1、
<form>
<input type="text" class="form-control" placeholder=" 姓名" id="username" value=""> （class使其居中）
2、ajax要引入jQuery库
3、前端传日期，后台先用String接收，再转成Date
https://www.cnblogs.com/zizaiwuyou/p/String_Date.html
https://blog.csdn.net/ljw619/article/details/79554281
long数据用Long接收，int用Integer
4、前端接收如图片地址，后台直接用String接收会报400错误
原因：服务器post大小限制 默认是2M //springboot由1.2.1升级为1.3.3产生的全新问题，AJAX上传图片老是400，Status Code:400 Bad Request
https://bbs.csdn.net/topics/392085620
5、java.lang.IllegalArgumentException: Invalid character found in the request target. The valid characters are defined in RFC 7230 and RFC 3986
https://www.cnblogs.com/wsygdb/p/7661220.html
6、登录界面：java.lang.IllegalStateException: Optional long parameter 'account' is present but cannot be translated into a null value due to being declared as a primitive type. Consider declaring it as object wrapper for the corresponding primitive type.
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.handleNullValue(AbstractNamedValueMethodArgumentResolver.java:245) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:115) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:126) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:166) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
问题描述：前端js代码可以接收到input传入的值，但ajax传到后台接收不到。
解决：把1、
<form>
<input type="text" class="form-control" placeholder=" 姓名" id="username" value=""> （class使其居中）
第4 5的这里的错误主要是我从前端上传文件，表单提交一堆东西，到了后台就报bug了，排查了一下所有数据就是整个上传文件有问题。大概的原因就是貌似tomcat是有文件大小限制的，2M左右。
解决方案大概是要改一下Tomcat的配置文件，但这里我还没有搞定。
6、登录界面：
问题描述：前端js代码可以接收到input传入的值，但ajax传到后台接收不到。
报bug： java.lang.IllegalStateException: Optional long parameter 'account' is present but cannot be translated into a null value due to being declared as a primitive type. Consider declaring it as object wrapper for the corresponding primitive type.
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.handleNullValue(AbstractNamedValueMethodArgumentResolver.java:245) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:115) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:126) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:166) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
解决：把ajax的data不要用表单传数据，直接传递数值
最近经常遇到前端ajax传一整个表单过去后台出错的，后台会接收不到数据报Null，这里的解决方案同上，将data改为数据一个个传输。
7、ERROR 10488 --- [nio-8080-exec-3] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request
常是因为缺少了某个注解，注意检查@Controller，@Autowired，@Service，@Mapper
8、关于Bootstrap的格式调整：
Bootstrap栅栏布局里col-xs-、col-sm-、col-md-、col-lg-之间的区别及使用方法
https://blog.csdn.net/Mr_JavaScript/article/details/79677503
解释
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