刚学SpringBoot，今天启动的时候报错了，长长的一堆报错信息
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userController': Unsatisfied dependency expressed through field 'userService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userServiceImpl': Unsatisfied dependency expressed through field 'userMapper'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userMapper' defined in file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\com\lzx\springboot\dao\UserMapper.class]: Unsatisfied dependency expressed through bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:660) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1431) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:619) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$211/1649320501.getObject(Unknown Source) ~[na:na]at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:955) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:920) ~[spring-context-5.3.26.jar:5.3.26]at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.26.jar:5.3.26]at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147) ~[spring-boot-2.7.10.jar:2.7.10]at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:731) [spring-boot-2.7.10.jar:2.7.10]at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408) [spring-boot-2.7.10.jar:2.7.10]at org.springframework.boot.SpringApplication.run(SpringApplication.java:307) [spring-boot-2.7.10.jar:2.7.10]at org.springframework.boot.SpringApplication.run(SpringApplication.java:1303) [spring-boot-2.7.10.jar:2.7.10]at org.springframework.boot.SpringApplication.run(SpringApplication.java:1292) [spring-boot-2.7.10.jar:2.7.10]at com.lzx.springboot.SpringbootApplication.main(SpringbootApplication.java:10) [classes/:na]Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userServiceImpl': Unsatisfied dependency expressed through field 'userMapper'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userMapper' defined in file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\com\lzx\springboot\dao\UserMapper.class]: Unsatisfied dependency expressed through bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:660) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1431) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:619) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$211/1649320501.getObject(Unknown Source) ~[na:na]at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1391) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1311) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657) ~[spring-beans-5.3.26.jar:5.3.26]... 21 common frames omittedCaused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userMapper' defined in file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\com\lzx\springboot\dao\UserMapper.class]: Unsatisfied dependency expressed through bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireByType(AbstractAutowireCapableBeanFactory.java:1534) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1417) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:619) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$211/1649320501.getObject(Unknown Source) ~[na:na]at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1391) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1311) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657) ~[spring-beans-5.3.26.jar:5.3.26]... 36 common frames omittedCaused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:658) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:638) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1352) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1195) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:582) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$211/1649320501.getObject(Unknown Source) ~[na:na]at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1391) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1311) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireByType(AbstractAutowireCapableBeanFactory.java:1519) ~[spring-beans-5.3.26.jar:5.3.26]... 48 common frames omittedCaused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.3.26.jar:5.3.26]at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:653) ~[spring-beans-5.3.26.jar:5.3.26]... 62 common frames omittedCaused by: org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:523) ~[mybatis-spring-1.3.2.jar:1.3.2]at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:380) ~[mybatis-spring-1.3.2.jar:1.3.2]at org.mybatis.spring.SqlSessionFactoryBean.getObject(SqlSessionFactoryBean.java:547) ~[mybatis-spring-1.3.2.jar:1.3.2]at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration.sqlSessionFactory(MybatisAutoConfiguration.java:153) ~[mybatis-spring-boot-autoconfigure-1.3.2.jar:1.3.2]at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$709bd116.CGLIB$sqlSessionFactory$0() ~[mybatis-spring-boot-autoconfigure-1.3.2.jar:1.3.2]at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$709bd116$$FastClassBySpringCGLIB$$724e6442.invoke() ~[mybatis-spring-boot-autoconfigure-1.3.2.jar:1.3.2]at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.3.26.jar:5.3.26]at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331) ~[spring-context-5.3.26.jar:5.3.26]at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$709bd116.sqlSessionFactory() ~[mybatis-spring-boot-autoconfigure-1.3.2.jar:1.3.2]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_31]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_31]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_31]at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_31]at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.3.26.jar:5.3.26]... 63 common frames omittedCaused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\myFile\JavaFile\springcloud\springcloud02\springboot\target\classes\mapper\UserMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:120) ~[mybatis-3.4.6.jar:3.4.6]at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:92) ~[mybatis-3.4.6.jar:3.4.6]at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:521) ~[mybatis-spring-1.3.2.jar:1.3.2]... 76 common frames omittedCaused by: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be emptyat org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:110) ~[mybatis-3.4.6.jar:3.4.6]... 78 common frames omitted报错信息大概说的是创建UserController bean出现错误
下面又说创建UserService bean出现错误和UserMapper也出错
于是我百度了一下，都说没加注解，我检查了一下，改加的都加了呀
@Repository@Mapperpublic interface UserMapper {List selectAll();}@Servicepublic class UserServiceImpl implements UserService{@Autowiredprivate UserMapper userMapper;@Overridepublic List selectAll() {return userMapper.selectAll();}}@RestControllerpublic class UserController {@Autowiredprivate UserService userService;@RequestMapping("/selectAll")public List selectAll(){return userService.selectAll();}}于是我又分别测试了一下mapper和service
public class Test01 implements ApplicationContextAware {private static ApplicationContext applicationContext;@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {Test01.applicationContext=applicationContext;}public static TgetBean(Class clazz) {return applicationContext != null?applicationContext.getBean(clazz):null;}@Testpublic void method_3() {UserServiceImpl bean = Test01.getBean(UserServiceImpl.class);bean.selectAll();}}又说报空指针异常
就这样折腾了好久，直到我把错误信息看完，原来最后一行说的是mapper没加namespace，原来是我忘了加了，加了之后终于可以正常运行了
一个这么简单的错误竟然折腾了我这么久，这提醒我们以后一定要把错误信息看完呀