Example of event listeners does not work (Crowd plugin)

[CARLOS MEDINA SANCHEZ]

Hi,

I'm trying to run the example of a Crowd plugin with Event Listeners but it does not work.

I see differences between the official documentation and the repository example. For example, in the repository there is no listener section in atlassian-plugin.xml.

I have replaced the "System.out.println" line with a slf4j logger, but it also does not print any logs when a user is created.

If I add the listener section in atlassian-plugin.xml, when I launch Crowd it returns an error of ClassNotFoundException:

2022-06-16 09:48:53,336 localhost-startStop-1 ERROR [atlassian.plugin.manager.DefaultPluginManager] There was an error loading the descriptor 'User Created Listener' of plugin 'com.atlassian.crowd.example.crowd-event-listener-example'. Disabling.
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.atlassian.crowd.event.listener.example.UserCreatedListener': Lookup method resolution failed; nested exception is java.lang.IllegalStateException: Failed to introspect Class [com.atlassian.crowd.event.listener.example.UserCreatedListener] from ClassLoader [com.atlassian.crowd.example.crowd-event-listener-example [28]]
at com.atlassian.crowd.console.listener.StartupListener.contextInitialized(StartupListener.java:101)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4705)
Caused by: java.lang.IllegalStateException: Failed to introspect Class [com.atlassian.crowd.event.listener.example.UserCreatedListener] from ClassLoader [com.atlassian.crowd.example.crowd-event-listener-example [28]]
Caused by: java.lang.ClassNotFoundException: com.atlassian.crowd.event.user.UserCreatedEvent not found by com.atlassian.crowd.example.crowd-event-listener-example [28]

This is the source code (without the listener section):

UserCreatedListener.java

package com.atlassian.crowd.event.listener.example;

import com.atlassian.crowd.event.user.UserCreatedEvent;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class UserCreatedListener{
    private static final Logger log = LoggerFactory.getLogger(UserCreatedListener.class);

    @com.atlassian.event.api.EventListener
    public void printUserCreatedEvent(UserCreatedEvent event) {
        log.debug("User " + event.getUser().getDisplayName() + " has been created.");
    }
}

atlassian-plugin.xml

<atlassian-plugin key="${project.groupId}.${project.artifactId}" name="${project.name}" plugins-version="2">
    <plugin-info>
        <description>${project.description}</description>
        <version>${project.version}</version>
        <vendor name="${project.organization.name}" url="${project.organization.url}" />
    </plugin-info>
</atlassian-plugin>

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.atlassian.crowd.event.listener.example</groupId>
    <artifactId>crowd-event-listener-example</artifactId>
    <version>1.0.1-SNAPSHOT</version>

    <organization>
        <name>Example Company</name>
        <url>http://www.example.com/</url>
    </organization>

    <name>event-listener-example</name>
    <description>This is an event listener plugin for Atlassian Crowd.</description>
    <packaging>atlassian-plugin</packaging>

    <repositories>
        <repository>
            <id>atlassian-public</id>
            <url>https://packages.atlassian.com/mvn/maven-external/</url>
            <snapshots>
                <enabled>true</enabled>
                <updatePolicy>never</updatePolicy>
                <checksumPolicy>warn</checksumPolicy>
            </snapshots>
            <releases>
                <enabled>true</enabled>
                <checksumPolicy>warn</checksumPolicy>
            </releases>
        </repository>
    </repositories>

    <pluginRepositories>
        <pluginRepository>
            <id>atlassian-public</id>
            <url>https://packages.atlassian.com/mvn/maven-external/</url>
            <snapshots>
                <enabled>true</enabled>
                <updatePolicy>never</updatePolicy>
                <checksumPolicy>warn</checksumPolicy>
            </snapshots>
            <releases>
                <enabled>true</enabled>
                <checksumPolicy>warn</checksumPolicy>
            </releases>
        </pluginRepository>
    </pluginRepositories>

    <dependencies>
        <dependency>
            <groupId>com.atlassian.crowd</groupId>
            <artifactId>crowd-events</artifactId>
            <version>${crowd.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.atlassian.event</groupId>
            <artifactId>atlassian-event</artifactId>
            <version>4.1.2</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>com.atlassian.maven.plugins</groupId>
                <artifactId>crowd-maven-plugin</artifactId>
                <version>8.2.3</version>
                <extensions>true</extensions>
                <configuration>
                    <productVersion>${crowd.version}</productVersion>
                    <productDataVersion>${crowd.data.version}</productDataVersion>
                    <enableQuickReload>true</enableQuickReload>

                    <instructions>
                        <Import-Package>
                            com.atlassian.event.*
                        </Import-Package>
                    </instructions>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <properties>
        <crowd.version>4.3.5</crowd.version>
        <crowd.data.version>4.1.10</crowd.data.version>
    </properties>
</project>

 Thanks!

[Roman Kovalov]

Hey @CARLOS MEDINA SANCHEZ and welcome to the community!

I tried to download and run this example and have same problem as you have: ClassNotFoundException, when I was running my Crowd.

I can describe my way to solve this issue:
1) I created my custom crowd plugin with command:

atlas-create-crowd-plugin

2) Then I updated my atlas-create-crowd-plugin-module. That will allow you to use Crowd 4.4. 

AMPS_PLUGIN_VERSION="8.5.0"

3) I added UserCreatedListener class and dependencies to newly created project.
Also you can use different log levels. Other way to enable DEBUG level use this how to. Just for fun I enabled them all:

System.out.println("User " + event.getUser().getDisplayName() + " has been created.");
log.info("User " + event.getUser().getDisplayName() + " has been created.");
log.warn("User " + event.getUser().getDisplayName() + " has been created.");
log.debug("User " + event.getUser().getDisplayName() + " has been created.");
log.error("User " + event.getUser().getDisplayName() + " has been created.");

4) Then I used this command to run Crowd 4.4 with my plugin.

mvn crowd:run

And after I created user I had this message in logs:

I hope this small guide will help you to resolve the issue.

[Roman Kovalov]

upd:
You can find atlas-create-crowd-plugin-module file in your atlassian-plugin-sdk folder. For me it was:

/usr/local/Cellar/atlassian-plugin-sdk/8.2.7/libexec/bin/atlas-create-crowd-plugin-module