When referencing simple .jar files, Eclipse shows an error stating:
The package java.awt is accessible from more than one module: <unnamed>, java.desktop
This happens for instance when javax.awt or javax.swing is included in the .jar files.
The simplest example would be the following:
package test;
import javax.swing.JDialog;
public class Test {
public static void main(String[] args) {
new JDialog();
}
}
Adding a .jar file to the classpath with only the folder structure javax/swing (no files needed) will cause the error to appear. I'm using JDK 10/12 (neither works). Setting the compiler compliance to 1.8 makes the whole thing work again.
On another machine with Eclipse 2018-09 this works with compiler compliance set to 10.
I'm on Eclipse 2019-03, on a (for testing purposes) freshly installed Eclipse 2018-09 it works fine. Why?
Edit June/2020 (Solution)
As the answers correctly stated, this is a restriction built into Java ages ago and only recently was forced upon us. I came into contact with it while migrating a big project with dozens of dependencies to Maven. There were libraries from around the year 2000! There were 'meta libraries' which consisted of several libraries packaged together.
So there was no other way than to identify what was still needed (into the trash with the rest!), update libraries which violate the rules or find replacements for them. This took me many, many hours.
In the end it worked out and we've got a nice Maven project to work with.
This is caused by
a JAR on the Classpath that contains the package java.awt that also exists in the system library but the
JRE System Library is on the Modulepath
In the Java Platform Module System (JPMS) it is not allowed to use the same package in more than one module. If the Modulepath and the Classpath is used, everything on the Classpath is handled as the <unnamed> module (in your case the package java.awt exists in the system module java.desktop and also via the JAR on the Classpath in the module <unnamed>).
Since the JRE System Library cannot be moved from the Modulepath to the Classpath (see this answer by Stephan Herrmann for details), you only have the following options:
Set the compiler compliance to 1.8 (as you already mentioned)
Rebuilt the JAR to avoid Java system library package names inside the JAR (if reflection is used, additional code changes may be necessary):
If you have the source code, change the package names (e.g. change the package and subpackae java to java_util and javax to javax_util) and recreate the JAR
If you have only the .class files you have to decompile the .class files first
Since I'll bet lots of people will be running into this problem with modular Java, I'll help and give the real answer.
This error happens when
you have a dependency in your project
that contains code
using packages
that are also in the modules
being referenced by your project
If your project has set the source compatibility to something like Java 12, it will start enforcing the rule, that has been there all along in Java:
"Don't use packages that belong to the JDK in your own code."
Unfortunately, lots of developers and vendors have done that over the years. Can't do that anymore.
If you set your project to Java 12 source compatibility, Eclipse adds the JDK modules which include everything "java.*" and "javax.*" and even "jdk.*", "org.w3c.*". These packages may be in use by your dependencies or their transitive dependencies.
How to fix
You need to:
look at which package its complaining about
and expand the "Projects and External Dependencies" node in the Package Explorer.
Find out which dependency is using that package.
Then you can simply exclude that dependency from your project.
Or you could get the source of that dependency, if available, and rebuild the jar with changed packages. Otherwise you have to remove that dependency and find a replacement for that technology. Pain huh?
If its a transitive dependency you can often just exclude it. Here is an example of that for Gradle based projects.
GradleConfig.xml:
configurations {
all*.exclude group: 'xml-apis'
}
In my case, it was because I included a dependency (Apache Tika) in the POM.xml file.
I had to force the exclusion of the module that contained the classes with errors while imported at that dependency:
<dependency>
<groupId>org.apache.tika</groupId>
<artifactId>tika-parsers</artifactId>
<version>1.24.1</version>
<exclusions>
<exclusion>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
</exclusion>
</exclusions>
</dependency>
It worked for me that way.
I found a simple solution to troubleshoot this in Eclipse. Hit Ctrl + Shift + T in Eclipse to open the Open Type prompt. Then type the name of the package that is causing the issue. For me, it was org.w3c.dom. Now the search results will show all the locations from where this package is being loaded. Remove every JAR from the classpath that comes in the result other than the JDK 11 library.
