Spring Boot Mustache

last modified July 13, 2020

In Spring Boot Mustache tutorial, we are going to create a simple Spring Boot web application with Mustache template engine and HSQLDB database.

Spring is a popular Java application framework. Spring Boot is an effort to create stand-alone, production-grade Spring based applications without musch hassle.

HSQLDB is an open source relational database management system created entirely in Java. It offers a small, fast multithreaded and transactional database engine with in-memory and disk-based tables and supports embedded and server modes. It includes a powerful command line SQL tool and simple GUI query tools.

Mustache

Mustache is a simple web template system. It is available for many programming languages including Java. Mustache is described as a logic-less because it does not have any explicit control flow statements, such as if and else conditionals or for loops. Looping and conditional evaluation can be achieved using section tags processing lists and lambdas.

Spring Boot Mustache example

The following example is a Spring Boot web application that uses Mustache template engine. The data of the application is located in HSQLDB database.

$ tree
.
├── pom.xml
└── src
    ├── main
    │   ├── java
    │   │   └── com
    │   │       └── zetcode
    │   │           ├── Application.java
    │   │           ├── bean
    │   │           │   └── Car.java
    │   │           ├── controller
    │   │           │   └── MyController.java
    │   │           └── service
    │   │               ├── CarService.java
    │   │               └── ICarService.java
    │   └── resources
    │       ├── application.yml
    │       ├── data-hsqldb.sql
    │       ├── schema-hsqldb.sql
    │       ├── static
    │       │   └── css
    │       │       └── style.css
    │       └── templates
    │           ├── index.html
    │           └── showCars.html
    └── test
        └── java

This is the project structure. The template files have .html suffix; they are located in the src/main/resources/template directory by default. Spring Boot automatically configures Mustache when it finds the dependency in the Maven POM file.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                             http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.zetcode</groupId>
    <artifactId>SpringBootMustache</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.3.RELEASE</version>
    </parent>

    <dependencies>

        <dependency>
            <groupId>org.hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mustache</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

This is the Maven build file. The spring-boot-devtools enables hot swapping, disables template cache and enables live reloading. The spring-boot-starter-mustache is starter for building Spring MVC applications with Mustache. The hsqldb is a driver for HSQLDB. The spring-boot-starter-jdbc is a starter for using JDBC in Spring Boot.

package com.zetcode.bean;

public class Car {

    private Long id;
    private String name;
    private int price;

    public Car() {}

    public Car(Long id, String name, int price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Car{" + "id=" + id + ", name=" + name + ", price=" + price + '}';
    }
}

This is Car bean class. It contains car id, name, and price fields.

server:
    context-path: /myapp

spring:
    main:
        banner-mode: "off"
    datasource:
        platform: hsqldb

logging:
    level:
        org:
            springframework: ERROR

The application.yml is the main Spring Boot configuration file. The context-path defines the name of the web application. We access our application at localhost:8080/myapp/ URL. With the banner-mode property we turn off the Spring banner. The platform value is used in SQL initialization scripts: schema-${platform}.sql and data-${platform}.sql. Also, we set the logging level for spring framework to ERROR.

Notice that we do not configure the datasource; Spring automatically configures HSQLDB in the in-memory mode if there is no configuration data. We wanted to have an in-memory database, so we leave Spring to do the automatic configuration.

CREATE TABLE CARS(ID BIGINT IDENTITY PRIMARY KEY,
                  NAME VARCHAR(30), PRICE INT);

This SQL script creates the CARS table. HSQLDB uses IDENTITY clause to create auto-incremented columns. By default, the ids start from zero.

INSERT INTO CARS(NAME, PRICE) VALUES('Audi', 52642);
INSERT INTO CARS(NAME, PRICE) VALUES('Mercedes', 57127);
INSERT INTO CARS(NAME, PRICE) VALUES('Skoda', 9000);
INSERT INTO CARS(NAME, PRICE) VALUES('Volvo', 29000);
INSERT INTO CARS(NAME, PRICE) VALUES('Bentley', 350000);
INSERT INTO CARS(NAME, PRICE) VALUES('Citroen', 21000);
INSERT INTO CARS(NAME, PRICE) VALUES('Hummer', 41400);
INSERT INTO CARS(NAME, PRICE) VALUES('Volkswagen', 21600);

This script fills the table with data. Both scripts are located in the root of the classpath.

