Well, we are long past the days of ActiveX controls running in Internet Explorer so my question is how does java manipulate the browser into displaying the applet on the web page?
how does java manipulate the browser into displaying the applet on the web page?
It doesn't. The user installs an NPAPI (Netscape Plugin API) plugin which tells the browser it can run Java applets. Then, when the browser sees a Java applet, it fires up the plugin.
It's worth noting that Chrome no longer supports the NPAPI on Linux, and they're scheduled to stop supporting it on Windows in September. As far as I know, officially Mozilla calls NPAPI plugins a "legacy" feature and recommends using other options, but is continuing to support them via click-to-play (at least for now)..
Java Applets consists of compiled byte-code, which is executed under
the control of a JVM. Applets may either be untrusted which limits their capabilities or may be trusted which increases their access permissions and allows them to access user data or hardware.
Java applet runs in browser using Java Plug-in technology (hereafter the "Java Plug-in"), which is included in the Java Runtime Environment (JRE), enables Java applets to run in web browsers on the desktop. The Java Plug-in provides powerful capabilities to applets in the web browser. With the Java Plug-in, applets are not run in the JVM inside the browser. Instead, they are executed in a separate process. The same JVM process can be shared between multiple applets, or applets can be placed into different processes depending on whether the existing JVMs match the applet requirements and have enough resources to execute the applet.
A web browser's JavaScript interpreter engine is single thread. The Java Plug-in is capable of managing multiple threads. The Java Plug-in creates a separate worker thread for every applet. Applets themselves may be multi-threaded.
The following figure shows the thread interactions between the JavaScript Interpreter, Java Plug-in, and an applet.
When the JavaScript interpreter is idle, the Java Plug-in executes a JavaScript to Java call on the per applet worker thread (JavaScript Interpreter Not Busy scenario).
When a Java to JavaScript call is in progress and a JavaScript to Java call is made, the latter is executed on the same thread that made the Java to JavaScript call (Round Trip scenario).
When a thread is executing a Java to JavaScript call, another thread wanting to do the same will be blocked till the first thread has received its result and is done (JavaScript Interpreter Busy scenario)
However, Java extension plugin itself is written using NPAPI plugin, the cross-browser API for plugins. Stands for, Netscape Plugin Application Programming Interface. It allowed third-party code in the form of precompiled plugins to be used by the browser to display vendor specific content seamlessly in web pages. Essentially, it lets you call the native binary code from your JavaScript code. But running NPAPI plugin, the code has the full permissions of the current user and has unrestricted access to the local machine. So all in all with NPAPI, security depends on the plugin’s good behaviour and most security considerations
are up to the plugin developer. For example, plugin instances can load
resources from different origins on request of a web page.
Architectural wise, Java needs these privileges to offer the kind of power and control it brings to the table. Java and some versions of Flash and Shockwave still use NPRuntime, and NPAPI needs to be enabled for Java to function correctly in a browser. At the same time many browsers like Chrome consider this (NPAPI plugin) as serious security vulnerability because if the plugin (that uses NPAPI) contains a vulnerability, an attacker might be able to exploit that vulnerability to install malicious software on the user's machine, also sine plugin (java or NPAPI) is exposed directly to web content, making it easier for a malicious web site to manipulate your plugin, which is why it has made it user permission controlled. Another reason why browsers are moving away from this is, NPAPI isn’t supported on mobile devices. Also there are newer problems such as jit spraying http://en.wikipedia.org/wiki/JIT_spraying
Though Chrome has officially stopped NPAPI support, As of Chrome Version 42, an additional configuration step is required to continue using NPAPI plugins. (Could only work till Sept 2015)
In your URL bar, enter:
chrome://flags/#enable-npapi
Click the Enable link for the Enable NPAPI configuration option.
Click the Relaunch button that now appears at the bottom of the configuration page.
