很奇怪的錯誤，但是錯誤原因難以啓齒。。。。記錄下來
記一次使用mybatis時發生的錯誤，全部錯誤信息如下
org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'str' in 'class java.lang.String'
at org.apache.ibatis.reflection.Reflector.getGetInvoker(Reflector.java:419) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.reflection.MetaClass.getGetInvoker(MetaClass.java:164) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.reflection.wrapper.BeanWrapper.getBeanProperty(BeanWrapper.java:162) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.reflection.wrapper.BeanWrapper.get(BeanWrapper.java:49) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java:122) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.DynamicContext$ContextMap.get(DynamicContext.java:94) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.DynamicContext$ContextAccessor.getProperty(DynamicContext.java:108) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.OgnlRuntime.getProperty(OgnlRuntime.java:2671) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.ASTProperty.getValueBody(ASTProperty.java:114) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.ASTNotEq.getValueBody(ASTNotEq.java:50) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.ASTAnd.getValueBody(ASTAnd.java:61) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:258) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:470) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:434) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:44) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.ExpressionEvaluator.evaluateBoolean(ExpressionEvaluator.java:32) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.IfSqlNode.apply(IfSqlNode.java:34) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:33) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.scripting.xmltags.DynamicSqlSource.getBoundSql(DynamicSqlSource.java:41) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.mapping.MappedStatement.getBoundSql(MappedStatement.java:292) ~[mybatis-3.4.5.jar:3.4.5]
at com.github.pagehelper.PageInterceptor.intercept(PageInterceptor.java:83) ~[pagehelper-5.1.2.jar:na]
at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:61) ~[mybatis-3.4.5.jar:3.4.5]
at com.sun.proxy.$Proxy80.query(Unknown Source) ~[na:na]
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141) ~[mybatis-3.4.5.jar:3.4.5]
at sun.reflect.GeneratedMethodAccessor211.invoke(Unknown Source) ~[na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) ~[mybatis-spring-1.3.1.jar:1.3.1]
at com.sun.proxy.$Proxy65.selectList(Unknown Source) ~[na:na]
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230) ~[mybatis-spring-1.3.1.jar:1.3.1]
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:137) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:75) ~[mybatis-3.4.5.jar:3.4.5]
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59) ~[mybatis-3.4.5.jar:3.4.5]
at com.sun.proxy.$Proxy115.query(Unknown Source) ~[na:na]
at cn.ancient_wars.service.impl.QuestionServiceImpl.query(QuestionServiceImpl.java:20) ~[classes/:na]
at cn.ancient_wars.controller.AncientController.query(AncientController.java:30) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_201]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:123) ~[druid-1.1.9.jar:1.1.9]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:800) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1471) [tomcat-embed-core-8.5.32.jar:8.5.32]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.32.jar:8.5.32]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_201]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_201]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.32.jar:8.5.32]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_201]
錯誤信息中的str爲我傳入dao層的參數，
錯誤原因如下：
在dao接口方法中只有一個參數時，在sal中需要判斷此參數是否爲null和""時，使用瞭如下語句
<if test="str !=null and str!='' ">
</if>
我們經常傳入實體，map作爲參數，這個test中的str理應作爲key來獲取值，但是由於我在dao層接口寫法如下
/**
* 查詢
* @param str
* @return
*/
public List<Question> query(String str);
並未指定參數str的key值，mybatis會默認給參數param1，param2之類的key，所有找不到str，纔會報出String中沒有str的get方法錯誤
解決方案：
在dao層使用@param註解指定str的key
/**
* 查詢
* @param str
* @return
*/
public List<Question> query(@Param("str")String str);
再次查詢，成功解決問題！