Null pointer for field injection - spring

Question

I'm missing fundamental things here that I do, I'm sorry for this question, basically I tried to simulate my own question from Autowring for #Sevice field failed , but in very simple form , I tried to somehow raise errors on purpose for building understanding, but when it comes, I just can't handle it.
x-servlet.xml
<beans xmlns= ...... >
<context:component-scan base-package="com" />
<context:annotation-config />
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>
</beans>
com.domain
Boss.java
package com.domain;
public class Boss {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Employee:
package com.domain;
import org.springframework.beans.factory.annotation.Autowired;
public class Employee {
#Autowired
private Boss boss;
String nameBoss;
public String getNameBoss() {
nameBoss = this.boss.getName();
return nameBoss;
}
}
com.controller
controller.java :
package com.controller
import com.domain.Boss;
import com.domain.Employee;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
#Controller
public class controller {
#RequestMapping("/try")
public String show() {
Boss b = new Boss();
b.setName(" hans");
Employee e = new Employee();
String bossName = e.getNameBoss();
System.out.println(bossName );
return "";
}
}
I was thinking that,
String bossName = e.getNameBoss();
in controller won't be null because Boss is already initialized right before Employee construction, but I'm wrong ..

Answer 1

Are you sure you want to have dependency injection (DI) for domain objects? This is not a typicall usage... For a DI, container have to create instances - so do not use new operator...
You can replace new operator using ApplicationContext.getBean() (iff the bean is of type prototype), but as I said above - even if you know how to create such beans, how should Spring know, which instance of Boss you want to have in Employee?
First thing you need is application context in controller, which should work to add interface org.springframework.context.ApplicationContextAware or you can simply autowire it and then use it "standard" way (ac is ApplicationContext):
Boss b = ac.getBean(Boss.class);
Employee e = ac.getBean(Employee.class, b);
I have Boss and Employee marked with annotations as:
#Component
#Scope("prototype")
public class Boss {
...
}
#Component
#Scope("prototype")
public class Employee {
// #Autowire - wrong
Boss boss;
public Employee(Boss boss) {
this.boss = boss;
}
...
}