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How to avoid "Sharing is only supported for boot loader classes because bootstrap classpath has been appended" warning during debug with Java 11?

Recently I switched to the Java 11 and start to debug my app and saw this message:
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot
loader classes because bootstrap classpath has been appended
Found only this commit and ticket, but it doesn't tell me much.
Do I need to worry about it?

I had this issue too after installing jdk-12.0.1_windows-x64_bin.zip when trying to use the debugger with IntelliJ IDEA. I was getting an error of (Java HotSpot(TM) 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended). I found, too, going into Setting and search for async and unchecking the Instrumenting agent box. Worked for me!

You can ignore this warning. It just means that class data sharing is disabled for classes not loaded by the bootstrap class loader.
From Improve Launch Times […] With Application Class-Data Sharing:
The JVM loads some of the JDK classes with the bootstrap class loader
and the rest with the system class loader, but includes all of them in
its default archive. When IntelliJ executes your project, it tells the
JVM to load some code with the bootstrap class loader by appending to
that class path (second part of the message). Now, that means that the
portion of the archive that contains classes loaded by the system
class loader is potentially invalidated and so the JVM partially
deactivates sharing (first part of the message).
You could disable class data sharing completely with -Xshare:off, but you would lose some performance.

I had this issue after installing Java12 when trying to use the debugger with Intellij Idea. The solution that I found was to go into Setting and searching for async and unchecking the Instrumenting agent box.

For me, the issue occurred only when I ran in Docker, and when I used a java command line agent like the DataDog APM agent (-javaagent:/dd-java-agent.jar).
When I ran in my JDK11 runtime environment (without the agent) I did not get the warnings.

For Intellij IDE -> Settings/Preferences dialog ( Ctrl+Alt+S ), go to Build | Execution | Deployment | Debugger | Async -> uncheck instrumenting agent

1.Open the Preferences option;
2.Find the Build,Execution,Deployment option;
3.Enter the Debugger --> Async Stack Traces ;
4.Uncheck the Instrumenting agent(requires debugger restart) ;
Please see this for detailed information.

Given this warning in IntelliJ is harmless (see https://stackoverflow.com/a/57957031/779173) you could just hide the line from your Console view by right-clicking on the line and selecting "Fold Lines Like This"
Having done this, you'll just see:
"C:\Program Files\Java\jdk-17.0.2\bin\java.exe" ... <1 internal line>

If it is not critical you can change your jdk version. I've changed from jdk14 to jdk 11. Hope it will work for you.

Got same problem, and tried to solve it as was written above.
But then i got another solution of problem without changing settings.
Press mouse right button on your file where you put break point and want to debug. Then choose "Debug ur file name.method()".
Don't use debug button from tools window. Seems the problem is that Idea can't understand which file u want to debug.
That worked for me without changing async settings.
Screenshot

Got the same problem, and tried to solve it as was written all the above methods.
But still, I wasn't able to debug my file the only reason is that before debugging your program you need to set debug point that till which point we want to debug. So just click on the place shown in the figure and set debug point then our program will debug easily. without doing anything else. enter image description here

Java version must be 9 or higher.

Today I found the same question as you.
Situation: debug while set no breakpoint
Solution: set at least one breakpoint before you click debug button!

You have to put the red dots at the left side of the code line you will make debug .
if not you get this massage on IntelliJ

How do I run a DropWizard / Jersey server locally without having to restart & repack to get asset file updates?

I'm working on the client side of a project that is using DropWizard. Unfortunately what I'm experiencing is that for me to make a change to assets I have to stop the server, package the assets with maven, and then rerun the server or the assets will not be updated.
I tried adding dropwizard-configurable-assets-bundle but I'm still seeing the same behavior. Here's the service after adding it:
Service.java
public void initialize(strap<ServiceConfiguration> strap) {
// Assets
strap.addBundle(new ConfiguredAssetsBundle(
"/dashboard/app/", "/dashboard/", "index.html"
));
// Redirect /dashboard to /dashboard/
strap.addBundle(new RedirectBundle(ImmutableMap.<String, String>builder()
.put("/dashboard", "/dashboard/").build()));
}
I'm currently running mvn package && java -jar target/pack.jar server config.yml. I tried using Eclipse but I was having to restart it manually and it wasn't repackaging for me so it was slowing things down even further.
This whole process is reaaaally slowing me down and I'm hoping it's just my ignorance to the world that is Java.

In my Intellij Idea, i am using JRebel plug-in for this purpose. JRebel also supports Eclipse.

If your assets are packaged under src/main/resources then they should just update automatically with Eclipse without a restart being required, so long as you're running the executable service main() from within the IDE.
You may need to check that your Maven plugin is set to "generate-resources" on changes but that is just the default setting so should be in place already.
What you're describing is definitely possible in Eclipse - I have personal experience of making resource changes (e.g. change and save an HTML asset) and then seeing an immediate update upon doing nothing more than a browser refresh.

