Spring入门总结（三）Autowired的配置

先看如下：

@Autowired
    private List<BeanInterface> list;

这是一个类的成员变量，当被@Autowired应用后，代表该list会自动去找Beaninterface相关的bean并加载进来。

通过如下案例便知。

申明一个接口：

package multibean;

public interface BeanInterface {

}

接口实现类1： 

package multibean;

import org.springframework.stereotype.Component;

@Component
public class BeanImplOne implements BeanInterface {

}

接口实现类2： 

package multibean;

import org.springframework.stereotype.Component;

@Component
public class BeanImplTwo implements BeanInterface {

}

 一个调用者：

package multibean;

import java.util.List;

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

@Component
public class BeanInvoker {
	@Autowired
	private List<BeanInterface> list;
	
	public void say() {
		if(list!=null) {
			for(BeanInterface bean : list) {
				System.out.println(bean.getClass().getName());
			}
		}
		else System.out.println("The list is null!");
	}
	
}

 下面我用的是《单元测试》的方式启动的，可以google一下，你也可以不用改方法。

package com.tutorialspoint;


import org.junit.After;
import org.junit.Before;
import org.springframework.beans.BeansException;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.util.StringUtils;

public class UnitTestBase {
	
	private ClassPathXmlApplicationContext context;
	
	private String springXmlpath;
	
	public UnitTestBase() {}
	
	public UnitTestBase(String springXmlpath) {
		this.springXmlpath = springXmlpath;
	}
	
	@Before
	public void before() {
		if (StringUtils.isEmpty(springXmlpath)) {
			//classpath相当于src
			springXmlpath = "classpath*:spring-*.xml";
		}
		try {
			//[,\\s]正则表达式，意思是以,和空格，tab作为分隔符，分成字符串数组
			context = new ClassPathXmlApplicationContext(springXmlpath.split("[,\\s]+"));
			context.start();
		} catch (BeansException e) {
			e.printStackTrace();
		}
	}
	
	@After
	public void after() {
		context.destroy();
//		System.out.println("after");
	}
	
	@SuppressWarnings("unchecked")
	protected <T extends Object> T getBean(String beanId) {
		try {
			return (T)context.getBean(beanId);
		} catch (BeansException e) {
			e.printStackTrace();
			return null;
		}
	}
	
	protected <T extends Object> T getBean(Class<T> clazz) {
		try {
			return context.getBean(clazz);
		} catch (BeansException e) {
			e.printStackTrace();
			return null;
		}
	}

}

package com.tutorialspoint;

import java.io.IOException;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.BlockJUnit4ClassRunner;

import multibean.BeanInvoker;
import services.InjectionService;
import services.InjectionServiceImpl;

@RunWith(BlockJUnit4ClassRunner.class)
public class TestInjection  extends UnitTestBase{

	public TestInjection() {
		super("classpath:spring-injection.xml");
		// TODO Auto-generated constructor stub
	}
	@Test
	public void test() throws IOException {
//		InjectionService service = super.getBean("injectionServiceImpl");
		InjectionService service = super.getBean(InjectionServiceImpl.class);
		service.save("Hello MVC");
	}
	@Test
	public void testMultiBean() {
		//方式一，通过获得类
//		BeanInvoker invoker = super.getBean(BeanInvoker.class);
		//方式二，通过获得Bean的名字
		BeanInvoker invoker = super.getBean(BeanInvoker.class);
		invoker.say();
	}
}

xml:配置 

<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:context="http://www.springframework.org/schema/context"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="
   http://www.springframework.org/schema/beans     
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/context 
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">

   
   <context:component-scan base-package="com.tutorialspoint,dao,services,multibean"></context:component-scan>
  <!--  <bean id="beanAnnotation" class="com.tutorialspoint.BeanAnnotation"></bean>--> 
   
</beans>

 执行结果是：

multibean.BeanImplOne
multibean.BeanImplTwo

为了验证最初说的正确性，我们把BeanImplTwo的Component注释掉，则运行结果是：

multibean.BeanImplOne

说明@Autowired注解会自动装配泛型里面相关的bean。