背景
前几天，碰到一个SimpleEvaluationContext类找不到的问题：
异常栈如下：
org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.NoClassDefFoundError: org/springframework/expression/spel/support/SimpleEvaluationContext
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:990) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:728) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:472) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:395) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:316) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:395) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:254) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:349) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:175) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468) [tomcat-embed-core-8.5.31.jar:8.5.31]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.31.jar:8.5.31]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_60]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_60]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.31.jar:8.5.31]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_60]
Caused by: java.lang.NoClassDefFoundError: org/springframework/expression/spel/support/SimpleEvaluationContext
at org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$ExpressionResolver.getContext(ErrorMvcAutoConfiguration.java:279) ~[spring-boot-autoconfigure-1.5.13.RELEASE.jar:1.5.13.RELEASE]
at org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$ExpressionResolver.<init>(ErrorMvcAutoConfiguration.java:275) ~[spring-boot-autoconfigure-1.5.13.RELEASE.jar:1.5.13.RELEASE]
at org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$SpelView.render(ErrorMvcAutoConfiguration.java:225) ~[spring-boot-autoconfigure-1.5.13.RELEASE.jar:1.5.13.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1286) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1041) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:984) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
... 28 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.springframework.expression.spel.support.SimpleEvaluationContext
at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_60]
at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_60]
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[na:1.8.0_60]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_60]
... 34 common frames omitted分析
中文资料没找到，于是去google资料，发现是spring-expression版本问题：
我使用的是springboot 1.5.13.RELEASE，eclipse的maven依赖树显示，对应的spring-expression版本是4.3.10.ELEASE。
另一个老外看到的版本跟我不一样，他显示的依赖版本是4.3.14.ELEASE。
最重要的信息来了：
- SimpleEvaluationContext was added in 4.3.15.RELEASE so the fact you can't find it in 4.3.14.RELEASE is perfectly normal.
- Spring Boot 1.5.13 uses Spring Framework 4.3.17.RELEASE.
由此可见，由于SimpleEvaluationContext 是4.3.15.RELEASE才增加的，只要把依赖的版本大于这个版本就行了。但由于官方推荐springBoot 1.5.13应该使用spring的4.3.17.RELEASE版本，那就把spring版本升级。
解决方案
在pom文件中添加
<properties>
...
<!-- 不把spring-core版本升级也没什么问题。-->
<spring.version>4.3.17.RELEASE</spring.version>
</properties>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>4.3.17.RELEASE</version>
</dependency>
...
文章结束。