My project being a legacy one, I had to remove a lot of JARs from the build path. Also, my project does not use Maven. So removing the JARs was a fairly straightforward step. The steps might vary for other build tools like ANT, Maven, Gradle, etc. I have just explained the troubleshooting steps above.
See also: The package org.w3c.dom is accessible from more than one module: <unnamed>, java.xml where I answered:
Disappointingly I don't see any compiler flags to show what jar the problem is with
Even -Xlint:module doesn't seem to show up anything useful and eclipse doesn't shed any light on the issue
Instead to find where java.awt comes from I've been using this script:
mvn dependency:copy-dependencies -DincludeScope=test -DoutputDirectory=deps
for i in deps/*.jar; do if unzip -l $i| grep -q java.awt; then echo $i; fi ; done
Strictly you don't have to specify the scope test as that's the default but I've included it as you might want to use compile instead
I think my flavour of the problem might be useful.
I got this error for classes under javax.xml.stream, by old Maven projects that depend on artifacts like xml-apis, stax-api, or geronimo-stax-api.
Technically, the problem is what others have already said: those artifacts expose the javax.xml.* package without any awareness of Java modules (they were invented later), so the package is automatically assigned to the unnamed module, which conflicts with the same package being included in the JDK's most recent versions, where the package has its own module name, and therefore the same package results in two different modules, which is forbidden.
That said, the practical solution is essentially to work with Maven exclusions to remove those dependencies from your project and let it use the JDK version instead (or, of course, remove them as direct dependencies, if that's your case). Use the equivalent if you're working with another build system.
In theory, the more recent flavours of these packages offered by the JDK might be non backward-compatible, in practice, I doubt such JSR specifications changed much over the years and so far, I haven't seen any issue with their replacement.
Since this is ranks quite high on Google I'm going to drop this here in case it's helpful for someone.
I've found some interesting behaviour with Java 11 and the xmlbeans library. The xmlbeans library is a transitive dependency of Apache POI, a very popular library for working with Microsoft Office documents, it is used to handle the internal XML structures of the newer Office formats. I've tested it with Apache POI 3.9 and it works perfectly fine, despite the error shown by Eclipse. So, I guess in Java 11 this rule it's not fully enforced.
For Apache POI version 5.0.0 using Maven, in the pom.xml:
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>5.0.0</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>5.0.0</version>
<exclusions>
<exclusion>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
</exclusion>
</exclusions>
</dependency>
Fixed: "The package javax.xml.parsers is accessible from more than one module"
I met a similar issue with the eclipse IDE while upgrading JDK from 1.8 to 11, "The package org.w3c.dom is accessible from more than one module: , java.xml". upgrading eclipse from 2019 to 2021 and setting system JDK home to 11 does not solve it. I don't think it's caused by "org.w3c.dom" existing in different jars of the classpath,dut to "Order and Export" should ordered the search sequence.
After several hours of searching and investigating, this issue is fixed by setting the Java Compiler - Compiler compliance level to 1.8(default is 11).
You can do what other people suggest which is to exclude xml-apis which worked fine with me, but if your are using and an old jaxb-api replace them with jakarta.xml.bind-api:
<dependency>
<groupId>jakarta.xml.bind</groupId>
<artifactId>jakarta.xml.bind-api</artifactId>
<version>2.3.3</version>
</dependency>
and of course upgrade your jaxb-impl to match the same api:
<dependency>
<groupId>com.sun.xml.bind</groupId>
<artifactId>jaxb-impl</artifactId>
<version>2.3.3</version>
</dependency>
Steps below helped me,
Right click Eclipse project > Properties > Java Build Path
In Libraries tab, remove all the external jar files under Modulepath and add them under Classpath (you can just select all the jars and drag them under Classpath)
Click Apply and Close
Hope it help you too.
Wow, this was a tough one!