Can I use Lombok with GWT in Development Mode?

I tried to follow the official instructions on running a lomboked GWT project in dev mode, but either I'm doing something wrong, or this doesn't work with current versions of GWT anymore?
The error I get is:
"The method setA(int) is undefined for the type MyData".
MyData is simple:
#Data
public class MyData {
private int a;
}
I'm specifying
-javaagent:/path/to/lombok.jar=ECJ
in my Eclipse Run Configuration (as a VM argument).
I also tried playing around with
-Xbootclasspath/p:/path/to/lombok.jar
, as well as starting dev mode from my ant file, etc.
The problem is, that I'm mostly just guessing how the whole setup should work, so instead of troubleshooting my poor attempts, I'd like to ask how a correct setup would look like?

You've probably got it working by now, but I can confirm it does work with GWT2.4 / Eclipse 3.7 . The only option needed is the -javaagent VM arg, and adding lombok.jar to the classpath/buildpath.
I think there's some issues when you first start to use it, to do with either the gwt-unitCache folder, and the war/WEB-INF/classes folder, clearing these is probably a good step when setting it up !

I think you've stumbled upon Issue 393. If that's the case you can try the latest edge release
Disclosure: I'm one of the project lombok developers.

Eclipse - debugger doesn't stop at breakpoint

I am trying to trouble shoot a JUnit. In the source code, I have set break point in two places: 1) in a line where a static member is initialized 2) the first line of one of the test cases.
The debugger stops in the static field initializing line. But it doesn't stop in the test case. No matter where I set the break point in the test case, the debugger doesn't stop there. I know for sure that the test case is executed as I can see the log messages that I have added appear in the log.
Any help would be greatly appreciated.
I am using Eclipse Galileo and JUnit4 launcher.

Fix could be as simple as clicking run/skip all breakpoints. Worked for me.

Make sure, under Run > Debug Configurations, that 'Stop in main' is selected, if applicable to your situation.

This could be related to one of the bugs in JDK 6 Update 14, as indicated in the release notes for JDK 6 update 15.
If this indeed turns out to be the issue, you should move to a higher version of the JDK (that's no guarantee though, since fixes have been released against 6u16, 6u18 and 7b1). The best bet is to use -XX:+UseParallelGC flag. Increasing the size of the minimum and maximum heap size, to delay the first GC, bring temporary relief.
By the way, use this bug report in Eclipse to track how others have been faring.

You might have accidentally skipped all break points in Eclipse toolbar. To fix this go to Eclipse -> Run -> Skip All Breakpoints.

Usually when this happens to me (rare but it does) means that the code being executed is different than the code in the editor. It will happen from time to time for Eclipse that the built classes and the code in editor are out of sync. When that happens I get all sort of weird debugger behavior (debugging empty lines, skipping lines of code etc).
Restarting Eclipse, clean all projects and rebuild everything usually clears things up. I had also the Maven plugins (older versions... had not had it for a while now) that had a tendency to do that too.
Otherwise it might be a bug, maybe the one Vineet stated,
Hope this helps

In my case the problem was that I hadn't Debug view open in Debug perspective, so:
1 - Be sure you have debug perspective opened:
2 - Be sure you have debug view opened:

Project -> Clean seemed to work for me on on JRE 8

In order to debugger work with remote, the java .class files must be complied along with debugging information. If "-g:none" option was passed to compiler then the class file will not have necessary information and hence debugger will not be able to match breakpoints on source code with that class in remote. Meanwhile, if jars/class files were obfuscated, then they also will not have any debug info. According to your responses, most probably this is not your case, but this info could be useful for others who face the same issue.

Remove all breakpoints and re-add them.

For JDK7, run->Debug Configurations, check "Keep JUnit running after a test run when debugging".

Happened to me once, when I had unchecked "Run > Build automatically" and forgot to re-check it.

Make sure you declare the package at the top.
In my groovy code this stops at breakpoints:
package Pkg1
import java.awt.event.ItemEvent;
isMule = false
class LineItem {
// Structure defining individual DB rows
public String ACCOUNT_CODE
public String ACCOUNT_DESC
...
This does not stop at breakpoints:
import java.awt.event.ItemEvent;
isMule = false
class LineItem {
// Structure defining individual DB rows
public String ACCOUNT_CODE
public String ACCOUNT_DESC
...

To remove the breakpoints:
Debug your class as a junit test
When your debugger stops, click the "breakpoints" tab next to "variables" and "expressions"
At the top right of the breakpoint tab, click the button with two 'X'
Stop the test, replace your breakpoint and run the debugger again

Also verify if breakpoints on other lines DO work, it may be a bug in the debugger. I have had a problem with the Eclipse debugger where putting a breakpoint on a boolean assignment whose code was on the next line didn't work I reported this here, but putting it on the previous or next line did.

