2 분 소요

Java Web Application with Spring and Hibernate (1)

/ @ResponseBody / @Controller / @RequestMapping / @RequestParam

Spring MVC Controller, @ResponseBody, @Controller

@Controller  
public class SayHelloController {  
  
    //"say-hello" => "Hello! What are you learning today?"  
  
    //say-hello    // http://localhost:8080/say-hello    
    @RequestMapping("say-hello")  
    @ResponseBody  
    public String sayHello() {  
        return "Hello! What are you learning today?";  
    }  
}
  • @Service, @Component 같은걸로 bean 인걸 알려줘야함
    • 여기서는 유저의 요청 처리 다음 뷰에 객체를 넘겨주는 역할을 하는 컨트롤러 콜 -> @Controller 사용
  • @RequestMapping <- URL 주소
  • 브라우저로 어떤걸 보여줄지 -> @ResponseBody

참고 : https://cheershennah.tistory.com/179 <- @ResponseBody

Enhancing Spring MVC Controller to provide HTML response

HTML Super Hard code

@RequestMapping("say-hello-html")  
@ResponseBody  
public String sayHelloHtml() {  
    StringBuffer sb = new StringBuffer();  
    sb.append("<html>");  
    sb.append("<head>");  
    sb.append("<title> My First HTML Page - Changed</title>");  
    sb.append("</head>");  
    sb.append("<body>");  
    sb.append("My first html page with body - Changed");  
    sb.append("</body>");  
    sb.append("</html>");  
  
    return sb.toString();  
}

Using JSP

application.properties

#server.port=8081  
spring.mvc.view.prefix=/WEB-INF/jsp/  
spring.mvc.view.suffix=.jsp  
logging.level.org.springframework=debug

pom.xml

<dependency>  
   <groupId>org.apache.tomcat.embed</groupId>  
   <artifactId>tomcat-embed-jasper</artifactId>  
</dependency>


// "say-hello-jsp" => sayHello.jsp  
// /src/main/resources/META-INF/resources/WEB-INF/jsp/sayHello.jsp  
// /src/main/resources/META-INF/resources/WEB-INF/jsp/welcome.jsp  
// /src/main/resources/META-INF/resources/WEB-INF/jsp/login.jsp  
// /src/main/resources/META-INF/resources/WEB-INF/jsp/todos.jsp  

@RequestMapping("say-hello-jsp")  
//@ResponseBody  
public String sayHelloJsp() {  
    return "sayHello";  
}

  • @ResponseBody 를 사용할 경우 return에 있는 값을 다이렉트로 갖고 온다.
    • 이 경우 그냥 sayHello 만 출력됨
  • 환경 설정을 맞춰주면 return에 파일이름.jsp 의 파일이름을 넣으면 해당 jsp 파일을 반환해준다.

Login JSP

package com.in28minutes.springboot.myfirstwebapp.login;  
  
import org.springframework.stereotype.Controller;  
import org.springframework.web.bind.annotation.RequestMapping;  
  
  
@Controller  
public class LoginController {  
  
    ///login => com.in28minutes.springboot.myfirstwebapp.login.LoginController => login.jsp  
  
    @RequestMapping("login")  
    public String gotoLoginPage() {  
        return "login";  
    }  
}
  • Spring 이 찾을 수 있도록 @Controller 사용해줘야함
  • 아까 패키지에 login.jsp 파일 내용 작성후 접속하면 끝

How does Web Work?

  • A : Browser sends a request
    • HttpRequest
  • B : Server handles the request
    • Your Spring Boot Web Application
  • C : Server returns the response
    • HttpResponse

Peek into History - Model 1 Arch.

  • All CODE in Views (JSPs, ….)
    • View logic
    • Flow logic
    • Queries to databases
  • Disadvantages:
    • VERY complex JSPs
    • ZERO separation of concerns
    • Difficult to maintain

Peek into History - Model 2 Arch.

  • How about separating concerns?
    • Model : Data to genereate the view
    • View : Show information to user
    • Controller : Controls the flow
  • Advantage : Simpler to maintain
  • Concern:
    • Where to implement common features to all controllers?
      • You have a number if services
      • There might be common features that you would want to implement acreoss all these services
      • For example, if you want to implement authentication.
      • The authentication logic is similar across all the servlet
      • How do you implement it in common across all this servlet?
      • That’s where we graduated into something called a friend controller pattern. -> Front Controller

Model2 Architecure - Front Controller

  • Concept : All requests flow into a central controller
    • Called as Front Controller
  • Front Controller controls flow to Controller’s and View’s
    • Common features can be implemented in the Front Controller
  • A : Receives HTTP Request
  • B : Processes HTTP Request
    • B1 : Identifies correct Controller method
      • Based on request URL
        • /login => LoginController.gotoLoginPage
    • B2 : Executes Controller method
      • Puts data into model
      • Returns Model and View Name
    • B3 : Identifies correct View
      • Using ViewResolver
        • /WEB-INF/jsp/login.jsp
    • B4 : Executes view
  • C : Returns HTTP Response

QueryParams using RequestParam and First Look at Model

package com.in28minutes.springboot.myfirstwebapp.login;

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;


@Controller
public class LoginController {
	
	///login => com.in28minutes.springboot.myfirstwebapp.login.LoginController => login.jsp
	
	//http://localhost:8080/login?name=Ranga
	//Model
	@RequestMapping("login")
	public String gotoLoginPage(@RequestParam String name, ModelMap model) {
		model.put("model_name", name);
		System.out.println("Request param is " + name); //NOT RECOMMENDED FOR PROD CODE
		return "login";
	}
}

<html>  
   <head>  
      <title> Login Page</title>  
   </head>  
   <body>  
      Welcome to the login page ${model_name}!  <-----
   </body>  
</html>

  • 컨트롤러에서 파라미터를 받으면 뷰로 넘겨줌
  • JSP에 있는 내용을 보여주기 위해서 Model이 필요함
  • Model에 넣으면 View가 알아서 픽업해줌
    • 파라미터의 name 을 모델에서 jsp에 있는 name(model_name) 픽업

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참고