Unable to pass multipart file using Ajax from JSP to Controller in Spring MVC

I am trying to create file upload JSP and in this I am not using default SUBMIT type button. Instead I am using normal button and I have set onClick function. After onClick function triggered, Form is successfully Validating but the AJAX function is not able to send multipart file request to the controller. Below mentioned is the respective JSP, Controller and the script.

**

• JSP:

<div class="container-fluid">
<div class="card">
<div class="card-header bg-info"> BERICHT DATEI IMPORTIEREN </div>
<div class="card-body">
<form id="blkuploadform1"  enctype="multipart/form-data">
<div class="form-group">
<h6>Datei Importieren Method :</h6>
<p>Diese Seite wird verwendet, um die Datei mit 1 oder mehr als 1 Berichtsdatensätzen gleichzeitig in die Datenbank hochzuladen.</p>
<br>
<div class="custom-file">
<input type="file" class="custom-file-input" id="blkUploadReport1" name="blkUploadReport1">
<label class="custom-file-label" for="blkUploadReport1">Choose the File <span class="fas fa-asterisk"></span></label>	                        
</div>
</div>
</form>
<div class="col-sm-offset-2 col-sm-6">
<button class="btn btn-success btn-raised btn-sm" id="saveEdit1" onClick="bulkupdValidator1()"> IMPORTIEREN <span class="fas fa-save"></span>
</button>
</div>
</div>
</div>
<br><br>
<div class="card">
<div class="card-header bg-info">
BERICHT DATEI IMPORTIEREN
</div>
<div class="card-body">
<form id="blkuploadform2" enctype="multipart/form-data">
<div class="form-group">
<h6>Datei Importieren Method :</h6>
<p>Diese Seite wird verwendet, um die Datei mit 1 oder mehr als 1 Berichtsdatensätzen gleichzeitig in die Datenbank hochzuladen.</p>
<br>
<input type="file" id="blkUploadReport2" name="blkUploadReport2">  <span class="fas fa-asterisk"></span>
</div>
</form>
<div class="col-sm-offset-2 col-sm-6">
<button class="btn btn-success btn-raised btn-sm" id="saveEdit2" onClick="bulkupdValidator2()">
IMPORTIEREN <span class="fas fa-save"></span> 
</button>					
</div>
</div>
</div>
</div>

**

**

• CONTROLLER:

	@RequestMapping(value="/bulkuploadreportstg",method=RequestMethod.POST)
public List<DTSBlkReportStg> blkReportStg (@RequestParam("blkreportexcel") MultipartFile blreportexcel) {
List<DTSBlkReportStg> stgresp= null;
logger.info(blreportexcel);
return stgresp;
}

**

**

• SCRIPT:

function bulkupdValidator2(){
if($('#blkuploadform2').valid()){
$('#confirm-save').modal('show');
console.log("I am success");
}
else{
document.getElementById("error").innerText="Bitte füllen Sie die erforderlichen Felder mit rotem Text aus.";
$('#error-message').modal('show');
}
}
$(document).ready(function(){
$('#blkuploadform2').validate({
rules:{
blkUploadReport2:{
required:true,
extension:'xlsx'
}
},
messages:{
blkUploadReport2:{
required:"Bitte laden Sie die Datei im gewünschten Format (.xlsx) hoch.",
extension:"Bitte laden Sie die Datei im gewünschten Format (.xlsx) hoch."
}
}
})
})
//Function to Validate the data from uploaded file and load them into staging tables accordingly.
function blksavedata(typeOfData){
$('#confirm-save').modal('hide');
var form=$('#blkuploadform2')[0]
console.log($('#blkuploadform2')[0]);
var data=new FormData(form.files);
console.log(data);
if (fileType=='report')
{
$.ajax({
type:"POST",
url:"/DTSDBL/bulkuploadreportstg?blreportexcel="+data,
processData: false,
enctype: "multipart/form-data",
contentType: false,
cache: false,
success:function(data){	  			
console.log("I am success returned form controller"); 	                                     		 
},
error:function(e){
console.log("I am error returned form controller"); 			 
}
});
}
}

**

Below is the error received in Controller log.

2020-07-28 16:57:54,804 [http-nio-8080-exec-415] DEBUG o.s.web.servlet.DispatcherServlet - Could not complete request
org.springframework.web.multipart.MultipartException: Current request is not a multipart request
at org.springframework.web.method.annotation.RequestParamMethodArgumentResolver.handleMissingValue(RequestParamMethodArgumentResolver.java:190)
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:109)
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:158)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:660)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:798)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:808)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
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)

Can some one advise how to fix this ?

Regarding the multipart config you must be sure to have your backend configured to that it has a dependency to commons-fileupload in your dependencies.

From spring's configuration side, you need to register this bean in your application context.

public CommonsMultipartResolver multipartResolver() {
CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver();
multipartResolver.setMaxUploadSize(100000);
return multipartResolver;
}

And from the controller point of view, the multipart is not a requestParam, it's part of the body, so try removing the @RequestParam before MultipartFile from your controller.

Also regarding the request, your js script should do a request containing the header "Accept: multipart/form-data" (either pass it from jquery, or set it on your form)

LE:
Also you are sending the file via a url parameter. Send it in the body of the request as here ```

type: 'POST',
// Form data
data: new FormData($('form')[0]),

</details>
# 答案2
**得分**: 0
我能够通过将控制器类中的注释从 @Controller 更新为 @RestController，并根据 Alex 的说明，将 ajax 请求的发送方式从请求参数更改为请求主体，来解决这个问题。
<details>
<summary>英文:</summary>
I am able to fix the issue by updating the annotation from @Controller to @RestController in my Controller class and updated ajax request to send the file as Request Body instead of Request Param as mentioned by Alex.
</details>