If nothing works-
Remove that Remote/Local Debug Configuration, and Create a new One.
Add the Source in Debug Configurations.

Another possible problem is that the debugger port may be blocked by the firewall. For example, I was using mule anypoint studio (v 5.4.3). The default debugger port is 6666. When a flow is executed, it would not stop at breakpoint. when I changed the port to another (e.g. 8099), it worked fine.

Go to Right click->Debug Configuration and check if too many debug instances are created.
My issue was resolved when i deleted multiple debug instances from configuration and freshly started debugging.

If you are on Eclipse,
Right click on your project folder under "Package Explorer".
Goto Source -> Clean up and choose your project.
This will cleanup any mess and your break-point should work now.

Creating a new workspace worked for me.

In my case I had multiple projects in same workspace. The java file I was trying to debug was present in more than one projects with same package.
I didn't need the other project, so simply closed unrelated projects (or remove the file from unrelated project).

One additional comment regarding Vineet Reynolds answer.
I found out that I had to set -XX:+UseParallelGC in eclipse.ini
I setup the virtual machine (vm) arguments as follows
-vmargs
-Dosgi.requiredJavaVersion=1.7
-Xms512m
-Xmx1024m
-XX:+UseParallelGC
-XX:PermSize=256M
-XX:MaxPermSize=512M
that solved the issue.

It happened to me when I had several project, I realized that I created a spring boot configuration of a project B from a project A (I clicked on Duplicate and change the parameter to have a config for the project B) and in that case I haven't the debug mode so I removed this config and I created directly a new one by clicking New in Spring Boot App

This is what works for me:
I had to put my local server address in the PHP Server configuration like this:
Note: that address, is the one I configure in my Apache .conf file.
Note: the only breakpoint that was working was the 'Break at first line', after that, the breakpoints didn't work.
Note: check your xdebug properties in your php.ini file, and remove any you think is not required.

Java Reflection not working on my system - working for team members

I am working on a team project in Java. One requirement is that we dynamically populate a drop-down menu of all classes that implement a certain interface. New classes can be added after compile time. To accomplish this we are using reflection.
Problem: All of the drop-down menus are blank on my system. I cannot for the life of me figure out why they are not populating. All other 5 team members have it working on their system.
Things I tired that didn't work:
1) Installing most recent eclipse (galileo) because rest team was using it
2) Re-install most recent java release (jdk1.6.0-17 and jre6)
3) Check PATH and JAVA_HOME variables
Any thoughts as to what else I can try or if something I did should have solved it and didn't? It is driving me crazy.
Edit:
I should have been clearer that we are developing in a team. We are using SVN for version control and we are all running the exact same source code. I even tried checking out a fresh copy of the entire tree from SVN, but I had the same issue with reflection on my system while it worked for teammates.
The team created an executable jar and that ran on everyone's system fine except for mine. Everything worked for me except the reflection bit.

You need to debug your application. This means you have to systematically explore possible causes of the problem. Here are some things that come to mind:
Could your GUI be failing rather than reflection? What if you output with System.out.println() rather than your menu?
Is your reflection code throwing an exception, and are you ignoring it?
Is your reflection code actually being called? Toss a println() in there to be sure!
Is the test for the interface suffering from a typo or similar error that's causing it to fail? Try finding classes that implement Serializable instead!
Is your reflection test running in the main thread and trying to update your GUI? You need to use SwingUtilities.invokeAndWait to get an update to the Swing worker thread.
You're working with Eclipse; Eclipse has a fantastic debugger. Set a breakpoint near where your main action is and then single step through the code.

PATH and JAVA_HOME won't help. PATH only affects dynamically-linked libraries ("native code"). JAVA_HOME is a scripting variable that happens to be used by some Java-based utilities like Ant and Tomcat; it means nothing to the Java runtime itself.
You need to be investigating the classpath, which should be specified by the -classpath option to the java command, in the Build Path in your Eclipse project properties, or in the Class-Path attribute of the main section of a JAR file if you're launching java with the -jar option.
From within your code, you should be able to list the contents of your classpath by examining the system property, "java.class.path"
System.out.println(System.getProperty("java.class.path"));

Problem solution:
Classpath leading to source code must have no spaces in it.
I am running windows XP and, for whatever reason, if the classpath that leads to the jar file or source code that is using reflection has any spaces in it, then the reflection fails.
I took the jar file that works for the rest of my team and ran it from C:\ on my system and the reflection worked perfectly fine.
I do not know why this is so please comment if you know what is happening.

Might be a long shot, but look for differences in security settings for you and your team mates. Article describing more details http://www.ibm.com/developerworks/library/j-dyn0603/ heading "Security and reflection"