Hot to Use Server for Uploading in Java

Document Information

Preface

Role I Introduction

ane.  Overview

2.  Using the Tutorial Examples

Part Two The Web Tier

3.  Getting Started with Web Applications

4.  JavaServer Faces Technology

five.  Introduction to Facelets

6.  Expression Language

7.  Using JavaServer Faces Engineering science in Web Pages

eight.  Using Converters, Listeners, and Validators

9.  Developing with JavaServer Faces Technology

10.  JavaServer Faces Technology: Avant-garde Concepts

11.  Using Ajax with JavaServer Faces Technology

12.  Composite Components: Advanced Topics and Example

13.  Creating Custom UI Components and Other Custom Objects

14.  Configuring JavaServer Faces Applications

15.  Java Servlet Engineering

xvi.  Uploading Files with Java Servlet Engineering science

The @MultipartConfig Annotation

The getParts and getPart Methods

17.  Internationalizing and Localizing Spider web Applications

Function III Spider web Services

18.  Introduction to Spider web Services

19.  Building Web Services with JAX-WS

20.  Building RESTful Web Services with JAX-RS

21.  JAX-RS: Advanced Topics and Example

Function Four Enterprise Beans

22.  Enterprise Beans

23.  Getting Started with Enterprise Beans

24.  Running the Enterprise Bean Examples

25.  A Bulletin-Driven Bean Example

26.  Using the Embedded Enterprise Bean Container

27.  Using Asynchronous Method Invocation in Session Beans

Role 5 Contexts and Dependency Injection for the Coffee EE Platform

28.  Introduction to Contexts and Dependency Injection for the Java EE Platform

29.  Running the Bones Contexts and Dependency Injection Examples

30.  Contexts and Dependency Injection for the Java EE Platform: Avant-garde Topics

31.  Running the Advanced Contexts and Dependency Injection Examples

Function VI Persistence

32.  Introduction to the Coffee Persistence API

33.  Running the Persistence Examples

34.  The Java Persistence Query Language

35.  Using the Criteria API to Create Queries

36.  Creating and Using String-Based Criteria Queries

37.  Controlling Concurrent Access to Entity Information with Locking

38.  Using a Second-Level Cache with Coffee Persistence API Applications

Part VII Security

39.  Introduction to Security in the Java EE Platform

40.  Getting Started Securing Web Applications

41.  Getting Started Securing Enterprise Applications

42.  Java EE Security: Advanced Topics

Part Viii Coffee EE Supporting Technologies

43.  Introduction to Java EE Supporting Technologies

44.  Transactions

45.  Resources and Resource Adapters

46.  The Resource Adapter Example

47.  Java Message Service Concepts

48.  Coffee Bulletin Service Examples

49.  Bean Validation: Advanced Topics

50.  Using Coffee EE Interceptors

Part Ix Case Studies

51.  Duke's Bookstore Case Study Instance

52.  Duke's Tutoring Case Written report Example

53.  Duke'south Forest Case Study Example

Index

The fileupload Example Application

The fileupload example illustrates how to implement and utilise the file upload feature.

The Knuckles's Forest case written report provides a more circuitous example that uploads an paradigm file and stores its content in a database.

Architecture of the fileupload Example Application

The fileupload example awarding consists of a single servlet and an HTML class that makes a file upload request to the servlet.

This example includes a very simple HTML form with two fields, File and Destination. The input type, file, enables a user to browse the local file system to select the file. When the file is selected, it is sent to the server as a role of a Post request. During this process two mandatory restrictions are practical to the grade with input type file:

• The enctype attribute must be prepare to a value of multipart/form-data.

• Its method must be Postal service.

When the grade is specified in this manner, the entire request is sent to the server in encoded form. The servlet and then handles the request to process the incoming file data and to extract a file from the stream. The destination is the path to the location where the file will be saved on your computer. Pressing the Upload push at the bottom of the form posts the data to the servlet, which saves the file in the specified destination.

The HTML form in tut-install /examples/web/fileupload/web/index.html is equally follows:

<!DOCTYPE html> <html lang="en">     <caput>         <title>File Upload</title>         <meta http-equiv="Content-Blazon" content="text/html; charset=UTF-8">     </caput>     <trunk>         <class method="POST" action="upload" enctype="multipart/form-data" >             File:             <input type="file" proper noun="file" id="file" /> <br/>             Destination:             <input type="text" value="/tmp" proper noun="destination"/>             </br>             <input type="submit" value="Upload" proper noun="upload" id="upload" />         </form>     </body> </html>

A POST request method is used when the client needs to send data to the server every bit part of the request, such as when uploading a file or submitting a completed form. In dissimilarity, a GET request method sends a URL and headers only to the server, whereas Mail service requests too include a message body. This allows arbitrary-length data of whatsoever type to be sent to the server. A header field in the Post request normally indicates the bulletin torso's Internet media type.

When submitting a form, the browser streams the content in, combining all parts, with each part representing a field of a form. Parts are named afterward the input elements and are separated from each other with cord delimiters named boundary.

