Add our JTE plugin to webtools (#10)

Author: nedtwigg

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Webtools releases
 
 ## [Unreleased]
+### Added
+- `com.diffplug.webtools.jte` plugin ([#10](https://github.com/diffplug/webtools/pull/10))
 
 ## [1.2.6] - 2025-08-22
 ### Fixed

README.md

@@ -2,6 +2,7 @@
 
 - [node](#node) - hassle-free `npm install` and `npm run blah`
 - [static server](#static-server) - a simple static file server
+- [jte](#jte) - creates idiomatic Kotlin model classes for `jte` templates (strict nullability & idiomatic collections and generics)
 
 ## Node
 
@@ -30,3 +31,38 @@ tasks.register('serve', com.diffplug.webtools.serve.StaticServerTask) {
   port = 8080 // by default
 }
 ```
+
+### JTE
+
+You have to apply `gg.jte.gradle` plugin yourself. We add a task called `jteModels` which creates a Kotlin model classes with strict nullability. Like so:
+
+```jte
+// header.jte
+@param String title
+@param String createdAtAndBy
+@param Long idToImpersonateNullable
+@param String loginLinkNullable
+```
+
+will turn into
+
+```kotlin
+class header(
+  val title: String,
+  val createdAtAndBy: String,
+  val idToImpersonateNullable: Long?,
+  val loginLinkNullable: String?,
+  ) : common.JteModel {
+
+  override fun render(engine: TemplateEngine, output: TemplateOutput) {
+    engine.render("pages/Admin/userShow/header.jte", mapOf(
+      "title" to title,
+      "createdAtAndBy" to createdAtAndBy,
+      "idToImpersonateNullable" to idToImpersonateNullable,
+      "loginLinkNullable" to loginLinkNullable,
+    ), output)
+  }
+}
+```
+
+We also translate Java collections and generics to their Kotlin equivalents. See `JteRenderer.convertJavaToKotlin` for details.

build.gradle

@@ -12,12 +12,39 @@ apply from: 干.file('spotless/java.gradle')
 apply from: 干.file('base/maven.gradle')
 apply from: 干.file('base/sonatype.gradle')
 
+def NEEDS_GLUE = ['jte']
+for (glue in NEEDS_GLUE) {
+	sourceSets.register(glue) {
+		compileClasspath += sourceSets.main.output
+		runtimeClasspath += sourceSets.main.output
+		java {}
+	}
+}
+jar {
+	for (glue in NEEDS_GLUE) {
+		from sourceSets.getByName(glue).output.classesDirs
+	}
+}
+
+spotless {
+	java {
+		target 'src/**/*.java'
+	}
+}
+
 dependencies {
+	// reflection for version decoupling
+	implementation 'org.jooq:joor:0.9.15'
 	// node.js
 	api 'com.github.eirslett:frontend-maven-plugin:1.15.1'
 	implementation 'com.diffplug.durian:durian-swt.os:5.0.1'
 	// static file server
 	String VER_JETTY = '11.0.25'
 	api "org.eclipse.jetty:jetty-server:$VER_JETTY"
 	api "org.eclipse.jetty:jetty-servlet:$VER_JETTY"
+	// jte codegen
+	String VER_JTE = '3.2.1'
+	jteCompileOnly gradleApi()
+	jteCompileOnly "gg.jte:jte-runtime:${VER_JTE}"
+	jteCompileOnly "gg.jte:jte:${VER_JTE}"
 }

gradle.properties

@@ -5,7 +5,7 @@ org=diffplug
 license=apache
 git_url=github.com/diffplug/webtools
 plugin_tags=node
-plugin_list=node
+plugin_list=node jte
 
 ver_java=17
 
@@ -15,3 +15,8 @@ plugin_node_id=com.diffplug.webtools.node
 plugin_node_impl=com.diffplug.webtools.node.NodePlugin
 plugin_node_name=DiffPlug NodeJS
 plugin_node_desc=Runs `npm install` and `npm run xx` in an efficient way
+
+plugin_jte_id=com.diffplug.webtools.jte
+plugin_jte_impl=com.diffplug.webtools.jte.JtePlugin
+plugin_jte_name=DiffPlug JTE
+plugin_jte_desc=Runs the JTE plugin and adds typesafe model classes

src/jte/java/com/diffplug/webtools/jte/JteRenderer.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2025 DiffPlug
+ *
+ * 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
+ *
