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A program to open jar files on a computer. How to open a .jar file? How to open jar file on computer

Hard drives
21.10.2020

The most common problem that users cannot open this file is an incorrectly assigned program. To fix this in Windows you need to right-click on the file, in the context menu, point to the "Open with" item, and select the "Select program ..." item in the drop-down menu. As a result, you will see a list of installed programs on your computer, and you can choose the appropriate one. We also recommend that you check the box next to "Use this application for all JAR files".

Another problem that our users also encounter quite often is that the JAR file is corrupted. This situation can arise in many cases. For example: the file was downloaded incompletely as a result of a server error, the file was damaged initially, etc. To fix this problem, use one of the recommendations:

  • Try to find the desired file in another source on the Internet. You may be lucky enough to find a more suitable version. Google search example: "File filetype: JAR". Just replace the word "file" with the name you want;
  • Ask to send you the original file again, it may have been damaged in transit;

The Java archive is not just a collection of classes

For most Java developers, JARs and their specialized cousins, WARs and EARs, are simply the end result of a long process of working in Ant or Maven. The standard procedure is to copy the JAR to the desired location on the server (or, less often, on the user's computer) and forget about it.

In fact, JAR files are useful for more than just storing source code. You just need to know their capabilities and how to implement these capabilities. Tips in this release Five secretshelp you get the most out of your Java archive files (and in some cases also WAR / EAR files), especially during deployment.

Because many Java developers use Spring (and because the Spring framework presents some challenges to the traditional use of JARs), some of the tips are specific to JAR files in Spring applications.

About this series of articles

Think you know everything about Java programming? In fact, most developers are just scratching the surface of the Java platform, learning enough to get the job done. In this, Ted Neward delves deeper into the functionality of the Java platform, revealing little-known facts that can help solve the most intricate programming problems.

I'll start with a quick example of a standard Java Archive file procedure that will serve as a basis for the following tips.

Saving to JAR

Typically, a JAR file is created after compiling the source code to collect Java code (which is separate from the package) into a single collection using the jar command line utility or, more commonly, the Ant jar task. The process is simple enough that I will not demonstrate it here, although we will return to the topic of JAR file construction later. For now, we just need to archive Hello, a standalone console utility that handles the incredibly useful task of printing a message to the console, as shown in Listing 1.

Listing 1. Archiving the console utility
package com.tedneward.jars; public class Hello (public static void main (String args) (System.out.println ("Howdy!");))

The Hello utility doesn't do much, but it's a useful example for exploring JAR files, starting with executing code.

1. JAR files are executable

Historically, languages \u200b\u200blike .NET and C ++ have the advantage of being OS-friendly: to launch an application, simply type its name at the command line (helloWorld.exe) or double-click the corresponding icon in the graphical user interface (GUI) shell. In Java programming, the application launcher - java - loads the JVM into the process and needs to be passed a command line argument (com.tedneward.Hello) that specifies the class whose main () method we want to run.

These additional steps make it difficult to create user-friendly Java applications. All of these elements need to be typed on the command line, which many end users try to avoid, and very often something goes wrong, and this leads to strange error messages.

You can get away with this by making the JAR file "executable" so that when it runs, the Java launcher automatically knows which class to run. To do this, simply enter the following entry in the JAR file manifest (MANIFEST.MF in the META-INF JAR archive subdirectory).

Listing 2. Specifying the entry point
Main-Class: com.tedneward.jars.Hello

A manifest is just a collection of name / value pairs. Sometimes the manifest can pick on whitespace and line returns, so the easiest way is to use Ant to create it. Listing 3 uses the manifest element of the Ant task jar to define the manifest.

Listing 3. Creating an entry point

Now, to execute the JAR file, the user just needs to enter its name on the command line using the command java -jar outapp.jar. In some GUI skins, this can also be done by double-clicking the JAR file.

2. JAR files can include dependency information

With the growing popularity of the Hello utility, it became necessary to vary its implementation. A lot of the details of this process are controlled by Dependency Injection (DI) containers such as Spring or Guice, but there is one drawback: Changing the code to include a DI container can produce results similar to Listing 4.

