Develop Reference

Eclipse skipping breakpoints

My issue isn't a new one, and I found several threads about it, yet no one was helpful for me.
I hope this one will.
I can't debug with eclipse. It recognizes breakpoints, switches to debug view, but somehow it gets out of sync and I can't debug my code. Sometimes It works, but after a while It happens again.
I work with JDK 1.6.0_24, Glassfish 3.1, eclipse INDIGO (but it also happens on HELIOS).
I tried (as I found in this site) to set eclipse to use Parallel GC. I tried put it in the eclipse.ini file, I tried to put in the glassfish VM arguments itself, and I tried to put it at eclipse JDK additional VM arguments (preference -> installed JRE-> JDK -> etc). Nothing seem to work for me. I also tried them all together.
Help me please..
Thank you all from advance,
Ido
EDIT:
OK, I noticed few more things:
On the Debug view, in my stck trace, I found the exact class with the breakpoint is paused and it had this comment: "(Suspended breakpoint at line XX)". When I clicked the line, suddenly the green line appeared. Yet, as soon as I clicked F6 to continue, It went out of sync again, just the next line became suspended. Weird.
I checked the processes running on my computer and found that there are several "java.exe" processes running at the same time. (eclipse runs on javaw.exe). Maybe this is why glassfish and eclipse refuse to work together.
I checked the build path and found that this is my output folder: project-name/target/classes. Is this good?
Any thoughts?
Ido

So, I couldn't fix this but I found a workaround that completely solves this - FINALLY!.
I just stopped using glassfish WTP for debugging and set a remote debug to my local glassfish. it works perfectly with few minor annoying things - but breakpoints finally noticed.
Set remote debug
Go to your glassfish admin console and set your glassfish to work on debug mode.
Click on configuration --> server-config --> JVM settings, and check debug enabled check box.
Restart server
In eclipse - start server on normal mode (not debug - it is useless).
Go to Debug configurations and locate "Remote Java Application"
Create a new Remote java app debug config
Enter name (lets say Glassfish-Debug)
Choose project to debug
Enter your own IP address in the host section and set the port to 9009
This is optional but it is more comfortable to work with:
Go to "Common" tab, and check the Debug check box. This will make this Glassfish remote debugging configuration constant on your debug menu.
That's it. Now all you have to do is always start your Glassfish in normal mode and then go to Debug configurations and run This Glassfish remote debugging you just set.
And now I'm getting to the annoying part: After rebuild your project, sometimes you might get again out of sync. You just need to disconnect the remote debugging session and run it again. Small price to pay.
I hope it helps..

I had faced similar issues, But it turned out to be a simpler problem of multiple versions of JREs/JDKs installed.
Try Debug -> Run Configuration -> JRE -> Alternate JRE -> select JDK 1.6.0_24.
Also check for project build paths if correct Jars are been used.
Hope this helps.

Intellij IDEA + FTP?

I'm running Intellij IDEA 10.5 and I've set up my default ftp server (File|Settings|Deployment),
but when I'm right-clicking on my project I still see Deployment option inactive (see below):
I'm new to IDEA, so I'm sure that it is not a bug, but my misunderstanding of
how one should enable ftp deployment in IDEA.
What should I do to enable it?
Please, give me a clue to solve this problem!
This is the only remaining thing that keeps me from
using IDEA instead of Eclipse in my development.

I think you need to make sure that the path mappings are correctly entered in the "Mappings" tab of your deployment configuration.
If the mappings tab is not correctly filled out, a warning will be shown in that tab (e.g. "Deployment path is not specified").
The upload/compare/download menu entries for the deployment configuration will be greyed out as long as the mappings are not defined.
I had the same problem and it was resolved by entering the correct path mappings.

Deployment is only available in the paid ultimate edition:
http://www.jetbrains.com/idea/webhelp/deployment.html
I'll bet you're using the free community edition.

eclipse/tomcat: deploy doesn't work any more (ClassNotFoundException)

I'm running Eclipse Helios Service Release 1, with Tomcat 7.0.12 in Linux Ubuntu Natty Narwhal.
I've been happily hot re-deploying my webapp until it stopped working for apparently no reason. The following exception is displayed:
SEVERE: Allocate exception for servlet Index
java.lang.ClassNotFoundException: obliquid.servlet.Index
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1676)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1521)
In Servers tab I've "Tomcat v7.0 Server at localhost [Started,Synchronized]
My project appears as a child of Tomcat v7.0 Server
In Properties, Java Build Path, Source I've Project/src Source folder
In Properties, Web Deployment Assembly, I've the following mappings: /WebContent -> /, /src -> /WEB-INF/classes, /test -> /build/classes
My src directory contains a Servlet in obliquid/servlet/Index.java
I tried already to click on Clean Module Work Directory... and Publish
I tried to stop and start the Server from within Eclipse Servers tab
What else should I check? Thank you.
UPDATE Despite now I'm working with the new project, I came back to check the old one, and mysteriously now it's working. I think I won't be able to find what has happened.
However today with the new project, I had 404 errors with no apparent reason and I found out that right clicking on the Tomcat server and selecting "Clean..." can be useful. Maybe it could have helped.
Selecting "Clean..." says: "Clean will discard all publish state and republish from scratch. Are you sure you want to clean all published resources?". Selecting yes, I solved the problem
UPDATE 2 It happened again on the new project. 404 errors, this time they don't go away.
Stop -> Clean... -> Start (404)
Stop -> Clean Tomcat Work Directory... -> Start (404)
Stop -> Clean Tomcat Work Directory... -> Clean... -> Start (404)
Stop -> Remove on the application -> Clean... -> Run As -> Run on Server -> (404)
Exit Eclipse, Start Eclipse
Start the server -> (404)
UPDATE 3 It turned out that this time I just didn't notice an exception caused by a listener-class during startup. After solving the problem, it worked. Guess I should stop working at 3 AM.

