I know there are many related questions, but after reading at least 5 of them, I still feel many questions remain unanswered.
This jar file is a generic argument parser for java programs, such that you will use less time writing arg parsers for each program, and instead use this. Although the program is well documented, a programmer like me who still has not used external .jar files, finds it odd that there is no documentation whatsoever about how I should import this(what classes etc).
So I know that I need to put the .jar file somehow in my classpath. And then probably run some additional commands when compiling my program. But how do I find out what to import from the .jar file?
Thanks in advance, and bear with me. I am an import-noob.
Importing classes
importing the classes is symply done by import package.subpackage.Classname;
Using libraries in Eclipse:
To add the .jar file to your libraries, you better use a proper IDE (interpreting your question your are using a texteditor). I recommend Eclipse.
Create a folder in your projects folder in the workspace called "lib"
(or anything that suggests it contains your libraries)
Move the .jar file inside the "lib" folder
Right click on your Java project and
select "Preferences"
Select "Java Build Path" in the appearing window (menu on the left)
Go to "Libraries" (menu on the top)
Select "Add JARS..." and select your .jar from the "lib" folder
You should now see the library listed under "Jars and class folders on the build path" Hit "Apply" and "Ok".
You need to import the classes you want to use just like any other program. If you want to know which classes you need to read the documentation or use you IDE to add the imports for you.
If you were to cut and paste the program into an IDE it would be able to work out the imports for you however, if you don't have an IDE you need to read the javadoc http://www.martiansoftware.com/jsap/doc/javadoc/index.html which lists the packages you need for each class.
Adding a JAR is the same for every JAR so I guess they assumed this knowledge is covered elsewhere. When writing documentation, some knowledge has to be assumed or you would have to start with step 1) turn on your computer 2) wait for it to boot up ....
Related
After developing a java app in Eclipse, I would like to deploy it by packaging it into a runnable .jar with only the minimum necessary by the main method and its dependencies.
I have several packages in my workspace I work with too, but do not need to be in the resulting .jar file.
When I try to export, it clearly says that the required libs will be there, but also the other independent packages are inside too. (With the Export option happen exactly the same)
I choose to export only the Main class of the com.project... package, but also the test.project... has been packaged.
In the project I have both com... and test... packages obviously.
How could I force it to truly package only the required ones?
Thanks in advance.
TEMPORARY ANSWER (2019-07-03):
Seems that, for now, there is no way to achieve this automatically, thus the answer from #arnonuem seems a good workaround.
If better news, please feel free to improve this thread.
Thank you all.
I would create an ANT file for this specific task. There you can freely customize which packages should be compiled into the jar and which not.
Please inspire yourself reading this example.
For a general overview what i am talking about you could take a quick look into this.
https://howtodoinjava.com/ant/ant-build-jar-file-example/
Please focus on
<javac srcdir="${src.dir}" destdir="${build.dir}" classpathref="classpath"
includes="src/path/to/TheClassToBeIncluded.java" />
For more detailed information on how to include or exclude files or packages you should refer to the documentation over here:
https://ant.apache.org/manual/Tasks/javac.html
At the bottom of this page there is a list with valid build parameters.
First of all, we have to distinguish build and export.
Build transfers .java source code into .class byte code and mostly copies other resources. While doing that it usually merges all source folders into a single bin folder.
Export runs a build (or relies on Build Automatically) and then modifies the resulting .class files and other resources. Usually it packages them into one or more .jar files.
Therefore, our solution includes two steps:
build everything that is unwanted for export into a separate folder (or more)
export from a specific folder (or more)
For step 1, refer to this answer on Stack Overflow.
In a nutshell: Go to Project Properties > Java Build Path > Source tab > Allow output folder for source folders. This enables you to configure a specific output folder for each source folder in the centered viewer.
For step 2, we need to understand that eclipse's Runnable Jar File Export relies on a Launch Configuration.
So before exporting, go to Run > Run Configurations..., select the Classpath tab, remove the default User Entries and hit Advanced.... Now you can Add Folders containing your built classes.
You might want to use separate Run Configurations for internal testing and exporting.
I have struggled with this problem on and off for years, supposing it was just me who was failing to find the right solution. Possible solutions always seem to involve detailed manual configuration e.g. configuration of the build path, or selection of the folders from which classes are exported into a jar, or learning ant, but which still requires manual configuration. The problem is that the inter-dependencies between classes (and packages) are complex - imagine drawing a network diagram from import statements. Manual configuration is time-consuming, error-prone and, I think, infeasible except in simple cases. I am a bit stunned. If there is no automatic solution for selecting necessary classes, I suppose people are regularly exporting their entire code base and that the world is full of bloated jars ... (and, incidentally, without obfuscation, the entire source code base is thereby made available through reverse engineering).