Listing 4. Hello, Spring world!
package com.tedneward.jars; import org.springframework.context. *; import org.springframework.context.support. *; public class Hello (public static void main (String args) (ApplicationContext appContext \u003d new FileSystemXmlApplicationContext ("./ app.xml"); ISpeak speaker \u003d (ISpeak) appContext.getBean ("speaker"); System.out.println (speaker .sayHello ());))

The launcher's -jar parameter overrides anything in the -classpath command line parameter, so when running this code, Spring must be present in the CLASSPATH and in an environment variable. Fortunately, JARs allow other JAR dependencies to be declared in the manifest that implicitly create a CLASSPATH without having to declare it, as shown in Listing 5.

Listing 5. Hello, Spring CLASSPATH!

Note that the Class-Path attribute contains a relative reference to the JAR files that the application depends on. This can be written as an absolute reference, or without a prefix at all, assuming the JAR files are in the same directory as the application JAR.

Unfortunately, the value attribute of the Class-Path Ant attribute must be on the same line as the JAR manifest cannot handle multiple Class-Path attributes. So all these dependencies must be on the same line in the manifest file. It's ugly of course, but being able to write java -jar outapp.jar is worth it!

3. JAR files can be referenced implicitly

When there are several different command line utilities (or other applications) that use the Spring framework, it is convenient to put the Spring JARs in a shared folder through which you can link to all of these utilities. This will avoid having to deal with multiple copies of JAR files scattered throughout the file system. By default, this location is the usual location of the Java runtime for JAR files, the so-called. The "extension directory", which is located in the lib / ext subdirectory of the JRE installation directory.

The location of the JRE can be changed, but this is rarely done, so it is safe for a given Java environment to assume that lib / ext is a safe place to store JAR files and that they will be implicitly present in the CLASSPATH of the Java environment.

4. Java 6 allows wildcards on the classpath

To avoid cumbersome CLASSPATH environment variables (which Java developers should have abandoned many years ago) and / or command line parameters -classpath, Java 6 introduced the concept wildcard classpath... Instead of running every JAR file explicitly specified in an argument, classpath wildcards let you write lib / *, and all JAR files listed in that directory will be included in the classpath (not recursively).

Unfortunately, classpath wildcards are not supported in the Class-Path attribute entry in the manifest discussed above. But they make it easier to run Java applications (including servers) for tasks such as working with code generation or analysis tools.

5. JAR files contain more than code

Spring, like many other parts of the Java ecosystem, depends on a configuration file that defines the organization of the environment. Namely, Spring relies on an app.xml file in the same directory as the JAR file - but developers often forget to copy the configuration file along with the JAR file.

Some configuration files are edited by the system administrator, but a significant number of them (for example, the composition of the Hibernate library) are outside of his control, which leads to errors during deployment. A smart solution is to package the config file along with the code - and that's doable because the JAR is basically a ZIP disguised. Just when building the JAR, include the configuration files in the Ant task or command line jar.

JAR files can contain not only configuration files, but other types of files as well. For example, if my SpeakEnglish component were to access a properties file, I would do it something like the one shown in Listing 6.

Listing 6. Arbitrary response
package com.tedneward.jars; import java.util. *; public class SpeakEnglish implements ISpeak (Properties responses \u003d new Properties (); Random random \u003d new Random (); public String sayHello () (// Select an arbitrary response int which \u003d random.nextInt (5); return responses.getProperty ("response . "+ which);))

Placing responses.properties in a JAR file means there are one fewer files to worry about when deploying along with the JAR files. To do this, simply include the responses.properties file when the JAR is generated.

However, how do I get those properties that are stored in the JAR file back? If the data you want resides within the same JAR file as in the previous example, you don't have to try to remember the location of that JAR file and open it with a JarFile object. Instead, let the ClassLoader of this class find it as a "resource" in the JAR file using the ClassLoader getResourceAsStream () method, as shown in Listing 7.

