Re: Java Jre 8 Archive
Christal Rasband
JAR stands for Java ARchive. It's a file format based on thepopular ZIP file format and is used for aggregating many files intoone. Although JAR can be used as a general archiving tool, theprimary motivation for its development was so that Java applets andtheir requisite components (.class files, images and sounds) can bedownloaded to a browser in a single HTTP transaction, rather thanopening a new connection for each piece. This greatly improves thespeed with which an applet can be loaded onto a web page and beginfunctioning. The JAR format also supports compression, whichreduces the size of the file and improves download time stillfurther. Additionally, individual entries in a JAR file may bedigitally signed by the applet author to authenticate theirorigin.
Th ARCHIVE attribute describes one or more JAR files containingclasses and other resources that will be "preloaded". The classesare loaded using an instance of an AppletClassLoader with the givenCODEBASE. It takes the formarchive = archiveList. The archives inarchiveList are separated by ",".
Once the archive file is identified, it is downloaded andseparated into its components. During the execution of the applet,when a new class, image or audio clip is requested by the applet,it is searched for first in the archives associated with theapplet. If the file is not found amongst the archives that weredownloaded, it is searched for on the applet's server, relative tothe CODEBASE (that is, it is searched for as in JDK1.0.2).
The Solaris 2.6 kernel has already been extended to recognizethe special "magic" number that identifies a JAR file, and toinvoke java -jar on such a JAR file as if it were a nativeSolaris executable. A application packaged in a JAR file can thusbe executed directly from the command line or by clicking an iconon the CDE desktop.
A JAR ("Java archive") file is a package file format typically used to aggregate many Java class files and associated metadata and resources (text, images, etc.) into one file for distribution.[4]
A JAR file allows Java runtimes to efficiently deploy an entire application, including its classes and their associated resources, in a single request. JAR file elements may be compressed, shortening download times.
A JAR file may contain a manifest file, that is located at META-INF/MANIFEST.MF. The entries in the manifest file describe how to use the JAR file. For instance, a Classpath entry can be used to specify other JAR files to load with the JAR.
Developers can digitally sign JAR files. In that case, the signature information becomes part of the embedded manifest file. The JAR itself is not signed, but instead every file inside the archive is listed along with its checksum; it is these checksums that are signed. Multiple entities may sign the JAR file, changing the JAR file itself with each signing, although the signed files themselves remain valid. When the Java runtime loads signed JAR files, it can validate the signatures and refuse to load classes that do not match the signature. It can also support 'sealed' packages, in which the Classloader will only permit Java classes to be loaded into the same package if they are all signed by the same entities. This prevents malicious code from being inserted into an existing package, and so gaining access to package-scoped classes and data.
An executable Java program can be packaged in a JAR file, along with any libraries the program uses. Executable JAR files have the manifest specifying the entry point class with Main-Class: myPrograms.MyClass and an explicit Class-Path (and the -cp argument is ignored). Some operating systems can run these directly when clicked. The typical invocation is java -jar foo.jar from a command line.
Native launchers can be created on most platforms. For instance, Microsoft Windows users who prefer having Windows EXE files can use tools such as JSmooth, Launch4J, WinRun4J or Nullsoft Scriptable Install System to wrap single JAR files into executables.
The manifest can contain information about the other files that are packaged in the archive. Manifest contents depend on the intended use for the JAR file. The default manifest file makes no assumptions about what information it should record about other files, so its single line contains data only about itself. It should be encoded in UTF-8.
If an application is contained in a JAR file, the Java Virtual Machine needs to know the application's entry point. An entry point is any class with a public static void main(String[] args) method. This information is provided in the manifest Main-Class header, which has the general form:
Optionally, a package within a JAR file can be sealed, which means that all classes defined in that package are archived in the same JAR file. A package might be sealed to ensure version consistency among the classes in the software or as a security measure.
