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README.md

Spring Boot

Overview

Spring Boot

The Spring Boot is a solution to make it easier to get started with Spring development:

  • Minimize the amount of manual configuration for us by performing auto-configuration based on props files and JAR classpath.
  • Help to resolve dependecy conflicts (even Maven or Gradle).
  • Provide an embedded HTTP server (Tomcat, Jetty, Undertow, ...) and we don't need to install a server separately.

Spring Initializr

The Spring Initializr is the website provided by Spring Boot project, it help developers quickly create a starter Spring project.

We can setup the project information and download the *.zip file. The file can be imported with any IDE or editor as we like. There are something to be awared when importing with Eclipse:

  • Add <maven-jar-plugin.version>3.1.1</maven-jar-plugin.version> in the pom.xml and update project with Maven.
  • Choose [Run As] > [Java Application] (not "Run on Server") to run the application.

Spring Boot Project Structure

Spring Boot Starts



Running Spring Boot Apps from Command Line

There are two options for running the application with command line:

  1. Use Java
  2. Use Spring Boot Maven Plugin
    • No need to have Maven installed or present on the path.
    • If correct version of Maven is Not found on the computer, it will automatically download Maven.
    • If we already have Maven installed previously, we can ignore or delete the mvnw files.
# [Option 1] Java
$ java -jar <NAME_OF_JAR>.jar

# [Option 2] Spring Boot Maven Plugin
$ mvnw clean compile test
$ mvnw package
$ mvnw spring-boot:run


Application Properties

By default, Spring Boot reads information from a standard properties file loacted at ./src/main/resources/application.properties. We can define ANY custom properties in the file and then access these properties using @Value annotations in application.

  1. Define Custom Application Properties

    # Define Custom Properties
coach.name=Mickey Mouse
team.name=The Mouse Club

  2. Inject Properties into Spring Boot App

@RestController
public class FunRestController {
    // inject properties for: coach.name and team.name
    @Value("${coach.name}")
    private String coachName;

    @Value("${team.name}")
    private String teamName;
    ...
}


Spring Data JPA

Overview

Spring Data JPA create a DAO (Data Access Object) and just plug in our entity type and primary key. Then the Spring will give us a CRUD implementation for minimizing boiler-plate DAO code.

  • Spring Data JPA provides the interface JpaRepository.
  • It exposes findAll(), findById(), save(), deleteById() and others.


Spring Data REST



Thymeleaf

Overview

Thymeleaf is a Java templating engine commonly used to generate the HTML views for web applications. Moreover, it's a general purpose templating engine that can also used outside of web applications.

  • Can be an HTML page with some Thymeleaf expressions.
  • Include dynamic content from Thymeleaf expressions.
  • Also can be used as Email Templates, CSV Template and PDF Template.

Add Thymeleaf to Maven pom.xml File

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

Spring will auto-configure to use Thymeleaf since we have Thymeleaf dependency in Maven POM.

Develop Spring MVC Controller

@Controller
public class DemoController {
    @GetMapping("/")
    public String sayHello(Model theModel) {
        theModel.addAttribute("theData", new java.util.Date());
        return "helloworld";
    }
}
  • In Spring, the Thymeleaf template files go in ./src/main/resources/templates.
  • For web applications, Thymeleaf templates have a *.html extension. e.g. helloworld.html.

The Thymeleaf Template

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
  <head> ... </head>
  <body>
    <p th:text="'Time on the server is ' + ${theDate}" />
  </body>
</html>