Listing 7. ClassLoader finds a resource
package com.tedneward.jars; import java.util. *; public class SpeakEnglish implements ISpeak (Properties responses \u003d new Properties (); // ... public SpeakEnglish () (try (ClassLoader myCL \u003d SpeakEnglish.class.getClassLoader (); responses.load (myCL.getResourceAsStream ("com / tedneward / jars / responses.properties "));) catch (Exception x) (x.printStackTrace ();)) // ...)

This procedure works with resources of any kind: configuration files, audio files, graphics files, etc. Almost any type of file can be put in a JAR received as an InputStream (via the ClassLoader) and used in any way.

Conclusion

This article uncovers five secrets of JAR files that are usually hidden from most Java developers - at least based on history and life stories. Note that all of the advice regarding JAR files is also true for WAR files. Some of them (in particular the Class-Path and Main-Class attributes) are not so useful in the case of WAR files, because the servlet framework itself collects all the contents of the directory and has a predefined entry point. Taken together, however, these tips take us beyond the "Let's start by copying everything into this directory ..." paradigm, while also greatly simplifying the process of deploying Java applications.

The next article in this series is Five Secrets to Monitoring Java Application Performance.

Java applications and games for mobile phones are still finding their users, although they are gradually being replaced by products developed for the popular Android or iOS operating systems. Java midlets have the JAR or JAD extension and are designed primarily to run from a phone. However, it is not uncommon for users to need to run the jar file first on their computer. And for this there are several utilities that perform the function of J2ME emulation (Java 2 Mobile Edition, a special modification of the Java language (Java), adapted for mobile phones) and launching java midlets.

We note right away that some emulators require a Java virtual machine installed on the system. To install it, download the Java SE JRE for Windows.

In the simplest case, you only need to click on the JAR file to see the output of the Java script. For example, so we will see a small application Minesweeper (Auth. Kenzhebekov Marat), made in the form:

Every major mobile phone manufacturer has its own developer kits (SDKs), which usually include emulators. But today we will look at universal emulators that allow you to run any jar files on your computer.

MidpX Java Application Emulator

The MidpX emulator allows you to quickly launch a JAD or JAR file on your computer with just one click. It can be a java game or any application for a mobile phone. Internet Explorer users can use the context menu and select the item Link MidpX.

For the rest of the users who prefer other browsers, it is better to first download the jar file, and then select the item in the Explorer context menu Open With - Midp2Exe Compiler.

After receiving the file, MidpX generates an executable EXE file and automatically runs it. The result of executing the exe-file, originally a JAR file, we see in the window with the image of a cell phone. To control an application or a game, there are standard keys available in any mobile phone. Although the program allows you to use the control keys of a normal computer keyboard or the number keys on the side keyboard to control the application. There are also buttons for stopping, restarting or starting the application. You can check the frame rate in the status bar. MidpX settings will help you change brightness and contrast, change transparency and volume of music.

By the way, the generated EXE file is saved by the program in the same folder where the original JAR file is located. Note also the possibility of installing a separate utility for converting jar files to exe called MIDP2EXE, but it is not very convenient to work with it, since all operations are performed via the command line. There is also a GUIMidp2Exe.exe graphical shell. It allows you to convert jar files and entire directories, shows full information about the selected jar file and an icon, is able to generate a JAD file, runs the generated exe file for verification, extracts all the file resources, including pictures, text and sounds to the temporary Test folder in the folder with the emulator (after closing all files are deleted), saves screenshots of mobile games in JPG.

Specifications:
Interface language: Russian, English, etc.
File size: 1.9 MB
License: free
Link to the office. website: kwyshell.myweb.hinet.net/Download/MidpX/MidpX.exe

SJBoy Java Games Emulator

We position SJBoy as a game emulator. This is due to the high speed of emulation and no less good quality, which allows you to run java games without problems. SJBoy provides you with one of four phone models to choose from: two Nokia, SonyEricsson and Motorola. Depending on the selected model, the skin of the front panel of the mobile phone changes. After installation, no unnecessary manipulations with jar files are required. It is enough to select a file in the list and double-click to launch it. SJBoy will pick up the file and immediately start emulating the java application. In most cases, it will be most convenient to use the SJBoy emulator.

