Question

我已经下载了一个Spring注释示例，但我无法看到它如何选择要注入的类，继承代码和配置。首先是IWriter接口的几个实现（未显示）

package writers;
import org.springframework.stereotype.Service;

@Service
public class NiceWriter implements IWriter {
    public void writer(String s)    {
        System.out.println("Nice Writer - " + s);
    }
}


package writers;
import org.springframework.stereotype.Service;

@Service
public class Writer implements IWriter{
    public void writer(String s)    {
        System.out.println("Writer - "+s);
    }
}

package testbean;

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

import writers.IWriter;

    @Service
    public class SpringBeanWithDI{
        private IWriter writer;

        @Autowired
        public void setWriter(IWriter writer)   {
            this.writer = writer;
        }

        public void run()   {
            String s = "This is my test";
            writer.writer(s);
        }
    }

测试bean： -

package main;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import testbean.SpringBeanWithDI;

public class TestBean  {
    public static void main(String[] args)  {
        ApplicationContext context = new ClassPathXmlApplicationContext("META-INF/beans.xml");
        BeanFactory factory = context;
        SpringBeanWithDI test = (SpringBeanWithDI) factory.getBean("springBeanWithDI");
        test.run();
    }
}

和beans.xml文件： -

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:aop="http://www.springframework.org/schema/aop"
  xmlns:context="http://www.springframework.org/schema/context"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
           http://www.springframework.org/schema/aop
           http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">

  <context:component-scan base-package="testbean" />
  <context:component-scan base-package="Writers" />

</beans>

一切都很简单，但为什么总是注入“作家”实施？

Answer 1

从文件中我发现： -

“对于后备匹配，bean名称被视为默认限定符值。这意味着可以使用id”main“而不是嵌套的限定符元素来定义bean，从而得到相同的匹配结果。

但请注意，虽然这可以用来通过名称来引用特定的bean，但@Autowired基本上是关于带有可选语义限定符的类型驱动注入。这意味着限定符值，即使使用bean名称回退，在类型匹配集中总是具有缩小语义;它们在语义上不表达对唯一bean id的引用。“ 所以在我的例子中，字段'writer'用于查找名为'Writer'的类。

私人IWriter作家;

聪明！（也许太聪明了！）

spring注释如何选择要注入的类？

1 个答案: