Spring @Component Annotation

The @Component Annotation Indicates that an annotated class is a “component“. Such classes are considered as candidates for auto-detection when using annotation-based configuration and classpath scanning. 
The @Component is a generic stereotype for any Spring-managed component. @Repository, @Service, and @Controller are specializations of @Component for more specific use cases, for example, in the persistence, service, and presentation layers, respectively.

 See the following example using component annotation:

Triangle.java

package com.dineshonjava.sdnext.componentstreatypeannotation.tutorail;

import javax.annotation.Resource;

import org.springframework.stereotype.Component;

@Component
public class Triangle
{
 private Point pointA;
 private Point pointB;
 private Point pointC;
 
 /**
  * Using @Resource annotation for wiring with bean dependency
  * @param pointA the pointA to set
  */
 @Resource
 public void setPointA(Point pointA) {
  this.pointA = pointA;
 }

 /**
  * Using @Resource annotation for wiring with bean dependency
  * @param pointB the pointB to set
  */
 @Resource
 public void setPointB(Point pointB) {
  this.pointB = pointB;
 }

 /**
  * Using @Resource annotation for wiring with bean dependency
  * @param pointC the pointC to set
  */
 @Resource
 public void setPointC(Point pointC) {
  this.pointC = pointC;
 }

 public void draw()
 {
System.out.println("Drawing Triangle");
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()+")");
 }
}

Here we are using @Component annotation with the Triangle class which auto detect as bean in Spring IoC Container.

Point.java

package com.dineshonjava.sdnext.componentstreatypeannotation.tutorail;

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.componentstreatypeannotation.tutorail;

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

/**
 * @author Dinesh
 *
 */
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();
 }
}

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:>
Here <context:component-scan/> scan the all classes in the base package given as "com.dineshonjava.sdnext.componentstreatypeannotation.tutorail" which are annotated with the @Component annotation or its specific annotations like @Component, @Repository, @Service & @Controller etc then these classes detect as bean of Spring IoC Container.
If every thing is OK then run that application we will get the following output.
Output:
Jul 14, 2012 8:54:13 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@ab50cd: startup date [Sat Jul 14 20:54:13 IST 2012]; root of context hierarchy
Jul 14, 2012 8:54:13 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Jul 14, 2012 8:54:14 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1198891: defining beans [pointA,pointB,pointC,center,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,circle,triangle,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchy

Drawing Triangle
PointA is (0, 0)
PointB is (-20, 0)
PointC is (20, 0)

Spring Related Topics you may like
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  5. Spring REST Interview Questions and Answers
  6. Spring Boot Interview Questions and Answers
  7. Spring Boot Microservices Interview Questions and Answers
  8. Dependency Injection (DI) in Spring
  9. Spring IoC Container
  10. What is Bean Factory in Spring
  11. ApplicationContext in Spring
  12. Bean Autowiring in Spring
  13. Spring Bean Scopes
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  19. Annotations in Spring and Based Configuration
  20. Spring JSR-250 Annotations
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  26. Spring AOP AspectJ @Before Annotation Advice Example
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  41. Spring Security Java Based Configuration with Example
  42. Spring Security XML Namespace Configuration Example

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Dinesh Rajput

Dinesh Rajput is the chief editor of a website Dineshonjava, a technical blog dedicated to the Spring and Java technologies. It has a series of articles related to Java technologies. Dinesh has been a Spring enthusiast since 2008 and is a Pivotal Certified Spring Professional, an author of a book Spring 5 Design Pattern, and a blogger. He has more than 10 years of experience with different aspects of Spring and Java design and development. His core expertise lies in the latest version of Spring Framework, Spring Boot, Spring Security, creating REST APIs, Microservice Architecture, Reactive Pattern, Spring AOP, Design Patterns, Struts, Hibernate, Web Services, Spring Batch, Cassandra, MongoDB, and Web Application Design and Architecture. He is currently working as a technology manager at a leading product and web development company. He worked as a developer and tech lead at the Bennett, Coleman & Co. Ltd and was the first developer in his previous company, Paytm. Dinesh is passionate about the latest Java technologies and loves to write technical blogs related to it. He is a very active member of the Java and Spring community on different forums. When it comes to the Spring Framework and Java, Dinesh tops the list!

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