Simply apply the @Required annotation will not enforce the property checking, you have to register an RequiredAnnotationBeanPostProcessor to aware of the @Required annotation in bean configuration file. Simply applying @Required annotion is not enough to enforce the property checking, you also have to register RequiredAnnotationBeanPostProcessor in bean configuration file to do so. This configuration is done in two ways one by Include and another way is Include RequiredAnnotationBeanPostProcessor in bean configuration file. which is shown in this example’s spring.xml file.
In this example Circle class has the center property as required field declare with the @Required annotation. The @Required when written on top of setCenter() method it make sure that center property must have be set else it will give compile time error message that org.springframework.beans.factory.BeanInitializationException: Property ‘center ‘ is required for bean ‘circle’ which is clearly shown in this example.
Circle.java
package com.dineshonjava.sdnext.annotation.tutorial; import org.springframework.beans.factory.annotation.Required; public class Circle { private Point center; /** * @param center the center to set * Here center is the required property for circle */ @Required 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.annotation.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.annotation.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:security="http://www.springframework.org/schema/security" xmlns:tx="http://www.springframework.org/schema/tx" 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-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-2.0.4.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"> <context:annotation-config></context:annotation-config> <bean class="com.dineshonjava.sdnext.annotation.tutorial.Circle" id="circle"> <!-- try without passing center and check the result --> <!--property name="center" ref="center"></property--> </bean> <bean class="com.dineshonjava.sdnext.annotation.tutorial.Point" id="center"> <property name="x" value="10"></property> <property name="y" value="10"></property> </bean> </beans>
<bean class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcess"></bean>
Exception in thread “main” org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘circle’ defined in class path resource [spring.xml]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanInitializationException: Property ‘center’ is required for bean ‘circle’
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:609)
at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:83)
at com.sdnext.annotation.tutorial.DrawingApp.main(DrawingApp.java:19)
Caused by: org.springframework.beans.factory.BeanInitializationException: Property ‘center’ is required for bean ‘circle’
at org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor.postProcessPropertyValues(RequiredAnnotationBeanPostProcessor.java:149)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517)
… 11 more
Next, we can try above example after removing comment from ‘center’ property as follows:
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:security="http://www.springframework.org/schema/security" xmlns:tx="http://www.springframework.org/schema/tx" 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-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-2.0.4.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"> <context:annotation-config></context:annotation-config> <bean class="com.sdnext.annotation.tutorial.Circle" id="circle"> <!-- try with passing center and check the result --> <property name="center" ref="center"></property> </bean> <bean class="com.sdnext.annotation.tutorial.Point" id="center"> <property name="x" value="10"></property> <property name="y" value="10"></property> </bean> </beans>
Now above example will produce following result:
Circle is drawn of center (10, 10)
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