Related
I've been applying the solutions from other similar questions.
I was getting a image from res folder using this line:
shell.setImage(new Image(display, ClassLoader.getSystemClassLoader().getResourceAsStream("icon_128.png")));
The file is inside "res" folder in the project.
It worked perfectly until I uploaded my project to a Git repo in Bitbucket. After cloning the project and importing it, now my project crash because getResourceAsStream("icon_128.png") returns null.
It's frustrating because it works perfectly in the other project which is not versioned into G|it, but crashes only in my cloned new directory project with Git.
In both versions of the project the file is inside the "res" folder.
What could be happening with this?
git has nothing to do with it. You didn't give enough detail to be sure about what's going on, but 2 obvious problems come to mind:
[1] getResourceAsStream looks for the named file in the same place that java looks for class files: The classpath. You're running this code either from an editor, or with java on the command line (in which case you're running a jar file and a build tool added a Class-Path entry to that jar, if you use the -jar switch, or you're not, in which case you're specifying the classpath on the command line), or with a build tool (in which case it will be supplying the classpath): icon_128.png needs to be in the root of one of the entries on the classpath, and now it isn't. The fix is to, well, fix that. Maven, for example, copies all resources find in /src/main/resources into any jars it makes. Your icon_128.png should be there.
[2] This isn't the right way to do it. The right way is ClassThisCodeIsIn.class.getResourceAsStream("/icon_128.png") (note: The starting slash; it is important). Your version has various somewhat exotic fail cases which this version skips. This version will look specifically in the classpath which produced your class file, and cannot NPE; your version will fail or throw NullPointerExceptions in various cases.
NB: When you cloned and re-built, the 'build' directories were effectively wiped because you don't check those into source control. That's why it worked before and doesn't now. git isn't to blame; you, or your IDE, copied icon_128.png to the build dir, and that step needs to be repeated every time you clone your git repo. A build tool automates this step and ensures that you can just do a fresh checkout from source control, and then invoke the build tool and all will be well after it finishes.
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.
I wanted to learn Java, as recommended by most of the people I downloaded "Thinking in Java" eBook and Source Code Example Lesson files from mindviewinc.com it's download location is this http://www.mindviewinc.com/TIJ4/CodeInstructions.html
These files don't work with Eclipse IDE for some reasons. So we have to build the files using the Build.xml file included in it's source code (Honestly, I do not have any idea what does "build" means here)
I tried building myself but of no use.. It did started building but after reaching some folder it stopped and gave error to install jboss-osgi-installer-1.0.0.jar .. After downloading it, I had no idea what to do with it, so I double clicked it and it asked me the location to install and I installed it in the default location, which was C:\Users\Username/jboss-osgi-1.0.0 and when I tried C:\Program Files\Java** the installation gave error that "this directory cannot be written, please choose another directory!" but anyway I installed it in the default location and it installed..
and again when I tried to build it, it gave me the same error and asked to Install Jboss....... I'm stuck.. This is happening again and again, wasted many days and didn't even crossed 100 pages of it's pdf because of this reason. It's a good eBook though.
I'm stuck in this from months... Please some one build it and make it like a project which could be easily and send me the project file, it would be really appreciated as I can not the solution to this anywhere on search engines..
Ok here's what I did to succesfully import the sources found in the "accesss" folder of you code samples:
Download the javassist jar as per Bruce's instructions, from here:
http://repo2.maven.org/maven2/javassist/javassist/3.9.0.GA/javassist-3.9.0.GA.jar
You must create an Eclipse project for the sources that are used as dependencies for most of the examples, that's the sources in the "net" folder:
in eclipse make new java project.
select the "net" directory, copy it, then in eclipse select the "src" entry in the project you just made, right click on it and select paste.
after eclipse finishes and auto-builds, it will complain about the missing javaassist jar. Right click on the project ->properties->java build path (on the left)->libraries (on the top)-> add external jars... (on the right), browse and select the javassist jar from where you down load it.
now the "net" project should be ok in eclipse
Now let's create the project for the sources in the "access" folder:
create a new java project in eclipse
Now, because Bruce structured his classes like crap, we'll have to make the proper structure in eclipse for them. This means:
a.create a new package called "access"
go to where your the access folder is on your drive, open it, select ONLY the folders (cookie2, desser, mypackage), copy them, then return to eclipse, right click on the "access" package u just made and click paste
now go back to the access dir on your drive, select ONLY the .java files (all of them, not the dirs), copy them, the back to eclipse, click on the src entry in the access project and click paste.
