ibatis的isnotempty参数 ibatis result

转载

mob64ca14068b0b 2024-04-30 19:34:02

文章标签 ibatis的isnotempty参数 java spring jar 文章分类 机器学习人工智能

iBatis和MyBatis 中返回数据对应关系

直接进入主题，现在的项目改用MyBatis了，感觉跟iBatis还是不一样的，比如在判断空值上面，iBatis是有标签的<isNotEmpty><isNotNull>等标签使用，MyBatis确是使用<if></if>来进行这些判断的。所以区别了还是有的，就是看怎么使用方便。不过个人还是觉得MyBatis方便，因为这是面向接口的编程。现在是比较流行的。下面说说我在使用中遇到的问题。

（一）：iBatis使用对应关系

iBatis中我们在查询多条数据的时候都会返回一个resultMap,那么我们查询的数据就和resultMap对应，那么有没有想过如果两边对不上会怎么样，特别是在resultMap公用的情况下，你在那边加会有什么影响等情况。

经过我的测试发现，如果查询的字段多了，resultMap对应的字段少了，不会报错，只是查询后后台取的的数据这个字段为NULL值

如果resultMap多了，查询数据的时候没有查询出来这个数据，那么此时就会报错,比如说我查询的时候没有查询name这个字段，但是resultMap里面对应的有这个字段，就会报如下错误

org.springframework.jdbc.UncategorizedSQLException: SqlMapClient operation; uncategorized SQLException for SQL []; SQL state [S0022]; error code [0];   
--- The error occurred in com/mouse/snow/pojo/sqlmap/User.xml.  
--- The error occurred while applying a result map.  
--- Check the Evaluation.get-Evaluation-list.  
--- Check the result mapping for the 'name' property.  
--- Cause: java.sql.SQLException: Column 'name' not found.; nested exception is com.ibatis.common.jdbc.exception.NestedSQLException:   
--- The error occurred in 
com/mouse/snow/pojo/sqlmap/User.xml.
--- The error occurred while applying a result map.  
--- Check the Evaluation.get-User-list.  
--- Check the result mapping for the 'name' property.  
--- Cause: java.sql.SQLException: Column 'name' not found.

这里就说明了，resultMap里面不能多，但是查询的数据是可以多的，只是resultMap里面没有对应，此时pojo里面的数据是空值。

（二）：MyBatis的使用

　　在我是使用MyBatis的时候，这种对应关系谁多谁少都不会报错的，不影响。我是在使用模糊查询的时候遇到了问题，下面说说模糊查询的方式

（1）：模糊查询的方式有好多的，当你传入一个单个数据模糊查询的时候，就是只传入一个keyword时候，传到*.xml里面，我每次都是使用如下

select * from t_user where id like '%${keyword}%'

