📋 Spring MVC - 2. 서블릿

// 서블릿이 호출되면 이 service가 호출된다.
@WebServlet(name = "helloServlet", urlPatterns = "/hello")
public class HelloServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.service(req, resp);
        System.out.println("HelloServlet");
        System.out.println("Request : " + req);
        System.out.println("Response : " + resp);

        String name = req.getParameter("name");
        System.out.println(name);
        resp.setCharacterEncoding("utf-8");
        resp.getWriter().write("hello" + name);
    }
}

request.getMethod() = GET
request.getProtocal() = HTTP/1.1
request.getScheme() = http
request.getRequestURL() = http://localhost:8080/request-header
request.getRequestURI() = /request-header
request.getQueryString() = username=hello
request.isSecure() = false

request.getHeaderNames().asIterator()
        .forEachRemaining(headerName -> System.out.println(headerName + ": " +
                request.getHeader(headerName)));
System.out.println("--- Headers - end ---");
System.out.println();

/**
 * 파라미터 전송 기능
 * http://localhost:8080/request-param?username=hello&age=20
 */

@WebServlet(name = "requestParamServlet", urlPatterns = "/request-param")
public class RequestParamServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("1. 전체 파라미터 조회");
        req.getParameterNames()
                .asIterator()
                .forEachRemaining(paramName ->
                        System.out.println(paramName + "=" + req.getParameter(paramName)));

        System.out.println("2. 단일 파라미터 조회 (더 많이 쓰는 방식)");
        String username = req.getParameter("username");
        System.out.println(username);

        System.out.println("3. 파라미터 이름이 같은 여러개 값이 있을 경우");
        String[] usernames = req.getParameterValues("username");
    }
}

@WebServlet(name = "requestBodyStringServlet", urlPatterns = "/request-body-string")
public class RequestBodyStringServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletInputStream inputStream = req.getInputStream(); // byte 코드를 얻음
        String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8); // 스프링이 제공하는 유틸리티
    }
}

@Getter
@Setter
public class HelloData {
    private String userName;
    private int age;
}

@WebServlet(name = "requestBodyJsonServlet", urlPatterns = "/request-body-json")
public class RequestBodyJsonServlet extends HttpServlet {
    private ObjectMapper objectMapper = new ObjectMapper();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletInputStream inputStream = req.getInputStream(); // byte 코드를 얻음
        String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8); // 스프링이 제공하는 유틸리티

        HelloData helloData = objectMapper.readValue(messageBody, HelloData.class);
    }
}

@WebServlet(name = "responseHeaderServlet", urlPatterns = "/response-header")
public class ResponseHeaderServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //[status-line] 상태코드 지정
        resp.setStatus(HttpServletResponse.SC_OK); //200
        //[response-headers] 응답 헤더 지정
        resp.setHeader("Content-Type", "text/plain;charset=utf-8");
        resp.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
        resp.setHeader("Pragma", "no-cache");
        resp.setHeader("my-header", "hello");
        //[Header 편의 메서드] content(response); cookie(response); redirect(response);
        //[message body] 응답 바디 지정
        PrintWriter writer = resp.getWriter();
        writer.println("ok");

        //Content-Type: text/plain;charset=utf-8
        //Content-Length: 2
        //response.setHeader("Content-Type", "text/plain;charset=utf-8");
        resp.setContentType("text/plain"); 
        resp.setCharacterEncoding("utf-8"); 
        //response.setContentLength(2); //(생략시 자동 생성)
    }
}

//Set-Cookie: myCookie=good; Max-Age=600; 
response.setHeader("Set-Cookie", "myCookie=good; Max-Age=600"); 

// 또는 
Cookie cookie = new Cookie("myCookie", "good"); 
cookie.setMaxAge(600); //600초
response.addCookie(cookie);

//Status Code 302
//Location: /basic/hello-form.html
response.setStatus(HttpServletResponse.SC_FOUND); //302
response.setHeader("Location", "/basic/hello-form.html");

// 또는
response.sendRedirect("/basic/hello-form.html");

@WebServlet(name = "responseHtmlServlet", urlPatterns = "/response-html")
public class HttpServletResponse extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, javax.servlet.http.HttpServletResponse resp) throws ServletException, IOException {
        // Content-Type: text:html; charset=utf-8
        resp.setContentType("text:html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter writer = resp.getWriter();
        writer.println("<html>");
        writer.println("<body>");
        writer.println(" <div>이건 아니지</div>");
        writer.println("</body>");
        writer.println("</html>");
    }
}

@WebServlet(name = "responseJsonServlet", urlPatterns = "/response-json")
public class ResponseJsonServlet extends HttpServlet {
    private final ObjectMapper objectMapper = new ObjectMapper();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //Content-Type: application/json
        resp.setHeader("content-type", "application/json");
        resp.setCharacterEncoding("utf-8");
        HelloData data = new HelloData();
        data.setUserName("mazzi");
        data.setAge(100);
        
        // JSON으로 변환
        String result = objectMapper.writeValueAsString(data);
        resp.getWriter().write(result);
    }
}