Spring 菜鸟教程 异常 集锦
异常1.空指针异常
异常信息摘要：
java.lang.NullPointerException
at com.jege.framework.service.UserServiceTest.get(UserServiceTest.java:36)异常信息说明：server接口没有注入
解决思路：可能的原因：
1.xml版本，没有写set方法，spring配置文件配置注入写的有问题
2.注解版本，没有写@Autowired或者@Resource
3.测试类上面没有标注
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext.xml")异常2.bean的名字name或者id已经存在
异常信息摘要：
org.springframework.beans.factory.parsing.BeanDefinitionParsingException:
Configuration problem: Bean name 'helleService' is already used in this element 异常信息说明：helleService bean对象已经存在
解决思路：把重复的名字改一下：
异常3.web项目找不到默认配置文件
异常信息摘要：
org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML
document from class path resource [applicationContext.xml]; nested exception is java.io.FileNotFoundException:
class path resource [WEB-INF/applicationContext.xml] cannot be opened because it does not exist 异常信息说明：web项目默认会在WEB-INF下找applicationContext.xml配置文件
解决思路：在web.xml配置一个上下文属性：
param>
<param-name>contextConfigLocationparam-name>
<param-value>classpath:applicationContext.xmlparam-value>
param>异常4.命名空间配置错误
异常信息摘要：
nested exception is org.xml.sax.SAXParseException: cvc-complex-type.2.4.c: The matching wildcard is strict,
but no declaration can be found for element 'aop:confog'. 异常信息说明：没有找到aop:confog的配置
解决思路：配置好schema的aop命名空间
xmlns:aop="http://www.springframework.org/schema/aop"
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd异常5.bean不是唯一的异常
异常信息摘要：
org.springframework.beans.factory.NoUniqueBeanDefinitionException:
No qualifying bean of type [com.jege.ssh.dao.IUserDao] is defined:
expected single matching bean but found 2: UserDao1,UserDao2
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:313) 异常信息说明：注入的接口有2个实现
解决思路：去掉一个实现类，一个接口最好只有一个实现
异常6.bean没有定义，不存在
异常信息摘要：
org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'userDao' is defined 异常信息说明：userDao没有定义
解决思路：在applicationContext.xml中找不到id为userDao的bean，配置一下或者注解没有标注@Repository
异常7.server接口没有注入
异常信息摘要：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.jege.framework.service.UserServiceTest': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.jege.framework.service.IUserService com.jege.framework.service.UserServiceTest.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.jege.framework.service.IUserService] 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)}
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.jege.framework.service.IUserService com.jege.framework.service.UserServiceTest.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.jege.framework.service.IUserService] 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)}
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.jege.framework.service.IUserService] 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)}异常信息说明：server接口没有注入
解决思路：可能的原因：
1.xml版本，没有写set方法，spring配置文件配置注入有问题
2.注解版本，<context:component-scan base-package="com.jege.framework包写错" />异常8.aspectjweaver-1.8.0.jar spring4要使用高版本
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