当时当我这样写的时候出现了错误：

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'keyword' in 'class java.lang.String'
    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:75) ~[mybatis-spring-1.2.2.jar:1.2.2]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:371) ~[mybatis-spring-1.2.2.jar:1.2.2]
    at com.sun.proxy.$Proxy16.selectList(Unknown Source) ~[na:na]
    at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:198) ~[mybatis-spring-1.2.2.jar:1.2.2]
    at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:119) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52) ~[mybatis-3.2.8.jar:3.2.8]
    at com.sun.proxy.$Proxy25.selecetStationByWord(Unknown Source) ~[na:na]
    at com.xpg.charge.service.impl.ChargingPileServiceImpl.selecetStationByWord(ChargingPileServiceImpl.java:270) ~[ChargingPileServiceImpl.class:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_25]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98) ~[spring-tx-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:266) ~[spring-tx-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95) ~[spring-tx-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207) ~[spring-aop-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at com.sun.proxy.$Proxy28.selecetStationByWord(Unknown Source) ~[na:na]
    at com.xpg.charge.controller.web.ChargingPileController.selectStationByKeyWord(ChargingPileController.java:220) ~[ChargingPileController.class:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_25]
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215) ~[spring-web-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132) ~[spring-web-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) ~[spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:781) ~[spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:721) ~[spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) ~[spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943) ~[spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877) ~[spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) [spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868) [spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:646) ~[servlet-api.jar:na]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) [spring-webmvc-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) ~[servlet-api.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) ~[catalina.jar:7.0.56]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat7-websocket.jar:7.0.56]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) ~[catalina.jar:7.0.56]
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) ~[shiro-core-1.2.3.jar:1.2.3]
    at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) ~[shiro-core-1.2.3.jar:1.2.3]
    at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383) ~[shiro-core-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) ~[shiro-web-1.2.3.jar:1.2.3]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344) ~[spring-web-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261) ~[spring-web-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) ~[catalina.jar:7.0.56]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) ~[spring-web-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.1.1.RELEASE.jar:4.1.1.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) ~[catalina.jar:7.0.56]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) ~[catalina.jar:7.0.56]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) ~[catalina.jar:7.0.56]
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) ~[catalina.jar:7.0.56]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) ~[catalina.jar:7.0.56]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) ~[catalina.jar:7.0.56]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070) ~[tomcat-coyote.jar:7.0.56]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) ~[tomcat-coyote.jar:7.0.56]
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) ~[tomcat-coyote.jar:7.0.56]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) ~[na:1.7.0_25]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) ~[na:1.7.0_25]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-coyote.jar:7.0.56]
    at java.lang.Thread.run(Thread.java:724) ~[na:1.7.0_25]
Caused by: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'keyword' in 'class java.lang.String'
    at org.apache.ibatis.reflection.Reflector.getGetInvoker(Reflector.java:380) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.reflection.MetaClass.getGetInvoker(MetaClass.java:170) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.reflection.wrapper.BeanWrapper.getBeanProperty(BeanWrapper.java:152) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.reflection.wrapper.BeanWrapper.get(BeanWrapper.java:48) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java:116) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.DynamicContext$ContextMap.get(DynamicContext.java:97) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.DynamicContext$ContextAccessor.getProperty(DynamicContext.java:116) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.ognl.OgnlRuntime.getProperty(OgnlRuntime.java:1657) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.ognl.ASTProperty.getValueBody(ASTProperty.java:92) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:333) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:310) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:45) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.TextSqlNode$BindingTokenParser.handleToken(TextSqlNode.java:64) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.parsing.GenericTokenParser.parse(GenericTokenParser.java:53) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.TextSqlNode.apply(TextSqlNode.java:41) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:32) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.scripting.xmltags.DynamicSqlSource.getBoundSql(DynamicSqlSource.java:40) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.mapping.MappedStatement.getBoundSql(MappedStatement.java:278) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:75) ~[mybatis-3.2.8.jar:3.2.8]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_25]
    at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49) ~[mybatis-3.2.8.jar:3.2.8]
    at com.github.pagehelper.SqlUtil._processPage(SqlUtil.java:351) ~[pagehelper-4.0.0.jar:na]
    at com.github.pagehelper.SqlUtil.processPage(SqlUtil.java:329) ~[pagehelper-4.0.0.jar:na]
    at com.github.pagehelper.PageHelper.intercept(PageHelper.java:150) ~[pagehelper-4.0.0.jar:na]
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60) ~[mybatis-3.2.8.jar:3.2.8]
    at com.sun.proxy.$Proxy36.query(Unknown Source) ~[na:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_25]
    at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49) ~[mybatis-3.2.8.jar:3.2.8]
    at tk.mybatis.mapper.mapperhelper.MapperInterceptor.intercept(MapperInterceptor.java:61) ~[mapper-3.1.2.jar:na]
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60) ~[mybatis-3.2.8.jar:3.2.8]
    at com.sun.proxy.$Proxy36.query(Unknown Source) ~[na:na]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108) ~[mybatis-3.2.8.jar:3.2.8]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102) ~[mybatis-3.2.8.jar:3.2.8]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_25]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:358) ~[mybatis-spring-1.2.2.jar:1.2.2]
    ... 80 common frames omitted
.14:02:03.888 DEBUG [http-bio-8088-exec-3] org.springframework.beans.factory.support.DefaultListableBeanFactory[247] - Returning cached instance of singleton bean 'sqlSessionFactory'

这个bug让我好无奈的感觉，所以我只能改了一种方式

select * from t_user where id like CONCAT('%',#{keyword},'%'),只有这样写才可以，弄得我相当郁闷啊。

我这里传入的值完整如下：

<select id="selecetUserByWord" resultType="java.lang.String" parameterType="java.lang.String">
      select id from t_user where
      id  like CONCAT('%',#{keyword},'%')
</select>

说明：我这里红色部分是指明了是传入单个参数的，如果你传入的是一个对象，然后'%${keyword}%'的话就可以，比如

<select id="selecetUserByWord" parameterType="com.mouse.snow.User" resultType="java.lang.String">
      select id from t_user where
      id  like '%${keyword}%'
</select>

我也还没找到具体原因，但是在一些群里让群友实验，他们说他们的可以，所以我也好郁闷，因为我个人认为是可以的，不知道是否是配置问题。

三：MyBatis返回键值对形式

我们都知道我们返回的数据都有个resultType对应，有时候我们都是自己写个对象来接收的，但是其实我们有时候又不用的对象的，可以直接把查询的数据转换为键值对的形式就行返回，这里其实可以百度试验下，

Mapper层：
public List<Map<String,Object>> getUserList();

*.xml层：
<select id="selecetUser" resultType="java.util.HashMap">
      select id from t_user
</select>

类似这样就可以把查询的数据转换为键值对形式。多条数据那么就是一个list了，这样还是比较方便的。

还有一点没说，就是查询数据的时候本来就是默认把数据转化为键值对的形式如果有对象，才会再去进一步转换的，所以觉得这样直接键值对的形式得到数据的速度会更加迅速的。

这一点是在这里看见的，。

总结

最近其实学到好多知识点，比如阿里云的跨域上传下载等。一些开源的知识等，希望自己每天都能抽出点时间来写点东西，昨天去了一趟香港买了电脑，mac pro，要还几个月的款子啊，努力上班的，boy

本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。