如何使用spring @Lookup注释？

问题描述

我需要从单身得到原型课。我发现方法注入是要去的，但是我并不知道如何使用spring @Lookup注释。

我是新来的依赖注入，我选择了注释配置，所以我想继续这个方向。

我发现@Lookup注释最近才被添加（），但我找不到任何地方如何使用它。

所以，在这里是简化的例子

配置类：

  @Configuration 
 @Lazy 
 public class ApplicationConfiguration实现ApplicationConfigurationInterface {
 
 @Bean 
 public MyClass1 myClass1（）{
 return new ContentHolderTabPaneController（）; 
} 
 
 @Bean 
 @Scope（prototype）
 public MyClass2 myClass2（）{
 return new SidebarQuickMenuController（）; 
} 
} 
  

这里是类示例：

  public class MyClass1 {
 doSomething（）{
 myClass2（）; 
} 
 
 //我想要这个方法返回MyClass2原型
 public MyClass2 myClass2（）{
} 
} 
  

如何使用@Lookup注释？

解决方案在 public MyClass2 myClass2（）方法之前，将 @Lookup 注释应用于

：

所以删除th e从 ApplicationConfiguration 之后的工厂方法样式bean声明：

  @Bean 
 public MyClass1 myClass1（）{
 return new ContentHolderTabPaneController（）; 
} 
  

并添加 @Component 注释让Spring实例化bean（也可以在方法中添加 @Lookup 注释）：

  @Component 
 public class MyClass1 {
 doSomething（）{
 myClass2（）; 
} 
 
 //我想要这个方法返回MyClass2原型
 @Lookup 
 public MyClass2 myClass2（）{
 return null; //这个实现将被动态生成的子类覆盖
} 
} 
  

现在得到 myClass1 bean的上下文，并且它的 myClass2 方法应该被替换/覆盖以获得一个新的原型bean每次。

---

更新：

使用工厂方法声明

实现 @Lookup 注释方法（查找方法 ）。没有 @Lookup 并保持您的配置类不变，现在 MyClass1 看起来像（其实Spring生成一个类似的实现子类如果 @Lookup 被使用）：

  public class MyClass1 {
 doSomething（）{
 myClass2（）; 
} 
 
 //我想要这个方法返回MyClass2原型
 @Autowired 
 private ApplicationContext applicationContext; 
 public MyClass2 myClass2（）{
 return applicationContext.getBean（MyClass2.class）; 
} 
} 
  

Spring注入 ApplicationContext 。

I need to get prototype class from singleton. I found that method injection is the way to go, but I don't really know how to use spring @Lookup annotation.

I'm new to dependency-injection, and I chose to go with annotation configuration, so I would like to continue in that direction.

I found out that @Lookup annotation was added only recently (https://spring.io/blog/2014/09/04/spring-framework-4-1-ga-is-here), but I cannot find anywhere how to use it.

So, here is simplified example

Configuration class:

@Configuration
@Lazy
public class ApplicationConfiguration implements ApplicationConfigurationInterface {

  @Bean
  public MyClass1 myClass1() {
    return new ContentHolderTabPaneController();
  }

  @Bean
  @Scope("prototype")
  public MyClass2 myClass2() {
    return new SidebarQuickMenuController();
  }
}

And here is class example:

public class MyClass1 {
  doSomething() {
    myClass2();
  }

  //I want this method to return MyClass2 prototype
  public MyClass2 myClass2(){
  }
}

How do I do that with @Lookup annotation?

解决方案

Before applying @Lookup annotation to your public MyClass2 myClass2() method, read this in @Lookup's Javadoc:

So remove the following factory method style bean declaration from ApplicationConfiguration:

  @Bean
  public MyClass1 myClass1() {
    return new ContentHolderTabPaneController();
  }

and add @Component annotation to let Spring instantiate the bean (also add the @Lookup annotation to the method):

@Component
public class MyClass1 {
  doSomething() {
    myClass2();
  }

  //I want this method to return MyClass2 prototype
  @Lookup
  public MyClass2 myClass2(){
    return null; // This implementation will be overridden by dynamically generated subclass
  }
}

Now get myClass1 bean out of context, and its myClass2 method should have been replaced/overridden to get a new prototype bean each time.

---

Update:

Using factory method declaration

It's not hard to implement the @Lookup annotated method (the "lookup method"). Without @Lookup and keeping your configuration class unchanged, now MyClass1 looks like (in fact Spring generates a similar implementation in a subclass if @Lookup were used):

public class MyClass1 {
  doSomething() {
    myClass2();
  }

  //I want this method to return MyClass2 prototype
  @Autowired
  private ApplicationContext applicationContext;
  public MyClass2 myClass2() {
      return applicationContext.getBean(MyClass2.class);
  }
}

Spring injects the ApplicationContext for you.

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