The access project in elcipse will still complain about missing classes form the "net" resouce. Right click on the project in eclipse->properties->java build path->projects (on the top)-> add(on the right)-> check the net project you created earlier-> click ok twice.
Now it should be ok
I hope you got the idea on how dependencies work in eclipse with this example.
For the other parts of you code samples, create separate java projects, add the classes to the proper package (create the packages if Bruce forgot to), and if you are missing external jars, go to http://search.maven.org search and download the jars. Good luck
"This code is designed to work outside of IDEs. Because packages are not introduced until later chapters, and some of the fancier IDEs like Eclipse require all code to be in packages, if you want to use the code inside those IDEs you will have to make some adjustments" - yep, bruce eckel would say that, cause that's the kind of guy he is. He also said there's ONLY checked exceptions in java, and asked for unchecked exeptions to be added as a bonus.
Now, if your sample code has no package, aka it's in the default package, aka when you look in the .java file, right at the top there's no line saying "package what.ever.bla" then all you have to do is:
-in Eclipse create a new Java se project
- open a windows explorer, go to your .java files, select them and copy them
- then in eclipse, right click the src folder in your project and chose "paste"
The files should be added to a "default" package in your eclipse project, without any error
Here is the simplest steps that I find to create a clean Eclipse project for the TIJ4 source code:
Download the source code zip from: http://www.mindviewinc.com/TIJ4/CodeInstructions.html, and unzip it to a folder, say 'TIJ4-code';
Download the additional libraries as in the previous URL, copy tools.jar from your current JDK's lib directory, and put them into TIJ4-code/lib;
Go into the 'TIJ4-code' folder, and run 'python Eclipse.py' (you need python installed on your system). This script adds the missing "package xxx" line to those source java files which don't yet have them, so as to make Eclipse happy. It also generates the Eclipse project files, which doesn't work well for some reason (beyond my limited knowledge on Eclipse), but they aren't needed here;
Open Eclipse and create a new empty java project, say with name 'TIJ4', choose JRE version 1.5, and "create separate folders for sources and class files";
Copy TIJ4-code/lib directory to your new Eclipse project folder;
Right click on the new project and select "Build Path" >> "Configure Build Path", then go to tab "Libraries", "add jars", then select all the jars under your project's lib folder;
Go to "File >> import", choose "General >> File System", select the unzipped folder 'TIJ4-code' as your "From directory". Check the root 'TIJ4-code' in the left panel of the import window, Click on "filter types" and select the .java, so that unnecessary files of other extensions, like *.class, *.py, *.xml, etc can be ignored during the import;
The zipped folder is no longer needed after the new Eclipse project is built. I hope you find this instruction helpful, and have fun learning TIJ4.
If you want to use this code in IDE rather than Eclipse and so on, for example in Intelij Idea or any other, the best way is to compile necessary classes from the TIJ4 with Ant, but it is not easy for the beginners, although it will be a good practice for you. You should make some changes in build.xml files which exists in every directory of TIJ4. Why?
to change version of Java(now we all use Java version higher than 1.5)
to include javaassist.jar library in the "classpath"
to put all compiled files in 'bin' directory(by default without adjustments TIJ4 build.xml puts .class files in the same directory with .java files. That is not a good deal.
For example you need to import and use within IDE(I use Intelij Idea) the class named net.mindview.util.Print ( see Chapter 3):
download TIJ4 and unzip in any directory you want(for example it would be c:\eckel)
download and install AntApache (you can find detailed instructions how to do it in Google) The result is - type in your console ant -version and you should see the answer. So Ant is working.
download javaassist.jar from http://jboss-javassist.github.io/javassist/ . Unzip to any directory, take out javassist.jar and past it to c:\eckel\net
4.There is build.xml file in c:\eckel\net. Now you should make adjustments. Open it with NotePad++ or other editor.