While on Tomcat 6 and Eclipse Ganymede I found out the following chain to work like charm:
1 stop server
2 project -> clean
3 project build (I had automatic build disabled)
4 delete server
5 delete Servers folder
6 restart Eclipse
7 create new server, add project and start :)
takes some time but worked like charm. My problem was a irritating Listener start problem, but this seems to be something similar: a property at tomcat. Btw: nowadays I am also a big Glassfish fan.

I found that this procedure is useful:
Click on Servers tab and Stop the server in use if it's running
Right click on the server again and select Clean...
Right click again and select Clean Tomcat Work Directory...
Hopefully the ClassNotFoundException should be gone now.
Another time I had a problem with a class launched at server startup, an exception in a listener class (ServletContextListener). When a ServletContextListener raises an exception during startup the application deployment is aborted, hence the 404 errors. In that case fixing the problem that caused the exception, made the application working again.
EDIT: This shorter procedure worked for me most of the times, but today didn't work and I had to follow Mico's extended procedure. My suggestion is, if you have a similar problem, first try this shorter procedure. If the problem persists, try with Mico's.

I'd recommend that you stop and start the Tomcat server again. Hot deploy does not work forever; there are some issues that will cause you to have to restart after a few redeploys.

I wonder when I see the accepted answer with +25 is it really accurate?
First if you are going to delete the server then whats the point in cleaning it? It will take your time unnecessarily and nothing useful will you gain.
So i will say just 5, 6, 7 steps should do the magic
5 delete Servers folder
6 restart Eclipse
7 create new server, add project and start

This could be something I learned on con-fess 2011. For me this sounds like a classloader problem.
The theory behind:
Java does not only use the type of the class but also the classloader which loaded it to identify the type of an instance. This means a simle operation could fail, e.g.
ClassA a1 = new a1;
ClassA a2 = SomeOtherClass.giveMeInstanceOfA();
a1 = a2;
This example would fail if SomeOtherClass uses a different classloader because Java would say that they are not the same.
The speaker also mentioned that some servers use per default about 45 different classloaders.
What does this mean in practice:
You deploy your webapp to the server, everything runs fine. The server caches the classes and everything he needs to load them somewhere. Now you make a hot deploymen and the server may loads new classes with a new (or different) classloader. This is the point where it starts to become dangerous because from now on you have two different classes in the memory which should be the same. Simple operations like casts (ClassA a = (ClassA) new ClassA()) fail, new Methods within the class are not found (because the server takes a cached version without this method),....
This is the point where I restart the server, clean the working directory (to get rid of the cached versions) and start thinking about hot deployment as critical thing.
If it is possible to try Mikkos procedere and this solves the problem this explanation could help you understand why.
I know this does not solve your problem but could give you some hints what maybe could have happened.

Speaking of hot deployment of Tomcat, you would indeed experience various problems, the least of which is memory leak, which is why you would have to restart the application. I would recommend to try JRebel for fast turnaround of "make and save any changes and then refresh the browser and see the changes immediately". You can find the JRebel hands-on lab, which shows how to use it with Tomcat and Eclipse. http://www.javapassion.com/rebels/jrebel_basics/

I have gained some new experience on programming and I am not anymore starving on Eclipse + Tomcat combination. Several ways here can help you out of the need of the usage of that combination:
First of all, don't use them together!
You can use other available IDEs, e.g. IntellijIdea (that is not free, but is worth of investing) has an property that when you debug a Java code, you can change code on fly and compile the Java files one by one and then it suggests if you'll want to have it updated on server. No restart needed almost never (of course it sometimes gets lost, but mainly it works).
Use standalone tomcat server, not the one inside Eclipse / your IDE. That first trick works only when you debug external server, nothing inside IDE. There comes the second tip: if you happen to change only jsp or html content, those files can be copied to the right place inside tomcat's webapp folder manually with unix cp or windows copy command and if you happen to develop files in same foulder long time, you can copy the folder content (e.g. myFolder/*.jsp) as many times as you wish and no restart is needed at all. The changes come visible when you touch or edit&save the web.xml file inside the webapps folder and then after that with refreshing the visible page on browser. Probably hard refresh with CTRL+F5 is the best way.
Thanks to #Verdan about his comment, otherwise I wouldn't have came back to answer again.

