Java Plug-in and Applet Architecture These documentation pages are no longer current. They remain available for archival purposes. Please visit for the most up-to-date documentation. Java Plug-in and Applet Architecture This document describes how the Java Plug-in controls the execution of applets and interactions between applets and the browser. The following topics are covered:.
Architecture Java Runtime Environment 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 may be placed into different processes depending on whether the existing JVMs match the applet requirements and have enough resources to execute the applet. An applet can request specific version of JRE to be used and can specify what options need to be passed to the JVM. An applet can also request to be executed in the separate JVM. The browser and the applet can still communicate with one another, however. Existing APIs have been re-engineered to use process sockets, so things continue to work as they did before, only better.
This architecture provides a number of benefits:. Applets that require different versions of the JRE can run simultaneously. Applets can specify JRE start-up parameters such as heap size. (A new applet uses an existing JRE if it's requirements are a subset of an existing JRE, otherwise, a new JRE instance is launched.);.
The message-passing interfaces are written in Java, so they run on all supported platforms, in the same way, so cross-browser compatibility is enhanced. With that architecture, a new JRE can be launched whenever it is needed. But an applet will run in an existing JRE as long as:. The JRE version required by the applet matches an existing JRE, and. The JRE's launch parameters satisfy the applet's requirements Note:. If two applets each require a large amount of memory, they might both run in the same JRE, causing one of them to run out of memory. But that's only a concern when you have multiple applets running simultaneously.
Particular versions of JRE can be marked as unavailable to the plugin by disabling them in the Java Control Panel. Java Runtime Environment Version Selection On all platforms, the Java Plug-in locates JREs to use from the entries listed in the Java Control Panel ('Java' tab, 'View' button). The available JREs in this list are encoded in the deployment.properties file whose location is platform-dependent.
On the Windows platform, it is generally located in C: Users username AppData LocalLow Sun Java Deployment. On Solaris, Linux, and Mac OS X platforms, it is generally located in /.java/deployment/deployment.properties. On Windows platforms, both the Java Control Panel and the Java Plug-in will automatically detect the installed JREs and add them to the available set. On Solaris, Linux, and Mac OS X platforms, auto-detection of installed JREs is not supported. The Java Runtime Environment Settings dialog, which is accessed by clicking View in the Java tab of the Java Control Panel, may be used to manually add JREs to the known list for the Java Plug-in. By default, the Java Plug-in will execute all applets in the latest JRE version named in this list.
It will only execute an applet on an earlier JRE version if explicitly requested. When considering a request to launch an applet on a specific JRE version (for example, a particular update release like '1.5.011'):. The list of available JREs is consulted.
If there is an exact match of the version string, that JRE version is selected. Otherwise, if there are one or more installed JREs in the same family, the latest version is selected. Otherwise, the latest available JRE on the machine is selected. The selected JRE version is compared against the security baseline for the family. (See for more information.) If it is equal to or more recent than that version, no further prompting is done and the applet is launched. Otherwise, the code for the applet is downloaded in a JVM instance of the selected JRE version. If the applet is signed and the user accepts the security dialog for the applet (or the code source has already been trusted), no further prompting is done and the applet is launched.
Otherwise, we are dealing with an unsigned applet on an 'older' JRE version. A dialog box is presented indicating that this applet is requesting to run on top of an older JRE release, and asks the user whether he or she wants to allow it to. If the user clicks 'yes', the applet is launched. If the user clicks 'no', the applet is re-launched on top of the latest available JRE version. When considering a request to launch an applet on a particular family, the most recent JRE from that family will be selected and the above steps starting from (2) will be followed. When considering a request to launch an applet on a particular family or any later family, the latest available JRE will be used to launch the applet.
Thread Considerations 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. Applets making JavaScript to Java calls and vice versa should be designed with the thread related issues in mind. The following picture shows the thread interactions between the JavaScript Interpreter, Java Plug-in and an applet (i.e.
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) In order to avoid thread related issues especially when multiple applets are running simultaneously, keep both Java to JavaScript and JavaScript to Java calls short and avoid round trips, if possible. Classloader Cache and Interaction between Applets Normally, if two applets have the same codebase and archive parameters, they will be loaded by the same class loader instance. This behavior is required for backward compatibility, and is relied on by several real-world applications. The result is that multiple applets on the same web page may access each others' static variables at the Java language level, effectively allowing the multiple applets to be written as though they comprised a single application.
While this feature enables certain kinds of applications to be conveniently written, it has certain drawbacks. It interferes with termination of applets, in particular when multiple instances of the same applet are active. It makes the programming model for applets more complex, since it is under specified exactly when the static fields of an applet will be re-initialized, and when they will be maintained from run to run of the same applet. It causes imprecise behavior of certain user interface operations within the Java Plug-in due to the inability to identify exactly which applet initiated a particular request.
For this reason, the Java Plug-in provides a way to opt out of the use of the on an applet by applet basis. Applet Garbage Collection Garbage collection occurs on an applet instance immediately after the destroy method finishes. The garbage collection applies to all memory acquired by the applet, except for static variables. Statics are preserved in the classloader cache, along with the classes themselves, for as long as the class loader is present. So when does the class loader go away?
