minte9
LearnRemember / SPRING-BOOT



Application

Spring web project with Thymealf and Spring Boot DevTools. 
 
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
    <optional>true</optional>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

Controller

The @Controller handle GET requests and parses the templates. 
 
/**
 * Spring Boot MVC Controller
 * The Controller handle GET requests and returns the name of 
 * the View responsible to render html content.
 * 
 * Keep in mind that templates will not work in case that 
 * you have a @RestController
 */

package com.minte9.templates;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class HelloController {

    @GetMapping("/")
    public String home() {
        return "index.html";
    }

    @GetMapping("/message")
    @ResponseBody
    public String message() {
        return "My message"; // just String
    }
    
    /**
     * RequestParam binds the value of GET username
     * into the name parameter of hello() method
     */
    @GetMapping("/hello")
    public String hello(
        @RequestParam(name="username", required=false, defaultValue="guest") 
        String str, Model model) 
    {
        
        model.addAttribute("name", str);
        return "hello"; // .html can be omitted
    }
}

Templates

Thymeleaf parses the resources/templates/hello.html template. 
 
<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>MyPage</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <p th:text="'Hello, ' + ${name} + '!'"/>
</body>
</html>

Run

With Spring Boot DevTools you don't need to restart the server, after code changes. 
 
mvn spring-boot:run

http://localhost:8080
http://localhost:8080/hello
http://localhost:8080/hello/?username=John

# Welcome!
# Hello, guest!
# Hello, John!






Questions and answers




To avoid restarting server on every change

  • a) use Spring Boot DevTools
  • b) use Spring Thymealf


References