package com.zetcode.service;

import com.zetcode.bean.Car;
import java.util.List;

public interface ICarService {

    public List<Car> findAll();
}

ICarService provides a contract method to get all cities from the data source.

package com.zetcode.service;

import com.zetcode.bean.Car;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;

@Service
public class CarService implements ICarService {

    @Autowired
    private JdbcTemplate jtm;

    @Override
    public List<Car> findAll() {

        String sql = "SELECT * FROM CARS";

        List<Car> cars = jtm.query(sql, new BeanPropertyRowMapper(Car.class));

        return cars;
    }
}

CarService contains the implementation of the findAll method. We retrieve all cars from the CARS table with the help of the JdbcTemplate.

@Autowired
private JdbcTemplate jtm;

JdbcTemplate is injected.

String sql = "SELECT * FROM CARS";

This is SQL to be executed. We select all cars from the CARS table.

List<Car> cars = jtm.query(sql, new BeanPropertyRowMapper(Car.class));

BeanPropertyRowMapper converts a row into a new instance of the specified mapped target class.

package com.zetcode.controller;

import com.zetcode.bean.Car;
import com.zetcode.service.ICarService;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class MyController {

    @Autowired
    private ICarService carService;

    @RequestMapping("/")
    public String index(Model model) {

        return "index";
    }

    @RequestMapping("/showCars")
    public ModelAndView showCars() {

        List<Car> cars = carService.findAll();

        Map<String, Object> params = new HashMap<>();
        params.put("cars", cars);

        return new ModelAndView("showCars", params);
    }
}

This is the controller class for the Spring Boot web application. A controller is decorated with the @Controller annotation. The controller has two mappings: one mapping for the home page and one for listing all cars. Spring Boot automatically configures Mustache views when it detects Mustache starter in the Maven POM file.

@Autowired
private ICarService carService;

We inject the ICarService into the field with the @Autowired annotation.

@RequestMapping("/")
public String index(Model model) {

    return "index";
}

The "index" is the name of the view located in the predefined template directory.

@RequestMapping("/showCars")
public ModelAndView showCars() {

    List<Car> cars = carService.findAll();

    Map<String, Object> params = new HashMap<>();
    params.put("cars", cars);

    return new ModelAndView("showCars", params);
}

This controller method serves a list of cars. We find all car objects from the car service and place the resulting list into the parameters. Spring will locate the Mustache view named showCars and let the engine join the template with the data.

h2 {color: blue}

td:nth-child(3) {
    text-align: right;
}

The style.css is a static file located in the src/main/resources/static/css directory. It sets the h2 tag to blue colour and right aligns the data of the third column.

<!DOCTYPE html>
<html>
    <head>
        <title>Home page</title>
        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    </head>
    <body>
        <a href="showCars">Show cars</a>
    </body>
</html>

The index.html template file is the home page of the application. It contains a link to retrieve all car objects.

<!DOCTYPE html>
<html>
    <head>
        <title>Cars</title>
        <link rel="stylesheet" href="css/style.css" />
        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    </head>
    <body>
        <h2>List of cars</h2>

        <table>
            <tr>
                <th>Id</th>
                <th>Name</th>
                <th>Price</th>
            </tr>
            {{#cars}}
            <tr>
                <td>{{id}}</td>
                <td>{{name}}</td>
                <td>{{price}}</td>
            </tr>
            {{/cars}}
        </table>
    </body>
</html>

The showCars.html is a Mustache template file that contains placeholders to be filled with data from the model. Mustache uses {{}} syntax.

<link rel="stylesheet" href="css/style.css" />

We include the static CSS file.

{{#cars}}
<tr>
    <td>{{id}}</td>
    <td>{{name}}</td>
    <td>{{price}}</td>
</tr>
{{/cars}}

The {{#cars}} syntax is called a section. Sections render blocks of text one or more times, depending on the value of the key in the current context. A section begins with {{#name}} and ends with {{/name}}. If the value is a non-empty list the section will be displayed multiple times. In each case the context of the section will be set to the element in the list.

package com.zetcode;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

We set up the Spring Boot application. The @SpringBootApplication annotation enables auto-configuration and component scanning.

The application is deployed on the built-in Tomcat server, which listens on port 8080.

In this tutorial, we have created a Spring Boot web application with Mustache and HSQLDB.