdnext.autowiredannotation.tutorial; import org.springframework.beans.factory.annotation.Autowired; public class Circle { //using autowired annotation with property @Autowired private Point center; public void setCenter(Point center) { this.center = center; } public void draw() { System.out.println("Circle is drawn of center ("+center.getX()+", "+center.getY()+")"); } }
Circle.java
package com.dineshonjava.sdnext.autowiredannotation.tutorial; import org.springframework.beans.factory.annotation.Autowired; public class Circle { private Point center; //using autowired annotation with constructor @Autowired public Center(Point center) { this.center = center; } public void draw() { System.out.println("Circle is drawn of center ("+center.getX()+", "+center.getY()+")"); } }
Circle.java
package com.dineshonjava.sdnext.autowiredannotation.tutorial; import org.springframework.beans.factory.annotation.Autowired; public class Circle { //using autowired annotation with property @Autowired(required=false) private Point center; public void setCenter(Point center) { this.center = center; } public void draw() { System.out.println("Circle is drawn of center ("+center.getX()+", "+center.getY()+")"); } }
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