Define custom @Required-style annotation in Spring

The

@Required

annotation is used to make sure a particular property has been set. If you are migrate your existing project to Spring framework or have your own

@Required-style

annotation for whatever reasons, Spring is allow you to define your custom

@Required-style

annotation, which is equivalent to

@Required

annotation.

In this example, you will create a custom

@Required-style

annotation named

@Mandatory

, which is equivalent to

@Required

annotation.

1. Create the @Mandatory interface

package com.mkyong.common;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Mandatory {
}

2. Apply it to a property

package com.mkyong.common;

public class Customer
{
private Person person;
private int type;
private String action;

@Mandatory
public void setPerson(Person person) {
this.person = person;
}
//getter and setter methods
}

3. Register it

Include your new

@Mandatory

annotation in ‘

RequiredAnnotationBeanPostProcessor

’ class.

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> 
<bean
class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor">
<property name="requiredAnnotationType" value="com.mkyong.common.Mandatory"/>
</bean>

<bean id="CustomerBean" class="com.mkyong.common.Customer">
<property name="action" value="buy" />
<property name="type" value="1" />
</bean>

</beans>

4. Done

Done, you just created a new custom

@Required-style

annotation named

@Mandatory

, which is equivalent to

@Required

annotation.