java - Spring file upload not binding to model attribute object -

i want build simple file upload functionality using spring mvc.

i have multipartresolver in place , working:

<bean id="multipartresolver" class="org.springframework.web.multipart.commons.commonsmultipartresolver">   <property name="maxuploadsize" value="10240000"/> </bean> 

when uploading file logged:

debug:[org.springframework.web.multipart.commons.commonsmultipartresolver]: found multipart file [imageupload] of size 29081 bytes original filename [xyz.jpg], stored @ [/home/myuser/workspace/myproject/target/tmp/upload_67f1107c_1b8f_402c_bebd_6cd8a6e4c830_00000032.tmp] 

which tells me it's working.

this part of jsp:

<form:form modelattribute="placeform" action="/platz/save" method="post" cssclass="placeform" enctype="multipart/form-data"> ...         <label for="imageupload">upload</label>         <form:input type="file" path="imageupload" id="imageupload" accept="image/*" /> ... </form:form> 

this model attribute object's class:

public class placeeditform {     @valid     private place place = new place();     private map<integer, placefeature> features;     private multipartfile imageupload; ... getter/setter omitted... } 

and part of controller method:

@requestmapping(value="/save", method=requestmethod.post) public string saveplace (@valid @modelattribute("placeform") placeeditform form, bindingresult result) {     logger.debug("savenewplace");     logger.debug("upload: "+form.getimageupload()); // null     ...     return "redirect:/platz/"+place.getplaceid(); } 

what happens is, imageupload attribute of form object not populated (null), whereas other form properties are.

i found work when use in controller:

@requestmapping(value="/save", method=requestmethod.post) public string saveplace (@valid @modelattribute("placeform") placeeditform form, bindingresult result, @requestparam("imageupload") multipartfile upload, bindingresult uploadresult) {     logger.debug("savenewplace");     logger.debug("upload: "+upload); // works!!     ...     return "redirect:/platz/"+place.getplaceid(); } 

so, having multipartfile @requestparam works, binding form's modelattribute object doesn't. found hundreds of examples on web same , don't find difference.

i'm still learning spring, might miss obvious point. use second version of controller, don't understand it, , said, i'm learning.

shouldn't <form:input path="abc"> properties inside <form:form modelattribute="xyz">...</form:form> bound xyz.abc? works properties except file upload.

any insights? thanks

i found problem:

i had method in controller, forgot add imageupload property. stupid , easy once found..!

@initbinder public void initbinder(webdatabinder binder) {     binder.setallowedfields("place.placeid", "place.name", "place.description", "place.directions", "place.coordinates*", "features*", "tmpfiles*", "removefiles*"); } 

this prevents binder bind other properties modelattribute ones specified. important security measure prevent evildoers feeding in dangerous information system, when validate expect on front-end.