問題描述

根據 Spring 3 文檔，IoC容器，@Named注解是標準等價于@Component注解.

Per Spring 3 document, The IoC container, the @Named annotation is a standard equivalent to the @Component annotation.

由于@Repository、@Service、@Controller都是@Component，所以我嘗試使用@Named 用于我的 Spring MVC 應用程序中的所有這些.它工作正常.但我發現 @Controller 的替換似乎有一個錯誤.在控制器類中，原來是

Since @Repository, @Service, and @Controller are all @Component, I tried to used @Named for all of them in my Spring MVC application. It works fine. But I found the replacement of @Controller seems to have a bug. In the controller class, originally, it was

@Controller
public class MyController{
    ...
}

它工作正常.當我將 @Controller 更改為 @Named

It works fine. When I changed @Controller to @Named

@Named
public class MyController{
    ...
}

失敗并出現錯誤:

沒有為帶有 URI ... 的 HTTP 請求找到映射".

"No mapping found for HTTP request with URI ...".

但是如果我將 @RequestMapping 添加到類中，如下所示

But if I added @RequestMapping to the class as follow

@Named
@RequestMapping
public class MyController{
     ...
 }

它會按預期工作.

對于 @Repository 和 @Service，我可以簡單地用 @Named 替換它們，沒有任何問題.但是 @Controller 的替換需要額外的工作.配置中有什么我遺漏的嗎?

For @Repository and @Service, I can simply replace them with @Named with no issue. But the replacement of @Controller needs extra work. Is there anything I am missing in the configuration?

推薦答案

@Named 與 @Component 的作用相同.但是，注釋 @Controller、@Service 和 @Repository 更具體.

@Named works the same as @Component. However, the annotations @Controller, @Service, and @Repository are more specific.

來自 Spring 文檔:

From the Spring docs:

@Component 是任何 Spring 管理的組件的通用構造型.@Repository、@Service 和 @Controller 是@Component 用于更具體的用例，例如，在分別是持久層、服務層和表示層.

@Component is a generic stereotype for any Spring-managed component. @Repository, @Service, and @Controller are specializations of @Component for more specific use cases, for example, in the persistence, service, and presentation layers, respectively.

例如，這些原型注釋是理想的目標切入點.@Repository、@Service 和@Controller 可能會在未來版本的春天框架.因此，如果您在使用 @Component 之間進行選擇或 @Service 為您的服務層，@Service 顯然更好選擇.同樣，如上所述，@Repository 已經被支持作為持久性中自動異常翻譯的標記層.

For example, these stereotype annotations make ideal targets for pointcuts. It is also possible that @Repository, @Service, and @Controller may carry additional semantics in future releases of the Spring Framework. Thus, if you are choosing between using @Component or @Service for your service layer, @Service is clearly the better choice. Similarly, as stated above, @Repository is already supported as a marker for automatic exception translation in your persistence layer.

本部分解釋了與 @Named 的區別.

This section explains the difference with @Named.

許多組件，例如 Spring 的 DispatcherServlet(WebApplicationContext 中的 MVC 配置)不是在尋找 Component，而是在尋找 @控制器.所以當它掃描你的類時，它不會在 @Named 中找到它.以類似的方式，使用 @Transactional 的事務管理查找 @Service 和 @Repository，而不是更通用的 @Component.