Related
I have made and compiled a Java applet and run it using java appletviewer. It is running fine as expected. But I am not able to run it usingany web browser like chrome or internet explorer even after enabling java. I have viewed lots of pages and forums with people facing the same problem with no use. My html code is:
`<html>
<head>
<title> Calculator </title>
<!--<meta name="discription" content="MultiPurpose Calculator">
<meta name="keywords" content="standard calculator;scientific calculator;loan calculator;calculator;applet">-->
</head>
<Applet code="cal3.class" width=500 height=600>
</Applet>
</html>`
cal3 is the name of the compiled java class. Thank you in advance!!
tl;dr
Wrap your Java applet in a JNLP file to be served as a Java Web Start app.
Oracle no longer supports Java Applet technology
Oracle officially deprecated the Applet API in JEP 289 for Java 9. The appletviewer tool is also deprecated. These are not marked for deletion in the next version after Java 9, but may go away in later versions.
Browsers no longer support Java Applet
Embedding Java Applets within web browsers has proven to be an insoluble security problem. The industry has given up on trying to make this work. Ditto for Flash and Silverlight.
Google Chrome browser no longer supports the NPAPI plugin architecture, and therefore no longer supports Java Applet technology.
Microsoft Edge web browser does not support plugins such as that needed for Java Applet.
Mozilla Firefox browser dropped support for the NPAPI plugin architecture, and therefore Java Applet, in version 52 and later. See this Question on SuperUser.StackExchange.com. For older versions, Mozilla gives instructions on how to disable Java Applet.
Apple has been taking steps to phase out Java Applet support for years. This includes giving directions to disable the necessary plugin, as well as defaulting to disabling, and later omitting, the necessary plugin. Now Safari 11 has no direct support, though you might get it to work by mimicking a Microsoft Internet Explorer browser as described here.
And speaking of Microsoft Internet Explorer browsers, you might be able to get Java Applet to work. Try these instructions. I do not recommend doing so.
Java Web Start
I do not recommend using Java Applets.
Instead, learn about Java Web Start technology. You get the convenience of obtaining and launching Java apps via the web browser, but the actual app runs as a separate local app on the user’s machine rather than inside the browser.
For security, they run by default in the same kind of limited “sandbox” as Java Applets. This sandbox restricts access to the various features of the host OS and hardware. You can take measures to relax the security restrictions, as appropriate to the needs of your app.
Wrap your applet
You can even wrap an existing Java Applet in a jar file with a JNLP file to deploy as a Java Web Start app.
Oracle and the Java community continue to actively support and advance Java Web Start, including an update to the JNLP spec in 2017-09.
Your code is okay the problem is on he browser. Most browsers now days are ending support for java. Browsers don't allow and don't support java code to run, like running applets on the browser. The good old days of java code on browser has come to an end. Newer version and updates of HTML are killing java same they did with flashplayer.
Maybe Internet Explorer might be a good option in this case.
A long time ago I made an applet, when I tried to a open it few days ago in website and it says that there is a security problem and it can not open it.
I Googled it and saw that I need to register it.
I tried to register it but nothing helped.
Can you explain what could make this problem?
The applet is fine and working when I run it from eclipse.
With recent updates to Java, security is much more strict. Your applet needs to be running the same java version and have a certificate. It's a very strict system...I can't open many java applets myself.
To make it run as an exception, copy the URL that the applet is on. Then open up your Java Control Panel, go to the Security Tab, and at the bottom hit Edit Site List at the bottom. From there, hit Add and paste in your link.
That'll allow it to run as an exception.
tl;dr
Java Applets are gone. You can modify your applet to run as a local app instead.
Today you can build local GUI apps in Java using your choice of three frameworks:
Swing (now in maintenance mode)
JavaFX (actively developed, led by Oracle and Gluon)
SWT (developed by the Eclipse Foundation)
For remote apps written in pure Java but delivered to users as a web app, see Vaadin Flow.
Yes, Java Applets are dead
Oracle has deprecated Java Applet technology, having proven too difficult to integrate securely into web browsers.
All the major web browser makers (Mozilla, Apple, Google, Microsoft, etc.) have phased out support for Java Applets.
