实际编写中的注解问题，@Autowired位置写错，报错java.lang.NullPointerException

淩亂°似流年 2021-07-09 11:33 247阅读 0赞

private CartypeDao ctd; @Autowired public CartypeDao getCtd() { return ctd; } public void setCtd(CartypeDao ctd) { this.ctd = ctd; }

这段代码中的@Autowired开始的时候写在这个位置就一直报空指针

java.lang.NullPointerException

的错，之后查了下资料，代码改成如下：

@Autowired private CartypeDao ctd; public CartypeDao getCtd() { return ctd; } public void setCtd(CartypeDao ctd) { this.ctd = ctd; }

之后就没空指针了，这是个查询的方法

/*************************查询所有车类****************************************/ public List<Map<String, String>> selectAll() { String sql="SELECT cartypeid,cartypename FROM cartype"; List<Map<String, String>> list=ctd.queryObjectsBySqlList(sql); return list; }

查询的结果：

![Center][]

第二次报错：

严重: StandardWrapper.Throwable  
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'regsController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.service.regsService com.controller.regsController.regsService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type \[com.service.regsService\] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: \{@org.springframework.beans.factory.annotation.Autowired(required=true)\}  
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:288)  
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1120)  
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:522)  
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)  
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)  
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)  
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)  
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:626)  
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)  
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)  
    at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:652)  
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:600)  
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:666)  
    at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:519)  
    at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:460)  
    at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)  
    at javax.servlet.GenericServlet.init(GenericServlet.java:158)  
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1284)  
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1197)  
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1087)  
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5253)  
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5543)  
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)  
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)  
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)  
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)  
    at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1263)  
    at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1978)  
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)  
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)  
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)  
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)  
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)  
    at java.lang.Thread.run(Thread.java:619)  
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.service.regsService com.controller.regsController.regsService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type \[com.service.regsService\] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: \{@org.springframework.beans.factory.annotation.Autowired(required=true)\}  
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:514)  
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)  
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285)  
    ... 34 more  
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type \[com.service.regsService\] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: \{@org.springframework.beans.factory.annotation.Autowired(required=true)\}  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:967)  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:837)  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:749)  
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:486)  
    ... 36 more  
2017-10-21 11:54:19 org.apache.catalina.core.StandardContext loadOnStartup  
严重: Servlet \[springmvc\] in web application \[/sshkaoshi2\] threw load() exception  
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type \[com.service.regsService\] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: \{@org.springframework.beans.factory.annotation.Autowired(required=true)\}  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:967)  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:837)  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:749)  
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:486)  
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)  
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285)  
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1120)  
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:522)  
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)  
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)  
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)  
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)  
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)  
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:626)  
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)  
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)  
    at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:652)  
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:600)  
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:666)  
    at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:519)  
    at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:460)  
    at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)  
    at javax.servlet.GenericServlet.init(GenericServlet.java:158)  
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1284)  
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1197)  
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1087)  
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5253)  
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5543)  
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)  
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)  
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)  
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)  
    at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1263)  
    at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1978)  
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)  
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)  
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)  
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)  
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)  
    at java.lang.Thread.run(Thread.java:619)

发现是controller层的

public class regsController {
    
    	
    	private regsService regsService;
    	@Autowired
    	public regsService getRegsService() {
    		return regsService;
    	}
    
    	public void setRegsService(regsService regsService) {
    		this.regsService = regsService;
    	}

放到下面就好了 。

[Center]: /images/20210708/34d5384d84d2438897c76e3930c193f5.png