最近在研究springMVC框架，做测试demo时添加ajax异步请求时出现问题，现在贴出请求端源码
<script type="text/javascript" src="./js/jquery-1.10.2.js"></script>
<script type="text/javascript">
function testLogin(){
alert("sdfs");
$.ajax({
type: "get",
url: "./login.do",
dataType: "json",
data: {
loginName: "111",loginPassword:"222"
},
beforeSend: function(XMLHttpRequest){
//ShowLoading();
alert("beforeSend");
},
success: function(data, textStatus){
alert(data);
},
complete: function(XMLHttpRequest, textStatus){
//HideLoading();
alert("Complete");
},
error: function(XMLHttpRequest, textStatus, errorThrown){
//请求出错处理
alert(XMLHttpRequest.status);
alert(XMLHttpRequest.readyState);
alert(textStatus);
}
});
}
</script>
能够成功请求后台，但是，在后台的controller处理过程中出现错误。经查找，觉得是springMVC框架没有加入json支持，所以去掉dataType: "json", 就用默认字符串传值，前台正常显示，可是控制台报错。
10:46:41,625 WARN DefaultHandlerExceptionResolver:127 - Handling of [org.springframework.web.HttpMediaTypeNotAcceptableException] resulted in Exception java.lang.IllegalStateException at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:421) at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.handleHttpMediaTypeNotAcceptable(DefaultHandlerExceptionResolver.java:219) at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.doResolveException(DefaultHandlerExceptionResolver.java:103) at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:136) at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1060) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:884) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:792) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:851) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:756) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:662) 2013-9-24 10:46:41 org.apache.catalina.core.StandardWrapperValve invoke 严重: Servlet.service() for servlet springMVC-flex threw exception org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation at org.springframework.web.servlet.mvc.method.annotation.support.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:181) at org.springframework.web.servlet.mvc.method.annotation.support.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:146) at org.springframework.web.servlet.mvc.method.annotation.support.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:103) at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:64) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:113) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:502) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:465) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:863) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:792) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:851) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:756) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:662)
于是再次查找错误，后度娘告诉我：servlet代码中有out.write(””)，这个和JSP中缺省调用的response.getOutputStream()产生冲突.
因为在jsp中，out变量是通过response.getWriter得到的，在程序中既用了 response.getOutputStream，又用了out变量，故出现以上错误，没办法只有
try {
PrintWriter out = response.getWriter();
out.println("ceshi ajax");
out.flush();
out.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mv.addObject("ajax测试！");
mv.setViewName("login");
return null;
reutrn null 变得正常，不知道大神们是怎么处理这个问题的呢？