I was able to solve this by disabling the maven nature (right click on project >> maven >> disable maven nature). Then re-enabling it (right click on project >> configure >> convert to maven project). I had tried all of the other tips and tricks above, but this is the one that finally worked.

I was running into the same problem - tried all of the above, Eclipse always freezed when i tried to start the server, even after i deleted all the server configs and created a new one with a freshly downloaded tomcat instance. Anyways, problem wasnt solved until i moved to a new workspace, reimported the projects and created a new server. Seems like an Eclipse bug to me...So in case nothing else works, this is the way to go...

I'm currently struggling with the same problem, but nothing mentioned here does not help me. Anyway, I found out that if I:
stop server in eclipse
run tomcat elsewhere (in my case the xamp distribution)
stop currently running tomcat
start tomcat in eclipse
everything works just fine, of course until I change something in code and try to test it again.

Trouble configuring existing Tomcat6 and Eclipse

I just got the Eclipse Java EE version and tried to configure Tomcat by going to the Window-->preferences-->Server
But when I went to "runtime environment" and gave it the location of the current tomcat directory, it didn't seem to recognize it and didn't let me go to next screen.
Did I do something wrong? The problem is that there are still the red squigly lines in the import statements of servlet libraries. Is there some correct way to refresh the page so I can ensure that Eclipse indeed does not recognize those libraries still?

I have been experiencing similar problems recently, sometimes even Eclipse not listing Apache Tomcat 6.0 among available servers. The solution was go to eclipse's metadata directory:
your_workspace/.metadata/.plugins/org.eclipse.core.runtime/.settings/
And delete following files:
org.eclipse.wst.server.core.prefs
org.eclipse.jst.server.tomcat.core.prefs
Then restart Eclipse and try again, everything should work.
Hope this helps!

Ensure that you're pointing to the real Tomcat root directory which contains the /bin, /conf, /lib, etc folders, not to a directory which contains just apache-tomcat-7.0.11 or something.
Also pay attention to the error/warning message in top of the wizard, if any, right below the title.

Eclipse keeps running my old web application

OMG - what is going on with Eclipse (3.3 Europa) - has anyone come accross this problem (bearing in mind I have been messing about with uninstalling different Tomat containers and installing others - but anyway thats another story)
When I change a line of code or remove a class within my project - when I come to debug - it actually goes to a line that is commented out and runs that line regardless!!!! e.g.
//System.out.println("you should not be able to read this!");
UPDATE: This can be solved by setting Project -> Build Automatically (see answer below).
REMAINING PROBLEM:
Eclipse is not keeping my hot deploy folder current with the latest changes to my project:
I found out to my horror that some old remenants of my project are 'hanging around' in the folder that I think Eclipse uses for hot deploys or something
C:\myJavaCode.metadata.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\myWebApp
basically it is not actually copying accross any changes made in the classes of my working dir!?!??
...anyway - in order to keep my project up to date - I have to modify this folder too - TOTALLY UNACCEPTABLE - as you can't develop in this way - it would take you eons! Anyway, if anyone can help explain to me what stupid thing I have done to get me in this mess and how I can get out of this mess - I would really appreciate it.

Have a look at:
Windows>Preferences>Server>Launching...
and:
Project>Build Automatically
maybe you accidentally disabled the auto-deploy features.

I had a similar problem, only without the added complexities of a web app. I'm just running a JUnit test and it's running the old code. I went into Configure Build Path, on the bottom of the Source tab, and looked at Default Output Folder, which said myproject/bin. The Package Explorer doesn't even show a bin folder, but when looking at the file system there's a bin folder there. I deleted the bin folder, refreshed the package explorer tree, and it worked. This behavior was in Helios and occurred with AND without Build Automatically selected...looks like a bug to me.
Dave

A super-silly question: Does all your webproject and related projects compile correctly?
Also check your output folder for classes (Project Properties -> Java Build Path -> Source Tab) then go to your filesystem and check permissions and modification dates.
Hope this will help you.

Probably the easiest way to get past this is to define a new server.
Right-click in the Servers window and select New, or when you do 'Run On Server' select Manually define a new server. You can have multiple servers defined using the same Tomcat runtime (they'll all have separate configs and deployment directories defined by -Dcatalina.base=...), but don't run them at the same time unless you change the ports they're listening on.
The new server will use a path like
<<yourEclipseWorkspace>>\.metadata\.plugins\org.eclipse.wst.server.core\tmp1
for the Tomcat conf and webapps directory.
Try running on this server. If it works, you can compare settings with the old one,
maybe try deleting the app from it and re-deploying, and figure out what you might have done to cause the problem. Or just delete the original server config.
As far as your second problem, I'm not sure. I'd try a new server config first, get it working, stop the server, do a 'Clean' on your project, delete anything in the tmp1\work\Catalina directory, and restart the server (you could remove and add your project to the server again too to be really clean).
Check the console messages too to make sure there were no errors related to this.