I have a little java project which is build in gradle. I imported the project to eclipse. The gradle task run starts the server and run the application in localhost(using Tomcat). Problem is, how to refresh my .java data instead of re-run the application always again. This takes time. I can change my .jsp files in build directory and after page refreshing data changes. But problem is .java files. In gradle there are task install which compile the whole project(shows errors if have), but the page content doesnt change, so i have to run project again to see the changes.
I have .class-es in 2 places. In build directory and exploded/WEB-INF. IMO, if application runs, it is using build directory files, but i dont know what files are in WEB-INF directory...
Redeployment has always been a great time consumer. There are a couple of tools(some comercial) that will help you, like JRebel. If you want to use Netbeans, there is a deploy on save option too. I don't know any other options, I'm sure there are a few more, but anyway, this should be a good start.
The easiest way is to start your application with debugger flags, then every time you update and compile your source code, the JVM will pick-up a new version automatically, without redeployment, it is called "hot-swapping".
You will need to add something similar to your run task:
-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5005
Then attach Eclipse debugger to localhost:5005 and you will be good to go. It will not work if you are changing method signatures, add new class attributes or constants. Apply your changes within existing methods, then once everything works as expected, refactor and restart.
More information on debugging with Eclipse: Debugging With Eclipse Platform
Related
I have a Maven project. After I make changes to the project, I package the project up into an Uber Jar file and upload that to my backups. I am wondering, if my computer were to break or I lose all the code to the project, can I get the project back using only the Uber Jar file or would the project be gone forever?
How can I open this Jar file as a project and view all the Java code inside of it?
It would be entirely gone; that jar file contains only class files, not your source files, and you can't 'recover' source files from class files (you can decompile them which is mostly useless for this purpose; all comments, most names, most structure - all gone. You can't feasibly continue your project with this).
As it isn't in there, it's not possible to 'open a jar file and see all java code inside it'.
You'll need to set up backups.
The proper way forward is to first set up version control; this ensures that you don't just have a backup of the latest state of your source files, but every state of it - you can travel back to any time. Protects against code you deleted by accident, and means you can freely remove code you think you no longer need without that nagging feeling of: Yeah but what if.... maybe later? - so stop commenting out stuff you don't need, just get rid of it. It also means if there's a bug, you can time travel to the exact point in time when you added the line, and you can review the changes made by others in a project (presumably you're writing this on your own for now, but at some point you'll work with more people than just yourself!)
Read up on git which is the version control system that 80%+ or so of the community uses, probably best not to spring for exotic options if you aren't familiar. There are a billion tutorials out there to find if you search the web.
Host your git on a site like github or bitbucket which therefore also takes care of backups. Alternatively, host it on your own server (it's not complicated; git is open source). If you can't do that either, just let git write to a local directory and then use e.g. backblaze or something similar to ensure that file is backed up.
Yes, you can view your code by using a decompiler. I have experience mostly with IntelliJ, and this IDE includes a decompiler of its own. In case you lose everything and have only the jar file. You can use this included decompiler to get your source back from your .class files. But instructions on doing that are a story for another question...
If you want to secure your code use GIT. A version control tool that is a must when it comes to programming. Google about it and after a few days of playing around with it, you will never worry about such things.
Right-click on your project.
Select Build Path.
Click on Configure Build Path.
Click on Libraries, select Modulepath and select Add External JARs.
Select the jar file from the required folder.
Click and Apply and Ok.
I have no idea why, but from today Eclipse doesn't compile .java files into .class. I press the "Run" button and Eclipse only tries to run the program rather then compiles it first, so i get this error all the time:
Exception in thread "main" java.lang.NoClassDefFoundError
open problems view from window -> show view -> problems, if there's any error, fix it
eclipse will reject to compile if there is any problems in your project
Close Project -> Open Project -> Clean -> Refresh
Hope it helps for someone else
This problem happens when "for some reasons" your project is corrupted and has a red icon near the project's name in Eclipse. The solution is to save the project's folder, delete the project in Eclipse, than create the project again in Eclipse coping all the previous files saved.
