Troubleshooting

Java Compiler Version Issue

The SDK requires a JDK 11, so when a JDK 8 is used, the following kind of errors are raised:

  • When fetching the MicroEJ Gradle plugin:

    A problem occurred configuring root project 'myProject'.
> Could not resolve all files for configuration ':classpath'.
> Could not resolve com.microej.gradle.plugins:plugins:0.3.0.
        Required by:
                project : > com.microej.gradle.addon-library:com.microej.gradle.addon-library.gradle.plugin:0.3.0:20221118.151454-1
        > No matching variant of com.microej.gradle.plugins:plugins:0.3.0:20221118.151454-1 was found. The consumer was configured to find a runtime of a library compatible with Java 8, packaged as a jar, and its dependencies declared externally, as well as attribute 'org.gradle.plugin.api-version' with value '7.4' but:
                - Variant 'apiElements' capability com.microej.gradle.plugins:plugins:0.3.0 declares a library, packaged as a jar, and its dependencies declared externally:
                        - Incompatible because this component declares an API of a component compatible with Java 11 and the consumer needed a runtime of a component compatible with Java 8
                        - Other compatible attribute:
                                - Doesn't say anything about org.gradle.plugin.api-version (required '7.4')
                - Variant 'javadocElements' capability com.microej.gradle.plugins:plugins:0.3.0 declares a runtime of a component, and its dependencies declared externally:
                        - Incompatible because this component declares documentation and the consumer needed a library
                        - Other compatible attributes:
                                - Doesn't say anything about its target Java version (required compatibility with Java 8)
                                - Doesn't say anything about its elements (required them packaged as a jar)
                                - Doesn't say anything about org.gradle.plugin.api-version (required '7.4')
                - Variant 'runtimeElements' capability com.microej.gradle.plugins:plugins:0.3.0 declares a runtime of a library, packaged as a jar, and its dependencies declared externally:
                        - Incompatible because this component declares a component compatible with Java 11 and the consumer needed a component compatible with Java 8
                        - Other compatible attribute:
                                - Doesn't say anything about org.gradle.plugin.api-version (required '7.4')
                - Variant 'sourcesElements' capability com.microej.gradle.plugins:plugins:0.3.0 declares a runtime of a component, and its dependencies declared externally:
                        - Incompatible because this component declares documentation and the consumer needed a library
                        - Other compatible attributes:
                                - Doesn't say anything about its target Java version (required compatibility with Java 8)
                                - Doesn't say anything about its elements (required them packaged as a jar)
                                - Doesn't say anything about org.gradle.plugin.api-version (required '7.4')

  • When using the MicroEJ Gradle plugin:

    Cause: com/microej/gradle/plugins/MicroejApplicationGradlePlugin has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

The solution is to use a JDK 11 or a higher LTS version (11, 17 or 21) to fix this error:

  • For the command line interface, make sure that a supported JDK version is defined in the PATH environment. To check, run java -version. You should see something like this:

    $ java -version
openjdk version "11.0.14.1" 2022-02-08
OpenJDK Runtime Environment Temurin-11.0.14.1+1 (build 11.0.14.1+1)
OpenJDK 64-Bit Server VM Temurin-11.0.14.1+1 (build 11.0.14.1+1, mixed mode)

    Alternatively, you can set the JAVA_HOME environment variable to point to the installation directory of the JDK.

  • For Android Studio and IntelliJ IDEA, go to File > Settings… > Build, Execution, Deployment > Build Tools > Gradle, and make sure the selected Gradle JVM is a supported JDK version:

    Project JDK in Android Studio and IntelliJ IDEA

    Project JDK in Android Studio and IntelliJ IDEA

Unresolved Dependency

If this kind of message appears when resolving plugins or modules dependencies:

* What went wrong:
Plugin [id: 'com.microej.gradle.application', version: '0.16.0'] was not found in any of the following sources:

or this kind:

* What went wrong:
Execution failed for task ':compileJava'.
> Could not resolve all files for configuration ':compileClasspath'.
  > Could not find com.mycompany:mymodule:M.m.p.
     Searched in the following locations:
       - https://my-company-first-repository/com/mycompany/mymodule/M.m.p/kf-M.m.p.pom
       - https://my-company-first-repository/com/mycompany/mymodule/M.m.p/ivy-M.m.p.xml
       - https://my-company-second-repository/com/mycompany/mymodule/M.m.p/kf-M.m.p.pom
       - https://my-company-second-repository/com/mycompany/mymodule/M.m.p/ivy-M.m.p.xml
     Required by:
         project :

First, check that either the requested plugin or module exists in your repository.

  • If the plugin or module does not exist,

    • if it is declared as a direct dependency, the module repository is not compatible with your source code. You can either check if another module version is available in the repository or add the missing module to the repository.
    • otherwise, this is likely a missing transitive module dependency. The module repository is not consistent. Check the module repository and make sure all the transitive dependencies exist.

  • If the module exists, this may be due to a missing repository in the configuration. Check that your repository appears in the list of URLs below the error line:

    Searched in the following locations:

    If the URL of your repository is not listed, add it to the list of the repositories.

  • If the repository is correctly configured, this may be a network connection error. We can check in the debug logs, by adding the --debug arguments in the Gradle command line.

Otherwise, if your module repository is an URL, check for an Invalid SSL Certificate issue.

