博物馆 网站 建设,广州网络推广公司排名,快速seo软件,网站建设行业研究同事自己在自己的电脑上写了一些小东西#xff0c;遇到了请求时API层注入的Service为空问题。整体代码接口伪代码如下#xff1a;
public Interface ParentService{public String hello(String msg);
}
public abstract class ChildrenOneService implements ParentService… 同事自己在自己的电脑上写了一些小东西遇到了请求时API层注入的Service为空问题。整体代码接口伪代码如下
public Interface ParentService{public String hello(String msg);
}
public abstract class ChildrenOneService implements ParentService{Overridepublic String hello(String msg){System.out.println(ChildrenOne saymsg);}}
public abstract class ChildrenTwoService implements ParentService{Overridepublic String hello(String msg){System.out.println(ChildrenTwo saymsg);}} RestController
public class TestApi{Resource(type ChildrenOneService.class)private Parent childrenOneService;Resource(type ChildrenTwoService.class)private Parent childrenTwoService;PostMapping(/test1)public String sayOne(String msg){childrenOneService.hello(msg);}PostMapping(/test2)public String sayTwo(String msg){childrenTwoService.hello(msg);}} 在执行过程中报空指针异常打断点发现childrenOneService和childrenTwoService全部为空。直接在AbstractApplicationContext里的refresh方法里最后一行finishRefresh打断点查看beanFactory里的beanDefinitionMap里的bean是否存在。经过排查发现Map里没有这两个类型的Bean。 第一步怀疑是Application.java的ComponentScan没有扫描到。 查看Application.java启动类发现Application类上没有配置ComponentScan那么SpringBoot默认扫描Application文件所在同级目录下的所有类。发现ChildrenOneService和ChildrenTwoService在Application文件所在的同级目录下。 第二步怀疑是ChildrenOneService和ChildrenTwoService不符合bean的规范。检查这两个类发现这两个类的类定义里使用了abstract关键字来修饰类名。 protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {AnnotationMetadata metadata beanDefinition.getMetadata();return (metadata.isIndependent() (metadata.isConcrete() ||(metadata.isAbstract() metadata.hasAnnotatedMethods(Lookup.class.getName()))));}在springboot源码中发现加载时会判断是否时符合要求的组件其中发现组件是抽象的且被Lookup注解才会被加载。所以在将ChildrenOneService和ChildrenTwoService类由抽象改为普通类后注入成功了。
改后(以ChildrenOneService为例)
//去掉了abstract
public class ChildrenOneService implements ParentService{Overridepublic String hello(String msg){System.out.println(ChildrenOne saymsg);}}
