找不到init方法

Posted 2021-10-03 dlage

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执行查找时出错，报错信息如下，原因是没有无参构造函数。

java.lang.NoSuchMethodException: com.example.mybatis.pojo.SysUser.<init>()
	at java.base/java.lang.Class.getConstructor0(Class.java:3349) ~[na:na]
	at java.base/java.lang.Class.getDeclaredConstructor(Class.java:2553) ~[na:na]
	at org.apache.ibatis.reflection.factory.DefaultObjectFactory.instantiateClass(DefaultObjectFactory.java:66) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.reflection.factory.DefaultObjectFactory.create(DefaultObjectFactory.java:54) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.reflection.factory.DefaultObjectFactory.create(DefaultObjectFactory.java:46) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.reflection.wrapper.BeanWrapper.instantiatePropertyValue(BeanWrapper.java:151) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.reflection.MetaObject.setValue(MetaObject.java:135) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyAutomaticMappings(DefaultResultSetHandler.java:527) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:402) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:354) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:328) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:301) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:194) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:65) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140) ~[mybatis-3.5.1.jar:3.5.1]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
	at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) ~[mybatis-spring-2.0.1.jar:2.0.1]
	at com.sun.proxy.$Proxy56.selectList(Unknown Source) ~[na:na]
	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230) ~[mybatis-spring-2.0.1.jar:2.0.1]
	at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:147) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:80) ~[mybatis-3.5.1.jar:3.5.1]
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:58) ~[mybatis-3.5.1.jar:3.5.1]
	at com.sun.proxy.$Proxy59.selectRolesByUserId(Unknown Source) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
	at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.3.9.jar:5.3.9]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.3.9.jar:5.3.9]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.9.jar:5.3.9]
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-5.3.9.jar:5.3.9]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.9.jar:5.3.9]
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.9.jar:5.3.9]
	at com.sun.proxy.$Proxy60.selectRolesByUserId(Unknown Source) ~[na:na]
	at com.example.mybatis.controller.UserController.test3(UserController.java:36) ~[classes/:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
	at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1064) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.52.jar:4.0.FR]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.9.jar:5.3.9]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.52.jar:4.0.FR]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.9.jar:5.3.9]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.9.jar:5.3.9]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1726) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.52.jar:9.0.52]
	at java.base/java.lang.Thread.run(Thread.java:829) ~[na:na]

我的角色类中添加了user类作为字段信息。当我查询出来角色对象，这句话报错了

List<SysRole> sysRoles = userMapper.selectRolesByUserId(1L);

可能是创建角色对象时，由于角色对象使用了user对象作为参数，要使用他的无参构造来实例化吧。

加上无参构造即可。

项目结构如下

├── pom.xml
├── src
│   ├── main
│   │   ├── java
│   │   │   └── com
│   │   │       └── example
│   │   │           └── mybatis
│   │   │               ├── MybatisApplication.java
│   │   │               ├── controller
│   │   │               │   ├── IndexController.java
│   │   │               │   └── UserController.java
│   │   │               ├── mapper
│   │   │               │   ├── PrivilegeMapper.java
│   │   │               │   ├── RoleMapper.java
│   │   │               │   ├── RolePrivilegeMapper.java
│   │   │               │   ├── TestUserMapper.java
│   │   │               │   ├── UserMapper.java
│   │   │               │   └── UserRoleMapper.java
│   │   │               └── pojo
│   │   │                   ├── SysPrivilege.java
│   │   │                   ├── SysRole.java
│   │   │                   ├── SysRolePrivilege.java
│   │   │                   ├── SysUser.java
│   │   │                   ├── SysUserRole.java
│   │   │                   └── User.java
│   │   └── resources
│   │       ├── application.yml
│   │       ├── mapper
│   │       │   ├── PrivilegeMapper.xml
│   │       │   ├── RoleMapper.xml
│   │       │   ├── RolePrivilegeMapper.xml
│   │       │   ├── TestUserMapper.xml
│   │       │   ├── UserMapper.xml
│   │       │   └── UserRoleMapper.xml
│   │       └── mybatis-config.xml
│   └── test
│       └── java
│           └── com
│               └── example
│                   └── mybatis
│                       └── MybatisApplicationTests.java
└── target
    ├── classes
    │   ├── application.yml
    │   ├── com
    │   │   └── example
    │   │       └── mybatis
    │   │           ├── MybatisApplication.class
    │   │           ├── controller
    │   │           │   ├── IndexController.class
    │   │           │   └── UserController.class
    │   │           ├── mapper
    │   │           │   ├── PrivilegeMapper.class
    │   │           │   ├── RoleMapper.class
    │   │           │   ├── RolePrivilegeMapper.class
    │   │           │   ├── TestUserMapper.class
    │   │           │   ├── UserMapper.class
    │   │           │   └── UserRoleMapper.class
    │   │           └── pojo
    │   │               ├── SysPrivilege.class
    │   │               ├── SysRole.class
    │   │               ├── SysRolePrivilege.class
    │   │               ├── SysUser.class
    │   │               ├── SysUserRole.class
    │   │               └── User.class
    │   ├── mapper
    │   │   ├── PrivilegeMapper.xml
    │   │   ├── RoleMapper.xml
    │   │   ├── RolePrivilegeMapper.xml
    │   │   ├── TestUserMapper.xml
    │   │   ├── UserMapper.xml
    │   │   └── UserRoleMapper.xml
    │   └── mybatis-config.xml
    ├── generated-sources
    │   └── annotations
    ├── generated-test-sources
    │   └── test-annotations
    └── test-classes
        └── com
            └── example
                └── mybatis
                    └── MybatisApplicationTests.class

GitHub:https://github.com/dlagez/dlagez-springboot-demos/tree/master/mybatis

参考：https://www.cnblogs.com/nastu/p/12718566.html

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