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Servlet download pdf file example

Servlet download pdf file example

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With This Code So Far I Get Errors As The Web Host Gives Access Denied. Its a zip file I just want to leave one comment. If you download xlsx Excel file, writing codes in JSP will result in file corruption.


servlet download pdf file example

The main point is: you are making an effort to stream the file, if you have to preload all of it before, then the streaming ends up making no difference, eh? To disallow all download requests, coming from other domains, you can check if the referer header contains your domain name. For this example, I will open a PDF document.


servlet download pdf file example

Servlets - File Uploading - If the file is generated correctly on your server, you can rule out iText as the cause of the problem.

 

You compiled them using the javac command and executed them with java, resulting in one or more PDF documents. For this topic, you need to install an application server. I use Tomcat in combination with Eclipse. Eclipse will start up an instance of Tomcat, and a browser window opens inside my IDE. The window at the lower right in the foreground is Eclipse; the windows in the background are browser windows: Firefox, Google Chrome, Microsoft Internet Explorer MSIE. To get to this result, you need to integrate the five steps in the PDF creation process in a servlet. For instance, a ServletOutputStream obtained from the HttpServletRe-sponse with the getOutputStream method. This is probably the simplest iText servlet you can write. If you want to deploy it in a web application, you have to adapt the web. Note that most IDEs have a wizard that updates this XML file for you. I made my web. You can use the ANT files that come with the examples to create your own WAR file if you want to test this functionality on your own server. The screenshots in figure 9. How can you determine whether a problem is caused by the browser, by the server, or by the wrong use of iText? Always begin writing code that runs as a standalone example. Gradually add complexity until something goes wrong. Look at the stack trace in the server logs. Most of the time, the error messages will tell you exactly what to do. An easy way to find out if a problem is caused by iText or by the browser is to replace the Serv-letOutputStream in step C with a FileOutputStream for debugging reasons only. If the file is generated correctly on your server, you can rule out iText as the cause of the problem. By following this last rule, you should be able to determine whether the problem is a client-side or a server-side problem. If something goes wrong in the try block, an IOException is thrown, resulting in an internal server error. The best way to debug problems like this is by saving the stream that is sent to the browser as a file. First try opening it in Adobe Reader. Newer versions of the Adobe Reader plug-in may ignore the HTML, but older versions will complain that the file is corrupt. The question marks should be binary characters. This can happen when your server flattens all bytes with a value higher than 127. Consult your web or application server manual to find out how to make sure binary data is sent correctly to the browser. Check whether you have added all the JARs you need to the classpath of your web application. Different versions can lead to conflicts. Finally, check whether the application is compiled with the correct compiler. A file that was available for the standalone example might not be available for the web application. Normally, the exception will give you an indication where to look. Maybe the working directory of the servlet is different from what you expected. For instance, read the bytes of the resource file, and write them to the ServletInputStream. If the file generated on the server side is OK, or if none of the situations mentioned so far matches your problem, chances are that your problem is browser-related. If all users experience the same problem, the problem is caused on the server side. The viewer receives the PDF syntax, but shows it as if it were plain text. The most elegant way to solve this problem is by using a URL pattern as shown in listing 9. If this is not an option, you could add a parameter ending in. For instance, Use this solution as a last recourse. A better solution is to set the content disposition in the response header: Note that not every version of every browser deals with this header correctly. THE PDF IS CORRUPT FOR ONLY A COUPLE OF BROWSERS When no content length is specified in the header of your dynamically generated file, the browser reads blocks of bytes sent by the web server. Most browsers detect when the stream is finished and use the correct size of the dynamically generated file. Some browsers are known to have problems truncating the stream to the right size—the real size of the PDF is smaller than the size assumed by the browser. The surplus of bytes can contain gibberish, and this can cause the viewer plug-in to show an error message saying the file is corrupt. You have to specify the content length of the PDF file in the response header. Setting this header has to be done before any content is sent. Instead, you must create the PDF on your filesystem or in memory first the next listing , so you can retrieve the length, add it to the response header, and send the PDF. This is also true for some other binary file formats. These headers make sure that the end user always gets the most recent version of the PDF, and not a PDF that is loaded from the cache on the client side. This is important if the content of the PDF changes frequently, which would happen if it reports about real-time data. C solves the problem caused by old browser and PDF viewer configurations. Note that there are several serious downsides to this solution. When you need to generate large files, you risk an OutOfMemoryException on the server side, and a timeout on the client side. The second problem, avoiding a browser timeout, can be solved by moving the five steps of the PDF creation process to a separate thread. You can add your Runnable implementation as an attribute to the HttpSession object. Check the thread with every hit; serve the PDF as soon as the document is closed. Not only does this solution solve the technical timeout problem, it also works on a psychological level. People tend to be impatient. Usually, I implement the doPost method to accept parameters and to set up the thread; then I cause a redirect to trigger the doGet method that serves the HTML and eventually the finished PDF. GET VERSUS POST A trivial problem, but one that is easily overlooked, is what happens when people bookmark pages that are the result of a POST action. When they want to return to that page using the bookmark, they initiate a GET request, getting a result that differs from what they expect. You can do the experiment with the example from listing 9. This page contains two simple forms: one that uses the GET method, the other using the POST method. Recall that neither doGet nor doPost were implemented in listing 9. Instead you overrode the service method that works in both cases. If I look in my server logs, I should see one line corresponding with this hit. This is true for most browsers, but some browsers hit the server several times for every dynamically generated binary file. If you want to avoid this multiple-hit problem, you can try setting the cache parameters like this: Another way to solve the multiple-hit problem is to embed the PDF in an HTML page using the embed tag. Using the tips and tricks summed up in this section, you should be able to tackle all the problems that can occur when writing a servlet that produces a PDF document. Writing a JSP page generating a PDF is another story. Let me explain why that is a bad idea, using this working! Several things can go wrong if you ignore my advice and deploy the code from listing 9. If you think writing a PDF servlet is more difficult than writing a PDF JSP page, think again. If you copy listing 9. Although this is good practice when you write JSP that produces HTML, it can be deadly if you want to generate binary content. This has the same effect as when you would open a JPG in a text editor and insert whitespace characters in arbitrary places. Maybe a colleague will open that JSP in an IDE that automatically formats the code to make it more readable. Maybe you can use this argument if using JSP is a requirement in your project. Enough about JSP already.

servlet download pdf file example

An easy way to find out if a problem is caused by iText or by the browser is to replace the Serv-letOutputStream in servlet download pdf file example C with a FileOutputStream for debugging reasons only. You can download it from. HTML Page for Java Uploading File to Server We can upload a for to server by sending a post request to servlet and submitting the form. The servlet then handles the request to process the incoming file data and to extract a file from the stream. Mail us on hr javatpoint. After retrieving the image from the database, you can save as in a glad on your server, then in the JSP you create an image tag points to your image path. Im just trying to upload a jar file tightvnc-jviewer. You need to create a java. We will use this object in the doPost method implementation to upload file to between directory. For instance, read the bytes of the resource file, and write them to the ServletInputStream.

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