Q: When I try running a Java webstart application or applet using one of Qoppa’s library jars, the application is blocked by Java Security due to an expired certificate. Can you help? A: Qoppa’s code signing certificate that was used to sign our jars expired on August 04 2016. However what matters is that the certificate […]
Category: Webstart Applications / Applets – Render, Print, Manipulate PDFs
All Qoppa’s developer knowledge base entries about Java PDF libraries and components that deal with applets.
What cipher suite is your Java applet using during connection
Q: How do I know what cypher suite is being used to run my applet? A: To debug an applet and output connection information to the console, run with the following system property: -Djavax.net.debug=all When we run our sample applets with Java 8, Java uses the following cipher suite on our server: Cipher Suite: TLS_RSA_WITH_AES_128_GCM_SHA256 […]
How can I remove a signature from a signed jar file / How can I unsign a jar?
Q: How can I unsign an existing jar file? A: Follow the steps below to remove a signature from a jar file Open the jar using WinRar or Winzip (jars are actually zip files) Go into the META-INF directory Delete all files (*.SF, *.RSA) but keep MANIFEST-MF. Open the MANIFEST.MF and Remove all entries below […]
How to view the HTML source code of an applet
Go to the applet web page for instance: https://www.qoppa.com/files/pdfprint/demo/applet.html Right-click on the white area of the HTML page and choose “View Page Source” in the context menu. Here is the page source for our applet: <HTML> <HEAD> <title>Qoppa Software – jPDFPrint Applet</title> <script src="https://java.com/js/deployJava.js"></script> </HEAD> <BODY> <font size="5"><strong> jPDFPrint – Applet</strong></font> <hr> <p>The applet below […]
Are Firefox, Google Chrome Right to Block Java Plugin?
We do not agree with Firefox or Google Chrome blocking plugins such as Java or Flash. It seems that Firefox is purposely making it difficult for users to run plugins even after the customers has agreed to enabled them. Each plugin has its vulnerabilities and in fact, the more powerful the plugin, the more vulnerabilities […]
How to resolve Firefox “Java Plugin has Crashed” Error when running applets
If you see this error when trying to run an applet in Firefox: most probably this issue is due to Firefox blocking the Java plugin because it is “outdated”. To resolve this, try the following: Update your Java Plugin to the latest version Update Firefox to the latest version Then restart Firefox and try again! […]
Applets: IE11 not seeing the latest version of Java and redirecting to Oracle
Q: We are currently upgrading all machines to IE11 and JRE 8 u66. Even though we have the latest version of Java, when we select a document to annotate it is redirecting to the Oracle home page. A: Sometimes, even after installing the latest version of Java, it will still not be recognized in Internet […]
How to Resolve Applet ClassNotFoundException – Handshake Failure – HTTPS – New Issue with Java 8 Latest Build
After a recent Java 8 update, our applets started giving us a ClassNotFoundException as though they could not find the main jar for the applet in the classpath (when it is actually present). This is what we find in the Java Console: java.lang.ClassNotFoundException: qoppa.webNotes.PDFWebNotes at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown […]
Convert your applet from HTML to Webstart jnlp easily (without changing your applet code)
With browsers being more and restrictive when it comes to running applets, it is recommended to move your applet to jnlp. If you have existing applets, you do not need to change any Java line to launch with Webstart (jnlp). You can use the applet-desc tag within the jnlp file. For example, we have converted […]
How can I run Java Applets in Chrome Browser?
Chrome on Mac and Windows To run Java applets on Mac and Windows in Chrome, one has to enable NPAPI starting with Chrome Version 42 and later. Enabling NPAPI As of Chrome Version 42, an additional configuration step is required to continue using NPAPI plugins. In your URL bar, enter: chrome://flags/#enable-npapi Click the Enable link for the Enable […]
Applet not starting due to https and mixed active content
Today, as I was trying out one of our sample applets on our website, it would not start. Investigate The Issue: I use Mozilla Firefox and to investigate the issue, I clicked on the “Open menu” and clicking on Developer -> Web Console to show the Web Console. The error message I saw was “Blocked […]
How to get an affordable code signing certificate to sign jars?
Q: Where can I buy an affordable code signing certificate to sign our application jar files? A: With security levels being raised with each newly released browser and Java version, it is necessary to obtain an official recognized PKCS12 code signing certificate to sign jars in applets and desktop applications. After some research here at Qoppa, we settled […]
How to sign jars using Ant “signjar” or Java “jarsigner”
Step 1: Get a code signing certificate Read this entry in our knowledge base how to get a code signing certificate. This will explain what type of certificate you need and also where you can purchase an affordable certificate. Step 2: Sign all the jar Files Using ANT Both the applet jar file as well […]
How to save files from a Java Applet in Safari
Apple recently introduced some security settings in Safari for Java. Most browsers will allow Java applets to access the file system (to save files for instance) if the correct permissions are set on the applet and the applet is signed. In the new Safari security update however, when trying to save a file, users receive […]
Caching applets on client computers
Q: When running one of Qoppa’s PDF library or component within an applet, can the java applet be configured to be cached on the client’s PC to improve loading time? A: The applet does cache on the client computer, this is controlled by Java and the Java control panel. After launching the first time, the […]
Running jPDFNotes PDF component within an applet
Q: We would like to enable our users to annotate PDF documents “online” and deploy jPDFNotes within an applet. Can jPDFNotes run in Internet browsers such as IE6 or Firefox or Safari? What are the best practice instructions on how to configure the applet for optimal performance and minimal user-intervention? A: jPDFNotes can run in […]
Configuring webeditor, webnotes, webviewer with a config xml file
Q: How can I configure the sample applets PDFWebEditor, PDFWebNotes, PDFWebViewer that Qoppa provides as samples? A: You can configure the applets through a config.xml file by adding it to the applet parameter tag of the HTML: Config:”config.xml” The config.xml file can be used to customize any of our 3 sample applets PDFWebViewer, PDFWebNotes and […]
Signing Java Applet
Why and how can I sign my Java applet? When running as an applet, Java is restricted by what it can do. For instance, it can not open files on your local machine or send content to the printer. To get around this, you need to ‘sign’ your applet. When you sign an applet, it […]
Show Java Console to Debug an Applet
The Java Console will log the Java version, the user home directory, and any error message that occurs while running an applet. Please find instructions below to enable / show the Java Console. Windows: On Windows, you can enable the Java Console using the Java Control Panel (Method 1) or the Java icon displayed in […]
How to add the new Manifest entries to jar files required when running applets
What are the new manifest entries required for applets? Java 1.7 has recently added new security requirements when running applets. Java now requires additional entries in the manifest files of the jars that the applet use. If these entries are not present, Java will show warning dialogs raising security concerns. Starting with Java 1.7 update […]
Applet not loading using HTTPS – ClassNotFoundException
Q: We have integrated Qoppa’s java component within an applet to display and review PDF documents. Everything works fine with JRE 1.6 . But with JRE 1.7, the applet can not be loaded (“ClassNotFoundException”) when using HTTPS. Note that we have all the necessary jars in the applet class path. A: Java 1.7 has implemented more security […]
Not Recommended: Creating your own self-signing certificate in Java
Not Recommended: Creating your Self-Sign Certificate Even though this option is attractive because it is free, we do not recommend it as there are more and more warnings around self-signed certificates and your users may have to click on a few warning dialogs before being allowed to access the applet. To create a self-signing certificate, follow […]
