Spring’s dependency checking in bean configuration file is used to make sure all properties of a certain types (primitive, collection or object) have been set. In most scenarios, you just need to make sure a particular property has been set, but not all properties..
For this case, you need @Required annotation, see following example :
@Required example
A Customer object, apply @Required in setPerson() method to make sure the person property has been set.
package com.mkyong.common;
import org.springframework.beans.factory.annotation.Required;
public class Customer {
private Person person;
private int type;
private String action;
public Person getPerson() {
return person;
}
@Required
public void setPerson(Person person) {
this.person = person;
}
}
Simply apply the @Required annotation will not enforce the property checking, you also need to register an RequiredAnnotationBeanPostProcessor to aware of the @Required annotation in bean configuration file.
The RequiredAnnotationBeanPostProcessor can be enabled in two ways.
- Include
<context:annotation-config />
Add Spring context and<context:annotation-config />in bean configuration file.
<beans ... xmlns:context="http://www.springframework.org/schema/context" ... http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd">
...
<context:annotation-config />
...
</beans>
Full example,
<?xml version="1.0"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" 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">
<context:annotation-config />
<bean id="CustomerBean" class="com.mkyong.common.Customer">
<property name="action" value="buy" />
<property name="type" value="1" />
</bean>
<bean id="PersonBean" class="com.mkyong.common.Person">
<property name="name" value="mkyong" />
<property name="address" value="address ABC" />
<property name="age" value="29" />
</bean>
</beans>
2. Include RequiredAnnotationBeanPostProcessor
Include ‘RequiredAnnotationBeanPostProcessor’ directly in bean configuration file.
<?xml version="1.0"?>
<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" />
<bean id="CustomerBean" class="com.mkyong.common.Customer">
<property name="action" value="buy" />
<property name="type" value="1" />
</bean>
<bean id="PersonBean" class="com.mkyong.common.Person">
<property name="name" value="mkyong" />
<property name="address" value="address ABC" />
<property name="age" value="29" />
</bean>
</beans>
If you run it , the following error message will be throw, because person property is unset.
org.springframework.beans.factory.BeanInitializationException: Property 'person' is required for bean 'CustomerBean'
Conclusion
Try @Required annotation, it is more flexible than dependency checking in XML file, because it can apply to a particular property only.
