spring mvc - Sending Multipart File as POST parameters with RestTemplate requests

Question

I am working with Spring 3 and RestTemplate. I have basically, two applications and one of them have to post values to the other app. through rest template.

When the values to post are Strings, it's work perfect, but when i have to post mixed and complex params (like MultipartFiles) i get an converter exception.

As example, i have this:

App1 - PostController:

@RequestMapping(method = RequestMethod.POST)
public String processSubmit(@ModelAttribute UploadDTO pUploadDTO, 
        BindingResult pResult) throws URISyntaxException, IOException {
    URI uri = new URI("http://localhost:8080/app2/file/receiver");

    MultiValueMap<String, Object> mvm = new LinkedMultiValueMap<String, Object>();
    mvm.add("param1", "TestParameter");
    mvm.add("file", pUploadDTO.getFile()); // MultipartFile

    Map result = restTemplate.postForObject(uri, mvm, Map.class);
    return "redirect:postupload";
}

On the other side... i have another web application (App2) that receives the parameters from the App1.

App2 - ReceiverController

@RequestMapping(value = "/receiver", method = { RequestMethod.POST })
public String processUploadFile(
        @RequestParam(value = "param1") String param1,
        @RequestParam(value = "file") MultipartFile file) {

    if (file == null) {
        System.out.println("Shit!... is null");
    } else {
        System.out.println("Yes!... work done!");
    }
    return "redirect:postupload";
}

My application-context.xml:

<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
    <property name="messageConverters">
        <list>
            <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter" />
            <bean class="org.springframework.http.converter.FormHttpMessageConverter" />
            <bean class="org.springframework.http.converter.StringHttpMessageConverter" />
            <bean class="org.springframework.http.converter.xml.SourceHttpMessageConverter" />
        </list>
    </property>
</bean>

<bean id="multipartResolver"  
    class="org.springframework.web.multipart.commons.CommonsMultipartResolver">  
    <property name="maxUploadSize">  
        <value>104857600</value>  
    </property>  
    <property name="maxInMemorySize">  
        <value>4096</value>  
    </property>      
</bean>  

Here is the stack of the exception that i am getting when i do the postForObject of the RestTemplate...

org.springframework.http.converter.HttpMessageNotWritableException: Could not write request: no suitable HttpMessageConverter found for request type [org.springframework.web.multipart.commons.CommonsMultipartFile]
at org.springframework.http.converter.FormHttpMessageConverter.writePart(FormHttpMessageConverter.java:292)
at org.springframework.http.converter.FormHttpMessageConverter.writeParts(FormHttpMessageConverter.java:252)
at org.springframework.http.converter.FormHttpMessageConverter.writeMultipart(FormHttpMessageConverter.java:242)
at org.springframework.http.converter.FormHttpMessageConverter.write(FormHttpMessageConverter.java:194)
at org.springframework.http.converter.FormHttpMessageConverter.write(FormHttpMessageConverter.java:1)
at org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:588)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:436)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:415)
at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:294)
at com.yoostar.admintool.web.UploadTestController.create(UploadTestController.java:86)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:175)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:421)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:409)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:774)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
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.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
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:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)

So my questions are:

1. Is it possible to send MultipartFile through RestTemplate using POST?
2. Are there some specific converters that I have to use to send this type of objects? I mean is there some MultipartFileHttpMessageConverter to use in my configuration?

Answer 1

A way to solve this without needing to use a FileSystemResource that requires a file on disk, is to use a ByteArrayResource, that way you can send a byte array in your post (this code works with Spring 3.2.3):

MultiValueMap<String, Object> map = new LinkedMultiValueMap<String, Object>();
final String filename="somefile.txt";
map.add("name", filename);
map.add("filename", filename);
ByteArrayResource contentsAsResource = new ByteArrayResource(content.getBytes("UTF-8")){
            @Override
            public String getFilename(){
                return filename;
            }
        };
map.add("file", contentsAsResource);
String result = restTemplate.postForObject(urlForFacade, map, String.class);

I override the getFilename of the ByteArrayResource because if I don't I get a null pointer exception (apparently it depends on whether the java activation .jar is on the classpath, if it is, it will use the file name to try to determine the content type)