I ran into this problem with Eclipse Luna, for some reason the Java builder was missing from the project. Verify that in your .project file you have something like
<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
You can also configure builders from Project Properties -> Builders
When I have had this exact same problem, its cause has always been the same and the solution has worked 100% of the time for me. It's caused by a missing jar file in the project's Java build path and it's indicated by a red exclamation point decoration on the project icon. To fix the problem, go to Project|Properties|Java Build Path, click on the Libraries tab and either remove or fix the path for all missing jar files. If your project is configured to rebuild automatically, it should start a build as soon as you apply your changes.
The eclipse needs to erase the output folder when building classes.
The folder is found on Project Properties -> Java Build Path -> Default Output Folder. It can differ from general output folder name found under Eclipse Preferences. If this output folder cannot be erased for some reason (for instance, on Windows, when a shell is opened on this location), the project is marked as corrupted (as Marco Micheli describes) and the classes then are not built.
You just need to make sure the output folder can be erased.
Yes I was facing this issue. Coz Eclipse cannot build the project for Build Path error. Check that your external jar files is not showing any error. Delete the Jar file which one is missing or which one is showing re color. delete that one. add a fresh one from the correct path or location. if all the error are gone. then in the project bin folder one class file will be created and then could not load main class error will be removed too.
there can be errors in your project, or other reasons like mentioned in above answers.
or you may be a fool like me
who moved the source code to other folder and not updated source path in project build properties. in this case it was not giving any error or class files too.
check that too.
goto
Project Properties -> Java Build Path -> Source
Add or Link new source folder location.
Do clean all projects ! This will erase all old class files, so eclipse is forced to generate them again.
Some times jars in the build path might be missing even though we are not using it. Since error is there, java files wont compile into classes.
Can check errors from problems view.
Either remove jars from build path or place the missing jars in the build path.
I had problem in eclipse for load module not found and no class file was getting created.
Solution: Go to Create New Project > Under JRE section Choose Use project Specific JRE.
Now Class files are created.
Please check if all the jars are there in your build path settings.
If any jar is missing this issue might come.
I had this problem, I tried the clean, the build manually, open, closing the project, deleting, and open, etc., nothing works, and after 4 hours I get a workaround what works for me.
Please, Make a RAR, ZIP, or copy from your entire project folder as a backup if it doesn't work and you mess around, OK, now:
Clean the Project. It cleaned all my class files from the output folder, but doesn't generate the class files after the clean with the building (but we already know that)
Delete the project (warning, make sure the Delete contents is not selected or your project will dissapear). For me it says something about that desynchronysation with code mix, and hibernate, blabla)
Close myEclipse
Restart your computer.
Open myEclipse
Import the project with the option "Projects from folder or Archive", not with the "existing projects into workspace" option.
Myeclipse start to build the class files, I don't know why, but works for me, I hope this helps somebody else.
Also ensure that there are no projects with fatal errors (projects with ! symbol over it) in the build path of the project which is not generating classes under the bin directory
Just restart your machine.
Its weird but it helps we had loads of problems this type in our company for unknown yet reason. Always restarting the machine helped.
It was normally encountered while trying to run Junit tests and it could not find a class even when the Run configuration was pointed to /bin.
I encountered a similar problem: previously compiled and running java files couldn't run anymore. Eclipse showed "couldn't find class xxxx". When I checked bin folder, the previous .class files were gone. That's why Eclipse couldn't run the files, NOT because of errors in files. I don't know why it can't just re-compile the file, and why the .class file gone missing in the first place.
But I found a solution:
Simply create a dummy java file in the same package (without doing anything just create), then run it. Then magically all previous .class files came back. And I can run those files as before.
Just Remove Your all Jars (Libraries) from the Build Path and refresh and add all jars and clean and build the project
This is probably a rare event but I declared a servlet with annotations and left off the "/" before the servlet mapping name. I spent over an hour chasing my tail, installing new servers, thinking I might even need to re-install my IDE and it was this simple error! Every time I tried to load any page from my Dynamic Web Project I got a 404 error. I could not even load a plain vanilla html page. There really needs to be better error logging with the IDE and Server interaction as there was zero indication of the error and my servlet was never called at the start of my web app. Hope this helps save someone else some frustration. Always name your servlet with a / slash like /myServlet never just myServlet.
