I’m working on a legacy Maven-based project. It uses an old version of Datanucleus and (the legacy) Google App Engine SDK. It’s a web application and I can’t (and don’t) see what is wrong with my configuration.

The project is plagued with several “Class was not found in the CLASSPATH” errors such as:

• Class "org.datanucleus.enhancer.asm.ASMClassEnhancer" was not found in the CLASSPATH.
• org.datanucleus.exceptions.ClassNotResolvedException: Class "com.element84.goodeatin.RestaurantMakerServlet" was not found in the CLASSPATH. Please check your specification and your CLASSPATH. (and many more other servlet not found in class path errors)

Downloading from central:
https://repo1.maven.org/maven2/org/datanucleus/datanucleus-rdbms/maven-metadata.xml
Exception in thread “Thread-2” Class
“org.datanucleus.enhancer.asm.ASMClassEnhancer” was not found in the
CLASSPATH. Please check your specification and your CLASSPATH.
org.datanucleus.exceptions.ClassNotResolvedException: Class
“org.datanucleus.enhancer.asm.ASMClassEnhancer” was not found in the
CLASSPATH. Please check your specification and your CLASSPATH. at
org.datanucleus.JDOClassLoaderResolver.classForName(JDOClassLoaderResolver.java:250)
at
org.datanucleus.enhancer.DataNucleusEnhancer.init(DataNucleusEnhancer.java:219)
at
org.datanucleus.enhancer.DataNucleusEnhancer.addClasses(DataNucleusEnhancer.java:370)
at
org.datanucleus.enhancer.EnhancerProcessor$EnhanceRunnable.run(EnhancerProcessor.java:163)
at java.lang.Thread.run(Thread.java:750) Downloaded from central:
https://repo1.maven.org/maven2/org/datanucleus/datanucleus-rdbms/maven-metadata.xml
(6.4 kB at 26 kB/s) Downloading from central:
https://repo1.maven.org/maven2/org/datanucleus/datanucleus-jpa/maven-metadata.xml
Downloading from DN_M2_Repo:
https://www.datanucleus.org/downloads/maven2/org/datanucleus/datanucleus-jpa/maven-metadata.xml
Downloaded from central:
https://repo1.maven.org/maven2/org/datanucleus/datanucleus-jpa/maven-metadata.xml
(1.2 kB at 6.5 kB/s) [INFO] DataNucleus Enhancer (version 1.1.4) :
Enhancement of classes DataNucleus Enhancer completed with success for
2 classes. Timings : input=396 ms, enhance=208 ms, total=604 ms.
Consult the log for full details

Here’s the complete project structure for reference:

goodeatin-appengine
│
│
├── src
│   ├── main
│       ├── java
│       │   └── com
│       │       └── element84
│       │           └── goodeatin
│       │               ├── AsynchronousCommentMakerServlet.java
│       │               ├── Comment.java
│       │               ├── CommentMakerServlet.java
│       │               ├── DefaultTaskQueueServlet.java
│       │               ├── EMF.java
│       │               ├── GoodEatinServlet.java
│       │               ├── MailHandlerServlet.java
│       │               ├── Restaurant.java
│       │               ├── RestaurantInfoRefresherServlet.java
│       │               ├── RestaurantMakerServlet.java
│       │               └── XMPPServlet.java
│       │
│       ├── resources
│       │   └── META-INF
│       │       ├── jdoconfig.xml
│       │       └── persistence.xml
│       │
│       └── webapp
│           ├── images
│           ├── stylesheets
│           └── WEB-INF
│               ├── appengine-web.xml
│               ├── cron.xml
│               ├── logging.properties
│               ├── web.xml
│               ├── header.jsp
│               ├── index.html
│               ├── listView.jsp
│               ├── newComment.jsp
│               ├── newRestaurant.jsp
│               └── tickle.html
│
├── pom.xml
└── README

The POM is quite long but the build is configured this way:

    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <!-- Include all files and directories under 'src/main/resources' -->
                <includes>
                    <include>**/*</include>
                </includes>
            </resource>
        </resources>

        <plugins>
            <!-- ... --> 
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>${maven.war.plugin.version}</version>
                <configuration>
                    <!-- Ensure classes are packaged within the WAR file -->
                    <archiveClasses>true</archiveClasses>
                    <webResources>
                        <resource>
                            <directory>${basedir}/src/main/webapp</directory>
                            <filtering>true</filtering>
                            <includes>
                                <include>**/appengine-web.xml</include>
                            </includes>
                        </resource>
                        <!-- Define additional resources for inclusion in the WAR. -->
                        <resource>
                            <!-- Source directory for the web configuration files. -->
                            <directory>${basedir}/src/main/webapp/WEB-INF</directory>
                            <!-- Enables Maven to replace placeholders with POM values. -->
                            <filtering>true</filtering>
                            <!-- Destination within the WAR file for these resources. -->
                            <targetPath>WEB-INF</targetPath>
                        </resource>
                        <!-- Include the META-INF directory containing the persistence.xml file -->
                        <resource>
                            <directory>${project.build.outputDirectory}/META-INF</directory>
                            <targetPath>WEB-INF/classes/META-INF</targetPath>
                            <includes>
                                <include>persistence.xml</include>
                                <include>jdoconfig.xml</include>
                            </includes>
                        </resource>
                        <!-- Ensure that the compiled classes are included -->
                        <resource>
                            <directory>${project.build.outputDirectory}</directory>
                            <targetPath>WEB-INF/classes</targetPath>
                        </resource>
                    </webResources>
                </configuration>
            </plugin>

            <plugin>
                <groupId>com.google.appengine</groupId>
                <artifactId>appengine-maven-plugin</artifactId>
                <version>${maven.gae.version}</version>
                <configuration>
                    <enableJarClasses>false</enableJarClasses>
                    <jvmFlags>
                        <jvmFlag>-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005</jvmFlag>
                    </jvmFlags>
                </configuration>
            </plugin>

            <plugin>
                <groupId>org.datanucleus</groupId>
                <artifactId>maven-datanucleus-plugin</artifactId>
                <version>${datanucleus.plugin.version}</version>
                <dependencies>
                    <dependency>
                        <groupId>org.datanucleus</groupId>
                        <artifactId>datanucleus-core</artifactId>
                        <version>${datanucleus.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.datanucleus</groupId>
                        <artifactId>datanucleus-enhancer</artifactId>
                        <version>${datanucleus.enhancer.version}</version>
                    </dependency>
                </dependencies>
                <executions>
                    <execution>
                        <goals>
                            <goal>enhance</goal>
                        </goals>
                        <phase>process-classes</phase>
                    </execution>
                </executions>
                <configuration>
                    <api>JPA</api>
                    <enhancerName>ASM</enhancerName>
                    <persistenceUnit>transactions-optional</persistenceUnit>
                    <mappingIncludes>**/*.class</mappingIncludes>
                </configuration>
            </plugin>
            <!-- ... --->
        </plugins>
    </build>

Running the project with mvn appengine:devserver what is wrong with how the project is structured and packaged that could cause these errors?