This is what submitted data from the fileupload form looks like, afterward selecting sample.txt as the file that will be uploaded to the tmp directory on the local file system:

POST /fileupload/upload HTTP/1.ane Host: localhost:8080 Content-Type: multipart/form-data;  boundary=---------------------------263081694432439 Content-Length: 441 -----------------------------263081694432439 Content-Disposition: grade-data; proper name="file"; filename="sample.txt" Content-Type: text/patently  Data from sample file -----------------------------263081694432439 Content-Disposition: form-data; name="destination"  /tmp -----------------------------263081694432439 Content-Disposition: form-data; proper noun="upload"  Upload -----------------------------263081694432439--

The servlet FileUploadServlet.java tin be found in the tut-install /examples/web/fileupload/src/coffee/fileupload/ directory. The servlet begins as follows:

@WebServlet(name = "FileUploadServlet", urlPatterns = {"/upload"}) @MultipartConfig public course FileUploadServlet extends HttpServlet {      individual last static Logger LOGGER =              Logger.getLogger(FileUploadServlet.class.getCanonicalName());

The @WebServlet annotation uses the urlPatterns holding to define servlet mappings.

The @MultipartConfig annotation indicates that the servlet expects requests to made using the multipart/grade-information MIME blazon.

The processRequest method retrieves the destination and file part from the request, then calls the getFileName method to retrieve the file name from the file part. The method then creates a FileOutputStream and copies the file to the specified destination. The mistake-treatment section of the method catches and handles some of the most common reasons why a file would non be constitute. The processRequest and getFileName methods look similar this:

protected void processRequest(HttpServletRequest request,         HttpServletResponse response)         throws ServletException, IOException {     response.setContentType("text/html;charset=UTF-viii");      // Create path components to save the file     final Cord path = request.getParameter("destination");     final Office filePart = request.getPart("file");     final String fileName = getFileName(filePart);      OutputStream out = zilch;     InputStream filecontent = null;     terminal PrintWriter writer = response.getWriter();      try {         out = new FileOutputStream(new File(path + File.separator                 + fileName));         filecontent = filePart.getInputStream();          int read = 0;         final byte[] bytes = new byte[1024];          while ((read = filecontent.read(bytes)) != -1) {             out.write(bytes, 0, read);         }         author.println("New file " + fileName + " created at " + path);         LOGGER.log(Level.INFO, "File{0}being uploaded to {1}",                  new Object[]{fileName, path});     } grab (FileNotFoundException fne) {         writer.println("You lot either did not specify a file to upload or are "                 + "trying to upload a file to a protected or nonexistent "                 + "location.");         writer.println("<br/> ERROR: " + fne.getMessage());          LOGGER.log(Level.Severe, "Bug during file upload. Fault: {0}",                  new Object[]{fne.getMessage()});     } finally {         if (out != null) {             out.close();         }         if (filecontent != null) {             filecontent.close();         }         if (author != null) {             writer.close();         }     } }  private String getFileName(final Part role) {     last String partHeader = part.getHeader("content-disposition");     LOGGER.log(Level.INFO, "Part Header = {0}", partHeader);     for (Cord content : function.getHeader("content-disposition").divide(";")) {         if (content.trim().startsWith("filename")) {             return content.substring(                     content.indexOf('=') + 1).trim().replace("\"", "");         }     }     return nada; }

Running the fileupload Case

You can use either NetBeans IDE or Ant to build, package, deploy, and run the fileupload example.

To Build, Package, and Deploy the fileupload Example Using NetBeans IDE

1. From the File menu, cull Open Projection.
2. In the Open Project dialog, navigate to:

                                               tut-install                      /examples/spider web/                    

3. Select the fileupload binder.
4. Select the Open up as Main Project checkbox.
5. Click Open Project.
6. In the Projects tab, right-click fileupload and select Deploy.

To Build, Package, and Deploy the fileupload Instance Using Pismire

1. In a concluding window, go to:

                                               tut-install                      /examples/web/fileupload/                    

2. Type the post-obit command:

                                                 ant                                          

3. Blazon the post-obit command:

                                                 pismire deploy                                          

To Run the fileupload Example

1. In a web browser, type the following URL:

                                                 http://localhost:8080/fileupload/                                          

   The File Upload folio opens.

2. Click Scan to brandish a file browser window.
3. Select a file to upload and click Open.

   The proper name of the file you lot selected is displayed in the File field. If you lot do not select a file, an exception will be thrown.

4. In the Destination field, blazon a directory proper noun.

   The directory must have already been created and must likewise exist writable. If you lot do non enter a directory name, or if you enter the proper name of a nonexistent or protected directory, an exception will exist thrown.

5. Click Upload to upload the file yous selected to the directory you specified in the Destination field.

   A message reports that the file was created in the directory you lot specified.

6. Go to the directory you specified in the Destination field and verify that the uploaded file is present.

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Source: https://docs.oracle.com/javaee/6/tutorial/doc/glraq.html

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