Long live Java GUI apps
See white paper by Oracle, Java Client Roadmap Update, 2020-05.
Oracle’s vision for local Java GUI apps is for the developer to deliver a "double-clickable" app bundled with its own JVM slimmed down to include only needed parts. Modern tooling includes jlink and jpackage. Oracle no longer sees Java being generally bundled with operating systems, nor generally being installed by users.
While Java Applets are dead, Swing is still maintained as a required part of every Java implementation. People continue to write Swing apps for use on a local computer. You just cannot run a Swing app within a browser any longer. If you have source code for a Swing-based Applet, you can easily modify it to run as a local Swing app.
Swing’s replacement, JavaFX, is under very active development in the open-source project OpenJFX, a subproject hosted on the OpenJDK project. Releases arrive every six months, around the same time as Java releases.
The Eclipse Foundation continues to offer Standard Widget Toolkit (SWT) as a third platform (besides Swing & JavaFX) for writing Java GUI apps on a local computer.
For an open-source implementation of Java Web Start, see OpenWebStart. Oracle has dropped support for the technology, but others continue to find it a handy way to deliver and launch local Java desktop apps.
If you want to write web apps in pure Java using a Swing/JavaFX style of coding, see Vaadin Flow. Your app executes server-side in a JVM while the user-interface is automatically rendered remotely in the web browser by way of standard web technologies (HTML, CSS, JavaScript/ECMAScript/TypeScript, Web Components).
It's my understanding that a lot of the Java VM security issues involve holes in the VM sandboxing mechanism that permit remotely sourced applications to break out and do naughty things to a client machine (not to be confused with a program someone downloads from the web and runs locally - in that case it's up to the user to make sensible choices about what to install and execute). As far as I can tell, the stock JREs available from Oracle are all hard-wired to allow the user to run code from the web. Is there some way to change this behavior? I checked the Java security settings and the 'max' setting still permits the execution of web-sourced code.
I'm asking because I'm working on a desktop application for which I'd like to take advantage of the extensive set of Apache language processing packages currently available. However, given all the security issues with Java, lots of folks are getting rid of it all together, which will hurt our ability to deploy the application to organizations with security policies that prevent Java from being installed on their computers.
So is there a pre-existing solution to this or am I going to have to hack a safer Java VM?
Any Java code that is "run from the web" is launched via the web browser. If you disable Java in the web browser, you've effectively disabled "running from the web".
Java provides instructions for disabling "Java content in the browser" for all browsers at once via the Java control panel, and for disabling it in individual browsers. Hint: This works on both Windows and Mac.
One thing that you may find useful is that the currently recommended way of distributing Java desktop applications on the Mac is to include a full JRE in the application bundle, especially since Java web browser integration is disabled by default on the Mac. This way you're not even dependent on a JRE being installed on the OS.
If only Windows had application bundles, but you may be able to do something similar on Windows. As far as I understand, Java is self-contained in the JRE folders. It's not dependent on other programs or registry entries if you're not expecting browser integration. You should be able to copy a JRE to their hard drive and launch from there.
Locally bundled JREs like this would not be integrated with the operating system, web browsers would not be aware of them, and thus they would not provide the ability to "run from the web".
It's unfortunate that customers are not able to understand this distinction and refuse to install a JRE on the system, which is harmless by itself (with browser integration disabled). Yet, if they find out that you're "installing Java" on their system, you may be out of luck.
I am trying to understand what are the use cases for using Java Web start. What are the advantages of it over a web application. Is Java web start still relevant today?
What are the advantages of Java WebStart over a web application
These two are very different approaches to implement an application:
A Web Application typically refers to an application which runs completely on the server side (keeping aside JavaScript, which executes inside the browser) and uses a web browser to visualize its user interface and handle user inputs. The main advantage of such an application is that no software needs to be installed on the client side, besides the browser (which is usually available on any system today). Sometimes this is referred to as "zero-deployment".
