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.
1. 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,
<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.
<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.
Please read this article about how to create a new custom @Required-style annotation.
@autowire(required=true)
@required
Both are same?
Why @Required Annotation using Java Configuration doesn’t throw an error if required value is not set.
public class Student {
public String name;
public String getName() {
return name;
}
@Required
public void setName(String name) {
this.name = name;
}
}
@Configuration
public class BeanDefination {
@Bean
public Student student() {
Student s = new Student();
// s.setName(“Shiva”);
return s;
}
}
public class TestDemo {
public static void main(String[] args) {
// TODO Auto-generated method stub
AnnotationConfigApplicationContext factory = new AnnotationConfigApplicationContext();
factory.register(BeanDefination.class);
factory.refresh();
Student student = (Student) factory.getBean(Student.class);
System.out.println(student.getName());
}
}
testing the comments… just for fun…
This is exactly what I was looking for. Thanks!
Wow that was odd. I just wrote an really long comment but after I clicked submit my comment didn’t appear. Grrrr… well I’m not writing all that
over again. Anyway, just wanted to say great blog!
How do you do this without using xml?
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Great post! I’m doing a lot of research on this at the moment and your blog is the best resource. Thanks again!