I have been trying to do a kind of plugin-system using the ServiceLoader. There are 2 modules, the first provides the abstract class LoadedRealmPlugin. The second one extends this class. I have added the file corresponding to the full name of the ServiceProvider and added the service-class to it. IntelliJ does not find any errors (but when changing the filename or classname it does). Here is the structure:
MainModule
src
main
java
com.interestingcompany.mainmodule
LoadedRealmPlugin
MainModule.iml
Plugin
META-INF
services
com.interestingcompany.mainmodule (-> Content: "PluginExtension")
src
PluginExtension
Plugin.iml
(This is simplified, I left out classes that (I think) are not important to the ServiceLoader. I can post a screenshot of the actual structure if anyone needs it)
Here is the code I use to load the Service:
File file = new File("Plugins/Plugin.jar");
URLClassLoader c = new URLClassLoader(new URL[]{file.getAbsoluteFile().toURI().toURL()});
ServiceLoader<LoadedRealmPlugin> loader = ServiceLoader.load(LoadedRealmPlugin.class, c);
LoadedRealmPlugin p = loader.iterator().next(); // Throws a java.util.NoSuchElementException
p.Initialize(RealmPath); // Abstract method implemented in the service
return p;
When trying to run it, I always get an empty ServiceLoader. I looked at this post, but I was not quite sure about how to apply that answer since I am trying to load my plugin from a file. In addition, I found this post. Yet, there was no answer, just some comments that did not seem to have answered the question.
As you might have been able to tell, this is my first time working with classloaders. If there is any additional information needed, just ask me. Thank you for reading through my beginner troubles.
package-less classes are in the unnamed package, which is inaccessible to rather a lot of code, notably including here.
Put PluginExtension.java in a package, make sure the content of your META-INF/services/com.ic.mainmodule file reflects this (content should be pkg.PluginExtension), and it'll work fine.
In a Tomcat 7 I have a pretty standar jar file on WEB-INF/lib. Inside this jar I have this class called Parser, and next to it (on the same dir) I have another one called AutomaticLocalLoader. Compilation gives no problem at all. In run time the AutomaticLoader class is found, and when It needs the Parser class, I get a NoClassDefFoundError
The Parser and AutomaticLoader class have been working without this problem for 15 years!! in many diferent vers of java and tomact; and now out of the blue, I am getting this NoClassDefFoundError, only for the Parser class. I already put a copy on a directory inside the WEB-INF/classes path and still got the same error. I already created my own ClassLoader to see if I get some error loading the class from the WEB-INF/classes directory by myself, but I can load it without problems.
log.info("Leer " + aFlInstructions[i].getAbsolutePath());
LoaderTest A = new LoaderTest();
A.test("com.hds.resolve.model.aguila.AutomaticLocalLoader");
LoaderTest B = new LoaderTest();
B.test("com.hds.resolve.model.aguila.Parser");
if(!bOverrideInputDir)
Psr = new Parser(aFlInstructions[i]);
else
Psr = new Parser(aFlInstructions[i], new String[] { StrLocalDirectory } );
The LoaderTest class, try to create the Class Object for the given name using Class.forName. If NoClassDefFoundError, then try to load the class using my own classloader and then create the class.
For the AutomaticLoader, it succed at the first try. For the Parser class if fails, then successfully load it with the custom classloader. Of course when the code reach the "new Parser" part, the old webclassloader still fails and throws the NoClassDefFoundError.
Both Parser and AutomaticLocalLoader belong to the same package and are stored on the same jar inside WEB-LIB.
Funny enough, the error does always happen on production... but never in my machine. I do not use customs classloaders except for doing this debug. Also, trying an old version of the software seems to fix the error. No idea why.
I think I can hack a solution messing with the tomcat's webclassloader, but I really would prefer to understand what is going wrong with this code.
I am having the following problem:
I have an Enum that was originally declared with 5 elements.
public enum GraphFormat {
DOT,
GML,
PUML,
JSON,
NEO4J,
TEXT {
#Override
public String getFileExtension() {
return ".txt";
}
};
Now I need to add an additional element to it (NEO4J). When I run my code or try to debug it I am getting an exception because the value can't be found in the enum.
I am using IntelliJ as my IDE, and have cleaned the cache, force a rebuild, etc.. and nothing happens. When I look at the .class file created on my target folder, it also has the new element.
Any ideas on what could be causing this issue ?
I found my problem and want to share here what was causing it. My code was actually for a Maven plug-in which I was pointing to another project of mine to run it as a goal. However the pom.xml of my target test project was pointing to the original version of the plug-in instead of the one I am working on, and that version of course is outdated and does not include the new value. Thank you.
