前端发送了一个http PUT请求，如下，
json_xml: 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svg_xml:
后端出现错误：
2019-06-05 18:43:38.268 ERROR 28652 --- [io-8094-exec-10] c.e.p.w.c.c.ELProcModelController : 缺少请求参数 org.springframework.web.bind.MissingServletRequestParameterException: Required String parameter 'name' is not present at org.springframework.web.method.annotation.RequestParamMethodArgumentResolver.handleMissingValue(RequestParamMethodArgumentResolver.java:202) ~[spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:113) ~[spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:126) ~[spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:166) ~[spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134) ~[spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) [spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:919) [spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at javax.servlet.http.HttpServlet.service(HttpServlet.java:663) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) [spring-webmvc-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.filters.RemoteIpFilter.doFilter(RemoteIpFilter.java:845) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.filters.RemoteIpFilter.doFilter(RemoteIpFilter.java:902) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:123) [druid-1.1.5.jar!/:1.1.5] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.1.5.RELEASE.jar!/:5.1.5.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:679) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_212] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_212] at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.16.jar!/:9.0.16] at java.lang.Thread.run(Thread.java:748) [na:1.8.0_212]
关键信息是：缺少请求参数
全局搜索，找到了：
@ResponseBody @ResponseStatus(code = HttpStatus.BAD_REQUEST) @ExceptionHandler(BindException.class) public CommonResponse MethodArgumentNotValidHandler(BindException exception) throws Exception { logger.error("参数绑定验证失败:", exception); return CommonResponse.createCustomCommonResponse(String.valueOf(HttpStatus.BAD_REQUEST.value()), "缺少请求参数"); } /** * @param * @return * @description 缺少参数 * @author lk * @version v1.0 * @date 2017/9/6 */ @ResponseBody @ResponseStatus(code = HttpStatus.BAD_REQUEST) @ExceptionHandler(MissingServletRequestParameterException.class) public CommonResponse handleMissingServletRequestParameterException(MissingServletRequestParameterException e) { logger.error("缺少请求参数", e); return CommonResponse.createCustomCommonResponse(String.valueOf(HttpStatus.BAD_REQUEST.value()), "缺少请求参数"); }
嗯， 应该就是绑定问题，应该是ELProcModelController 的某个mvc方法的绑定问题。（实际上是 save 方法）但是，从错误日志来看，是找不到具体哪个方法的，因为根本都还没进去调用那个方法！ 而是绑定参数的阶段就出了问题！ 所以尝试去设置断点调试那个方法是没有用的！！
当然，调试handleMissingServletRequestParameterException 或MethodArgumentNotValidHandler 方法则是有用的。
奇怪的是，之前都是好好的， 怀疑是升级到spring boot-2.1.3 后就出现了这个问题。 网上的解决方案是 增加这么一个 FIlter，HttpPutFormContentFilter， 不过，这个类已经deprecated 了！why ，看这里：https://github.com/spring-projects/spring-boot/issues/13363
HttpPutFormContentFilter对delete方法不支持，FormContentFilter 更友好！
另外，需要注意到 前端收到400 ，并不是说前端的错误，其实还是 后端的错误。 虽然4xx是表示了前端请求的某些错误。其实不然。
参考
http://www.th7.cn/Program/java/201608/925805.shtml
https://www.oschina.net/question/2621611_2217526
https://blog.csdn.net/geloin/article/details/7444590