Develop Reference

allowed names for java packages and modules

I want to migrate my old java code to the java9 modules. E.g. in the classpath there is a jar-file named org.eclipse.jface.3.7.0.v20110928.jar. In the classpath it is referenced as org.eclipse.jface_3.7.0.v20110928.jar. The point in the filename after jface is replaced with an underscore in the classpath. Don't know how it works. Maybe it is because .3.7.0. is not a legal java identifier.
But now I want to use it as a module. I get an error for the modulename. The part '.7.0.' is not allowed, because a number can not be a java identifier. The underscore is a reserved word in java9.
First I used the same name for the module as it saw it in the classpath (org.eclipse.jface_3.7.0.v20110928.jar). But it is an error. The I tried to use the name of the file (org.eclipse.jface.3.7.0.v20110928.jar), same error.
module iDEpdf.src
{
exports org.idepdf.ri.common.utility.annotation;
...
requires org.eclipse.jface.3.7.0.v20110928;
}
'.3.7.0' is marked and the error is 'illegal token'. When I use org.eclipse.jface_3.7.0.v20110928 the marked substring is '.7.0'. The error is the same.
If it is possible I don't want to rename the jar-file. I don't understand how it works for the classpath and I don't understand why it does not work for the module. How should I handle this?

I think you are using a very old library of JFace. You probably need to update or add Automatic-Module-Name.
Since the library doesn’t have a module descriptor yet, the module isn’t recognized as valid.
My question is also: why migrate to the module system before updating libraries to recent versions?
Please also see this question or this one.

How to fix undefined MqttChannelInitializer constructor in HiveMQ Client?

I was using HiveMQ Client version 1.0.1 but I decided to update to the recently released version 1.1. I completely started from scratch and imported the project as a Gradle project and tried to build. The build work only after ignoring a few failed tests. I'm getting 3 errors in 3 different classes. I realize this is likely related to the Dagger dependency injection tool and I had already successfully built the project and added the directory of build/generated/source/apt/main/ to my build path as noted by my previous stack post where I had issues with a DaggerSingletonComponent not being found: How to fix DaggerSingletonComponent not resolved in HiveMQ (MQTT protocol) . This seems to be a new issue and I'm not sure what's wrong. I tried rebuilding by project but the errors still persist. I've left some screenshot below as well as the specific errors.
HiveMQ:
https://github.com/hivemq/hivemq-community-edition
https://github.com/hivemq/hivemq-mqtt-client
Errors:
The constructor MqttChannelInitializer(MqttClientConfig, MqttConnAckFlow, MqttEncoder, MqttConnectHandler, MqttDisconnectHandler, MqttAuthHandler, Lazy) is undefined
The constructor MqttSession(MqttClientConfig, MqttSubscriptionHandler, MqttIncomingQosHandler, MqttOutgoingQosHandler) is undefined
The method provideBootstrap(NettyEventLoopProvider, MqttChannelInitializer) in the type ConnectionModule is not applicable for the arguments (MqttClientConfig, NettyEventLoopProvider, MqttChannelInitializer)
Screenshots:

Executing ./gradlew clean build on the command line will fix your error.
But I also think that the real solution for your use case is to create a new empty project (gradle or maven) and add the client library as a dependency, like described here: https://hivemq.github.io/hivemq-mqtt-client/docs/installation.html

The issue turned out to be caused by an issue with the source folder in the directory build/generated/source/apt/main/ not having the option “Update exclusion filters in other source folders to solve nesting” selected. Selecting that option solved all of the errors.

Unable to derive module descriptor: Provider {class X} not in module

I am getting this error message when I try to compile my new modularized Java 11 application:
Error occurred during initialization of boot layer
java.lang.module.FindException: Unable to derive module descriptor for C:\Users\inter\.m2\repository\xalan\xalan\2.7.2\xalan-2.7.2.jar
Caused by: java.lang.module.InvalidModuleDescriptorException: Provider class org.apache.bsf.BSFManager not in module
This appears to be an issue from a dependency of a dependency. I can't even find which module is pulling it in so I can update it.
I am using openjdk 11.0.2, IntelliJ 2018.3.4, Maven
Any advice how I can troubleshoot or fix this? I have found very little documentation on this issue.