I have been working on an assignment for my class in programming. I am working with NetBeans. I finished my project and it worked fine. I am getting a message that says "No main class found" when I try to run it. Here is some of the code with the main:
package luisrp3;
import java.io.FileNotFoundException;
import java.io.PrintStream;
public class LuisRp3 {
public static void main(String[] args) throws FileNotFoundException {
java.io.File newFile = new java.io.File("LuisRamosp4.txt");
if (newFile.exists()) {
newFile.delete();
}
System.setOut(new PrintStream(newFile));
Guitar guitar = new Guitar();
I posted this before but had a couple issues. i have fixed the others and now have just this one remaining. Any advice will be greatly appreciated.
Right click on your Project in the project explorer
Click on properties
Click on Run
Make sure your Main Class is the one you want to be the entry point. (Make sure to use the fully qualified name i.e. mypackage.MyClass)
Click OK.
Run Project :)
If you just want to run the file, right click on the class from the package explorer, and click Run File, or (Alt + R, F), or (Shift + F6)
Also, for others out there with a slightly different problem where Netbeans will not find the class when you want when doing a browse from "main classes dialog window".
It could be that your main method does have the proper signature. In my case I forgot the args.
example:
public static void main(String[] args)
The modifiers public and static can be written in either order (public static or static public), but the convention is to use public static as shown above.
Args: You can name the argument anything you want, but most programmers choose "args" or "argv".
Read more here:
http://docs.oracle.com/javase/tutorial/getStarted/application/
When creating a new project - Maven - Java application in Netbeans
the IDE is not recognizing the Main class on 1st class entry. (in Step 8 below we see no classes).
When first a generic class is created and then the Main class is created Netbeans is registering the Main class and the app could be run and debugged.
Steps that worked for me:
Create new project - Maven - Java application
(project created: mytest; package created: com.me.test)
Right-click package: com.me.test
New > Java Class > Named it 'Whatever' you want
Right-click package: com.me.test
New > Java Main Class > named it: 'Main' (must be 'Main')
Right click on Project mytest
Click on Properties
Click on Run > next to 'Main Class' text box: > Browse
You should see: com.me.test.Main
Select it and click "Select Main Class"
Hope this works for others as well.
The connections I made in preparing this for posting really cleared it up for me, once and for all. It's not completely obvious what goes in the Main Class: box until you see the connections. (Note that the class containing the main method need not necessarily be named Main but the main method can have no other name.)
I had the same problem in Eclipse, so maybe what I did to resolve it can help you.
In the project properties I had to set the launch configurations to the file that contains the main-method (I don't know why it wasn't set to the right file automatically).
In project properties, under the run tab, specify your main class.
Moreover, To avoid this issue, you need to check "Create main class" during creating new project. Specifying main class in properties should always work, but if in some rare case it doesn't work, then the issue could be resolved by re-creating the project and not forgetting to check "Create main class" if it is unchecked.
If the advice to add the closing braces work, I suggest adding indentation to your code so every closing brace is on a spaced separately, i.e.:
public class LuisRp3 {
public static void main(String[] args) throws FileNotFoundException {
// stuff
}
}
This just helps with readability.
If, on the other hand, you just forgot to copy the closing braces in your code, or the above suggestion doesn't work: open up the configuration and see if you can manually set the main class. I'm afraid I haven't used NetBeans much, so I can't help you with where that option is. My best guess is under "Run Configuration", or something like that.
Edit: See peeskillet's answer if adding closing braces doesn't work.
There could be a couple of things going wrong in this situation (assuming that you had code after your example and didn't just leave your code unbracketed).
First off, if you are running your entire project and not just the current file, make sure your project is the main project and the main class of the project is set to the correct file.
Otherwise, I have seen classmates with their code being fine but they still had this same problem. Sometimes, in Netbeans, a simple fix is to:
Copy your current code (or back it up in a different location)
Delete your current file
Create a new main class in your project (you can name it the old one)
Paste your code back in
If this doesn't work then try to clear the Netbeans cache, and if all else fails, then just do a clean un-installation and re-installation of Netbeans.
In the toolbar search for press the arrow and select Customize...
It will open project properties.In the categories select RUN.
Look for Main Class.
Clear all the Main Class character and type your class name.
Click on OK.
And run again.
The problem is solved.
If that is all your code, you forgot to close the main method.
Everything else looks good to me.
public class LuisRp3 {
public static void main(String[] args) throws FileNotFoundException {
java.io.File newFile = new java.io.File("LuisRamosp4.txt");
if (newFile.exists()) {
newFile.delete();
}
System.setOut(new PrintStream(newFile));
Guitar guitar = new Guitar();
}}
Try that.
You need to add }} to the end of your code.
You need to rename your main class to Main, it cannot be anything else.
It does not matter how many files as packages and classes you create, you must name your main class Main.
