#541 Create a simple mechanism for merging small templates in code

Author: Igor Polevoy

javalite-common/src/main/java/org/javalite/common/Templator.java

@@ -0,0 +1,97 @@
+/*
+Copyright 2009-2016 Igor Polevoy
+
+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.javalite.common;
+
+
+import java.util.Map;
+
+import static org.javalite.common.Util.readResource;
+
+/**
+ * Simple implementation of small quick templates filled with dynamic data.<br/>
+ * An example of a template:
+ *
+ *
+ * <pre>
+ *     Hello, {{name}}!
+ * </pre>
+ *
+ *
+ * Usage:
+ *
+ * <pre>
+ *     Templator templator = new Templator("/hello_template.txt");
+ *     System.out.println(templator.merge(map("name", "Kyla"))); // prints: Hello, Kyla!
+ * </pre>
+ *
+ * <p></p>
+ * Note: Yes, I'm aware of existence of Mustache, Freemarker, Velocity, etc.
+ * This implementation is for quickly loading small snippets  of text merged with data.
+ * The goal is to eliminate code pollution. If you need more power, use bigger frameworks.
+ *
+ * @author Igor Polevoy on 9/30/16.
+ */
+public class Templator {
+
+    private String template;
+
+    /**
+     * @param templatePath path to a template on classpath
+     */
+    public Templator(String templatePath){
+        template = readResource(templatePath);
+    }
+
+    /**
+     * This method is used in repeated operations, since it will load a resource once.
+     *
+     * @param values values to merge into a template
+     * @return result of merging
+     */
+    public String merge(Map<String, ?> values){
+        return mergeFromTemplate(template, values);
+    }
+
+    /**
+     * This method  is used in one-off operations, where it is OK to load a template every time.
+     *
+     * Example:
+     * <code>
+     *     String result = Templator.mergeFromPath(readResource("/message_template.txt", valuesMap));
+     * </code>
+     *
+     * @param templatePath template to merge
+     * @param values values to merge into a template
+     * @return result of merging
+     */
+    public static String mergeFromPath(String templatePath, Map<String, ?> values) {
+        return mergeFromTemplate(readResource(templatePath), values);
+    }
+
+    /**
+     * Merges from string as template.
+     *
+     * @param template template content, with placeholders like: {{name}}
+     * @param values  map with values to merge
+     */
+    public static String mergeFromTemplate(String template, Map<String, ?> values) {
+        for (String param : values.keySet()) {
+            template = template.replace("{{" + param + "}}", values.get(param) == null ? "" : values.get(param).toString());
+        }
+        return template.replaceAll("\n|\r|  ", "");
+    }
+}

javalite-common/src/test/java/org/javalite/common/TemplatorSpec.java

@@ -0,0 +1,25 @@
+package org.javalite.common;
+
+import org.junit.Test;
+
+import static org.javalite.common.Collections.map;
+import static org.javalite.test.jspec.JSpec.a;
+
+/**
+ * @author igor on 9/30/16.
+ */
+public class TemplatorSpec {
+
+    @Test
+    public void shouldMergeTemplateWithTemplatorInstance(){
+        Templator t = new Templator("/templator/hello.txt");
+        a(t.merge(map("name", "Igor", "greeting", "Hi"))).shouldBeEqual("Hi, Igor");
+    }
+
+    @Test
+    public void shouldMergeTemplateWithStaticTemplator(){
+        a(Templator.mergeFromPath("/templator/hello.txt", map("name", "Igor", "greeting", "Hi"))).shouldBeEqual("Hi, Igor");
+    }
+}
+
+

javalite-common/src/test/resources/templator/hello.txt

@@ -0,0 +1 @@
+{{greeting}}, {{name}}