使用Autowire检索范围内的原型的bean

Question

In my XML configuration I have this:

<bean id="soap" class="org.grocery.item.Soap" scope="prototype">
        <property name="price" value="20.00" />
</bean>

And in my service class I have the "soap" autowired like this:

@Autowired
private Soap soap;
//Accessor methods

And I created a test class like this:

Item soap = service.getItem(ITEM.SOAP);
Item soap2 = service.getItem(ITEM.SOAP);

if(soap2 == soap ){
    System.out.println("SAME REFERENCE");
}

And this is my getItem method in my service class:

public Item item(Item enumSelector) {
        switch (enumSelector) {
            case SOAP:
                return this.getSoap();
        }
        return null;
    }

@Autowired
private Soap soap;
//Accessor methods

Now what I am expecting is that the when I call the this.getSoap(); it will return a new Soap object. However, it did not, even though the soap is declared scoped as prototype. Why is that?

Answer 1

创建服务对象时，spring会将肥皂对象实例注入到服务对象中，因此对服务的getSoap()的所有调用都将检索创建服务时注入的相同肥皂对象。

Answer 2

Renjith explained the why in his answer. As for the how, I know of 2 ways to achieve this:

1. lookup method:

Don't declare the soap dependency as a field, but rather as an abstract getter method:

protected abstract Soap getSoap();

Whenever you need the soap in your service (like in the getItem method), call the getter.

In the xml config, instruct Spring to implement that method for you:

<bean id="service" class="foo.YourService">
  <lookup-method name="getSoap" bean="soapBeanId"/>
</bean>

The Spring supplied implementation would fetch a fresh instance of Soap whenever called.

1. Scoped proxies

This instructs Spring to inject a proxy instead of the real Soap instance. The injected proxy methods would lookup the correct soap instance (a fresh one since it's a prototype bean) and delegate to them:

<bean id="soap" class="foo.Soap">
  <aop:scoped-proxy/>
</bean>