Java WebStart on the other hand is a deployment technology which allows to download applications and run them locally on the client. The starting point is again the everywhere-available browser (or more specifically a URL), but once clicked, the URL downloads binary components (.jar files, but also system dependent native binaries) to the local system and then they are run locally. This also requires a very low effort from deployment perspective, but at least a Java Runtime environment needs to be available locally. But still, it is much less effort to run an application than having to download a installer, launch the installer, choose an installation directory etc. Java WebStart does that for you. Additionally, it also automatically handles updates - when the url is clicked subsequently, WebStart checks if the files have changed since the last run and downloads them as necessary. Otherwise, it uses the files from a local cache.
Is Java web start still relevant today?
Yes, definitely. If you have a rich (Java) application which needs to run locally on the client, you can use WebStart to deploy it with very low effort - all you need to send to the users is a URL.
See also
https://stackoverflow.com/tags/java-web-start/info
Is it possible to use Java webstart execute .exe or dll?
Java Web Start and Web applications solve two very different problems. A Web Start program is a regular graphical application program that is downloaded to and run on the user's computer. It acts like any other downloaded program written in Java, and typically uses a toolkit like Swing for its interface. It'll need to be digitally signed and approved by the user, and the user will have to have a JRE installed on the client computer. Web Start is just a convenient way to get the jars for the application downloaded and kept up to date. Web Start is useful for applications that need quick response times, lots of computation, or to access files on the user's computer (e.g., a photo uploader).
Web applications, on the other hand, are Web sites with interactive features. Examples include everything from Google's search suggestions to Facebook to Stack Exchange. Java is a useful language to write Web applications in, with tools like Spring and Hibernate, but a Web application is just a Web site that's delivered to the user as HTML and Javascript and runs in a Web browser.
If I am getting it right from what I am reading, JavaFX 2.0 allows you to code all your logic using Java and design screens with FXML. Then, web apps run as an applet on the client side.
But:
Are all browsers and mobiles devices capable of running applets?
Is it efficient (i.e., nice user experience)?
In other words, how portable are JavaFx 2.0 web applications on the client side? Anyone has experience to share?
From How to run Applets on Android?, it seems like android is not capable of running applets.
So, it seems like JavaFX 2.0 is ok on most browsers, but not for portable devices such as smartphones.
JavaFX produces Java applets. So what I say here applies for Java applets.
Most browsers for desktop machines are Java compatible: IE, Firefox, Chrome, Safari, Opera on Windows, Mac, Linux and Solaris. For smartphones, it seems a lot more complicated. I think it must be a definitive no for iOS, Blackberry and Android. For Windows Phone, it might be possible, but probably too complicated for the mainstream user.
Efficient is a broad idea. It has advantages (performance once started, openess to the rich Java ecosystem) and drawbacks (time to startup, size, all applets running in the same JVM instance). Java 7 improves the experience, as you can read here: http://www.oracle.com/technetwork/articles/java/javaclient-484666.html
JavaFX applications can be packaged in a numerous amount of ways. They can run as applets in a web page, they can be launched through java web start, they can even be distributed as os native applications. So yes, JavaFX is as portable as portable can be. Other people in this thread has already talked about JavaFX applets, which is what governs your question. So I shall not elaborate on that. However, I feel you might have missed the fact that JavaFX clients must not only be distributed as an applet in a browser in order to talk to the back end. Indeed I would not even consider that as an alternative, judging by my own past experience of applets and how ugly they look in the context of a web page.
As an alternative to applets, you can write a JavaFX stand alone application who talks to the back end using a SOAP- or REST based web service. Internet is full of these examples. Moreover, you can have the application be launched through Java Web Start and do dependency injection to get hold of proxy objects to resources on the server. This last part is not talked about by blog posters and Oracle articles. Indeed I haven't found a standardized way of doing that. But if you package a regular Java SE application in a EAR package you can inject resources in this application's Main class and let the thread startup a new JavaFX application and forward those resources. Here is a tutorial I wrote that takes you through the entire process:
http://blog.martinandersson.com/the-enterprise-side-of-javafx-the-missing-part/