diff --git a/README.md b/README.md index 2aa3189..4db595b 100644 --- a/README.md +++ b/README.md @@ -14,3 +14,55 @@ In VsCode press `cmd+shif+p` and type `Spring Initilizr`. Choose next dependenci - Thymeleaf - Spring Boot DevTools +# Web Controller + +In Spring’s approach to building web sites, HTTP requests are handled by a controller. You can easily identify the controller by the [`@Controller`](http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/stereotype/Controller.html) annotation. In the following example, `GreetingController` handles GET requests for `/greeting` by returning the name of a [`View`](http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/servlet/View.html) (in this case, `greeting`). A `View` is responsible for rendering the HTML content. The following listing (from `src/main/java/djmil/hellomvc/GreetingController.java`) shows the controller: + +```java +package djmil.hellomvc; + +import org.springframework.stereotype.Controller; +import org.springframework.ui.Model; +import org.springframework.web.bind.annotation.GetMapping; +import org.springframework.web.bind.annotation.RequestParam; + +@Controller +public class GreetingController { + + @GetMapping("/greeting") + public String greeting(@RequestParam(name="name", required=false, defaultValue="World") String name, Model model) { + + // NOTE: Here we can request some data from our RESTful backend as well + model.addAttribute("name", name); + + return "greeting"; // <<-- template + } +} +``` + +This controller is concise and simple, but there is plenty going on. We break it down step by step. + +The `@GetMapping` annotation ensures that HTTP GET requests to `/greeting` are mapped to the `greeting()` method. + +[`@RequestParam`](http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestParam.html) binds the value of the query string parameter `name` into the `name` parameter of the `greeting()` method. This query string parameter is not `required`. If it is absent in the request, the `defaultValue` of `World` is used. The value of the `name` parameter is added to a [`Model`](http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/ui/Model.html) object, ultimately making it accessible to the view template. + +# Model, View and a Template + +The implementation of the `greeting()` method body relies on a view technology (in this case, [Thymeleaf](http://www.thymeleaf.org/doc/tutorials/2.1/thymeleafspring.html)) to perform server-side rendering of the HTML. + +> [!note] Make sure you have Thymeleaf on your classpath. Artifact co-ordinates: `org.springframework.boot:spring-boot-starter-thymeleaf` + +Thymeleaf parses the `greeting.html` template and evaluates the `th:text` expression to render the value of the `${name}` parameter that was set in the controller. The following listing `src/main/resources/templates/greeting.html` shows the template: + +```html + + +
+