在Spring中使用批注（注入，自动装配）或getBean创建对象

Question

I try to understand DI in spring. Where should I use an object with context.getBean and where with @inject anntotation?

public class App {
    public static void main(String[] args) {
        new Controller().iniController();

    }
}

---

public class Controller {

    public void iniController() {       

        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("com/beans/beans.xml");
        Address address = context.getBean("address", Address.class);
        Person person = context.getBean("person", Person.class);
        Employee employee = context.getBean("employee", Employee.class);

        address.setCity("my city");
        person.setName("my name");

        System.out.println(employee);

        context.close();
    }

}

Is this correct to get address, person and employee objects with context.getBean method?

---

@Component
public class Employee {

    @Inject
    private Person person;
    @Inject
    private Address address;

    @Override
    public String toString() {
        return "Employee: "+ person.getName() +" from "+ address.getCity();
    }
}

Here I got person and address objects with Inject, can I also get these with getBean method?

---

@Component
public class Address {

    private String city;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

}

---

@Component
public class Person {

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

---

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd">


    <context:annotation-config></context:annotation-config>
    <context:component-scan base-package="com.model"></context:component-scan>
</beans>

Answer 1

You should always prefer dependency injection, over getBean, or should i say avoid using getBean at all..

Dependency injection is very effective at associating loosely coupled components, and at configuring these components. Especially if the association between the components lasts throughout the lifetime of the components.

More specifically, dependency injection is effective in these situations:

1. You need to inject configuration data into one or more components.
2. You need to inject the same dependency into multiple components. You
3. You need to inject different implementations of the same dependency. You
4. You need to inject the same implementation in different configurations.
5. You need some of the services provided by the container.

Defining DI helps you to easily change underlying implementations, without actually worrying about those who use this implementation..

And if this all still leaves you puzzled, you can find dozens of reasons for using DI on google