Adding Spark and Velocity

Dependencies:

compile 'com.sparkjava:spark-core:2.2'
compile group: 'org.apache.velocity', name: 'velocity', version: '1.7'

Copy and paste the following into a new Java file, Velocity Template Engine:

/*
 * Copyright 2013 Per Wendel
 *
 *  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.
 */

import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;
import spark.ModelAndView;
import spark.TemplateEngine;

import java.io.StringWriter;
import java.nio.charset.StandardCharsets;
import java.util.Map;
import java.util.Optional;
import java.util.Properties;

/**
 * Template Engine based on Apache Velocity.
 */
public class VelocityTemplateEngine extends TemplateEngine {

    private final VelocityEngine velocityEngine;
    private String encoding;

    /**
     * Constructor
     */
    public VelocityTemplateEngine() {
        Properties properties = new Properties();
        properties.setProperty("resource.loader", "class");
        properties.setProperty(
                "class.resource.loader.class",
                "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        this.velocityEngine = new VelocityEngine(properties);
    }

    /**
     * Constructor
     *
     * @param encoding The encoding to use
     */
    public VelocityTemplateEngine(String encoding) {
        this();
        this.encoding = encoding;
    }

    /**
     * Constructor
     *
     * @param velocityEngine The velocity engine, must not be null.
     */
    public VelocityTemplateEngine(VelocityEngine velocityEngine) {
        if (velocityEngine == null) {
            throw new IllegalArgumentException("velocityEngine must not be null");
        }
        this.velocityEngine = velocityEngine;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String render(ModelAndView modelAndView) {
        String templateEncoding = Optional.ofNullable(this.encoding).orElse(StandardCharsets.UTF_8.name());
        Template template = velocityEngine.getTemplate(modelAndView.getViewName(), templateEncoding);
        Object model = modelAndView.getModel();
        if (model instanceof Map) {
            Map<?, ?> modelMap = (Map<?, ?>) model;
            VelocityContext context = new VelocityContext(modelMap);
            StringWriter writer = new StringWriter();
            template.merge(context, writer);
            return writer.toString();
        } else {
            throw new IllegalArgumentException("modelAndView must be of type java.util.Map");
        }
    }

}

Create a new App.java file:

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import dao.Sql2oToDoDao;
import models.ToDo;
import org.sql2o.Sql2o;
import spark.ModelAndView;
import static spark.Spark.*;

public class App {

    public static void main(String[] args) {

        String connectionString = "jdbc:postgresql://localhost:5432/toDoList";
        Sql2o sql2o = new Sql2o(connectionString, "student", "");
        Sql2oToDoDao todoDao = new Sql2oToDoDao(sql2o); // create an instance to call methods on

        get("/", (req, res) -> {
            Map<String, Object> model = new HashMap<>(); // allows us to pass objects into the vtl template
            List<ToDo> todos = todoDao.all();
            model.put("todos", todos); // pass all ToDos into template
            return new ModelAndView(model, "index.vtl");
        }, new spark.template.velocity.VelocityTemplateEngine());


        get("/tasks/delete", (req, res) -> {
            Map<String, Object> model = new HashMap<>();
            todoDao.clearAll();
            res.redirect("/");
            return null;
        };
    }
}