If you don't have Java 1.5 installed on your PC, so change all 'vesion1.5' to 'vesrion1.8' or other version that you have installed.
after tag description put property name = "classpath" value="./;./javassist.jar"/>
<property name = "src_util" value="./mindview/util"/>
<property name = "src_simple" value="./mindview/simple"/>
<property name = "src_atunit" value="./mindview/atunit"/>
<property name = "destdir" value="bin"/>
Then we make targets that will complile util simple or atunit automatically
Change tag available <available
classname="javassist.bytecode.ClassFile"
classpath="${classpath}"
property="javassist"
/>
Now classpath of available = property named 'classpath'. Classpath is the path where java compiler looks for .class files because some of your .java files want them by having import statement. There won't be error message "You must install the Javassist library " any more
Create targets for compiling util simple and so on See the following link with code
Code with targets
You can modify exists targets not to write all the code.
at the top of build.xml file change default="simple"
open cmd, then cd c:\eckel\net , then ant -simple or just ant (simple will run as default)
Please write if you will have some problems. Possibly i forgot mention about something.
Go to Intellij Idea, press Ctrl+Alt+Shift+S
Press +,
Library or directories
choose your c:\eckel\net\bin
5.now you can use import statement for all classes that exist in net.mindview
6.you can make the same with other dirs.
If you wish to you skip the entire Ant build process, I have converted the project to a Maven project (over JDK8), which you can simply import into your Eclipse workspace.
https://github.com/gauravojha/tij4-maven
Thanks to #Sergey Oliv's example. In addition, I needed to provide uncompiled javaassist package with all java files in the 'net' folder too. The .jar wouldn't work by itself.
I must say, this was a lot of work to get going.
As a Java/Eclipse noob coming from a Visual Studio .NET background, I'm trying to understand how to set up my run/debug environment in the Eclipse IDE so I can start stepping through code.
I have built my application with separate src and bin hierarchies for each library project, and each project has its own jar. For example, in a Windows environment, I have something like:
c:\myapp\myapp_main\src\com\mycorp\myapp\main
...and a parallel "bin" tree like this:
c:\myapp\myapp_main\bin\com\mycorp\myapp\main
Other supporting projects are, similarly:
c:\myapp\myapp_util\src\com\mycorp\myapp\util
(and a parallel "bin" tree), etc.
So, I end up with, e.g., myapp_util.jar in the ...\myapp_util\bin... path and then add that as an external archive to my myapp_main project.
I also use utilities like gluegen-rt.jar, which I add ad external dependencies to the projects requiring them.
I have been able to run outside of the Eclipse environment, by copying all my project jars, gluegen-rt DLL, etc., into a "lib" subfolder of some directory and executing something like:
java -Djava.library.path=lib
-DfullScreen=false -cp lib/gluegen-rt.jar;lib/myapp_main.jar;lib/myapp_util.jar;
com.mycorp.myapp.Main
In the IDE, however, When I first pressed F11 to debug I got a message about something like /com/sun/../glugen... not being found by the class loader.
So, to debug, or even just run, in Ecplipse, I tried setting up my VM arguments in the Galileo Debug -> (Run/Debug) Configurations to be the command line above, beginning at "-Djava.libary.path...". I've put a lib subdirectory - just like the above with all jars and the native gluegen DLL - in various places, such as beneath the folder that my main jar is built in and as a subfolder of my Ecplipse starting workspace folder, but now the debugger can't find the main class:
java.lang.NoClassDefFoundError:
com.mycorp.myapp.Main
Although the Classpath says that it is using the "default classpath", whatever that is. Bottom line, how do I assemble the constituent files of a multi-project application so that I can run or debug in Eclipse?
if you want project A to have project B (and its libs) on its classpath, then goto project A's properties, select Java Build Path, then select the Projects tab. Here you Add project B.
Although you may be generating jars for each project, eclipse doesn't pay much attention to the jars. If you are going to have lots of java projects with lots of 3rd party dependencies, you may want to look at something like m2eclipse.
The recommended way of doing things is to configure the build path. This is a nice article describing the process.
I have a sample code that was built with Netbeans.
It has a build.xml file so I downloaded ant and try to run it.
I've got this error message:
...... nbproject\build-impl.xml:76: Platform is not correctly set up
For what I can see, this is fixed by "simply" downloading Netbeans and running the sample from there, but... I don't want to install it to run a 10 files sample.
Is there a workaround to run Netbeans projects with Java? What's the correct .properties file I have to modify?
It is possible to run the NetBeans generated projects straight from Java/ANT, but you may need to manually set some of the properties and/or add paths to jar files.
