今天看到spring的自动装配组件，照着书上的敲了下来报错了
代码：
接口
public interface CompactDisc {
void play();}
实现类
import org.springframework.stereotype.Component;
@Componentpublic class SgtPeppers implements CompactDisc {
private String title = "命运交响曲"; private String artist = "Ludwig van Beethoven"; @Override public void play() { System.out.println("player:"+title+ " by " +artist); }}
配置类
import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;
@Configuration@ComponentScanpublic class CDPlayerConfig {}
测试类
import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import static org.junit.Assert.assertNotNull;
@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(classes = CDPlayerConfig.class)public class CDPlayerTest {
@Autowired private CompactDisc cd;
@Test public void cdShouldNotBeNull(){ assertNotNull(cd); }
}
jdk1.7,spring4.3
然后执行测试类，错误
Error creating bean with name ‘org.springframework.context.annotation.internalAsyncAnnotationProcessor‘ defined in class path resource
[org/springframework/scheduling/annotation/ProxyAsyncConfiguration.class]: Bean instantiation via factory method failed; nested exception
is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.scheduling.annotation.AsyncAnnotatio
nBeanPostProcessor]: Factory method ‘asyncAdvisor‘ threw exception; nested exception is java.lang.IllegalArgumentException:
@EnableAsync annotation metadata was not injected
类中的方法 cdShouldNotNull,错误
java.lang.IllegalStateException: Failed to load ApplicationContext
错误是加载不到配置文件，明明用的javaconfig代替了xml文件了
@ContextConfiguration(classes = CDPlayerConfig.class)这是怎么回事，于是，我创建了一个ApplicationContext就试着写成了
@ContextConfiguration(value = "classpath:/ApplicationContext.xml")
方法报错，这次和上次不一样了，ApplicationContext加载到了,但是又无法创建bean了Error creating bean with name ‘CDPlayerTest‘: Unsatisfied dependency expressed through field ‘cd‘; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type ‘CompactDisc‘ available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}于是写成....
@ContextConfiguration(locations = {"classpath:/ApplicationContext.xml","classpath:/CDPlayerConfig.java"})还是报错...最后发现，是因为我把这几个类直接放到了src文件夹下的缘故，解决方法：把这些类都放到了新建的一个三级包下。书上的示例代码确实是放在了包下，这一点我没有注意，但也没想到这会有影响，细节还是很重要。
新人起步！欢迎指正！
原文地址：https://www.cnblogs.com/ffyg/p/10906041.html