Spring中@Resource与@Autowired

问题

　　这其实就是@Autoware与@Resource没有正确的使用，这个错误是因为wmPoiOplogService这个变量装配方式是@Resource，按照@Resource的按名字查找的方式，并没有找到bean id为wmPoiOplogService的bean所以就报出这个错误。

举个栗子🌰

　　

　　Bean.java

package service.test;


import java.util.List;

/**
 * Created by zhengbin on 16/8/28.
 */
public interface Bean {
    public String sayHello();
    
    public List<String> sayHellos();
}

　　BeanImpl.java

package service.test;

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

import javax.annotation.Resource;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

/**
 * Created by zhengbin on 16/8/28.
 */
@Component("Bean")
public class BeanImpl implements Bean {
    @Resource
    private Hello hello2;
    
    @Autowired
    private Hello hello1;
    
    @Autowired
    private List<Hello> hellos;
    
    @Override
    public String sayHello() {
        return "say " + hello2.say();
    }
    
    @Override
    public List<String> sayHellos() {
        List<String> stringList = new ArrayList<String>();
        for (Hello hello : hellos) {
            stringList.add(hello.say());
        }
        return stringList;
    }
}

 

　　Hello.java

package service.test;

/**
 * Created by zhengbin on 16/8/28.
 */
public interface Hello {
    public String say();
}

　　HelloImpl.java

package service.test;

import org.springframework.stereotype.Component;

/**
 * Created by zhengbin on 16/8/28.
 */
@Component("hello1")
public class HelloImpl implements Hello {
    @Override
    public String say() {
        return "Hello1";
    }
}

　　HelloImple.java

package service.test;

import org.springframework.stereotype.Component;

/**
 * Created by zhengbin on 16/8/28.
 */
@Component("hello2")
public class HelloImple implements Hello {
    @Override
    public String say() {
        return "Hello2";
    }
}

　　BeanTest.java

package service.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by zhengbin on 16/8/28.
 */
public class BeanTest {
    
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext-test.xml");
        Bean bean = context.getBean("Bean", Bean.class);
        System.out.println(bean.sayHello());
        System.out.println(bean.sayHellos());
    }
    
}

　　改动BeanImpl.java

private Hello hello2;

　　改为：

private Hello hello1;

　　运行结果也由

say Hello2

　　变为：

say Hello1

　　这说明@Resource是按变量名去找相应的Bean

　　而当用第20行的@Autoware方式去执行sayHello()方法时，会报出这个错误：

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'Bean': Injection of resource dependencies failed; 
nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: 
No qualifying bean of type [service.test.Hello] is defined: expected single matching bean but found 2: hello1,hello2

　　‘bean of type’说明@Autoware匹配bean的方式是按类型，按类型查找Hello，查找出2个，也就是：‘expected single matching bean but found 2: hello1,hello2’

　　所以相应的第23行的hellos与第31行的sayHellos方法就说明了，当按@Autoware匹配切有该类型有多个时，可用List装载

private List<Hello> hellos;

public List<String> sayHellos() {
　　List<String> stringList = new ArrayList<String>();
   　　for (Hello hello : hellos) {
      　　stringList.add(hello.say());
      }
   return stringList;
37 }

@Resource

　　@Resource要求提供一个Bean名称的属性(name)，如果属性为空，则自动采用标注处的变量名或方法名作为Bean的名称。

　　　　type属性：

　　　　name属性：

@Autoware

　　@Autoware默认按类型匹配注入Bean

　　　　required属性：如果希望Spring即使找不到匹配的Bean完成注入也不要抛出异常，那么可以使用@Autoware(required=false)进行标注：

@Autowired(required = false)
private List<Hello> hellos;

　　@Qualifier：指定注入Bean的名称

@Autowired
@Qualifier("hello1")
private Hello hello;

 　　这也就解决了容器中有一个以上匹配的Bean时，报错：expected single matching bean but found 2: hello1,hello2

详细文档

　　3.11. 基于注解（Annotation-based）的配置