+ *     https://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 com.diffplug.webtools.jte;
+
+import gg.jte.ContentType;
+import gg.jte.TemplateConfig;
+import gg.jte.compiler.TemplateParser;
+import gg.jte.compiler.TemplateParserVisitorAdapter;
+import gg.jte.compiler.TemplateType;
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import org.gradle.api.file.FileType;
+import org.gradle.work.ChangeType;
+import org.gradle.work.InputChanges;
+
+public class JteRenderer {
+	public static void renderTask(JtePlugin.RenderModelClassesTask task, InputChanges changes) throws IOException {
+		var templateConfig = new TemplateConfig((ContentType) task.getContentType().get(), task.getPackageName().get());
+		var renderer = new JteRenderer(task.getInputDir().getAsFile().get(), templateConfig);
+		for (var change : changes.getFileChanges(task.getInputDir())) {
+			if (change.getFileType() == FileType.DIRECTORY) {
+				return;
+			}
+			String name = change.getFile().getName();
+			if (!name.endsWith(".jte") && !name.endsWith(".kte")) {
+				continue;
+			}
+			var targetFileJte = task.getOutputDir().file(change.getNormalizedPath()).get().getAsFile().getAbsolutePath();
+			var targetFile = new File(targetFileJte.substring(0, targetFileJte.length() - 4) + ".kt");
+			if (change.getChangeType() == ChangeType.REMOVED) {
+				targetFile.delete();
+			} else {
+				targetFile.getParentFile().mkdirs();
+				Files.write(targetFile.toPath(), renderer.render(change.getFile()).getBytes(StandardCharsets.UTF_8));
+			}
+		}
+	}
+
+	static String convertJavaToKotlin(String javaType) {
+		if (javaType.equals("boolean")) {
+			return "Boolean";
+		} else if (javaType.equals("int")) {
+			return "Int";
+		} else {
+			// e.g. `@param Result<?> records` -> `val records: Result<*>`
+			return javaType
+					.replace("<?>", "<*>")
+					.replace("java.util.Collection", "Collection")
+					.replace("java.util.List", "List")
+					.replace("java.util.Map", "Map")
+					.replace("java.util.Set", "Set");
+		}
+	}
+
+	final File rootDir;
+	final TemplateConfig config;
+
+	JteRenderer(File rootDir, TemplateConfig config) {
+		this.rootDir = rootDir;
+		this.config = config;
+	}
+
+	String render(File file) throws IOException {
+		var pkg = file.getParentFile().getAbsolutePath().substring(rootDir.getAbsolutePath().length() + 1).replace(File.separatorChar, '.');
+		var name = file.getName();
+		var lastDot = name.lastIndexOf('.');
+		name = name.substring(0, lastDot);
+		String ext = file.getName().substring(lastDot);
+
+		var imports = new LinkedHashSet<String>();
+		imports.add("gg.jte.TemplateEngine");
+		imports.add("gg.jte.TemplateOutput");
+		var params = new LinkedHashMap<String, String>();
+
+		new TemplateParser(Files.readString(file.toPath()), TemplateType.Template, new TemplateParserVisitorAdapter() {
+			@Override
+			public void onImport(String importClass) {
+				imports.add(importClass.replace("static ", ""));
+			}
+
+			@Override
+			public void onParam(String parameter) {
+				var idxOfColon = parameter.indexOf(':');
+				if (idxOfColon == -1) { // .jte
+					// lastIndexOf accounts for valid multiple spaces, e.g `Map<String, String> featureMap`
+					var spaceIdx = parameter.lastIndexOf(' ');
+					var type = parameter.substring(0, spaceIdx).trim();
+					var name = parameter.substring(spaceIdx + 1).trim();
+					if (name.endsWith("Nullable")) {
+						type += "?";
+					}
+					params.put(name, convertJavaToKotlin(type));
+				} else { // .kte
+					var name = parameter.substring(0, idxOfColon).trim();
+					var type = parameter.substring(idxOfColon + 1).trim();
+					params.put(name, type);