I tried many different potential solutions: cleaning, rebuilding, removing, re importing, Update Maven Project and nothing. I still couldn't run my app from Eclipse. In my case the reason was that I was running Eclipse using openjdk-11 while my project was in Java 8. After I've reconfigured Eclipse to be ran from Java 8 everything started to work (in eclipse.ini).
-vm
/usr/lib/jvm/jdk1.8.0_202/bin
I'll explain my solution to this problem: "eclipse not compiling java files into class files". I'm using Eclipse version '2020-03 (4.15.0)'. I have a project that is dependent on a java project. For the dependent project, I was not able to export a jar file containing the compiles classes and resources. To be more precise, the exported jar file did not contain any class files. The output bin folder for the project is empty after doing a project build. In examining the console output when I tried to build all projects indicated that the build failed because the dependent project was missing. In looking at one of the log outputs, I saw something indicating that the build failed because some eclipse class was missing.
One of the things I tried was to do an eclipse update. Eclipse offered up the list of changes and I tried to apply them, but the update failed. I tried to update several times but they all failed. Looking more carefully at the offered up list of updates I noticed that one of the suggested update involved "deleting" Java Development Tools. That line had an warning indicating that the entire feature could not be deleted due to other dependencies and that only the non dependent features would be deleted. Doesn't that sound suspicious. Why was the update trying to delete Java Development Tools? My speculation is that something got deleted from the Java Development tool that was causing the build process to fail. The missing class I saw earlier also suspiciously sounds like it might be part of the Java Development Tools feature.
So what I did to solve the problem was to reinstall eclipse. I used the eclipse loader application to do the reinstall. (Note, I did not uninstall it first). After the reinstall, the dependent project was able to produce classes, and things once again worked as they should.
I certainly don't know how the eclipse release got into this compromised state, but in my situation the re-install of eclipse was the only way I could find to resolve the problem.
There would be the case : if you have opened project explorer in eclipse then it may not show you classes generated under /**/build/classes, in such case open Navigator view of that project and check build directory under the same project.
Some weeks ago at work I took over a Java-based back-end web application written using Eclipse. The nature of the application is that it cannot be adequately tested locally, and instead changes need to be tested on our testing network (which involves pushing the changes to an AWS Micro server that we connect to via SSH).
Until now, I pushed changes in the same way as my predecessor: compile the program using Eclipse's Export to Runnable JAR File option, then scp the jar to the remote server and run it. However, this process has a huge problem. While compilation takes only seconds, the jar is well over 30MB, and pushing the entire thing from the office to the remote server over our fairly ordinary internet connection takes well over 10 minutes. If I'm having a particularly bad day and, say, introduce several minor bugs to the code and then discover them one by one, I can easily end up losing an hour or more in total twiddling my thumbs while pushing the whole jar over and over for a series of one-line changes.
Clearly, a saner solution than scping the entire jar for every change would be to simply remotely pull only the changed .java files from source control, and then compile the new version entirely remotely. However, I'm quite new to Java (and indeed programming generally) and all my Java work has been on existing Eclipse projects that I've taken over partway through development. As such, I know very little about compiling Java, and I have found the tutorials about this online are mostly either opaque or completely fail to address the question of how to compile code that uses external libraries.
I will relate here what information about the project's dependencies I can find from Eclipse, and my questions are these: what do I need to copy to the remote server, and where do I need to put it, to be able to compile remotely? What tools, if any, do I need to install on the remote server to be able to compile there? And once I've got everything set up, what do I actually type at the command line to get it to compile?
Anyway, here's what I know about the dependencies and directory structure (I've anonymised our application name by calling it “bunnies”):
The application source code is located in bunnies/src
We compile to bunnies/bin/main.jar
bunnies/dependencies contains three jars of external libraries that we use.