Some helpful tips (a summary of my journey through this maze):
This started when I migrated from Java 1.8 to 11.0.11
Right out of the gate this caused problems. I needed to change the syntax for how to specify the Java version for the maven build plug in as shown below:
Before
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
After
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
<release>11</release>
</configuration>
</plugin>
After that, everything compiled at a command prompt. However, when opening the project in Eclipse, I got a bunch of errors as shown in the next section.
Getting "<class> cannot be resolved to a type" errors
When I got errors in Eclipse and not at the command line I immediately started looking at configuration settings in Eclipse to no avail. After some googling I came to this post. The post at https://www.eclipse.org/forums/index.php/t/1110036/ was also very helpful.
Finding what resources were the problem
The answer to this post by #Anu suggesting using <shift><ctrl>T to bring up the type search window was very helpful using this I was able to see what resources were causing the problem (i.e. any resource that is also included in the JDK, in my case it was the ErrorHandler in the xml-apis jar). Type the name of one of the resources giving a "cannot be resolved to type" to see the name of the jar file, in my case the jar is xml-apis-1.4.01.jar.
All of this is shown in the screen shot below (click on the image to get a cleaner view).
Finding the Dependency that contains the offending jar
We can now use the information from https://www.eclipse.org/forums/index.php/t/1110036/ to find the dependency in our pom.xml file that contains the offending resource.
Open the pom.xml file in Eclipse and select the "Dependency Hierarchy". In the filter type the name of the jar file we found in the previous step (in my case it was xml-apis).
This will pull up the dependencies creating the problem. A screen shot of the Dependencies Hierarchy filtered for "xml-apis". From this we can see the offending dependencies in our pom.xml file are xercesImpl and xlsx-streamer.
Solving the problem
We can now add exclusions to these dependencies that will resolve the problem as shown below.
<dependency>
<groupId>com.monitorjbl</groupId>
<artifactId>xlsx-streamer</artifactId>
<version>2.1.0</version>
<exclusions>
<exclusion>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>xerces</groupId>
<artifactId>xercesImpl</artifactId>
<version>2.12.0</version>
<exclusions>
<exclusion>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
</exclusion>
</exclusions>
</dependency>
And this fixes the current problem.
For anyone who suffer with this problem when refering to the org.w3c or javax.xml imports, be careful with this one module dependency: xml-apis it conflicts with java default xml classes.
One big project who references it is called DynamicJasper
Here's the image of my app
It seems to me the real problem here is that the JDK (in my case, JDK-19) has org.w3c.dom embedded in it, so everything else that was doing the correct thing by referencing libraries from external-lib, rather than embedding is now broken. I removed xml-apis and xerces, but it still complains about org.w3c.dom. the only place it is referenced in my project is the JDK.
Removing jar files, (xml-apis.jar and xerces_2_5_0.jar) Does not fix the issue. I cannot remove batik, project depends upon it.
I have a standard Java build, no maven. There is no decompiling/removing a valid reference that can be done with 3rd party software like batik.
Any suggestions on how to remove the embedded org.w3c.dom from JDK-19 so I can build?
I had this problem with the Stanford Core NLP package. As mentioned above adding an exclusion in the pom.xml solved the problem:
<dependency>
<groupId>edu.stanford.nlp</groupId>
<artifactId>stanford-corenlp</artifactId>
<version>4.5.2</version>
<exclusions>
<exclusion>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
</exclusion>
</exclusions>
</dependency>
First of all, make sure your pom is actually correct by running
mvn install
if that works, and eclipse still complains look at build path and find the library it is holding onto that is not in your pom.
Sometimes I just
rm .classpath
rm -rf .settings
rm -rf project
mvn eclipse:clean eclipse:eclipse
I created a mixed project Java+Kotlin in eclipse oxygen. I added the kotlin plugin to eclipse and added kotlin nature to the project. No problem compiling or building with maven.
When I executed the project I got an exception because the kotlin runtime jar is not there. No problem again, I added the jar manually in the run configuration like so:
But this is a hack.
Can anybody tell me the most elegant way to tell eclipse to add the same runtime used by the eclipse kotlin plugin when I execute the program so that said runtime jar will stay in sync if I ever update the plugin.
If it helps, this is what the library looks like in the project's build path:
It seems simple enough but I can't figure the right way to do it...
As I mentioned in the comment above, the fact that one doesn't need to add anything in Maven to have eclipse compile the Kotlin classes but needs the maven dependency to run it, confused me.
In order to run a Maven project with a Kotlin nature, containing Java and Kotlin code in Eclipse + Kotlin plugin, it is necessary to add the runtime as a dependency in the pom.xml.
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-runtime</artifactId>
<version>${kotlin.version}</version>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-stdlib</artifactId>
<version>${kotlin.version}</version>
</dependency>
Incidentally it is also advisable to add the standard library since, in all likelyhood, classes from it will be needed by the code.
The second part is finding out the right version of Kotlin to use, which has to be the same used by the plugin.
For that, we can check the plugin version
The version of the compiler is already there (1.1.1 in this case), but we can also ensure this by going to the public Kotlin plugin source code repository.
In github select the correct branch. Probably "master" if the plugin is up to date. And check the Kotlin version in the pom.xml.
If that version is not in the maven central it will be necessary to add the pertinent repository both under the repositories and pluginRepositories sections in the pom.xml.
Don't remove the Kotlin library from the libraries tab in the classpath section of the project properties dialog (it's what appears in the image in my question above)
Please bear with me. I am quite new to Maven and tried many solutions I gathered here but to no avail, unsuccessful.
I have previous enum called DialogResponse in my project, together with other classes that make up a simple dialog functionality in my JavaFX project. Recently I decided to recreate this feature into a separate library and published it in Maven Central.
I now deleted the previous enum and classes from my current project and applied the new dependency in my pom file:
<dependency>
<groupId>com.github.daytron</groupId>
<artifactId>SimpleDialogFX</artifactId>
<version>2.0.0</version>
</dependency>
This works well in importing other enums and class, but somehow the new DialogResponse cannot be imported. It gives me cannot find symbol.
I tried using search Maven Repo feature in netbeans and it points me back to my library and if I click it nothing happens.
I also double check that enum class exist in my Dependency folder.
I tried mvn -U clean install but it didn't solve the problem.
I tried opening a new project and apply the dependency, but weirdly enough it does have the same problem.
I also tried reverting to v1.0.0 and works well on any project, but I need the latest version.
I tried typing the import code but resulted to cannot find symbol.
I also tried to use:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.github.daytron</groupId>
<artifactId>SimpleDialogFX</artifactId>
<version>2.0.0</version>
</dependency>
</dependencies>
</dependencyManagement>
But it didn't solve it.
Last night, it was working well when I created a new project. But today when I tried to apply this to my JavaFX project, it seems Maven "forgot" about it.
Is this because Maven only remembers the previous enum? If so, how do I force Maven to now point to the new enum in the library. (I have deleted the original enum in the project). To make it clear, only this enum is in question, the rest of library enum and classes can be imported.
Here are more information:
- You check the library source code in here: https://github.com/Daytron/SimpleDialogFX
- Apache Maven 2.2.1 (rdebian-14)
- Java version: 1.8.0_20
- Java home: /usr/local/java/jdk1.8.0_20/jre
- Platform encoding: UTF-8
- OS name: "linux" version: "3.13.0-36-generic" arch: "amd64" Family: "unix"
I finally managed to solved it by editing the jar class in question (added few extra whitespaces) so it won't be the same with the similar deleted class in the main program.
I saved the edited library jar and recompiled it (not the jar but the program that depends on the api. I also restarted the machine. This difference, finally recognize the class in library.
I'm trying to use RichFaces in my learning JSF application. I have set up Maven using
https://repository.jboss.org/nexus/content/groups/public-jboss/
I have included the dependencies
<dependency>
<groupId>org.richfaces.ui</groupId>
<artifactId>richfaces-components-ui</artifactId>
<version>4.0.0.Final</version>
</dependency>
<dependency>
<groupId>org.richfaces.core</groupId>
<artifactId>richfaces-core-impl</artifactId>
<version>4.0.0.Final</version>
</dependency>
<dependency>
<groupId>org.richfaces.ui</groupId>
<artifactId>richfaces-components-api</artifactId>
<version>4.0.0.Final</version>
<type>pom</type>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.richfaces.core</groupId>
<artifactId>richfaces-core-api</artifactId>
<version>4.0.0.Final</version>
<type>pom</type>
<scope>compile</scope>
</dependency>
This has fetched guava-r08.jar.
When I try to run the project in Tomcat7 I see a lot of class load exceptions - failing to load classes that I can see exist within guava-r08.jar along with sac-1.3 and cssparser-0.9.5.
If I try to use the source instead - taking source from guava-r09 - Eclipse tells me that it cannot find classes such as javax.annotation.Nullable. Problem is neither can I!
Where can I find these classes, or am I taking the wrong approach from the start?
Thanks
Richard
Maven configuration for RichFaces dependencies
Tomcat fails to load these classes, because RichFaces' dependency on Guava has a runtime scope. Contrary to the compile scope, these dependencies are not added to the classpath when compiling. You must include them yourself.
To achieve this, you should include richfaces-bom in the dependency management section of your POM, as explained in this JBoss wiki article. This will include Guava and all other required dependencies RichFaces might need.
This is the "Bill of Materials" (BOM) pattern. The JBoss wiki explains this pattern far better than I would, and links to other articles on the subject.
javax.annotation.Nullable warnings in the Guava source
These occur because Guava uses JSR 305 annotations. It is not required to depend on the JSR 305 jar when using Guava, because annotations do not require to be present on the classpath once compiled. Of course, if you want to use #Nullable and other such annotations in your code (you definitely should), you'll need to add a dependency on the JSR 305 jar.
I have started from scratch using instructions at jboss.org
I installed Maven 3.0.3
I copied the supplied settings.xml to my .m2 directory and added the JBOSS section from 1
I used the command line to create the project:
mvn archetype:generate -DarchetypeGroupId=org.richfaces.archetypes \
-DarchetypeArtifactId=richfaces-archetype-simpleapp \
-DarchetypeVersion=4.0.0-SNAPSHOT \
-DgroupId=uk.m0rjc \
-DartifactId=jsfplay
I then built the project. I had to remove the previously downloaded guava jars from my m2 repository because they were corrupt - perhaps my initial problem.
mvn clean package
I copied the WAR file it produced to Tomcat and navigated to the sample page at localhost:8080/jsfplay-1.0-SNAPSHOT/
I had some issues making the project work in Eclipse. These may be due to my setup from previous experiments.
I used the "Import -> Maven -> Existing Maven Project" to import it
I had to switch the project to JDK 1.6 and 1.6 compatibility mode.
I was unable to use the JavaServer Faces facet. This does not seem to matter.
I had to set my Server Profile to use the right JDK
I had to map *.xhtml to the Faces Servlet in web.xml. It may have been corrupted when I pressed a wrong button to accept a JSF addin.
Then it worked!!
Now to try porting my existing code to the new project.
I am trying to use the Apache Java library SystemUtils to determine the operating system being used. Here is a link:
https://commons.apache.org/proper/commons-lang/download_lang.cgi
I am using netbeans to create my application. I can not figure out how to use the library. I have tried importing it but it does not seem to be installed. I have tried finding a download and adding that but I am unable to find one.
Could someone please give me some advice on how to get this library working using netbeans?
Cheers
Eef
Download the commons-lang-2.5-bin.zip
Extract it, and find the commons-lang-2.5.jar
Add that jar to the classpath of your project by:
right click your project > Properties > Libraries > Add Jar/Folder
Instructions for Netbeans 6.7. It should not be too different in other versions.
Select your project
Open Run > Set Project Configuration > Customize...
In Categories, select Libraries
In the Compile tab, click on Add JAR/Folder...
Select the commons-lang JAR.
If you are using Maven, just include the commons-lang dependency in the <dependencies> section of your pom.xml:
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.4</version>
</dependency>