+				}
+			}
+		}, config).parse();
+
+		var builder = new StringBuilder();
+		builder.append("package " + pkg + "\n");
+		builder.append("\n");
+		for (var imp : imports) {
+			builder.append("import " + imp + "\n");
+		}
+		builder.append("\n");
+		builder.append("class " + name + "(\n");
+		params.forEach((paramName, type) -> {
+			builder.append("\tval " + paramName + ": " + type + ",\n");
+		});
+		builder.append("\t) : common.JteModel {\n");
+		builder.append("\n");
+		builder.append("\toverride fun render(engine: TemplateEngine, output: TemplateOutput) {\n");
+		builder.append("\t\tengine.render(\"" + pkg.replace('.', '/') + "/" + name + ext + "\", mapOf(\n");
+		params.forEach((paramName, type) -> {
+			builder.append("\t\t\t\"" + paramName + "\" to " + paramName + ",\n");
+		});
+		builder.append("\t\t), output)\n");
+		builder.append("\t}\n");
+		builder.append("}");
+		return builder.toString();
+	}
+}

src/main/java/com/diffplug/webtools/jte/JtePlugin.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2025 DiffPlug
+ *
+ * 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
+ *
+ *     https://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 com.diffplug.webtools.jte;
+
+import static org.joor.Reflect.on;
+import static org.joor.Reflect.onClass;
+
+import java.io.File;
+import java.io.IOException;
+import org.gradle.api.DefaultTask;
+import org.gradle.api.Plugin;
+import org.gradle.api.Project;
+import org.gradle.api.file.DirectoryProperty;
+import org.gradle.api.plugins.JavaPluginExtension;
+import org.gradle.api.provider.Property;
+import org.gradle.api.tasks.*;
+import org.gradle.work.Incremental;
+import org.gradle.work.InputChanges;
+
+public class JtePlugin implements Plugin<Project> {
+	@Override
+	public void apply(Project project) {
+		project.getPlugins().apply("gg.jte.gradle");
+		project.getPlugins().apply("org.jetbrains.kotlin.jvm");
+		var extension = on(project.getExtensions().getByType(onClass("gg.jte.gradle.JteExtension").type()));
+
+		JavaPluginExtension javaPluginExtension = project.getExtensions().getByType(JavaPluginExtension.class);
+		SourceSet main = javaPluginExtension.getSourceSets().findByName("main");
+
+		project.getTasks().named("classes").configure(task -> {
+			task.getInputs().dir(extension.call("getSourceDirectory"));
+		});
+
+		@SuppressWarnings("unchecked")
+		var jteModelsTask = project.getTasks().register("jteModels", RenderModelClassesTask.class, task -> {
+			var jteModels = new File(project.getLayout().getBuildDirectory().getAsFile().get(), "jte-models");
+			main.getJava().srcDir(jteModels);
+			task.getOutputDir().set(jteModels);
+			task.getInputDir().set((File) extension.call("getSourceDirectory").call("get").call("toFile").get());
+			task.getPackageName().set((Property<String>) extension.call("getPackageName").get());
+			task.getContentType().set((Property<Enum<?>>) extension.call("getContentType").get());
+		});
+		project.getTasks().named("compileKotlin").configure(task -> task.dependsOn(jteModelsTask));
+	}
+
+	public static abstract class RenderModelClassesTask extends DefaultTask {
+		@Incremental
+		@PathSensitive(PathSensitivity.RELATIVE)
+		@InputDirectory
+		abstract DirectoryProperty getInputDir();
+
+		@OutputDirectory
+		abstract DirectoryProperty getOutputDir();
+
+		@Input
+		abstract Property<String> getPackageName();
+
+		@Input
+		abstract Property<Enum<?>> getContentType();
+
+		@TaskAction
+		public void render(InputChanges changes) throws IOException {
+			onClass("com.diffplug.webtools.jte.JteRenderer").call("renderTask", this, changes);
+		}
+	}
+}