反正@Autowire一个bean，需要构造函数的参数？ [英] Anyway to @Autowire a bean that requires constructor arguments?

问题描述

我使用Spring 3.0.5和我使用@Autowire注释为我的类成员尽可能多。我需要autowire的一个bean需要参数的构造函数。

在XML中，我可以使用作为bean定义的一部分。是否有类似的@Autowire注释机制？

例如：

  @Component 
 public class MyConstructorClass {
 
 String var; 
 public MyConstructorClass（String constrArg）{
 this.var = var; 
} 
 ... 
} 
 
 
 @Service 
 public class MyBeanService {
 @Autowired 
 MyConstructorClass myConstructorClass; 
 
 .... 
} 
  

如何在MyBeanService中使用@Autowire注释指定constrArg的值？有任何方法可以做到吗？

谢谢，

Eric

解决方案

您需要 @Value 注释。

< >

一个常见的用例是使用
＃{systemProperties.myProp}样式表达式分配默认字段值。

  public class SimpleMovieLister {
 
 private MovieFinder movieFinder; 
 private String defaultLocale; 
 
 @Autowired 
 public void configure（MovieFinder movieFinder，
 @Value（＃{systemProperties ['user.region']}} String defaultLocale）{
 this.movi​​eFinder = movieFinder; 
 this.defaultLocale = defaultLocale; 
} 
 
 // ... 
} 
  
 
 
 
 请参阅：表达式语言>注释配置 
 
 
 
 
 
 
为了更清楚：在你的场景中，你将连接两个类， MybeanService 和 MyConstructorClass ，像这样：
  @Component 
 public class MyBeanService implements BeanService {
 @Autowired 
 public MybeanService（MyConstructorClass foo）{
 //使用foo 
执行操作
} 
 
 @Component 
 public class MyConstructorClass {
 public MyConstructorClass（@Value（＃{some expression here}）String value）{
 //做某些值为
} 
} 
  
更新：如果您需要使用不同值的 MyConstructorClass 的几个不同实例， href =http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/beans.html#beans-autowired-annotation-qualifiers>使用限定词注释 
 
I'm using Spring 3.0.5 and am using @Autowire annotation for my class members as much as possible.  One of the beans that I need to autowire requires arguments to its constructor.  I've looked through the Spring docs, but cannot seem to find any reference to how to annotate constructor arguments.

In XML, I can use  as part of the bean definition.  Is there a similar mechanism for @Autowire annotation?

Ex:
@Component
public class MyConstructorClass{

  String var;
  public MyConstructorClass( String constrArg ){
    this.var = var;
  }
...
}


@Service
public class MyBeanService{
  @Autowired
  MyConstructorClass myConstructorClass;

  ....
}
In this example, how do I specify the value of "constrArg" in MyBeanService with the @Autowire annotation?  Is there any way to do this?

Thanks,

Eric
解决方案
You need the @Value annotation.

  
A common use case is to assign default field values using
  "#{systemProperties.myProp}" style expressions.


public class SimpleMovieLister {

  private MovieFinder movieFinder;
  private String defaultLocale;

  @Autowired
  public void configure(MovieFinder movieFinder, 
                        @Value("#{ systemProperties['user.region'] }"} String defaultLocale) {
      this.movieFinder = movieFinder;
      this.defaultLocale = defaultLocale;
  }

  // ...
}
See: Expression Language > Annotation Configuration



To be more clear: in your scenario, you'd wire two classes, MybeanService and MyConstructorClass, something like this:
@Component
public class MyBeanService implements BeanService{
    @Autowired
    public MybeanService(MyConstructorClass foo){
        // do something with foo
    }
}

@Component
public class MyConstructorClass{
    public MyConstructorClass(@Value("#{some expression here}") String value){
         // do something with value
    }
}
Update: if you need several different instances of MyConstructorClass with different values, you should use Qualifier annotations

                        
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