Invalid SSL Certificate

If a dependency cannot be retrieved from a remote repository, this may be due to a missing or incorrect SSL certificate. It can be checked in the debug logs, by adding the --debug and -Djavax.net.debug=all arguments in the Gradle command line, for example:

./gradlew build --debug -Djavax.net.debug=all

If the SSL certificate is missing or incorrect, the following line should appear:

PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

This can be raised in several cases, such as:

  • an artifact repository configured in the MicroEJ Module Manager settings using a self-signed SSL certificate or a SSL certificate not trusted by the JDK.
  • the requests to an artifact repository configured in the MicroEJ Module Manager settings are redirected to a proxy server using a SSL certificate not trusted by the JDK.

In all cases, the SSL certificate (used by the artifact repository server or the proxy) must be added to the JDK trust store that is running Gradle.

Before updating the SSL certificate, it is recommended to exit all your IDE projects and stop Gradle daemons (all versions). One simple way is to list all Java processes and kill the ones named GradleDaemon:

     ./jps
     12768
     17792 GradleDaemon
     16920
     4712 Jps
     1820 GradleDaemon

Also, if you don’t know which JDK is running Gradle, you can first fix the JDK used by Gradle by following How To Define a Specific Java Home for Gradle.

Ask your System Administrator, or retrieve the SSL certificate and add it to the JDK trust store:

  • on Windows

    1. Install Keystore Explorer.
    2. Start Keystore Explorer, and open file [JRE_HOME]/lib/security/cacerts or [JDK_HOME]/jre/lib/security/cacerts with the password changeit. You may not have the right to modify this file. Edit rights if needed before opening it or open Keystore Explorer with admin rights.
    3. Click on Tools, then Import Trusted Certificate.
    4. Select your certificate.
    5. Save the cacerts file.

  • on Linux/macOS

    1. Open a terminal.

    2. Make sure the JDK’s bin folder is in the PATH environment variable.

    3. Execute the following command:

      keytool -importcert -v -noprompt -trustcacerts -alias myAlias -file /path/to/the/certificate.pem -keystore /path/to/the/truststore -storepass changeit

If the problem still occurs, there should be a trace which indicates the beggining of the handshake phase of the SSL negotiation:

2023-12-15T17:32:47.442+0100 [DEBUG] [org.apache.http.conn.ssl.SSLConnectionSocketFactory] Starting handshake

The error very probably occurs during this phase. There should be the following trace before the error:

Consuming server Certificate handshake message

The traces below this one indicates the SSL certificate (or the SSL certificates chain) presented by the server. This certificate or one of the root or intermediate certificates must be added in the JDK truststore as explained previously.

Failing Resolution in adp Task

During the build of a project, the error Cannot locate module version for non-maven layout may be raised:

Execution failed for task ':adp'.
> Could not resolve all files for configuration ':addonProcessorClasspath'.
        > Could not download binary-nls-processor-2.4.2.adp (com.microej.tool.addon.runtime:binary-nls-processor:2.4.2)
                > Cannot locate module version for non-maven layout.
        > Could not download js-processor-0.13.0.adp (com.microej.tool.addon.runtime:js-processor:0.13.0)
                > Cannot locate module version for non-maven layout.
        > Could not download junit-processor-1.7.1.adp (ej.tool.addon.test:junit-processor:1.7.1)
                > Cannot locate module version for non-maven layout.

This is due to a wrong pattern in the declaration of the Ivy repositories. Check your Ivy repositories and make sure the value of the artifact of the patternLayout block is set to [organisation]/[module]/[revision]/[artifact]-[revision](-[classifier])(.[ext]). For example:

ivy {
        url = uri("https://repository.microej.com/5/artifacts/")
        patternLayout {
                artifact("[organisation]/[module]/[revision]/[artifact]-[revision](-[classifier])(.[ext])")
                ivy("[organisation]/[module]/[revision]/ivy-[revision].xml")
                setM2compatible(true)
        }
}

Missing Version for Publication

If the following message is displayed when publishing a module:

The project version must be defined.

It means the version property is missing and should be defined in the module build file. See Publish a Project for more information.

Fail to load a VEE Port as dependency

When a VEE Port is defined as a dependency, the build of the project can fail with the following message:

      > No 'release.properties' and 'architecture.properties' files found.
The given file <path/to/file> is not a VEE Port archive.

If the dependency is a valid VEE Port, this error probably means that several artifacts of the VEE Port have been published with the default Ivy configuration. To fix this issue, you can select the right artifact by adding information on the one to fetch in the artifact block, for example:

microejVee("com.mycompany:myveeport:1.0.0") {
        artifact {
                name = "artifact-name"
                type = "zip"
        }
}

This will select the artifact with the name artifact-name and with the type zip.

Slow Build because of File System Watching

In some cases, Gradle may take a lot of time to execute its build. One of the possible reasons is the file system watching feature which allows Gradle to track any change on the file system. Depending on your environment, this feature can impact the build execution time significantly. For example, when network drives are mapped and the network connection experiences instability.

This feature can be disabled for a build by passing the --no-watch-fs option in the command line, for example:

./gradlew build --no-watch-fs

or for all builds by setting the following property in the $USER_HOME/.gradle/gradle.properties file:

org.gradle.vfs.watch=false

Missing Tasks in the Gradle view of Android Studio

In some cases, Android Studio may not build all the Gradle tasks, the Task list not built… message is displayed:

Incomplete Gradle tasks list in Android Studio

To build all the Gradle tasks in Android Studio:

  • Go to File > Settings > Experimental,
  • Enable the option: Configure all Gradle tasks during Gradle Sync (…).

Back in the Gradle task view:

  • Right-click on the project name,

  • Select Reload Gradle Project.

    Reload the Gradle Project in Android Studio

Note

By default, all supported IDEs require the user to explicitly trigger the reload of a Gradle project when its configuration has changed. However you can configure your IDE to automatically reload your project. Refer to the How To Automatically reload a Gradle project section for more information.