Question

用于方法注入的Spring lookup-method属性，有助于在每次调用该方法时创建新实例。容器也动态地为该类创建子类并覆盖该方法。但是，对我来说，只为正常注射和方法注射创建了一个实例。我已经发布了我尝试过的完整代码。我想完全理解查找方法如何工作以及它与正常注入的不同之处。

<bean id="processor" class="org.RequestProcessor">
        <lookup-method name="getResourceA" bean="resourceA"/>
    </bean>

    <bean id="resourceA" class="org.ResourceA"/>
    <bean id="resourceB" class="org.ResourceB"/>


public abstract class RequestProcessor {
    @Autowired
    ResourceB resourceB;
    public ResourceB getResourceB(){
        return resourceB;
    }

    abstract ResourceA getResourceA();
}


public class ResourceA {
    String url ="http://localhost:8080";
    public ResourceA(){
        System.out.println("Resource A instance creation");
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
}


public class ResourceB {
    String url ="http://localhost:8081";
    public ResourceB(){
        System.out.println("Resource B instance creation");
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
}


public class SpringExample {
    public static void main(String[] args) {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("org/applicationContext.xml");
        RequestProcessor processor = (RequestProcessor)applicationContext.getBean("processor");     
        for (int i=0;i<3;i++){
            ResourceA resource = processor.getResourceA();
            System.out.println(resource.getUrl());
        }
        for (int i=0;i<3;i++){
            ResourceB resource = processor.getResourceB();
            System.out.println(resource.getUrl());
        }       
    }
}

上述程序的输出是：

Resource B instance creation
Resource A instance creation
http://localhost:8080
http://localhost:8080
http://localhost:8080
http://localhost:8081
http://localhost:8081
http://localhost:8081

Answer 1

我找到了问题的答案。我在两个bean中遗漏了scope属性。我必须将scope =“prototype”添加到两个bean中，如：

<bean id="resourceA" class="org.ResourceA" scope="prototype"/>
<bean id="resourceB" class="org.ResourceB" scope="prototype"/>

现在更改后输出为：

Resource B instance creation
Resource A instance creation
http://localhost:8080
Resource A instance creation
http://localhost:8080
Resource A instance creation
http://localhost:8080
http://localhost:8081
http://localhost:8081
http://localhost:8081

Spring查找方法实例创建

1 个答案: