Exception encountered during context initialization ； No default constructor found； nested exception_no default constructor found; nested exception is

问题

七月 26, 2020 2:05:03 下午 org.springframework.context.support.AbstractApplicationContext refresh
警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService' defined in class path resource [bean.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.wei.service.impl.UserServiceImpl]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.wei.service.impl.UserServiceImpl.<init>()
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService' defined in class path resource [bean.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.wei.service.impl.UserServiceImpl]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.wei.service.impl.UserServiceImpl.<init>()
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1320)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1214)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:893)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:144)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:85)
	at Client.main(Client.java:15)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.wei.service.impl.UserServiceImpl]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.wei.service.impl.UserServiceImpl.<init>()
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:83)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1312)
	... 13 more
Caused by: java.lang.NoSuchMethodException: com.wei.service.impl.UserServiceImpl.<init>()
	at java.lang.Class.getConstructor0(Class.java:3082)
	at java.lang.Class.getDeclaredConstructor(Class.java:2178)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:78)
	... 14 more

Process finished with exit code 1

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原因

该异常的重点在于这句。没有默认构造函数。

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.wei.service.impl.UserServiceImpl]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.wei.service.impl.UserServiceImpl.<init>()
1

解决

如果写了有参构造函数就会不存在默认构造函数，需要手动创建无参构造函数。

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