RESTEasy Advanced guide

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RESTEasy Advanced guide - File Upload

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RESTEasy is a JBoss project that provides various frameworks to help you build RESTful Web Services and RESTful Java applications. It is a fully certified and portable implementation of the JAX-RS 2.1 specification, a JCP specification that provides a Java API for RESTful Web Services over the HTTP protocol. It is licensed under the Apache 2.0.

This article is a continuation of previous article

RESTEasy - A guide to implement CRUD Rest API

RESTEasy Advanced Guide - Filters and Interceptors

In this article, we will explain about how to upload files using Rest API.

File Upload Service

Create a simple form to provide the file name to be persisted and file upload form control as below.


<html>
  <body>
     <h1>JAX-RS File Upload Example</h1>
     <form action="rest/upload-file" method="post" enctype="multipart/form-data">
     <p>
            File name : <input type="text" name="fileName" />
      </p>
      <p>
            Choose the file : <input type="file" name="selectedFile" />
     </p>
            <input type="submit" value="Upload" />
    </form> 
 </body>
</html>

In Rest controller, annotate the resource method with @MultipartForm and the data type received bean will be MultipartFormDataInput which has map of all field name and values.


 @POST
 @Path("/upload")
 @Consumes("multipart/form-data")
 public Response uploadFile(@MultipartForm MultipartFormDataInput form) {

    Map<String, List<InputPart>> formDataMap = form.getFormDataMap();
    String fileName = null;

    try
    {
         fileName = formDataMap.get("fileName").get(0).getBodyAsString();
         if (fileName == null) {
            throw FileNotFoundException();
         }

         String completeFilePath = "/tmp/" + fileName;
         File file = new File(completeFilePath);

        if (!file.exists())
        {
           file.createNewFile();
        }

        FileOutputStream fos = new FileOutputStream(file);
        List<InputPart> inputParts = formDataMap.get("selectedFile");
        for ( InputPart inputPart: inputParts) {
             InputStream inputStream = inputPart.getBody(InputStream.class, null);
             byte[] filedatabytes = IOUtils.toByteArray(inputStream);
             fos.write(filedatabytes);
        }

        fos.flush();
        fos.close();
    }
   catch (Exception e)
   {
       e.printStackTrace();
   }

   return Response.status(200)
         .entity("uploadFile is called, Uploaded file name : " + fileName).build();
 }

On successful submit of the form, file gets uploaded to the server. The framework sends MultipartFormDataInput as argument to the resource method, the argument will have information of filename and InputStream. We receive the form file data and copy the same to /tmp/filename.

Reference:

RESTEasy Framework - https://resteasy.github.io/index.html

Code samples - https://github.com/nagappan080810/resteasy_workbook

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Nagappan Subramanian

Nagappan is a techie-geek and a full-stack senior developer having 10+ years of experience in both front-end and back-end. He has experience on front-end web technologies like HTML, CSS, JAVASCRIPT, Angular and expert in Java and related frameworks like Spring, Struts, EJB and RESTEasy framework. He hold bachelors degree in computer science and he is very passionate in learning new technologies.

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