The Name header's value is the package's relative pathname. Note that it ends with a '/' to distinguish it from a filename. Any headers following a Name header, without any intervening blank lines, apply to the file or package specified in the Name header. In the above example, because the Sealed header occurs after the Name: myCompany/myPackage header with no intervening blank lines, the Sealed header applies (only) to the package myCompany/myPackage.
Several manifest headers hold versioning information. One set of headers can be assigned to each package. The versioning headers appear directly beneath the Name header for the package. This example shows all the versioning headers:
A jar can be optionally marked as a multi-release jar. Using the multi-release feature allows library developers to load different code depending on the version of the Java runtime.[10] This in turn allows developers to leverage new features without sacrificing compatibility.
The Apache Ant build tool has its own package to read and write Zip and JAR archives, including support for Unix filesystem extensions. The org.apache.tools.zip package is released under the Apache Software Foundation license and is designed to be usable outside Ant.
A Java Archive, or JAR file, contains all of the various components that make up a self-contained, executable Java application, deployable Java applet or, most commonly, a Java library to which any Java Runtime Environment can link.
There are two key benefits of using a JAR file. The first is the ability to aggregate hundreds, if not thousands, of different files that make up an application. The second is the means to compress all of the contained files, greatly reducing the size of the application, and making it easier to move the JAR file over a network and between environments.
Java applications and libraries can contain hundreds of different files, including compiled Java source code, a manifest file, XML-based configuration data, JSON-based data files, images, sound clips and even security certificates. A JAR file is simply an aggregation of all of these resources into a single, compressed file.
Although optional, it is recommended that JAR files contain a manifest file named MANIFEST.MF in a folder named META-INF. This manifest file contains metadata about the JAR, including properties such as the code version, the primary author of the code and the name of the organization that maintains the code.
For an executable JAR file that contains a stand-alone application, a Main-Class attribute should exist that provides the name of the first piece of code for the Java Runtime Environment (JRE) to invoke when the application is run.
Each installation of the Java Development Kit (JDK) includes a JAR utility (named jar.sh on Unix and jar.exe on Windows) that provides a variety of helpful functions for working with JAR files, including the ability to:
To open a JAR file and extract the contents to the file system, you must use two JAR utility switches, namely, "x" to extract the contents, and "f" to specify the name of the JAR file being opened. The utility then extracts the contents to the file system.
Any Java code that has a method called "main" is considered to be a stand-alone application. For example, the code below has a main method that triggers a dialog box to pop up that says "Hello World" in it.
If this code was packaged in a JAR file, the JAR file would execute it because it contains code that can be run directly by the JRE. However, to run the executable JAR file, you don't use the JAR utility of the JDK. Instead, you use the special java.exe utility, and, thus, the name of the jar file is specified.
Can you please let me know the steps on wat software to install and where to get the necessary jar files from PI - so that I can open a *.zip - Imported archive file (which seems to include .java & .class files).
once imported you can edit the code and once done with editing save the code and then check the exporting tab in the same link pasted above to export the jar file. Now you can use that new jar file to import into ESR.
A JAR file is a compressed archive format that contains multiple Java-related files, such as class files, resources, and metadata. It allows developers to bundle Java applications, libraries, or modules into a single file for easier distribution and deployment.
JAR files can be created using the jar command-line tool provided by the java development kit (JDK). Developers can specify the files and directories to include in the JAR, along with optional manifest and security information. The resulting JAR file can then be used on any platform that supports Java.
JAR files provide a convenient way to package and distribute Java applications and libraries. They simplify the deployment process by encapsulating all the necessary files and resources into a single file. This makes it easier for developers to share their code and for users to run Java programs without worrying about missing dependencies.
Yes, JAR files can contain executable code in the form of Java class files. When a JAR file is executed, the java virtual machine (JVM) can load and run the classes contained within it. This makes JAR files a popular choice for distributing standalone Java applications or applets that can be launched directly.
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