ssh做项目，总是报空指针不能进入userservice，调试，userservice为null，

Posted 2023-03-31

ssh做项目，总是报空指针不能进入userservice，调试，userservice为null，网上的解法，一种是看是否userservice已经getset，这步做了，再一种是把struts配置的action的bean class改为spring的bean id，但是改成spring的bean id，直接跑不动了，报action的classnotfound

参考技术A 1.service为null的情况一般有几种情况：spring的配置文件没有配置；依赖注入由于写的不仔细而没有实现注入等原因。首先检查是否在spring的配置文件中注入了你想要的service如果有，检查是否因为大小写的小错误而不能实现注入。
2.可以在action的这样处理：
让action继承一个自己编写的BaseAction 在让BaseAction去继承DispatchAction 在BaseAction中实现service的获取
public class BaseAction extends DispatchAction
protected Object getBean(String id)
WebApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(this.servlet.getServletContext());
return context.getBean(id);


然后在你的action中就可以直接通过方法得到你想要的service。
IService service = (IService) getBean("你想要的service");
你就可以用service调用你的CRUD方法执行了！
这里主要用到的是spring的DI（依赖注入）spring的核心之一！ 参考技术B 这样说很难判断啊

我的构造函数里面报空指针异常了！求大神帮忙

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'shiroFilter' defined in class path resource [spring/applicationContext-shiro.xml]: Cannot resolve reference to bean 'securityManager' while setting bean property 'securityManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'securityManager' defined in class path resource [spring/applicationContext-shiro.xml]: Cannot resolve reference to bean 'customRealm' while setting bean property 'realm'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'customRealm': Unsatisfied dependency expressed through field 'imUserService': Error creating bean with name 'imUserService' defined in class path resource [spring/applicationContext-service.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.sinosoft.sinoims.service.impl.ImUserServiceImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'imUserService' defined in class path resource [spring/applicationContext-service.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.sinosoft.sinoims.service.impl.ImUserServiceImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:359)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:108)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1481)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1226)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)

Caused by: java.lang.NullPointerException
at com.sinosoft.sinoims.util.SpringUtils.getBean(SpringUtils.java:44)
at com.sinosoft.sinoims.service.impl.ImUserServiceImpl.<init>(ImUserServiceImpl.java:29)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:142)
... 94 more

从最后一段可以看出，是你的ImUserServiceImpl.java类里面的29行有问题，而且后面说问题就出在BeanUtils这个方法上里有问题，所以是注入失败问题。使用注解配置试试看。追问

厉害啦，问题真实这样，已解决！

参考技术A 我，鲁智深，无话可说追问

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