cannot find column's cache for so you cannot used class com.baomidou.mybatisplus.core.conditions.que

在尝试使用Mybatis-Plus的Lambda表达式时遇到问题,错误提示'cannot find column's cache for...'. 通过在GitHub上搜索问题,发现可能是由于Eclipse的编译器不支持Lambda导致。解决方案是更改Eclipse的Java Compiler设置,或者切换到IDEA进行开发,问题即可得到解决。

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org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.builder.BuilderException: Error evaluating expression 'ew.sqlSegment != null and ew.sqlSegment != '' and ew.nonEmptyOfWhere'. Cause: org.apache.ibatis.ognl.OgnlException: sqlSegment [com.baomidou.mybatisplus.core.exceptions.MybatisPlusException: cannot find column's cache for org.jeecg.modules.system.service.impl.SysDepartServiceImpl, so you cannot used class com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper!]
	at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:77)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
	at com.sun.proxy.$Proxy86.selectList(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230)
	at com.baomidou.mybatisplus.core.override.PageMapperMethod.executeForMany(PageMapperMethod.java:173)
	at com.baomidou.mybatisplus.core.override.PageMapperMethod.execute(PageMapperMethod.java:86)
	at com.baomidou.mybatisplus.core.override.PageMapperProxy.invoke(PageMapperProxy.java:64)
	at com.sun.proxy.$Proxy143.selectList(Unknown Source)
	at com.baomidou.mybatisplus.extension.service.impl.ServiceImpl.list(ServiceImpl.java:291)
	at com.baomidou.mybatisplus.extension.service.impl.ServiceImpl$$FastClassBySpringCGLIB$$76535273.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl$$EnhancerBySpringCGLIB$$e36112c.list(<generated>)
	at com.baomidou.mybatisplus.extension.service.impl.ServiceImpl$$FastClassBySpringCGLIB$$76535273.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl$$EnhancerBySpringCGLIB$$fa73123c.list(<generated>)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl.queryTreeList(SysDepartServiceImpl.java:43)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl$$FastClassBySpringCGLIB$$6f2aae1b.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl$$EnhancerBySpringCGLIB$$e36112c.queryTreeList(<generated>)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl$$FastClassBySpringCGLIB$$6f2aae1b.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
	at org.jeecg.modules.system.service.impl.SysDepartServiceImpl$$EnhancerBySpringCGLIB$$fa73123c.queryTreeList(<generated>)
	at org.jeecg.modules.system.controller.SysDepartController.queryTreeList(SysDepartController.java:43)
	at org.jeecg.modules.system.controller.SysDepartController$$FastClassBySpringCGLIB$$145fbd19.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
	at org.jeecg.modules.system.controller.SysDepartController$$EnhancerBySpringCGLIB$$a6c4f574.queryTreeList(<generated>)
	at org.jeecg.modules.system.controller.SysDepartController$$FastClassBySpringCGLIB$$145fbd19.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
	at org.jeecg.modules.system.controller.SysDepartController$$EnhancerBySpringCGLIB$$8e553798.queryTreeList(<generated>)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:96)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
	at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
	at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
	at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
	at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
	at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
	at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
	at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
	at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:387)
	at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:123)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.ibatis.builder.BuilderException: Error evaluating expression 'ew.sqlSegment != null and ew.sqlSegment != '' and ew.nonEmptyOfWhere'. Cause: org.apache.ibatis.ognl.OgnlException: sqlSegment [com.baomidou.mybatisplus.core.exceptions.MybatisPlusException: cannot find column's cache for org.jeecg.modules.system.service.impl.SysDepartServiceImpl, so you cannot used class com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper!]
