mybatis诡异报错：数值转换。java.lang.NumberFormatException: For input string: "custom"

先贴出报错信息：

### Error querying database.  Cause: java.lang.NumberFormatException: For input string: "custom"
### Cause: java.lang.NumberFormatException: For input string: "custom"] with root cause
java.lang.NumberFormatException: For input string: "custom"
	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
	at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
	at java.lang.Double.parseDouble(Double.java:538)
	at org.apache.ibatis.ognl.OgnlOps.doubleValue(OgnlOps.java:259)
	at org.apache.ibatis.ognl.OgnlOps.compareWithConversion(OgnlOps.java:143)
	at org.apache.ibatis.ognl.OgnlOps.isEqual(OgnlOps.java:186)
	at org.apache.ibatis.ognl.OgnlOps.equal(OgnlOps.java:578)
	at org.apache.ibatis.ognl.ASTEq.getValueBody(ASTEq.java:51)
	at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170)
	at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210)
	at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:333)
	at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:310)
	at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:45)
	at org.apache.ibatis.scripting.xmltags.ExpressionEvaluator.evaluateBoolean(ExpressionEvaluator.java:32)
	at org.apache.ibatis.scripting.xmltags.IfSqlNode.apply(IfSqlNode.java:33)
	at org.apache.ibatis.scripting.xmltags.ChooseSqlNode.apply(ChooseSqlNode.java:34)
	at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:32)
	at org.apache.ibatis.scripting.xmltags.ForEachSqlNode.apply(ForEachSqlNode.java:82)
	at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:32)
	at org.apache.ibatis.scripting.xmltags.IfSqlNode.apply(IfSqlNode.java:34)
	at org.apache.ibatis.scripting.xmltags.MixedSqlNode.apply(MixedSqlNode.java:32)
	at org.apache.ibatis.scripting.xmltags.DynamicSqlSource.getBoundSql(DynamicSqlSource.java:40)
	at org.apache.ibatis.mapping.MappedStatement.getBoundSql(MappedStatement.java:278)
	at com.github.pagehelper.PageInterceptor.intercept(PageInterceptor.java:83)
	at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)
	at com.sun.proxy.$Proxy43.query(Unknown Source)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:358)
	at com.sun.proxy.$Proxy22.selectList(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:198)
	at net.cnki.dao.impl.BaseDaoImpl.getObjectList(BaseDaoImpl.java:199)
	at net.cnki.service.impl.BaseServiceImpl.getObjectList(BaseServiceImpl.java:78)
	at net.cnki.controller.StandardListController.listData(StandardListController.java:91)
	at net.cnki.controller.StandardListController$$FastClassBySpringCGLIB$$59ece575.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:717)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
	at org.springframework.aop.framework.adapter.ThrowsAdviceInterceptor.invoke(ThrowsAdviceInterceptor.java:125)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:653)
	at net.cnki.controller.TestLockListController$$EnhancerBySpringCGLIB$$dd2b15ae.listData(<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:221)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:777)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:706)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
	at com.orangefunction.tomcat.redissessions.RedisSessionHandlerValve.invoke(RedisSessionHandlerValve.java:26)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1082)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:623)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
	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)

从报错信息来看，就是custom被错误的转换成了数值。

回过头来看我自己的代码，并没有声明'custom'为数值的地方。贴出部分代码如下：

	<select id="getPageList" resultType="map" parameterType="map">
		select * from test_lock where 1=1
		<if test="filters != null and filters.size() > 0">
			and 
	        <foreach collection="filters" index="index" item="filter"
	            open="(" separator="and" close=")">
	            <choose>
	            	<when test="filter.type == 'like' or filter.type == 'LIKE'">
			            ${filter.propertyPath} ${filter.type} '%${filter.value}%'
	            	</when>
	            	<when test="filter.type == '='">
			            ${filter.propertyPath} = #{filter.value}
	            	</when>
	            	<when test="(filter.type == 'custom' or filter.type == 'CUSTOM') and filter.sql != null and filter.sql != ''">
			            ${filter.sql}
	            	</when>
	            </choose>
	        </foreach>
		</if>
	</select>

由以上代码，并未发现为何会出现以上问题，于是debug mybatis源代码进行排查。在排查过程中，发现在进行mybatis表达式判断时，其中的一个条件为 filter.type == '='的表达式，执行时，抛出异常。而非 filter.type == 'custom'.故而将'='变更为'equals',即一切恢复正常。

结论

在mybatis的if test表达式中，右值不能填'='这个符号（会自动转成数值？？），虽然是个字符串。