java Spring：@Value 与 @Autowired
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Spring: @Value vs. @Autowired
提问by Jeff Levine
I'm having some issues with injection in the application I'm working on (using Spring Version 3.1.2). To start with, I'm seeing a lot of code like this:
我在我正在处理的应用程序中遇到了一些注入问题（使用 Spring 版本 3.1.2）。首先，我看到很多这样的代码：
@Value("#{searchRequestBean}")
private SearchRequest searchRequest;
@Value("#{searchResponseBean}")
private SearchResponse searchResponse;
@Autowired
private SavedSearchService service;
Each of these three appears to have the effect of autowiring the specified bean/service into the class. What I don't understand is, what's the difference between @Valueand @Autowiredin these cases? Every example I find online seems to use @Valueto inject values from a properties file. In this case, SearchResponseand SearchRequestare abstract classes.
这三个中的每一个似乎都具有将指定的 bean/服务自动装配到类中的效果。我不明白的是，在这些情况下@Value和之间有什么区别@Autowired？我在网上找到的每个示例似乎都用于@Value从属性文件中注入值。在这种情况下，SearchResponse和SearchRequest是抽象类。
I'm hoping that a better understanding of this will help me solve some issues I'm having with my Session bean.
我希望更好地理解这一点将帮助我解决我在使用 Session bean 时遇到的一些问题。
回答by Daniel Kaplan
@Valuecan be used for injecting default values. A good example is to inject the default of a Stringto be the value of a property file. In your example, @Valueis used to set the default value of a class to be a Spring managed bean.
@Value可用于注入默认值。一个很好的例子是将 a 的默认值注入String为属性文件的值。在您的示例中，@Value用于将类的默认值设置为 Spring 托管 bean。
@Autowiredcan't be used for the first example: It's not property file aware. @Autowiredis onlyfor DI of a bean. It is more specific than @Value, but you can use @Valueto do the same thing.
@Autowired不能用于第一个示例：它不知道属性文件。 @Autowired是唯一一个bean的DI。它比 更具体@Value，但您可以用@Value它来做同样的事情。
Here is a good tutorial for @Value: http://www.mkyong.com/spring3/spring-value-default-value/
这是一个很好的教程@Value：http: //www.mkyong.com/spring3/spring-value-default-value/