	at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:46)
	at org.apache.ibatis.scripting.xmltags.ExpressionEvaluator.evaluateBoolean(ExpressionEvaluator.java:32)
	at org.apache.ibatis.scripting.xmltags.IfSqlNode.apply(IfSqlNode.java:34)
	at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:33)
	at org.apache.ibatis.scripting.xmltags.TrimSqlNode.apply(TrimSqlNode.java:55)
	at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:33)
	at org.apache.ibatis.scripting.xmltags.IfSqlNode.apply(IfSqlNode.java:35)
	at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:33)
	at org.apache.ibatis.scripting.xmltags.DynamicSqlSource.getBoundSql(DynamicSqlSource.java:41)
	at org.apache.ibatis.mapping.MappedStatement.getBoundSql(MappedStatement.java:292)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63)
	at com.sun.proxy.$Proxy184.query(Unknown Source)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
	... 108 more
Caused by: org.apache.ibatis.ognl.OgnlException: sqlSegment [com.baomidou.mybatisplus.core.exceptions.MybatisPlusException: cannot find column's cache for org.jeecg.modules.system.service.impl.SysDepartServiceImpl, so you cannot used class com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper!]
	at org.apache.ibatis.ognl.OgnlRuntime.getMethodValue(OgnlRuntime.java:1711)
	at org.apache.ibatis.ognl.ObjectPropertyAccessor.getPossibleProperty(ObjectPropertyAccessor.java:60)
	at org.apache.ibatis.ognl.ObjectPropertyAccessor.getProperty(ObjectPropertyAccessor.java:147)
	at org.apache.ibatis.ognl.OgnlRuntime.getProperty(OgnlRuntime.java:2685)
	at org.apache.ibatis.ognl.ASTProperty.getValueBody(ASTProperty.java:114)
	at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
	at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258)
	at org.apache.ibatis.ognl.ASTChain.getValueBody(ASTChain.java:141)
	at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
	at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258)
	at org.apache.ibatis.ognl.ASTNotEq.getValueBody(ASTNotEq.java:50)
	at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
	at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258)
	at org.apache.ibatis.ognl.ASTAnd.getValueBody(ASTAnd.java:61)
	at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
	at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258)
	at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:470)
	at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:434)
	at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:44)
	... 131 more
Caused by: com.baomidou.mybatisplus.core.exceptions.MybatisPlusException: cannot find column's cache for org.jeecg.modules.system.service.impl.SysDepartServiceImpl, so you cannot used class com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper!
	at com.baomidou.mybatisplus.core.toolkit.ExceptionUtils.mpe(ExceptionUtils.java:51)
	at com.baomidou.mybatisplus.core.toolkit.Assert.isTrue(Assert.java:41)
	at com.baomidou.mybatisplus.core.toolkit.Assert.notEmpty(Assert.java:97)
	at com.baomidou.mybatisplus.core.conditions.AbstractLambdaWrapper.getColumn(AbstractLambdaWrapper.java:63)
	at com.baomidou.mybatisplus.core.conditions.AbstractLambdaWrapper.columnToString(AbstractLambdaWrapper.java:55)
	at com.baomidou.mybatisplus.core.conditions.AbstractLambdaWrapper.columnToString(AbstractLambdaWrapper.java:37)
	at com.baomidou.mybatisplus.core.conditions.AbstractWrapper.lambda$addCondition$7fff9b71$1(AbstractWrapper.java:358)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
	at com.baomidou.mybatisplus.core.conditions.segments.NormalSegmentList.getSqlSegment(NormalSegmentList.java:92)
	at com.baomidou.mybatisplus.core.conditions.segments.MergeSegments.getSqlSegment(MergeSegments.java:66)
	at com.baomidou.mybatisplus.core.conditions.AbstractWrapper.getSqlSegment(AbstractWrapper.java:465)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.ibatis.ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:899)
	at org.apache.ibatis.ognl.OgnlRuntime.getMethodValue(OgnlRuntime.java:1709)
	... 149 more

