@SpringBootApplication

• the starting point of the entire project
• mandatory for the project, otherwise the SpringBoot project can’t be run

@SpringBootApplication
public class DemoApplication {

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

@RestController = @Controller + @ResponseBody

• the class as a web route controller handing HTTP requests

  • by using different path to reach the view/data

  @RestController

  • return the data directly (usually in JSON or XML format)

  @RestController
  @RequestMapping("/api")
  public class MyRestController {
  
  		//http://localhost:8080/api/hello
  		@GetMapping("/hello")
  		public String hello() {
  			return "Hello, World!";
  		}
  
  		//http://localhost:8080/api/welcome
  		@GetMapping("/welcome")
  		public String hello() {
  			return "Welcome to there!";
  		}
  
  }
  
  //we can without @RequestMapping("/api") to reach the page.
  //http://localhost:8080/hello
  //http://localhost:8080/welcome
  

@Controller + @ResponseBody

• handle a view (html)

In this case, we should have a "greetPage.html" file in your resources/templates folder with the HTML content. After entering http://localhost:8080/greet, you can achieve the content in "greetPage.html" .

If you don’t have "greetPage.html" file, the page will prompt an error

@Controller
public class GreetingController {
    @GetMapping("/greet")
    public String greet() {
        return "greetPage";
    }
}

With @ResponseBody, you can achieve the content “greetPage” in the page, even if you don’t have the "greetPage.html" file in your project.

@Controller
public class GreetingController {
    @GetMapping("/greet")
    @ResponseBody
    public String greet() {
        return "greetPage";
    }
}

If you use @RestController , you don’t need to consider the issue.

@RestController
public class GreetingController {
    @GetMapping("/greet")
    public String greet() {
        return "greetPage";
    }
}

Summary

@RequestParam

@PathVariable

• If you want to do CRUD through HTTP request, you may need to pass the value to retrieve your required data or page.
• In this section, you will learn how to pass the request data through HTTP to retrieve the data.

Example:

http://localhost:8080/api/v1/student/{id}?{parameter}

http://localhost:8080/api/v1/student/1?name=&[email protected]

since @RequestParam sets to false, we can pass optional data to the path and update the email only.