Right-clicking on the project in Eclipse, going to the Java Build Path section, and selecting the Libraries tab, I see
the three libraries above
(appearing in the form, e.g. “json-simple-1.1.1.jar - /home/mark/workspace/bunnies/dependencies”)
a fourth jar file in another location
(“M2_REPO/com/google/guava/guava/r09/guava-r09.jar - /home/mark/.m2/repository/com/google/guava/guava/r09/guava-r09.jar”)
JRE System Library [java-6-openjdk-i386]
But there's more! We also use two libraries, mahout-core and mahout-integration, that are included as separate projects in the same workspace rather than as jar files in the dependencies folder. They appear by name on the Projects tab of the Java Build Path section of the bunnies project, and are located at /home/mark/workspace/mahout-core and /home/mark/workspace/mahout-integration respectively.
Since I am not a Java whiz, perhaps there are also some other hidden dependencies I'm missing, that don't appear in any of the places I've looked so far?
If anyone can walk me through the steps of compiling this huge mess from the command line, without needing to use the Export option in Eclipse, so that I can ultimately compile it all remotely, I would be highly appreciative.
Look into Apache Ant. It's a build-suite for Java, sort of like an XML based Makefile system.
I have a Java system running on a remote server. I have a directory structure separated into /src and /build. I then just scp the .java files from my local machine to the /src folder and build using ant.
Alright, so I have a web service that was created using an eclipse dynamic web project. It is currently shared on a CVS repository, but the versioning system used is irrelevant. At the moment, I have literally NEVER been able to pull this project out as is and get it working. It leads to countless errors that cannot be fixed. Every time I need to work on this webservice in a new machine I have to create an entirely new dynamic project, copy over the source files, add all the necessary libraries and make the deployment assembly work correctly again. After finally making it run I share the project as the same one, stop after a second, and then synchronize again (in a way tricking eclipse into thinking this was the shared project all along).
I feel like others must have run into this problem and found a way around it. So if you have a web service or any dynamic web project, what files do you share, and how do you successfully pull it from the repository and get it to run on another machine besides what I currently do now?
Your help is much appreciated,
-Asaf
Edit: After reading some of the responses I feel that this question is actually more specific to those who use WTP to create/test their web services. Just wanted to add the clarification.
Edit2: Let me also clarify that the other 20 or so projects not using WTP are shared just fine. I am able to pull and run them with no problem. Only web service projects are an issue.
In general, you want to check in everything that's not "derived" (generated or compiled - that's usually the contents of the bin directory or other place where your code is compiled/built into). For Eclipse Java projects, you want to include the .project, .classpath, .settings, and any other similar files that Web Tools might create for Dynamic Web projects. The Eclipse CVS client will ignore files marked as Derived so you shouldn't have to worry to much about it.
Without more detail about what kind of problems you've run into, it's not possible to guess what was causing them. My only guess is that perhaps you had different versions of Eclipse and/or the WTP (Web Tools Platform) plugins installed on the different machine. That's just a wild guess, but could explain some incompatibility when you check out the project from CVS.
Bottom line, checking in those .* files is the long recommended approach from Eclipse gurus. Maven can kind of change things, but you didn't mention it so I'm assuming you aren't using it.
I am primarily sharing my experience, may be you can find some help.
Conceptually speaking, the files which the IDE can generate itself while creating new project should not be pushed. I.e the IDE specific files should not be pushed. And everything which the IDE cannot generate on its own must be pushed.
Forexample in case of eclipse, following files should not be pushed:
.settings
build
.classpath
.project
For setting the project on new machine, first pull the files from server, and then create a project from IDE using pulled files.
EDIT: If your project has external jars/libraries, then you will have to add to the classpath manually. You could also push .classpath but that might give errors while creating a new project.
I think it's easiest to use a build system and let the IDE generate the project from your build system.
