Support specifying classpath for additional velocity tool classes

src/main/java/com/github/davidmc24/gradle/plugin/avro/GenerateAvroJavaTask.java

@@ -18,11 +18,11 @@
 import java.io.File;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
 import java.nio.charset.Charset;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 import java.util.stream.Collectors;
 import javax.inject.Inject;
 import org.apache.avro.Conversion;
@@ -42,10 +42,8 @@
 import org.gradle.api.provider.Property;
 import org.gradle.api.provider.Provider;
 import org.gradle.api.specs.NotSpec;
-import org.gradle.api.tasks.CacheableTask;
-import org.gradle.api.tasks.Input;
+import org.gradle.api.tasks.*;
 import org.gradle.api.tasks.Optional;
-import org.gradle.api.tasks.TaskAction;
 
 /**
  * Task to generate Java source files based on Avro protocol files and Avro schema files using {@link Protocol} and
@@ -54,6 +52,7 @@
 @SuppressWarnings("WeakerAccess")
 @CacheableTask
 public class GenerateAvroJavaTask extends OutputDirTask {
+    private FileCollection classpath;
     private static Set<String> SUPPORTED_EXTENSIONS =
         new SetBuilder<String>().add(Constants.PROTOCOL_EXTENSION).add(Constants.SCHEMA_EXTENSION).build();
 
@@ -79,6 +78,7 @@ public class GenerateAvroJavaTask extends OutputDirTask {
     @Inject
     public GenerateAvroJavaTask(ObjectFactory objects) {
         super();
+        this.classpath = GradleCompatibility.createConfigurableFileCollection(getProject());
         this.outputCharacterEncoding = objects.property(String.class);
         this.stringType = objects.property(String.class).convention(Constants.DEFAULT_STRING_TYPE);
         this.fieldVisibility = objects.property(String.class).convention(Constants.DEFAULT_FIELD_VISIBILITY);
@@ -103,6 +103,19 @@ public GenerateAvroJavaTask(ObjectFactory objects) {
         this.resolver = new SchemaResolver(projectLayout, getLogger());
     }
 
+    public void setClasspath(FileCollection classpath) {
+        this.classpath = classpath;
+    }
+
+    public void classpath(Object... paths) {
+        this.classpath.plus(getProject().files(paths));
+    }
+
+    @Classpath
+    public FileCollection getClasspath() {
+        return this.classpath;
+    }
+
     @Optional
     @Input
     public Property<String> getOutputCharacterEncoding() {
@@ -340,10 +353,11 @@ private void compile(SpecificCompiler compiler, File sourceFile) throws IOExcept
             compiler.setTemplateDir(getTemplateDirectory().get());
         }
         if (getAdditionalVelocityToolClasses().isPresent()) {
+            ClassLoader loader = assembleClassLoader();
             List<Object> tools = getAdditionalVelocityToolClasses().get().stream()
                     .map(s -> {
                         try {
-                            return Class.forName(s);
+                            return Class.forName(s, true, loader);
                         } catch (ClassNotFoundException e) {
                             throw new RuntimeException("unable to load velocity tool class " + s, e);
                         }
@@ -394,4 +408,17 @@ private void registerLogicalTypes() {
     private void registerCustomConversions(SpecificCompiler compiler) {
         customConversions.get().forEach(compiler::addCustomConversion);
     }
+
+    private ClassLoader assembleClassLoader() {
+        getLogger().debug("Using additional classpath: {}", classpath.getFiles());
+        List<URL> urls = new LinkedList<>();
+        for (File file : classpath) {
+            try {
+                urls.add(file.toURI().toURL());
+            } catch (MalformedURLException e) {
+                getLogger().debug(e.getMessage());
+            }
+        }
+        return new URLClassLoader(urls.toArray(new URL[0]), Thread.currentThread().getContextClassLoader());
+    }
 }

src/test/groovy/com/github/davidmc24/gradle/plugin/avro/AvroBasePluginFunctionalSpec.groovy

@@ -15,6 +15,9 @@
  */
 package com.github.davidmc24.gradle.plugin.avro
 
+import com.github.davidmc24.gradle.plugin.avro.test.custom.CommentGenerator
+import com.github.davidmc24.gradle.plugin.avro.test.custom.TimestampGenerator
+
 import static org.gradle.testkit.runner.TaskOutcome.SUCCESS
 
 class AvroBasePluginFunctionalSpec extends FunctionalSpec {
@@ -125,4 +128,50 @@ class AvroBasePluginFunctionalSpec extends FunctionalSpec {
         projectFile("build/generated-main-avro-avsc/org/apache/avro/Node.avsc").file
         projectFile("build/generated-main-avro-avsc/org/apache/avro/Interop.avsc").file
     }
+
+    def "supports classpath property for instantiating of velocity tools"() {
+        given:
+        copyAvroTools("src/main/java")
+        def templatesDir = projectFolder("templates")
+        copyResource("user.avsc", avroDir)
+        copyResource("record-tools.vm", templatesDir, "record.vm")
+        applyPlugin("java")
+        buildFile << """
+        |avro {
+        |    templateDirectory = "${templatesDir.toString()}/"
+        |    additionalVelocityToolClasses = ['com.github.davidmc24.gradle.plugin.avro.test.custom.TimestampGenerator',
+        |                                     'com.github.davidmc24.gradle.plugin.avro.test.custom.CommentGenerator']
+        |}
+        |tasks.register("compileTools", JavaCompile) {
+        |   source = sourceSets.main.java
+        |   classpath = sourceSets.main.compileClasspath
+        |   destinationDir = file("build/classes/java/main")
+        |}
+        |tasks.register("generateAvro", com.github.davidmc24.gradle.plugin.avro.GenerateAvroJavaTask) {
+        |    dependsOn compileTools
+        |    classpath = files("build/classes/java/main")
+        |    source file("src/main/avro")
+        |    include("**/*.avsc")
+        |    outputDir = file("build/generated-main-avro-java")
+        |}
+        |""".stripMargin()
+
+        when:
+        def result = run("generateAvro")
+
+        then: "the task succeeds"
+        result.task(":generateAvro").outcome == SUCCESS
+        def content = projectFile("build/generated-main-avro-java/example/avro/User.java").text
+
+        and: "the velocity tools have been applied"
+        content.contains(CommentGenerator.CUSTOM_COMMENT)
+        content.contains(TimestampGenerator.MESSAGE_PREFIX)
+    }
+
+    private void copyAvroTools(String destDir) {
+        copyFile("src/test/java", destDir,
+            "com/github/davidmc24/gradle/plugin/avro/test/custom/CommentGenerator.java")
+        copyFile("src/test/java", destDir,
+            "com/github/davidmc24/gradle/plugin/avro/test/custom/TimestampGenerator.java")
+    }
 }