In this tutorial you will learn about how to wire References to list element in spring framework
In this tutorial you will learn about how to wire References to list element in spring frameworkSpring 3 provides powerful Expression Language which can be used to wire a property to null . Lets take an example to demonstrate how <null/> element of SpEL is used to ensure that a property is null.
MyClass.java: The MyClass class contains property named "person" which is of Person type.
package spel.wiringnull;
import spel.wiringnull.Person;
public class MyClass
{
private Person person;
public void setPerson(Person person) {
this.person = person;
}
public Person getPerson() {
return person;
}
}
Person.java: This class contains the name of the person.
package spel.wiringnull;
public class Person
{
private String name;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
spring-beans.xml: Using Spring expression language the property person of MyClass bean is wired with the null value using <null/> element.
<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 id="myClass" class="spel.wiringnull.MyClass">
<property name="person"><null/></property>
</bean>
</beans>
AppMain.java: This class loads the context configuration file spring-beans-list.xml from the class path.
package spel.wiringnull;
import org.springframework.context.ApplicationContext;
import
org.springframework.context.support.ClassPathXmlApplicationContext;
import spel.wiringnull.MyClass;
public class AppMain{
public static void main( String[] args ){
ApplicationContext appContext = new ClassPathXmlApplicationContext(new
String[] {"spel\\wiringnull\\spring-beans-list.xml"});
MyClass myObj = (MyClass)appContext.getBean("myClass");
System.out.println("-------------------------------------");
System.out.println("Person Object in MyClass: "+myObj.getPerson());
System.out.println("-------------------------------------");
}
}
The output of the above program will be as below:
-------------------------------------
Person Object in MyClass: null
-------------------------------------