从模拟器相册中选择一个JPG图片，通过POST方式上传到服务器，服务器端用servlet负责接收，用servletInputStream输入流接收上传的图片内容，后来发现保存的图片格式不对，不知道哪里出了问题？

jsp经编译后就变成了Servlet.（JSP的本质就是Servlet，JVM只能识别java的类，不能识别JSP的代码，Web容器将JSP的代码编译成JVM能够识别的java类）jsp更擅长表现于页面显示，servlet更擅长于逻辑控制。Servlet中没有内置对象，Jsp中的内置对象都是必须通过HttpServletRequest对象，HttpServletResponse对象以及HttpServlet对象得到。Jsp是Servlet的一种简化，使用Jsp只需要完成程序员需要输出到客户端的内容，Jsp中的Java脚本如何镶嵌到一个类中，由Jsp容器完成。而Servlet则是个完整的Java类，这个类的Service方法用于生成对客户端的响应。

在Tomcat中使用CSE的时候，经常碰到A filter or servlet of the current chain does not support asynchronous operations这个错误。 错误栈如下：[ERROR] 2018-08-03 14:33:10,124 [http-bio-8443-exec-3] - Servlet.service() for servlet [RestServlet] in context with path [] threw exception -org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/].[RestServlet]java.lang.IllegalStateException: A filter or servlet of the current chain does not support asynchronous operations.at org.apache.catalina.connector.Request.startAsync(Request.java:1675)at org.apache.catalina.connector.Request.startAsync(Request.java:1668)at org.apache.catalina.connector.RequestFacade.startAsync(RequestFacade.java:1022)at org.apache.servicecomb.transport.rest.servlet.ServletRestDispatcher.service(ServletRestDispatcher.java:49)at org.apache.servicecomb.transport.rest.servlet.RestServlet.service(RestServlet.java:47)at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)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 com.huawei.wcc.secas.ResponseHeaderFilter.doFilter(ResponseHeaderFilter.java:68)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)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:203)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:607)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:962)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)at org.apache.catalina.valves.RequestFilterValve.process(RequestFilterValve.java:364)at com.huawei.wcc.secas.RequestHeaderNameValve.invoke(RequestHeaderNameValve.java:70)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)at org.apache.tomcat.util.net.JIoEndpoint$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)