MyBatis中二级缓存和延时加载同时开启的问题

首先，二级缓存默认不开启！

要配置 <setting name="cacheEnabled" value="true"/>

在MyBatis中：一级缓存会维护一个HashMap，key为hashcode+statementId+sql语句，Value为查询出来的结果集映射成的java对象。作用域是SqlSession

二级缓存是namespace级的，还需要在配置文件处配置缓存<cache/>

在配置了分布查询

 <select id="selectEmployees" resultMap="emps">
         select id,last_name,gender,descr,did from employee
 </select>

 <resultMap type="com.atguigu.bean.Employee" id="emps">
         <id column="id" property="id"/>
         <result column="last_name" property="lastName"/>
         <result column="gender" property="gender"/>
         <result column="descr" property="descr"/>

         <association property="dept" select="com.atguigu.mapper.DepartmentMapper.selectDepartmentById"
             column="{id=did}"></association>
 </resultMap>

和延时加载后

 <setting name="lazyLoadingEnabled" value="true"/>
 <setting name="aggressiveLazyLoading" value="false"/>

此时刷新查询结果页面会报错

   1 type Exception report
   2
   3 message javax.el.ELException: Error reading 'dept' on type com.atguigu.bean.Employee_$$_jvst6ff_0
   4
   5 description The server encountered an internal error that prevented it from fulfilling this request.
   6
   7 exception
   8
   9 org.apache.jasper.JasperException: javax.el.ELException: Error reading 'dept' on type com.atguigu.bean.Employee_$$_jvst6ff_0
  10     org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:561)
  11     org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
  12     org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
  13     org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
  14     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  15     org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  16     org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:209)
  17     org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:266)
  18     org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1225)
  19     org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1012)
  20     org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
  21     org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
  22     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
  23     org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
  24     javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
  25     org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
  26     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  27     org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  28     org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
  29     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
  30     org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
  31     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
  32 root cause
  33
  34 javax.el.ELException: Error reading 'dept' on type com.atguigu.bean.Employee_$$_jvst6ff_0
  35     javax.el.BeanELResolver.getValue(BeanELResolver.java:110)
  36     org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:104)
  37     org.apache.el.parser.AstValue.getValue(AstValue.java:184)
  38     org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
  39     org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:950)
  40     org.apache.jsp.pages.list_jsp._jspx_meth_c_005fforEach_005f0(list_jsp.java:212)
  41     org.apache.jsp.pages.list_jsp._jspService(list_jsp.java:124)
  42     org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
  43     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  44     org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
  45     org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
  46     org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
  47     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  48     org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  49     org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:209)
  50     org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:266)
  51     org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1225)
  52     org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1012)
  53     org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
  54     org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
  55     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
  56     org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
  57     javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
  58     org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
  59     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  60     org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  61     org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
  62     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
  63     org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
  64     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
  65 root cause
  66
  67 org.apache.ibatis.executor.ExecutorException: Cannot get Configuration as configuration factory was not set.
  68     org.apache.ibatis.executor.loader.ResultLoaderMap$LoadPair.getConfiguration(ResultLoaderMap.java:220)
  69     org.apache.ibatis.executor.loader.ResultLoaderMap$LoadPair.load(ResultLoaderMap.java:191)
  70     org.apache.ibatis.executor.loader.AbstractEnhancedDeserializationProxy.invoke(AbstractEnhancedDeserializationProxy.java:78)
  71     org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedDeserializationProxyImpl.invoke(JavassistProxyFactory.java:186)
  72     com.atguigu.bean.Employee_$$_jvst6ff_0.getDept(Employee_$$_jvst6ff_0.java)
  73     sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  74     sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  75     sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  76     java.lang.reflect.Method.invoke(Method.java:498)
  77     javax.el.BeanELResolver.getValue(BeanELResolver.java:99)
  78     org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:104)
  79     org.apache.el.parser.AstValue.getValue(AstValue.java:184)
  80     org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
  81     org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:950)
  82     org.apache.jsp.pages.list_jsp._jspx_meth_c_005fforEach_005f0(list_jsp.java:212)
  83     org.apache.jsp.pages.list_jsp._jspService(list_jsp.java:124)
  84     org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
  85     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  86     org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
  87     org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
  88     org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
  89     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  90     org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  91     org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:209)
  92     org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:266)
  93     org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1225)
  94     org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1012)
  95     org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
  96     org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
  97     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
  98     org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
  99     javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
 100     org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
 101     javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
 102     org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
 103     org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
 104     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
 105     org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
 106     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
 107 note The full stack trace of the root cause is available in the Apache Tomcat/7.0.79 logs.

错误页面

这可能是由于第一次查询将结果保存在了二级缓存中，在第二次查询时，由于设置了延时加载，在缓存中只查到了Employee对应的属性，但对于第二步却无法一次性而出现问题。

解决办法是关闭二级缓存。

（问别人的时候还以为二级缓存默认开启真鸡儿丢人）