Management in the menu is carried out both by clicking on the drawn phone keys, and by the control and number keys of the computer keyboard. Among the useful functions, we can note the ability to create a screenshot (menu Tools - Snapshot). The picture is saved to a BMP file.

Specifications:
Interface language: English
File size: 1 Mb
License: free
Link to the office. website: files.ddvhouse.ru/soft/96_sjboyemulator.rar

How to extract data from a jar file

In some cases, users need not run the jar file, but open it to see the contents. Many people know that a jar file, although it has this extension, is actually a zip archive. Accordingly, you can view the contents of the jar file in any archiver that supports the ZIP format. We just open the jar file, select the required files and extract them from the archive. If you have a file manager Total Commander, you can rename the extension of the jar file to zip, then go into the archive and see its contents, and later extract the data.

- The extension (format) is the characters at the end of the file after the last point.
- The computer determines the type of the file precisely by the extension.
- Windows does not show file name extensions by default.
- Some characters cannot be used in the file name and extension.
- Not all formats are related to the same program.
- Below are all the programs with which you can open the JAR file.

Bandizip is a handy archiver for Windows operating systems. The program supports most of different formats and has a unique algorithm for skipping incompressible files. Bandizip integrates into the explorer context menu, which greatly facilitates the management of the program itself, because all the necessary operations, for example, creating archives or unpacking data, can be performed directly from the explorer. In addition, it has an encryption algorithm to protect the file from unwanted opening. In addition, the program has a function to set a password for a file. This password, as you know, cannot be cracked ...

Universal Extractor is a handy utility for unpacking various archives, as well as some additional file types. This program is primarily suitable for those users who create archives on a computer, but only download various archives from the Internet, and then unpack them. The Universal Extractor utility does the job well. It allows you to unpack all known archives, as well as dll, exe, mdi and other file types. In fact, the program can serve, to some extent, as a kind of program installer, since it allows you to unpack some of the installers and then run ...

HaoZip is a Chinese clone of the popular Winrar archiver, both in terms of functionality and interface as a whole. The archiver can work with all popular formats, including 7Z, ZIP, TAR, RAR, ISO, UDF, ACE, UUE, CAB, BZIP2, ARJ, JAR, LZH, RPM, Z, LZMA, NSIS, DEB, XAR, CPIO, SPLIT, WIM, IMG and others. In addition, using Haozip, you can mount ISO images and view images through the built-in viewer, which is a very useful feature for archivers. As for the interface, the Chinese developers have done a good job here. They not only copied the design and functionality from the Winrar archiver, but also added ...

WinRAR is a well-known program designed to work with archives. The utility includes a wide range of built-in capabilities. WinRAR compresses data faster than competitors, saving disk space and user time. Supports well-known archive formats and is suitable for compressing multimedia files. Automatic file format recognition, special data compression algorithm and optimal packing method are the advantages of the application. WinRAR is able to compress executable, multimedia files and libraries of object modules. The application allows you to divide archives into separate volumes and save them on different storage devices.

Peazip is a versatile and powerful graphical archiver. An excellent replacement for the paid analogue - Winrar. PeaZip supports data encryption, creating multivolume archives, working with multiple archives at the same time, exporting a job as a command line, setting filters on the contents of an archive. In addition, the archiver supports all known and even unknown archive formats including 7Z, 7Z-sfx, BZ2 / TBZ2, GZ / TGZ, PAQ / LPAQ, TAR, UPX, ZIP and others. PeaZip's interface is very primitive and at the same time full of useful features. You can use the assistant to integrate into Windows Explorer or return it back, install ...

FileOptimizer is a handy file compression application created by an independent team of programmers. This application features improved compression algorithms and high speed. The program allows you to compress files of almost all types, including archives, text formats, image formats, etc. Also, this program can work with scripts, as well as through the command line, which will be especially useful for experienced users. For novice users, everything is very simple. The program integrates into the context menu, which allows you to very quickly compress files located on any disk and in any folder.

