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How to run the JPedal PDF to Image Converter on the Azure cloud

This tutorial explains how to setup the JPedal PDF to Image Converter on the Azure Cloud service with a simple example. It will guide you through how to create a working web application. This application will let you upload a PDF file, convert each page of that file into a PNG file and then will download a zip containing those PNG’s to your computer. It will be using the JPedal-trial.jar which you candownload here.

If you are new to the Azure cloud, you may want to read the introductory article on the Java PDF blog ‘How to use the Microsoft Azure cloud on the NetBeans IDE’ before you start.

What you will need to have done before you start:

  • Completed my previous tutorial: ‘How to use the Microsoft Azure cloud on the NetBeans IDE’to set up your Azure account and create a web application instance on a Tomcat server. We will deploy a WAR file to this instance later so you need to have these steps completed before completing this tutorial. That tutorial will also show you how to set up NetBeans in order to test your application locally before you deploy it.
  • Downloaded the JPedal-trial.jar fromhere

Create a new project

First lets create a Web application in NetBeans. Right click in your Projects window and select New Project. Then choose the Java Web categories Web Application project. Click Next and give the project a meaningful name like PDF2ImageConverter.

1

On the Server and Settings screen you should select your Tomcatserver that you created in the previous tutorial. Java EE should be set to version 7. Select Finish.

ServerAndSettings

You should get a project that’s structure resembles this:

2.ProjectStructure

At this point you can run your application to ensure it is set up and will correctly deploy. You can do this by right clicking the top-most node of your project and clicking Run.

Create index.jsp

Index.jsp lives in the Web Pages directory, which is where files should be placed if you want clients to be able to access them via their web browsers. Index.jsp will display a HTML form on the client’s computer, which will let you select a file and upload it to a servlet. The servlet works on the server’s machine and does all of the heavy work so that the client machine can just sit back and wait for it’s file to be converted. If you have an index.html then delete this so your index.jsp is always used as the default web page upon starting your application.
 
You also need to add a form with two elements: File and Submit. Your file should be given an ID as “pdfFile”. This is important because later on the servlet will use this ID to extract the file from the form request.
 
The form will post to a servlet called PDF2ImageConverter and we will create that in the next step.

Your index file should look like this:

You can test your applicaion locally now (just right click and select Run) and your form should appear allowing you to select a file. The convert button will return an error page though as we have not created the servlet yet.

Create the servlet / PDF2ImageConverter

At the end of this tutorial I will post the full code for this class without the majority of my comments. You can use the code as a quick reference to make sure you are on the right track.

Your servlet should be created and stored in the Source Packages directory since it is essentially a Java class. To create this right click your Source Packages directory, go to the New menu and select the Other menu item. This will open the New File wizard. Choose from the Web category a Servlet file type. Click Next,name your servlet “PDF2ImageConverter” and clickNextagain.

selectServletFileType

On the Configure Servlet and Deployment step tick Add information to deployment desciptor (web.xml). This will create a web.xml file for you in the WEB-INF directory and add your servlet mapping details to it. We will discuss more on web.xml in the next step.

addInfoToWeb

As you can see servlets have some predefined methods like doPost() and processRequest(). When the servlet receives a request via the post method it’s doPost() method is called. This method calls processRequest() and passes in the HttpServletRequest and a HttpServletResponse. We can get any data that was passed along with the HttpServletRequest e.g. a file and similarly attach data to the HttpServletResponse e.g. HTML.
 

@MultipartConfig is needed to tell the servlet to expect requests conforming to the multipart/form-data MIME type (so that requests containing a file can be retrieved).
 

This class has 3 jobs so we will make 3 methods and call them in the processRequest method. Your new ProcessRequest() should look like below. We pass the request into getFile() because we need the request in order to extract the file from it. Similarlyresponse is passed into downloadFile() because that method that will carry out the download, which will be put into the response for the client.

Modify/check web.xml

I am creating a version 2.5 web application which requires a file called web.xml. This file will hold the information the application will need in order to correctly find the servlet when the application is deployed and will let us set an URL that we will access the servlet from in the browser. It is stored in the WEB-INFfolder. You will have to make a few changes or ensure that web.xml is set up correctly for the web application.
 
You need to check your web-app version, servlet class and your servlet mapping. The servlet-class will tell your web application which package the servlet is in and the servlet-mapping will tell the browser which URL you can access the servlet at.
Your web.xml should look like this:

Copy the PDF file to a local file on the server / getFile()

In your servlet we are going to add the first method which will copy the file to the server. You should be aware that different servers have different file systems. In this example we are using a Tomcat server both locally and on the Azure cloud.

Convert the data into a PNG file / convertPdf2Image()

Before we can start this method we need to add the jar to the project library. If we don’t then we can’t use the functions and classes we need to convert the file. To add the jar, right click your project’s top most node and select Properties. Look down the category tree on the left and select Libraries. Then select the Add JAR/Folder button and navigate to your JPedal-trial.jar. Click Open and then OK.

jpedal5

We are using the simplest conversion with no options. We can use the example code fromhereto help us. This code creates a BufferedImage to hold the created PNG pages. ConvertPagesToImage() takes the byte[] and every page is converted in the for loop. ImageIO then writes the BufferedImage to the file we created earlier.

Download file onto the client’s computer / downloadFile()

We will create the downloadFile() method now. This will return a zipped folder to the client’s browser, which the browser will automatically download. We will do this by creating a byte[] from the zipped content ofthe output folder. We will carry out this functionality in another method called zipFiles().
 
ZipFiles() will create a byte[] by using a variety of InputStreams,OutputStreams and a buffer. The InputStreams are used when we want to read data in and the OutputStreams are used when we want the data to be written to another object. The buffer is used as a placeholder. We also need an int (length) which will tell the OutputStream how many bytes to read.

Create the WAR file

To create a WAR file go to your File view. Right click build.xml and go to Run Target and select dist. This will create a dist directory with a WAR file for your application.

warFile

Deploy and run application

If you have completed my earlier tutorial on How to use the Microsoft Azure cloud on the NetBeans IDEthen you will have an Azure account set up and are running a Web application on a Tomcat server. Deploying this application is the same as in the tutorial. You create a WAR file of your project and use the Kudo application to navigate your servers file system. You then drag your WAR tosite/wwwroot/bin/apache-tomcat-versionNumber/webapps (making sure you avoid the Upload and Unzip section).
 
Then go back to the Azure Portal and restart your server. Now navigate to your web application. I would have to navigate to http://myApp.azurewebsites.net/myProjectif my web application instance on Azure was called myApp and the WAR I uploaded contained a project named myProject.
 
We haven’t changed the context root in the application but if you did change it before uploading your application through Kudo then just change myProject to what your current context root is. You should see a screen similae to the image below:

jpedalConverter

Choose your file and click the convert button. Please note that large PDF sizes may cause the server to time out. If this happens you will receive a Proxy Error with the reason: Error reading from remote server. If the conversion is successful your browser should receive a download like below.

zipFileDownload

Complete PDF2ImageConverter code

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