HBX-3234: Improve the Maven hbm2orm Mojo

  - Execute the mojo in a classloader including the project's classpath
    (to include the project classes possibly referenced in the hbm.xml)
  - Add an example illustrating the use of a UserClass in hbm.xml
  - Add an integration test to 'ExamplesTestIT' testing the above example

Signed-off-by: Koen Aers <[email protected]>

Author: koentsje

maven/docs/examples/hbm2orm/with-user-type/README.md

@@ -0,0 +1,19 @@
+<!--
+  ~ Copyright 2004 - 2025 Red Hat, Inc.
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" basis,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+To run this example:
+- Have [Apache Maven](https://maven.apache.org) installed
+- Issue the following commands from a command-line window opened in this folder:
+  `mvn compile org.hibernate.tool:hibernate-tools-maven:${hibernate.version}:hbm2orm`

maven/docs/examples/hbm2orm/with-user-type/pom.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2018 - 2025 Red Hat, Inc.
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" basis,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+<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/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>org.hibernate.tool.maven.test</groupId>
+    <artifactId>hbm2orm-simple-default</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+
+ </project>

maven/docs/examples/hbm2orm/with-user-type/src/main/java/org/foo/Bar.java

@@ -0,0 +1,44 @@
+/*
+ * Hibernate Tools, Tooling for your Hibernate Projects
+ *
+ * Copyright 2016-2025 Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.foo;
+
+import org.hibernate.usertype.UserType;
+
+public class Bar implements UserType<Integer> {
+
+    @Override
+    public int getSqlType() {
+        return 0;
+    }
+
+    @Override
+    public Class<Integer> returnedClass() {
+        return null;
+    }
+
+    @Override
+    public Integer deepCopy(Integer integer) {
+        return 0;
+    }
+
+    @Override
+    public boolean isMutable() {
+        return false;
+    }
+
+}

maven/docs/examples/hbm2orm/with-user-type/src/main/resources/user-type.hbm.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2004 - 2025 Red Hat, Inc.
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" basis,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+<!DOCTYPE hibernate-mapping PUBLIC
+	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
+	"https://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+<hibernate-mapping>
+
+	<class name="org.bar.Foo">
+		<id name="id" type="long">
+			<generator class="assigned"/>
+		</id>
+		<property name="name" type="org.foo.Bar"/>
+	</class>
+
+</hibernate-mapping>

maven/src/functionalTest/java/org/hibernate/tool/maven/TransformHbmTestIT.java

@@ -63,8 +63,9 @@ private void runTransformHbmToOrm() throws Exception {
     	assertFalse(ormXmlFile.exists());
         new MavenCli().doMain(
                 new String[] {
-                		"-Dmaven.repo.local=" + localRepo.getAbsolutePath(),
-                		"org.hibernate.tool:hibernate-tools-maven:" + Version.versionString() + ":hbm2orm"
+                        "-Dmaven.repo.local=" + localRepo.getAbsolutePath(),
+                        "compile",
+                        "org.hibernate.tool:hibernate-tools-maven:" + Version.versionString() + ":hbm2orm"
                 },
                 projectPath.toAbsolutePath().toString(),
                 null,

maven/src/main/java/org/hibernate/tool/maven/TransformHbmMojo.java

@@ -23,14 +23,19 @@
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.Serial;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 
+import org.apache.maven.artifact.DependencyResolutionRequiredException;
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugins.annotations.Mojo;
 import org.apache.maven.plugins.annotations.Parameter;
 import org.apache.maven.plugins.annotations.ResolutionScope;
+import org.apache.maven.project.MavenProject;
 import org.hibernate.boot.MetadataSources;
 import org.hibernate.boot.jaxb.Origin;
 import org.hibernate.boot.jaxb.SourceType;
@@ -62,14 +67,25 @@ public class TransformHbmMojo extends AbstractMojo {
     @Parameter(defaultValue = "true")
     private boolean format;
 
+    @Parameter(defaultValue = "${project}", readonly = true, required = true)
+    private MavenProject project;
+
     @Override
     public void execute() {
-        MappingBinder mappingBinder = new MappingBinder(
-                MappingBinder.class.getClassLoader()::getResourceAsStream,
-                UnsupportedFeatureHandling.ERROR);
-        List<File> hbmFiles = getHbmFiles(inputFolder);
-        List<Binding<JaxbHbmHibernateMapping>> hbmMappings = getHbmMappings(hbmFiles, mappingBinder);
-        performTransformation(hbmMappings, mappingBinder, createServiceRegistry());
+        ClassLoader original = Thread.currentThread().getContextClassLoader();
+        try {
+            Thread.currentThread().setContextClassLoader(createClassLoader(original));
+            getLog().info("Starting " + this.getClass().getSimpleName() + "...");
+            MappingBinder mappingBinder = new MappingBinder(
+                    MappingBinder.class.getClassLoader()::getResourceAsStream,
+                    UnsupportedFeatureHandling.ERROR);
+            List<File> hbmFiles = getHbmFiles(inputFolder);
+            List<Binding<JaxbHbmHibernateMapping>> hbmMappings = getHbmMappings(hbmFiles, mappingBinder);
+            performTransformation(hbmMappings, mappingBinder, createServiceRegistry());
+            getLog().info("Finished " + this.getClass().getSimpleName() + "!");
+        } finally {
+            Thread.currentThread().setContextClassLoader(original);
+        }
     }
 
     private ServiceRegistry createServiceRegistry() {
@@ -174,6 +190,18 @@ private List<File> getHbmFiles(File f) {
         return result;
     }
 
+    private ClassLoader createClassLoader(ClassLoader parent) {
+        ArrayList<URL> urls = new ArrayList<>();
+        try {
+            for (String cpe : project.getRuntimeClasspathElements()) {
+                urls.add(new File(cpe).toURI().toURL());
+            }
+        } catch (DependencyResolutionRequiredException | MalformedURLException e) {
+            throw new RuntimeException("Problem while constructing project classloader", e);
+        }
+        return new URLClassLoader(urls.toArray(new URL[0]), parent);
+    }
+
     private static class HbmXmlOrigin extends Origin {
 
         @Serial