MVC theme integration

ccm-core/src/main/java/org/libreccm/mvc/freemarker/FreemarkerViewEngine.java

@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.mvc.freemarker;
+
+import freemarker.template.Configuration;
+import freemarker.template.Template;
+import freemarker.template.TemplateException;
+import org.eclipse.krazo.engine.ViewEngineBase;
+import org.eclipse.krazo.engine.ViewEngineConfig;
+
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.nio.charset.Charset;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import javax.annotation.Priority;
+import javax.enterprise.context.ApplicationScoped;
+import javax.enterprise.context.spi.Context;
+import javax.enterprise.context.spi.CreationalContext;
+import javax.enterprise.inject.spi.Bean;
+import javax.enterprise.inject.spi.BeanManager;
+import javax.inject.Inject;
+import javax.mvc.MvcContext;
+import javax.mvc.engine.ViewEngine;
+import javax.mvc.engine.ViewEngineContext;
+import javax.mvc.engine.ViewEngineException;
+import javax.servlet.http.HttpServletRequest;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+@ApplicationScoped
+@Priority(ViewEngine.PRIORITY_APPLICATION)
+public class FreemarkerViewEngine extends ViewEngineBase {
+
+    @Inject
+    private BeanManager beanManager;
+
+    @Inject
+    @ViewEngineConfig
+    private Configuration configuration;
+    
+    @Inject
+    private MvcContext mvc;
+
+    @Override
+    public boolean supports(String view) {
+        return view.endsWith(".ftl");
+    }
+
+    @Override
+    public void processView(final ViewEngineContext context)
+        throws ViewEngineException {
+
+        final Charset charset = resolveCharsetAndSetContentType(context);
+
+        try (final Writer writer = new OutputStreamWriter(
+            context.getOutputStream(), charset
+        )) {
+            final Template template = configuration.getTemplate(
+                resolveView(context)
+            );
+
+            final Map<String, Object> model = new HashMap<>();
+            model.put("mvc", mvc);
+            model.put("request", context.getRequest(HttpServletRequest.class));
+
+            final Map<String, Object> namedBeans = beanManager
+                .getBeans(Object.class)
+                .stream()
+                .filter(bean -> bean.getName() != null)
+                .map(this::findBeanInstance)
+                .filter(Optional::isPresent)
+                .map(Optional::get)
+                .collect(
+                    Collectors.toMap(
+                        NamedBeanInstance::getName,
+                        NamedBeanInstance::getBeanInstance
+                    )
+                );
+
+            model.putAll(namedBeans);
+            model.putAll(context.getModels().asMap());
+
+            template.process(model, writer);
+        } catch (TemplateException | IOException e) {
+            throw new ViewEngineException(e);
+        }
+    }
+
+    @SuppressWarnings("rawtypes")
+    private Optional<NamedBeanInstance> findBeanInstance(final Bean<?> bean) {
+        final Context context = beanManager.getContext(bean.getScope());
+        final CreationalContext creationalContext = beanManager
+            .createCreationalContext(bean);
+        @SuppressWarnings("unchecked")
+        final Object instance = context.get(bean, creationalContext);
+
+        if (instance == null) {
+            return Optional.empty();
+        } else {
+            return Optional.of(
+                new NamedBeanInstance(bean.getName(), instance)
+            );
+        }
+    }
+
+    private class NamedBeanInstance {
+
+        private final String name;
+
+        private final Object beanInstance;
+
+        public NamedBeanInstance(String name, Object beanInstance) {
+            this.name = name;
+            this.beanInstance = beanInstance;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public Object getBeanInstance() {
+            return beanInstance;
+        }
+
+    }
+
+}