That behavior is not specified. It's up to the implementation of the Java virtual machine and its interactions with the operating system. You can expect it be retained for as long as possible, but to be discarded when the memory is needed for other purposes. Applet Privileges All applets should be signed with a certificate from a recognized certificate authority. The user must agree to run an applet and having a valid certificate provides the user with some assurance that the applet is safe to run. An applet runs in a secure sandbox that prevents it from interacting with the users system, unless authorized.
To obtain that authorization, the applet must request permissions when it is launched and the user must agree to run the applet. Permissions are needed to:. Print. Access the file system.
Access browser cookies. Access other system resources The basic applet security model is an all or nothing proposition. An applet with permissions has full access to the user's system. Without permissions, the applet has virtually no access at all.
Deployment of applets using JNLP allows them to avail a more fine-grained security model (similar to Java Web Start applications), that gives them controlled access to a user's system, under control of the user. (For example, the ability to save or open a file selected by the user and the ability to print.) Proxy Configuration See for details. Security See for details.
Use Internet Explorer (Even on Windows 10) RELATED: Internet Explorer is Microsoft’s legacy browser, and Microsoft still supports it with security updates. Even on Windows 10, where Microsoft Edge is the default web browser, Microsoft still includes the old version of Internet Explorer 11 for compatibility purposes. This is important because Microsoft Edge, Microsoft’s modern browser, doesn’t support any -based plugins. It only supports its own built-in version of Adobe Flash. Whether you’re using Windows 7, 8, or 10, you’ll find Internet Explorer in your Start menu. On Windows 10, you’ll find it hidden under Start Windows Accessories Internet Explorer.
If you use Microsoft Edge, you can click menu Open With Internet Explorer on any web page to quickly open that web page in Internet Explorer. You probably won’t want to use Internet Explorer as your browser all the time, but you can launch it whenever you need to use a website that requires a plugin. To install these plugins, just launch IE and visit the appropriate website— or, for example. If Java doesn’t run properly, make sure the browser plugin is enabled in its control panel. You’ll find the Java control panel at Control Panel Programs Java.
On the “Security” tab, ensure “Enable Java content in the browser” is enabled. You may need to restart your browser after changing this setting. RELATED: If you have to access an old web page that doesn’t work with Internet Explorer 11 and requires an older version of Internet Explorer, you can. This requires the Professional version of Windows 10, though, and isn’t available on the Home version. Install Mozilla Firefox ESR on Windows, macOS, or Linux Mozilla ended support for traditional NPAPI browser plugins, aside from Flash, with Firefox 52 on March 7, 2017.
Java Applet Plugin Ins Downloads For Machine Dan Activex
However, Mozilla offers an “Extended Support Release”, or ESR, branch of the Firefox browser. This browser is intended for organizations to have a stable, long-term platform that only receives security updates, not the frequent feature updates and changes that the main version of Firefox receives. Was released on March 7, 2017 and includes support for non-Flash browser plugins. Mozilla will continue supporting Firefox 52 ESR with security updates until. At that point, the next ESR version of Firefox will drop support for NPAPI plugins. Visit the to download the ESR version of Firefox.
If you’re not sure which version to download, choose the 32-bit version of Firefox for maximum compatibility with older plugins. Older plugins may not have 64-bit versions available. You can verify you’re using the ESR version of Firefox by clicking menu Help About Firefox. You’ll see “Firefox ESR” here if you’re on the ESR update channel.
Java Applet Plugin Edge
Enable Plugins in Safari on macOS Apple has in Safari on macOS. Even Flash won’t play by default, and you’ll have to enable it whenever you visit a web page you want to use Flash on.
Despite these aggressive moves, Apple hasn’t removed NPAPI plugin support from Safari—at least as of macOS Sierra 10.12. Safari continues to support Java, Silverlight, Unity, and other NPAPI-based plugins. In fact, it’s the last modern browser to continue supporting these plugins.
Even if you normally use Chrome or Firefox on your Mac, you’ll need to use Safari when you want to access a web page that requires a plugin. We wouldn’t be surprised to see Apple completely drop support for plugins in a future version of macOS. But Apple hasn’t publicly announced a timeline for this.
You can use these plugins normally in Safari. You’ll just have to enable them first. To do so, install the plugin normally. For example, you can from Oracle’s website. Head to Safari Preferences Security Plug-in Settings. Enable the installed plugin you want to use.
You can enable the plugin for all websites or only for specific websites. For example, to make Safari ask you if you want to use a plugin whenever a web page you’re visiting wants it, select the plugin and then set the “When visiting other websites” option at the bottom of the window to “Ask”. Of course, the real solution is moving on from web content that requires plugins. Applications created with Java, SIlverlight, and Unity still function properly outside of the web browser. Desktop applications written in Java or Silverlight are safe and will work normally.
For delivering video to web browsers, Microsoft now recommends instead of its own Silverlight plugin. Netflix was the most famous user of Silverlight, and has dropped Silverlight for cross-platform HTML5 video. Flash is still widespread, which is why it’s been spared the axe.
It’s also integrated by default into Chrome and Edge, which helps keep it sandboxed and updated. But even Flash will likely be left behind one day.