Ok the deal is, I've made a small class library (*.Jar file) to help make a more visually organized code and to help with some common tasks.
Before you tell me to go to: Tools > Preferences > Libraries.
I have done that, over and over and over again.. I also tried to manually add it to: C:\Program Files\BlueJ\lib\userlib\"jar file here"
And yes, i did restart BlueJ to load the newly added libraries.
No matter what i seem to try it won't let me import it to my project using the import command, but without it, it just won't compile.
I know i can just add the classes manually, but as the class library slowly grow, so does the effort of adding all the classes in that library.
In advance, thanks for your help and consideration.
If adding your jar file in the Preferences > Libraries tab doesn't work, you can try adding the jar to the "userlib" directory at <bluej-dir>/lib/userlib (where <bluej-dir> is the folder where BlueJ was installed).
A third option you can try is adding your jar file directly to a project by creating a +libs directory inside your project directory and copying the jar to that directory. This has the drawback that you have to manually copy the jar to each project +libs subfolder that needs your library. On the plus side, it allows you to distribute your project (library jars included) just by zipping up the root project directory.
On Windows I create directory named "+libs" on my blueJ project directory,
then add .jar to that directory, and restart blueJ ,
that´s help me, and import after that work fine
Despite the post's oldness for who stumble upon i can say with the newest version of BlueJ (actually 4.1.3) in an old Ubuntu distro(Lucid Lynx aka 10.04LTS) all work as intended per default without any hack
I want to create a runnable JAR that include referenced libraries, namely jackson, in eclipse via the export. There used to be fat jar that seemed to be the goto solution before Eclipse offered to export to runnable JAR.
From this question, the first option would be what I'm looking for. Since it is for the moment a small project, it wouldn't be a problem to always have everything together (plus it's easier for me since I'm just starting with JARs, runnables and jnlp)
When I try to launch it, there's an alert window saying there was a problem and to try to find it in the console (which I can't get to open).
If I remove any use of this referenced library everything runs perfectly (except the part that it's not doing what I want at all). The window looks the way I designed it, but no functionality without the library.
I don't even have a stack trace to help with the problem. I've created other projects without any referenced libraries and everything is fine. So I've pretty much narrowed it down.
Since I let Eclipse handle the exporting and everything, I don't suppose you need the manifest to see if it is alright. Any questions you might have, I'll provide the informations you need. It goes without saying that the project runs directly from Eclipse.
Eclipse
Version: Indigo Service Release 2
Build id: 20120216-1857
Edit following Baqueta's answer
What happens when I do that is that I get a custom RuntimeException. I'm a bit baffled here. Here's a simple explanation of my code.
I have a utility class (UtilityJSON) that uses the referenced library (jackson). The constructor of that utility class instantiate an object defined in the referenced library, let's call it mapper.
A method of UtilityJSON uses a method of 'mapper'. At this point the exception is raised. Why I'm baffled is that 'mapper' is succesfully instantiated but using its method raises an exception. If the jar couldn't find the referenced library, it probably couldn't create the object 'mapper'. But running the project from Eclipse is all fine.
Is there any way to debug when running an executable jar? Maybe echo something in the console.
Edit 2
I may have found the error. My program reads a *.txt file in a folder inside the project. When exploring the content of the jar I see that this folder was not included, thus the exception. So the question now becomes: how do I include this folder? It's in the root folder of the project.
You could try the following:
In Eclipse, go to Project->Properties.
Select 'Java Build Path' from the column on the left.
Select the 'Order and Export' tab.
Find 'jackson' in the list and make sure it's checked.
EDIT
To answer your updated question:
In Eclipse, find the *.txt file in the Package Explorer. Right-click it and select Build Path->Add to Build Path. Then follow the instructions above to make sure the file gets included in the Jar. Finally, do a clean and rebuild.
If you're ever going to add more resources, it is common practice (and makes sense!) to have a resources folder (often called 'res'). You can then add the entire folder to the build path, so that all the resources in there get included in the Jar.
Enable the java console by writing
javaws -viewer
in a terminal. Close the Cache Viewer and click the advanced tab. There open Java-Console and click "enable console".
I'm having trouble adding a .jar file I downloaded for my Java project. This is really the first time I've used eclipse, so please bear with me and for some reason (I have no clue why), I just find it somewhat confusing.
I know that in order reference different class files you simply need to create a class library and add it to the build path. From there, all which needs to be done (unless I'm misunderstanding this for whatever reason) is use the "import" keyword to import whatever .jar, .java, or .class/.interface file necessary into the project.