Eclipse, Netbeans, and Intellij are all pretty good at building projects from maven or ant build files. With this solution you have a simple build that is easy to setup in CI (Hudson, Bamboo, whatever) and you don't have any IDE specific files checked in. If my workspace is totally different than yours, with different versions, plugins, whatever, I'm not stuck with your project file and you're not stuck with mine. My IDE creates the project appropriate for my environment and your IDE does the same for yours.
Since you mentioned having to manually add libraries, I assume you are not using any build manager (like, maven or ant) besides ecplise.
For ecplise to handle the project properly you need the source files (*.java) in their respective directories, any resources bundled with the web service (e.g. services.xml), the ".project", ".classpath", ".settings", etc. files for eclipse. This should be enough for eclipse to generate anything else necessary to build the project.
Any files/directories that are generated by eclipse during the build process (e.g. target & bin directory, *.class, *.war) should not be checked in -- they will be generated when needed during the build.
I am thinking that, since you are adding the necessary 3rd-party jars manually, these libraries might reside in a different path between computers (e.g. if the path contains the username, it will not be transferable to another computer for a different user). To fix that you can set up the classpath using an eclipse classpath variable. In Preferences->Java->Build Path->Classpath Variables set up a varable linked to the "root" folder where the 3rd party jars a stored. Then add the libraries to the project using this new variable, not their full path. To make it work on someone else's computer, you would only need to set this classpath variable to have the build path point to the correct libraries.
It might be beneficial if you migrated your project from eclipse only to a build manager (e.g. maven) that takes care of many of these issues for you. Eclipse can build a project from the configuration of the build manager, making it easier to manage the project.
You know how Eclipse reloads classes automatically running in Tomcat when resource files they depend on such as spring context files are updated so that you don't have to re-start Tomcat? How do I make a class dependent on a resource file so that Eclipse re-publishes it when the resource file changes? Eclipse would re-publish Spring classes when their dependent resource files are updated, but would not re-publish mine.
I'm not sure if it's Spring that's doing this for you. Are you developing in an IDE like Eclipse or Netbeans? What might be happening is as you make code changes your IDE is 'publishing' (i.e. re-deploying) your app code, so the app re-initializes every time the IDE publishes it, giving the illusion that Spring is reloading context files as they change.
This is useful with a small app but get's very annoying the larger your app gets.
If you're looking for this behavior for development, take a look at JRebel:
http://www.zeroturnaround.com/jrebel/
You say that you want the class to be republished ? Do you mean that you want the contents of the bean in the application context to be updated ? If that's the case, then what you can do is the following :
1) Write a file system monitor to monitor the resource(s) for changes. There's an example on google code
2) Have that file system monitor fire a custom Spring ApplicationEvent whenever the file / resource changes, providing that event the information for the resource, if necessary. ie the file name, the previous modified time, the last modified time, etc.
3) Have the bean you want to be updated implement ApplicationEventListener and reload the resource when it catches your file system monitor event.
A simple but working workaround can be to add an ant builder to your project. Steps to take:
read the article
here
http://help.eclipse.org/help33/index.jsp?topic=/org.eclipse.platform.doc.user/gettingStarted/qs-93_project_builder.htm
create a simple ant file, that
contain a target, which touches
(simply changes the date of
modification) the dependent classes,
but nothing else (if you need help in it, let me know). Eclipse will provide you variables inside the script. You can print them easily with task. You will see the list in console.
right click on the project, and
press properties
open "builders" tab in properties
add your ant script as a builder to
the project
restrict the set of resources this
ant builder is called for. This can
be done in "build options" tab in ant
builder options. This way your
project will be fast, and the ant
script will only run for the changes
of the property file
set the set of resources (classes depending on properties) to refresh after running the ant script in "Refresh" tab
Set your ant script target to be called for "Auto build" in "target" tab. Others like after and before clean and manual build should be empty
You may redirect log of the ant script to file if you want. Otherwise it will open console view.
move your builder to be the first in the list of builders, since it must run before java builder
This is a workaround, and should work. It will have no bad side effect, since the content of java file will not change, and it will not affect the version control system, as well as the whole thing is workspace independent, if the ant script is in your project.