Xalan
I had a look at their bug tracker following their index page and wasn't able to find this reported and not sure how actively is the library being maintained either.
General Explanation
Just to explain what has caused the issue in your code, I would share a screenshot and then try to add details around it.
So within the JAR that for version 2.7.2, there are service declarations (META-INF/services) which include org.apache.xalan.extensions.bsf.BSFManager as one of them. The service file here has to indicate the Provider thereby for itself and the class is supposed to be present on the modulepath to be resolved for reliable configuration of modules.
In this case for the module xalan(automatic module), the service listed doesn't have the provider class packaged within the dependency itself. (See the package org.apache, it doesn't further have package bsf and the class BSFManager thereby. Hence the exception as you get.
Short term hack
One of the tweaks to get that resolved would be to get update the library jar (patch it) and get rid of the service file if you're not using it. Or to add the provider copied from the corresponding artifact.
If you don't directly depend on this artifact or its parent dependencies, you can let those remain on the --classpath and get resolved as an unnamed module for your application.
Long term solve
An ideal way would be to report this to the maintainers and getting it resolved. It depends though on how actively are they maintaining it e.g. the last release for xalan was almost 5 years back, might just want to look for an actively participated alternative in my opinion.

I tried to install update for TestNG in eclipse:
"Help -> Check for updates -> deselect all and select TestNG check box. Then
install latest version i installed the version which starts with 7.2.0.
It fixed the issue for me.

NoSuchMethodError after cleaning the project

I'm currently getting this error:
java.lang.NoSuchMethodError: org.json.JSONObject.keySet()Ljava/util/Set;
at ee.ut.cs.Parser.accessLint(Parser.java:39)
I have tried cleaning the project to no awail.
I suspect I have an error in the src/plugin/parse-htmlraw/build.xml while creating the jar file but I'm not certain. I understand that this error is because the function does not exist at runtime, but the object is created which means that the class is there, just not that function. I decompiled the .class file in created jar and it has the necessary functions.
Code is available at https://github.com/jaansusi/WCAGgrader
Q: What is wrong with the build that produces this error?
The problem is that even if I put the necessary class files in the jar I create, they are not linked correctly and the class that's called in the jar can't locate functions inside the other classes. The class object JSONObject is created but the functions inside the JSONObject class can't be found.

If you do not find the problematic version, there is a possibility you get it (especially if you are using Spring) from the following dependency -
<artifactId>android-json</artifactId>
<groupId>com.vaadin.external.google</groupId>
excluding it worked for me,
An easy way of analyzing dependencies is the maven-helper plugin in Intellij, see here

Check for the version you have used.
There might be a case where 2 different versions are being used which in turn causes this error.

To their own maven local repository com\Google\code\gson\gson, see if there are two or more version about json, will have to do is to delete the old, and remember to look at any other place in the project is introduced into the old version of the dependence, if any, change the old version of the dependence to the new version is perfectly solved this problem

compile error: The import xxxx cannot be resolved

I am developing a Java project using Eclipse. The project uses another project called engine, which I have added in my project build-path. As I need to call a dabo class, called House, in one of my project class, named Window, I have used the following code as usual:
import ee.asus.kernel.House;
I got however the following error in compiling time:
Exception in thread "main" java.lang.Error: Unresolved compilation problems:
The import ee cannot be resolved
House cannot be resolved to a type
House cannot be resolved to a type
House cannot be resolved to a type
at main.ee.asus.GUI.FrameWindow.Window.<init>(Window.java:10)
at main.ee.asus.GUI.StartApplication.main(StartApplication.java:13)
It's worth to point out that my prject and the dabo project use the same directory/packages names. Does anyone have a clue where the error may be?

The error can't resolve the first part of the package name: ee. Are you sure the package starts with ee? I see your Window class package starts with main.ee, does your engine project start with the same package structure?

I sometimes get weird behaviour with missing class files etc. when Eclipse is out of sync with the filesystem.
You could try refreshing all of your projects and doing a full rebuild.

I have been experiencing the same problem. I have an app A1(tablet version app) calling another app A2(phone version app). Upon calling, I see the same error message:
java.lang.Error: Unresolved compilation problems:
The import xxxxx cannot be resolved
xxxx cannot be resolved to a type
xxxx cannot be resolved to a type
xxxx cannot be resolved to a type
After poking around for a while, I realized the problem was the A2 doesn't run on tablet at all. It's weird because the immediate previous version of A2 runs perfectly on the same tablet(I have been on board only for 1 month). So I decided there was something wrong in the build config.
Finally, I fixed the problem by changing the order of Java Build Path. Although I have no idea why it worked, hopefully this will shed some light on your problem.

Look for the House class in your second project, opens it and see what package it is in.
(line "package xxx.yyy.zzz;" at the beginning of the House.java file)
Then make sure your Window.java file (class main.ee.asus.GUI.FrameWindow.Window) does have the line "import xxx.yyy.zzz.House;" in it.

In my case it was a version conflict.
I'm using maven and updated many packages and bumped versions of many projects. Maybe the reactor built mixed something up, or the transitive dependencies weren't up-to-date, or it was a change in a project without a version increment. However, rebuilding that project explicitly via maven fixed the problem.
Edit: When I think about it, it might also have been a conflict between eclipse's auto-build and building via maven on the command line.