I've tried that with my .jar. I have it referenced in the build path (all I did was just copy the jar to the project directory, and then use the build path option to add it externally), but when ever try to call the object "Delegator", which obviously is a part of the .jar file, it won't read.
Am I missing something here? Seriously, anyone who knows the answer to this - you're relieving a mother of a headache. And before anyone asks - yes, I've searched this one to death. I've found similar questions, but nothing which quite hit what I was looking for. Either that, or I really just lack the common sense.
Right click on project->BuildPath->Libraries->Addexternaljar and then press ok and if it doesnot worked then you should go to the Order and Export tab and checked the jar you have just added in your project. It will solved your problem.
There are several possible reasons, for the question hasn't mentioned the specific failure, and where it has occurred. The following is a list of possible reasons I could think of, but this may not be exhaustive:
You can import a class, in a different package only if the class is public. The only exception is when you are using the class in the same package. If the class is an inner class marked as private, then you're well and truly out of luck. The Delegator class in question might not be public, and that's why you may be unable to use it. This issue ought to be caught by the compiler.
The directory structure within the JAR might not match your package import statements in your classes. This might not be necessary, for Eclipse ought to provide possible fixes, but it is better to verify that nevertheless. Again, the compiler should complain if this is the case.
If the issue is at runtime, then, it is most likely that the JAR is not available in the runtime classpath. You'll need to configure the Runtime configuration, to add the JAR to the runtime classpath. Refer to the Eclipse documentation on run configurations, if you need to know how to change the runtime classpath.
Note:
Exporting the build classpath entries would matter to other projects that depend on the pertinent project; unexported entries will have to be re-imported if required in other projects. This would not apply to a run configuration.
Update
Every Java application needs a main(String[] args] method to start execution. This is the entrypoint for the application. From the comment, it appears that the main method is in a different class. If so, the said class ought to be used to start the application. In Eclipse, a "Run configuration" might be used for the class that lacks this entrypoint, resulting in the described error. One can rectify this by creating a new Run configuration for the class with the said entrypoint. This may be done by one of the following:
editing the existing Run configuration to use the desired Class (the one with the main method). See the above link, in the third bullet point. Edit the value of the class to be launched.
creating a new Run configuration for the desired Class. Usually, you'll need to traverse to the desired class, and run your application (using the Alt+Shift+X+J shortcut) from the said class.
i was facing similar issue with spring jar files but then tried with different jar files and it work so I think , classes defined in jar files were private and not available outside of jar hence you were not able to access the file .
thanks ,
Raju Rathi
Right click on the project--->Build Path--->Configure Build Path...--->In left side you have to choose Java Build Path--->Libraries--->Add External JARs--->ok--->ok
Steps to add jar file in eclipse
1. right click on project
2. click on Bulid Path->configure path
3. click on java Build path
4. Click on libraries tab
5. click on add external jar tab
6. choose jar file
7 click on ok
Copy the .jar file in libs folder which you want to add in your project.
Right click on .jar file -> Add Build Path
Done.
I was about to report a but to Eclipse, but I was thinking to give this a chance here first:
If I add an external package, the application cannot find the referenced native library, except in the case specified at the below:
If my workspace consists of a single project, and I import an external package 'EX_package.jar' from a folder outside of the project folder, I can assign a folder to the native library location via:
mouse over package ->
right click ->
properties ->
Native Library ->
Enter your folder.
This does not work. In runtime the application does not load the library, System.mapLibraryName(Path) also does not work.
Further more, if I create a User Library, and add the package to it and define a folder for the native library it still does not.
If it works for you then I have a major bug since it does not work on my computer I test this in any combination I could think of, including adding the path to the windows PATH parameter, and so many other ways I can't even start to remember, nothing worked, I played with this for hours and had a colleague try to assist me, but we both came up empty.
Further more, if I have a main project that is dependent on few other projects in my workspace, and they all need to use the same 'EX_package.jar' I MUST supply a HARD COPY INTO EACH OF THEM, it will ONLY (I can't stress the ONLYNESS, I got freaked out by this) work if I have a hard copy of the package in ALL of the project folders that the main project has a dependency on, and ONLY if I configure the Native path in each of them!!
This also didn't do the trick.
please tell me there is a solution to this, this drives me nuts...
Update:
if anyone wants to try this for them selfs you can try to use JMF.jar and to refer to the native dlls, or the jmf.properties file, on my XP, I refer to the dll files and I don't need the jmf.properties file.
Thanks,
Adam Zehavi.
I missed the point that Eclipse does not export the native library.
here is a solution to what I was facing: Other answer