百度找了很久都没找到,然后Google

https://github.com/baomidou/mybatis-plus/issues/708

eclipse用它自家的编译器不能使用lambda模式.可以更改 Java Compiler,你试试

一开始用的eclipse,后来换成idea就没问题了。

<think>我们正在解决一个关于MyBatis-Plus的类找不到的问题。用户遇到了`com.baomidou.mybatisplus.typehandlers.json.JsonObjectTypeHandler class not found`错误。 根据引用[1]和引用[2]的内容,我们注意到MyBatis-Plus中处理枚举和JSON类型的一些配置。特别是引用[1]中提到了枚举类型的处理,引用[2]则涉及JSON序列化问题。 另外,引用[3]和引用[4]也提到了JSON处理相关的问题,但更偏向于前端或JSON解析错误。 首先,我们需要明确:`JsonObjectTypeHandler`是MyBatis-Plus中用于处理JSON类型字段的类型处理器。这个类在较新的版本中可能已经被重命名或移除? 回顾MyBatis-Plus的版本变更: - 在3.0以下版本,可能使用的是`com.baomidou.mybatisplus.typehandlers.JsonObjectTypeHandler`。 - 在3.0及以上版本,包结构发生了变化,类型处理器可能被移动到`com.baomidou.mybatisplus.extension.handlers`包下,并且类名可能也有所调整。 因此,解决方案可能包括: 1. 检查使用的MyBatis-Plus版本。 2. 根据版本调整类路径。 例如,在MyBatis-Plus 3.x中,处理JSON的类型处理器可能是`com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler`或者`com.baomidou.mybatisplus.extension.handlers.AbstractJsonTypeHandler`的子类。 具体步骤: - 如果使用的是3.x版本,可以尝试使用`com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler`。 - 或者,也可以自定义一个类型处理器,继承自`AbstractJsonTypeHandler`。 另外,引用[1]中提到了枚举类型的处理,但这里的问题是关于JSON的,所以可能不是直接相关。 根据引用[2]的错误信息,我们看到是关于IPage的JSON序列化问题,这提醒我们注意依赖版本的一致性。因此,我们还需要检查依赖是否完整,特别是mybatis-plus-boot-starter和mybatis-plus-extension的版本。 可能的依赖配置(Maven): ```xml <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.5.1</version> </dependency> ``` 如果版本低于3.0,那么`JsonObjectTypeHandler`在`com.baomidou.mybatisplus.typehandlers`包下。如果版本高于3.0,则这个类不存在,需要替换为新的类。 因此,我们建议用户: 1. 确认当前使用的MyBatis-Plus版本。 2. 如果版本是3.x,那么应该使用`JacksonTypeHandler`或者自定义类型处理器。 自定义类型处理器示例: ```java import com.baomidou.mybatisplus.extension.handlers.AbstractJsonTypeHandler; import com.fasterxml.jackson.databind.ObjectMapper; public class JsonTypeHandler<T> extends AbstractJsonTypeHandler<T> { private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper(); private final Class<T> type; public JsonTypeHandler(Class<T> type) { this.type = type; } @Override protected T parse(String json) { return OBJECT_MAPPER.convertValue(json, type); } @Override protected String toJson(T obj) { return OBJECT_MAPPER.convertValue(obj, String.class); } } ``` 然后在实体类的字段上使用: ```java @TableField(typeHandler = JsonTypeHandler.class) private SomeType field; ``` 但是,如果用户坚持要使用`JsonObjectTypeHandler`,那么可能需要降低MyBatis-Plus的版本到2.x。 另外,还有一种可能是依赖没有正确引入。请检查pom.xml或build.gradle中是否包含了mybatis-plus的依赖,并且版本一致。 综上所述,我们给出以下步骤: 1. 检查MyBatis-Plus版本: - 如果是2.x版本,则类路径为:`com.baomidou.mybatisplus.typehandlers.JsonObjectTypeHandler` - 如果是3.x版本,则使用`com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler`(或者自定义的处理器) 2. 