TUGZip is a handy archiver with a clear user interface and a number of additional features. TUGZip allows you to work with almost all popular archives. However, the possibilities of the TUGZip program are not limited to this. The TUGZip utility allows you to work with optical disc images such as img, nrg, iso, etc. Also, the TUGZip program can be integrated into the context menu. But if most archivers only add a submenu to it, then the TUGZip program boasts the ability to use various scripts to automate the process of creating archives, or decompose them ...

ExtractNow is a handy program that allows you to unpack zipped files quickly enough: with just one click. This option is especially convenient for those users who regularly have to unpack a lot of files. The only drawback is that the program does not support creating archives. is exclusively an unpacker (high quality and convenient), not an archiver. To unpack the file, drag the archives into the program window and press the Extract button. Supports popular archive formats. Thus, the program can unpack all popular and most commonly used ...

Ashampoo ZIP is an archiving program that helps you compress and store the information you need. Works with a variety of formats, allowing users to send bulky documents in a compressed form. Ashampoo ZIP has a wide range of different features. Through the application, you can create, unpack and split archives. In addition, the program supports reading, recovery, encryption, and instant conversion. The list of formats supported by Ashampoo ZIP is quite impressive. In addition to creating archives, the program supports unpacking documents of more than 30 different archive formats.

IZArc is a convenient program for working with archives, featuring a clear and simple interface, as well as a number of additional features. IZArc supports a huge number of formats, including the most popular rar and zip. The unique algorithms used in the program can increase the speed of working with archives. However, the main feature of the IZArc program is that it can easily convert archives from one format to another. This is especially necessary if you need to transfer some files to another user who does not have a corresponding archiver. In addition, the IZArc program allows viewing ...

Free Opener is a fairly functional viewer of the most popular files, including Winrar archives, Microsoft Office documents, PDFs, Photoshop documents, torrent files, icons, web pages, text documents, audio and video files, graphic files including Flash, and much more. The number of files supported is over seventy. The program lacks the settings and options we are used to, with the exception of a design change. It should also be noted that there is no Russian language, but given the simplicity, do not underestimate the program. Free Opener is a versatile and very handy program for reading various types of files.

You can open file with JAR using special software abopted to do this. To open this format, download one of the proposed programs.

How to open a jar file

JAR (from the English Java ARchive) is a ZIP archive containing programs in the Java language. The JAR format belongs to the category of file archives and is actively used by popular browsers to store add-ons and themes.
JAR files can be opened on Windows, Mac OS X, Linux, Android platforms.
The Java archive was developed in 1995 by Sun Microsystems and Oracle. Traditionally, a coffee cup is used as a JAR icon. Some IDEs (Integrated Development Environment) use a glass jar image.

For mobile systems

A JAR file is also used on mobile systems. However, it contains metadata in its structure and is executable.
No special software is needed to run such a file on the device. Mobile JAR files are application installers and run automatically.

Jar openers

The extension can be opened by JAVA programs. Also, since a JAR file is an archive, any archiver is suitable for opening and unpacking it.

  1. Windows (all versions):
    • Oracle Java Runtime Environment
    • Eclipse
    • 7-Zip
    • WinRAR
    • IZArc
    • WinZIP
    • ZipZag
    • Java Development Kit
  2. Linux:
    • Eclipse
    • Java Runtime Environment
  3. Mac OS X:
    • Apple Jar Launcher
    • WinZip Mac
    • Java Runtime Environment
  4. Android:
    • File Viewer

Conversion

JAR files can be converted both online, on special conversion sites, and using programs. The most popular conversion software includes:

  • JAR / JAD to APK Online Converter:
    APK file
  • Eclipse for Linux:
    JAD
  • 7-zip:
    ZIP
  • Java Development Kit:
    JAD

Java Archive (JAR) file used by the Java Runtime Environment (JRE), a wrapper used to run Java programs. May contain extension files, application resources, and an additional declaration file (META-INF / MANIFEST). Can serve as a program library or as a standalone program that runs if the JRE is installed on the computer.

Java Archive files are compressed using compression and can be optionally signed using the jarsigner tool included with the Java SDK. JAR files can be created using the jar tool and can be accessed using the java.util.jar API from Java.