Unfortunately, NetBeans tends to include taskdef's using their own JAR files and reference properties that are defined only in the /nbproject/private/private.properties files, which usually get set when you first open the NetBeans project or modified as you edit the project in the IDE.
If you inspect the build-impl.xml you should be able to find the property and derive what value needs to be set(OS platform), then either:
create/set the property in the
/nbproject/private.properties
add that property definition in the
parent build.xml
pass in the commandline when invoking your ant
target using -DPlatform=Foo
Personally, I like the structure of the NetBeans generated ANT files and targets, but hate how much custom/proprietary stuff they jam in that makes it hard to run without NetBeans.
For example:
ant -Dplatforms.JDK_1.7.home=/opt/jdk
I've just successfully built NetBeans project with ant. These were the things I had to do:
Copy <NetBeans-folder>/java2/ant to a "Netbeanless" machine
Copy nbproject/project.properties to, say, ant.properties
Replace every ${} expression in ant.properties with it's value
Add platform.<platform-name>.home=<path to platform>
Add libs.CopyLibs.classpath=<path to nb-ant>/extra/org-netbeans-modules-java-j2seproject-copylibtask.jar
Add other needed classpaths into javac.classpath (e.g. path to servlet-api.jar)
ant -propertyfile ant.properties
It works, but doesn't make me happy. I would either like to find the way to reuse project.properties, or to automatically translate it to a "resolved" version (step 3). Build could then be automated.
I just went through this exercise with my NetBeans 7.0 project. What I was able to do was copy my build.properties file from my .netbeans\7.0 directory on my Windows system and make a server.properties file for my build server. This isn't much of a stretch, since every developer's build.properties may vary, so having another file for the server is to be expected. I then put together a simple server-build.xml file that references this file and does only the basics of init, compile, dist, and clean. I committed these two files to my CVS repository at the top level of my project directory, since they don't conflict with other project files and serve as a reminder in case something needs to be updated. Now I can build my project on my CI server with "ant -f server-build.xml" and everything just works.
My whole init section looks like this, giving my server paths priority, but including the necessary information from the NetBeans project properties.
<target name="init">
<property file="server.properties"/>
<property file="nbproject/project.properties"/>
</target>
I also had to do something similar when defining the ant tasks for my nested projects:
<target name="compile">
<ant antfile="${project.MyProj-common}/build.xml" inheritall="false" target="jar">
<property location="${build.dir}" name="dist.ear.dir"/>
<property file="server.properties"/>
<property file="${project.MyProj-common}/nbproject/project.properties"/>
</ant>
...
</target>
I had to copy the j2ee.platform.classpath from project.properties to my server.properties file to ensure the references to j2ee.server.home resolved as I needed. I didn't expect to have to do this, but the classpath was wrong otherwise, causing the build to fail.
Thanks for the information on this question, as it helped guide me to this solution.
I just faced the same problem. I hope I could get rid of netbeans to go to eclipse and maven, just for that.
But here is a good link to export a ant built project from netbeans into a continuous integration server (or could be into any other IDE too).
Technique is going pretty well. Here is a summary:
install netbeans on the CI server (there is an option to do it without gui, use -silent on the netbeans installer)
include nbproject in SVN
add to ignore list the private folder
create your own private folder on CI server
make it point to a folder of your CI server (mimicking a private user folder in the account used for CI)
copy a real folder from a user to this folder and change every path (replace strings) to point to your netbeans install on your CI server.
And it should work.
Just to add to Mads' answer... usually, you need to install and open Netbeans at least once on the target machine. The ANT projects also rely on a few settings from the USERDIR/.netbeans/... directory. This may have changed with 6.5+.
This will get some of the base settings configured and define the classpath's to netbeans jars. If your dependencies (i.e. libraries) or project is being run from a different directory since the last time you opened the project in Netbeans, you will need to tweak a few settings in the private.properties file as Mads' described.
I'm using Netbeans 6.8 and java projects that were created with Netbeans can be run from the Netbeans auto generated build files with just ant on the cli. All the regular targets like ant compile,ant run,ant clean, etc "just work". (I'm using Fedora 13 if that matters)
You can use this repo just for that https://github.com/albfan/ant-netbeans
It overcomes all the oddities of netbeans wrapped ant config so you just need:
To compile:
$ ant.sh compile
To run:
$ ant.sh run
To whatever (autocompletion):
$ ant.sh <tab><tab>