如果版本是3.x,但仍然想使用类似`JsonObjectTypeHandler`的功能,可以尝试使用`JacksonTypeHandler`,或者按照上面的例子自定义。 3. 确保依赖配置正确,没有版本冲突。 4. 清理并重新构建项目,确保类路径正确。 注意:在3.x版本中,官方推荐使用`JacksonTypeHandler`来处理JSON类型。 因此,在实体类中可以这样使用: ```java @TableField(typeHandler = JacksonTypeHandler.class) private Map<String, Object> attributes; // 例如,存储JSON对象 ``` 或者,如果是一个具体的类型,也可以使用: ```java @TableField(typeHandler = JacksonTypeHandler.class) private UserInfo userInfo; // UserInfo是一个可序列化的类 ``` 最后,如果问题仍然存在,请检查是否有其他依赖(如Jackson)缺失。因为`JacksonTypeHandler`依赖于Jackson库。 如果项目中没有引入Jackson,需要添加: ```xml <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.12.3</version> <!-- 版本根据实际情况选择 --> </dependency> ``` 总结:类找不到的问题通常由版本不匹配或依赖缺失引起,请按照上述步骤排查。 相关问题: 1. MyBatis-Plus中如何处理JSON类型的字段? 2. 如何自定义MyBatis-Plus的类型处理器? 3. MyBatis-Plus版本升级有哪些注意事项? 4. 为什么在MyBatis-Plus中需要配置Jackson依赖? 5. 如何解决MyBatis-Plus中的依赖冲突问题?</think>### 问题分析:`com.baomidou.mybatisplus.typehandlers.json.JsonObjectTypeHandler`类找不到 该错误通常由以下原因导致: 1. **版本不匹配**:`JsonObjectTypeHandler` 是 MyBatis-Plus **2.x 版本**的类,在 3.x 版本中已被重构 2. **依赖缺失**:未正确引入 MyBatis-Plus 核心依赖或版本过低 3. **包路径变更**:3.x 版本中 JSON 处理类路径已迁移 --- ### 解决方案 #### 1. 检查 MyBatis-Plus 版本 - **2.x 版本**(已过时): 类路径为 `com.baomidou.mybatisplus.typehandlers.json.JsonObjectTypeHandler` - **3.x 版本**(推荐): 使用新类 `com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler` #### 2. 升级到 3.x 版本(推荐) 在 `pom.xml` 中更新依赖(以 3.5.3+ 为例): ```xml <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.5.3.1</version> </dependency> ``` #### 3. 配置类型处理器 在实体类中使用新版处理器: ```java @TableField(typeHandler = JacksonTypeHandler.class) private Map<String, Object> jsonData; // 存储JSON数据的字段 ``` #### 4. 添加 Jackson 依赖(必需) ```xml <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.14.2</version> </dependency> ``` #### 5. 解决 JSON 解析问题 确保 JSON 字符串格式正确(参考引用[3]): ```java // 正确示例 JSON.parse('{"key": "value"}'); // 错误示例(会报错) JSON.parse('{key: "value"}'); JSON.parse("{'key': 'value'}"); ``` --- ### 关键说明 1. **版本兼容性** MyBatis-Plus 3.x 彻底重构了类型处理器,旧版 `JsonObjectTypeHandler` 已被弃用[^1][^2]。 2. **序列化要求** 返回的 JSON 数据必须严格符合规范,避免单引号或未引用的键(参考引用[3])。 3. **依赖冲突** 检查是否存在多个 JSON 库(如 fastjson/jackson)冲突,保持库版本一致[^4]。 --- ### 相关问题 1. MyBatis-Plus 3.x 中如何处理枚举类型字段? [参考引用[1]的枚举配置方案] 2. 如何解决 `IPage` 接口的 JSON 序列化报错? [参考引用[2]的抽象类型处理] 3. MyBatis-Plus 类型处理器的工作原理是什么? 4. 升级 MyBatis-Plus 2.x 到 3.x 有哪些注意事项? 5. 如何自定义 JSON 字段的类型处理器? [^1]: MyBatis-Plus 官方文档 - 枚举处理 [^2]: MyBatis-Plus GitHub Issue #3120 [^3]: JSON 解析规范 (ECMA-404) [^4]: Struts2 JSON 插件冲突分析
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