In this post under Spring Core, I will explain with example how to use “@Lookup” annotation with arguments.
In the previous post under Spring Core, I showed the purpose and how to use “@Lookup” annotation without any arguments.
Just for recap,
1) “@Lookup” annotation is applied on the method level
2) It tells Spring to create a bean of a type, which is used as return type of the annotated method.
So if we use the below code
@Lookup
public ContainedBean createContainedBean() {
return null;
}
This tells the Spring to override the default implementation of method “createContainedBean” in such a way that it returns an instance of “ContainedBean” (i.e., return type) every time this method is called.
Now if I replace the above code snippet by providing an argument to “@Lookup” annotation as shown below
@Lookup("displayBean")
public ContainedBean createContainedBean() {
return null;
}
This new change tells the Spring to override the default implementation of method “createContainedBean” in such a way that it returns an instance of bean named “displayBean” every time this method is called.
This is how “@Lookup” works when used with arguments.
Below is the classes used for our example for your reference
ContainedBean
package core.package43;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
@Component("displayBean")
@Scope("prototype")
public class ContainedBean {
private static int instanceCount = 0;
private int id;
public ContainedBean() {
id = instanceCount;
instanceCount = instanceCount + 1;
}
public void display() {
System.out.println("ContainedBean Instance Id: " + id);
}
}
ContainerBean
package core.package43;
import org.springframework.beans.factory.annotation.Lookup;
import org.springframework.stereotype.Component;
@Component
public class ContainerBean {
public void display() {
ContainedBean containedBean = createContainedBean();
containedBean.display();
}
@Lookup("displayBean")
public ContainedBean createContainedBean() {
return null;
}
}
Main class
package core.package43;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.*;
@Configuration
@ComponentScan(basePackages = "core.package43")
public class Example43 {
public static void main(String[] args) {
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Example43.class);
ContainerBean containerBean = applicationContext.getBean("containerBean", ContainerBean.class);
containerBean.display();
containerBean.display();
containerBean.display();
}
}
Code Recipes Blog 