在Java中@Autowired注解的好处 [英] benefit of @Autowired annotation in Java

问题描述

也许，因为我的英语错了，我不明白使用@Autowired注解的利益。

据我们可以简化第（一）案件第二种情况教程（二）通过@Autowired的手段。

的我的问题是，什么是@Autowired意思？因为它没有告诉任何更多，因为没有使用@Autowired编译器可以弄清楚，EmpDao emDao和EmpManager密切根据声明有关。的

code从<被引href=\"http://www.developer.com/article_comments.php/3756831/2/Java-Tip-Simplify-Spring-Apps-with-Autowired.htm\">here

我。

 ＆LT;豆的id =empDao级=EmpDao/＆GT;
    ＆LT;豆的id =empManager级=EmpManager＆GT;
       ＆LT;属性名=empDaoREF =empDao/＆GT;
    ＆LT; /豆＆GT;公共类EmpManager {   私人EmpDao empDao;   公共EmpDao getEmpDao（）{
      返回empDao;
   }   公共无效setEmpDao（EmpDao empDao）{
      this.empDao = empDao;
   }   ...
}
 

二，

 ＆LT;背景：注解配置/＆GT;＆LT;豆的id =empManager级=autowiredexample.EmpManager/＆GT;
＆LT;豆的id =empDao级=autowiredexample.EmpDao/＆GT;进口org.springframework.beans.factory.annotation.Autowired;公共类EmpManager {   @Autowired
   私人EmpDao empDao;}
 

解决方案

@Autowired 是特定的春天。 @Inject 是标准equivallent。这是一个注解，告诉背景（春，或 @Inject 的情况 - 所有的DI框架）来尝试设置对象到该字段

编译器有没有关系这一点 - 它是DI框架（春季）的实例化对象的在运行时的，然后设置它们的依赖在您指定的点 - 无论是通过XML或通过注释。

我同意它是一个的DI框架，试图注入依赖到各个领域可能的情况下，即使他们没有注释。 （如果要排除某一特定领域，进行注解）。但他们选择了其他战略（配置环比约定）。顺便说一句：

• 如果使用XML配置，选择某种形式的自动装配，bean的依赖将被自动无需自动连接到指定任何


• 您可以指定每个上下文自动装配的设置。

Maybe, because of my wrong English, I couldn't understand the benefit of using @Autowired annotation.

According to the tutorial we can simplify the first(I.) case to second case(II.) by means of @Autowired.

My question is, what is the meaning of the @Autowired ? Because it doesnt tell any more, since without using @Autowired the compiler can figure out that "EmpDao emDao" and "EmpManager" are closely related according the declaration.

code cited from here

I.

    <bean id="empDao" class="EmpDao" />
    <bean id="empManager" class="EmpManager">
       <property name="empDao" ref="empDao" />
    </bean>

public class EmpManager {

   private EmpDao empDao;

   public EmpDao getEmpDao() {
      return empDao;
   }

   public void setEmpDao(EmpDao empDao) {
      this.empDao = empDao;
   }

   ...
}

II.

<context:annotation-config />

<bean id="empManager" class="autowiredexample.EmpManager" />
<bean id="empDao"     class="autowiredexample.EmpDao" />

import org.springframework.beans.factory.annotation.Autowired;

public class EmpManager {

   @Autowired
   private EmpDao empDao;

}

解决方案

@Autowired is spring-specific. @Inject is the standard equivallent. It is an annotation that tells the context (spring, or in the case of @Inject - any DI framework) to try to set an object into that field.

The compiler has nothing to do with this - it is the DI framework (spring) that instantiates your objects at runtime, and then sets their dependencies at the points you have specified - either via XML or via an annotation.

I agree it is a possible scenario for a DI framework to try to inject dependencies into all fields, even if they are not annotated. (And if you want to exclude a particular field, to annotate it). But they chose the other strategy (configuration-over-convention). By the way:

• if using xml config and choose some form of autowiring, the dependencies of the bean will be automatically autowired without the need to specify anything
• you can specify per-context autowiring settings.

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