That's all.
import java.util.Scanner;
public class FarenheitToCelsius{
public static void main(String[]args){
Scanner input= new Scanner(System.in);
System.out.println("Enter Degree in Farenheit:");
double Farenheit=input.nextDouble();
//convert farenheit to celsius
double celsuis=(5.0/9)*(farenheit 32);
system.out.println("Farenheit"+farenheit+"is"+celsius+"in celsius")
{
I also experienced Netbeans complaining to me about "No main classes found". The issue was on a project I knew worked in the past, but failed when I tried it on another pc.
My specific failure reasons probably differ from the OP, but I'll still share what I learnt on the debugging journey, in-case these insights help anybody figure out their own unique issues relating to this topic.
What I learnt is that upon starting NetBeans, it should perform a step called "Scanning projects..."
Prior to this phase, you should notice that any .java file you have with a main() method within it will show up in the 'Projects' pane with its icon looking like this (no arrow):
After this scanning phase finishes, if a main() method was discovered within the file, that file's icon will change to this (with arrow):
So on my system, it appeared this "Scanning projects..." step was failing, and instead would be stuck on an "Opening Projects" step.
I also noticed a little red icon in the bottom-right corner which hinted at the issue ailing me:
Unexpected Exception
java.lang.ExceptionInInitializerError
Clicking on that link showed me more details of the error:
java.security.NoSuchAlgorithmException: MD5 MessageDigest not available
at sun.security.jca.GetInstance.getInstance(GetInstance.java:159)
at java.security.Security.getImpl(Security.java:695)
at java.security.MessageDigest.getInstance(MessageDigest.java:167)
at org.apache.lucene.store.FSDirectory.<clinit>(FSDirectory.java:113)
Caused: java.lang.RuntimeException
at org.apache.lucene.store.FSDirectory.<clinit>(FSDirectory.java:115)
Caused: java.lang.ExceptionInInitializerError
at org.netbeans.modules.parsing.lucene.LuceneIndex$DirCache.createFSDirectory(LuceneIndex.java:839)
That mention of "java.security" reminded me that I had fiddled with this machine's "java.security" file (to be specific, I was performing Salvador Valencia's steps from this thread, but did it incorrectly and broke "java.security" in the process :))
Once I repaired the damage I caused to my "java.security" file, NetBeans' "Scanning projects..." step started to work again, the little green arrows appeared on my files once more and I no longer got that "No main classes found" issue.
Had the same problem after opening a project that I had downloaded in NetBeans.
What worked for me is to right-click on the project in the Projects pane, then selecting Clean and Build from the drop-down menu.
After doing that I ran the project and it worked.
Make sure the access modifier is public and not private. I keep having this problem and always that's my issue.
public static void main(String[] args)
My scenario is: One step in my jira workflow should have the ability to unschedule a task i.e. set a Fix Version to "None".
I noticed that I was not able to update fix version in a workflow post function - I don't know exactly why, but anyway I did implement a jira plugin to help me solve my problem but I know I'm going against jira structure (even java good coding practices :)). I am not sure if my implementation can cause problems, but indeed it is working in my jira instance 4.1.x.
How I've implemented a plugin to update fix version in a post function, 2 very similar ways:
public class BrandsclubPostFunctionUnschedule extends AbstractJiraFunctionProvider {
// Here I create an empty Collection to be the new value of FixVersion (empty because I need no version in Fix Version)
public void execute(Map transientVars, Map args, PropertySet ps) throws WorkflowException {
MutableIssue issue = this.getIssue(transientVars);
Collection<Version> newFixVersion = new ArrayList<Version>();
issue.setFixVersions(newFixVersion);
issue.store();
}
}
public class BrandsclubPostFunctionUnschedule extends AbstractJiraFunctionProvider {
// here I clear the Collection I got from "old" Fix Version and I have to set it again to make it work.
public void execute(Map transientVars, Map args, PropertySet ps) throws WorkflowException {
MutableIssue issue = this.getIssue(transientVars);
Collection fixVersions = issue.getFixVersions();
fixVersions.clear();
issue.setFixVersions(fixVersions);
issue.store();
}
}
I presume that a real solution should use classes like: ChangeItemBean, ModifiedValue, IssueChangeHolder - taking as example the updateValue methods from CustomFieldImpl (from jira source code, project: jira, package: com.atlassian.jira.issue.fields).
My point of publishing this here is:
Does anyone know how to implement a jira plugin containing a post function to change Fix Version correctly?
If you want to do it properly take a look in the code for
./jira/src/java/com/atlassian/jira/workflow/function/issue/UpdateIssueFieldFunction.java processField()
Postfunctions that take input parameters are not documented yet it seems. Other places to go for code are other open source plugins.
Atlassian has a tutorial on doing just about exactly what you want to do, here:
I do it like in this snippet:
List<GenericValue> genericValueList = issueManager.getIssues(issues);
versionManager.moveIssuesToNewVersion(genericValueList, lastVersion, newVersion);