프로젝트 생성
🚫 war로 프로젝트 생성 시
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해당 에러를 만날 수 있는데 이 때 해결법은 preference > gradle 검색 > Build and run using 옵션을 Gradle로 바꾸면 된다.
Hello 서블릿
🙋♀️ 참고
서블릿은 톰캣 같은 웹 애플리케이션 서버를 직접 설치하고, 그 위에 서블릿 코드를 클래스 파일로 빌드해서 올린 다음 톰캣 서버를 실행하면 된다. 하지만 스프링 부트는 톰캣 서버를 내장하고 있으므로 톰캣 서버 설치 없이 편리하게 서블릿 코드를 실행할 수 있다!
@ServletComponentScan
현재 내 패키지 하위의 모든 패키지들을 내에 서블릿을 찾아 자동으로 등록하여 실행할 수 있도록 해줌
@WebServlet
name : 서블릿 이름
urlPatterns : URL 매핑
HTTP 요청을 통해 매핑된 URL이 호출되면 서블릿 컨테이너가 service 메서드를 자동 실행
HttpServletRequest 개요
HTTP 요청 메시지를 개발자가 편리하게 사용할 수 있도록 개발자 대신 HTTP 요청 메시지 파싱 후 객체에 담아 제공
HttpServletRequest 기본 사용법
package hello.servlet.basic.request;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet(name = "requestHeaderServlet", urlPatterns = "/request-header")
public class RequestHeaderServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
printStartLine(request);
printHeaders(request);
printHeaderUtils(request);
printEtc(request);
}
private void printStartLine(HttpServletRequest request) {
System.out.println("--- REQUEST-LINE - start ---");
System.out.println("request.getMethod() = " + request.getMethod()); //GET
System.out.println("request.getProtocal() = " + request.getProtocol()); //HTTP/1.1
System.out.println("request.getScheme() = " + request.getScheme()); //http
// http://localhost:8080/request-header
System.out.println("request.getRequestURL() = " + request.getRequestURL());
// /request-test
System.out.println("request.getRequestURI() = " + request.getRequestURI());
//username=hi
System.out.println("request.getQueryString() = " + request.getQueryString());
System.out.println("request.isSecure() = " + request.isSecure()); //https 사용 유무
System.out.println("--- REQUEST-LINE - end ---");
System.out.println();
}
//Header 모든 정보
private void printHeaders(HttpServletRequest request) {
System.out.println("--- Headers - start ---");
/*
Enumeration<String> headerNames = request.getHeaderNames();
while (headerNames.hasMoreElements()) {
String headerName = headerNames.nextElement();
System.out.println(headerName + ": " + headerName);
}
*/
request.getHeaderNames().asIterator()
.forEachRemaining(headerName -> System.out.println(headerName + ": " + headerName));
System.out.println("--- Headers - end ---");
System.out.println();
}
private void printHeaderUtils(HttpServletRequest request) {
System.out.println("--- Header 편의 조회 start ---");
System.out.println("[Host 편의 조회]");
System.out.println("request.getServerName() = " + request.getServerName()); //Host 헤더
System.out.println("request.getServerPort() = " + request.getServerPort()); //Host 헤더
System.out.println();
System.out.println("[Accept-Language 편의 조회]");
request.getLocales().asIterator()
.forEachRemaining(locale -> System.out.println("locale = " + locale));
System.out.println("request.getLocale() = " + request.getLocale());
System.out.println();
System.out.println("[cookie 편의 조회]");
if (request.getCookies() != null) {
for (Cookie cookie : request.getCookies()) {
System.out.println(cookie.getName() + ": " + cookie.getValue());
}
}
System.out.println();
System.out.println("[Content 편의 조회]");
System.out.println("request.getContentType() = " + request.getContentType());
System.out.println("request.getContentLength() = " + request.getContentLength());
System.out.println("request.getCharacterEncoding() = " + request.getCharacterEncoding());
System.out.println("--- Header 편의 조회 end ---");
System.out.println();
}
//기타 정보
private void printEtc(HttpServletRequest request) {
System.out.println("--- 기타 조회 start ---");
System.out.println("[Remote 정보]");
System.out.println("request.getRemoteHost() = " + request.getRemoteHost()); //
System.out.println("request.getRemoteAddr() = " + request.getRemoteAddr()); //
System.out.println("request.getRemotePort() = " + request.getRemotePort()); //
System.out.println();
System.out.println("[Local 정보]");
System.out.println("request.getLocalName() = " + request.getLocalName()); //
System.out.println("request.getLocalAddr() = " + request.getLocalAddr()); //
System.out.println("request.getLocalPort() = " + request.getLocalPort()); //
System.out.println("--- 기타 조회 end ---");
System.out.println();
}
}
HTTP 요청 데이터 개요
HTTP 요청 데이터 - GET 쿼리 파라미터
package hello.servlet.basic.request;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Enumeration;
/*
* 1. 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 request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("파라미터 조회 START");
request.getParameterNames().asIterator()
.forEachRemaining(paramName -> System.out.println(paramName + "=" + request.getParameter(paramName)));
System.out.println("파라미터 조회 END");
System.out.println();
System.out.println("단일 파라미터 조회 START");
String username = request.getParameter("username");
String age = request.getParameter("age");
System.out.println(username+" "+age);
System.out.println();
System.out.println("복수 파라미터 조회");
String[] usernames = request.getParameterValues("username");
for (String name : usernames) {
System.out.println(name);
}
response.getWriter().write("ok");
}
}
HTTP 요청 데이터 - POST HTML Form
🙋♀️참고
HTTP 요청 데이터 - API 메시지 바디
package hello.servlet.basic.request;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletInputStream;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.util.StreamUtils;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
@WebServlet(name="requestBodyStringServlet", urlPatterns = "/request-body-string")
public class RequestBodyStringServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ServletInputStream inputStream = request.getInputStream();
String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);
System.out.println("messageBody = " + messageBody);
response.getWriter().write("ok");
}
}
package hello.servlet.basic.request;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.json.JsonMapper;
import hello.servlet.basic.HelloData;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletInputStream;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.util.StreamUtils;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
@WebServlet(name="requestBodyJsonServlet", urlPatterns = "/request-body-json")
public class RequestBodyJsonServlet extends HttpServlet {
private ObjectMapper objectMapper = new ObjectMapper();
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ServletInputStream inputStream = request.getInputStream();
String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);
System.out.println(messageBody);
HelloData helloData = objectMapper.readValue(messageBody, HelloData.class);
System.out.println(helloData.getUsername() + " " + helloData.getAge());
response.getWriter().write("OK");
}
}
HttpServletResponse 기본 사용법
package hello.servlet.basic.response;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
@WebServlet(name = "responseHeaderServlet", urlPatterns = "/response-header")
public class ResponseHeaderServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// status-line
response.setStatus(HttpServletResponse.SC_OK);
// response-header
// response.setHeader("Content-Type", "text/plain;charset=utf-8"); 적용안됨
response.setContentType("text/plain;charset=utf-8");
response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
response.setHeader("Pragma", "no-cache");
response.setHeader("my-header", "hello");
// header 편의 메서드
// content(response);
// cookie(response);
redirect(response);
response.getWriter().write("OK 성공");
}
private void content(HttpServletResponse response) {
//Content-Type: text/plain;charset=utf-8
//Content-Length: 2
// response.setHeader("Content-Type", "text/plain;charset=utf-8");
response.setContentType("text/plain");
response.setCharacterEncoding("utf-8");
// response.setContentLength(2); //(생략시 자동 생성)
}
private void cookie(HttpServletResponse response) {
//Set-Cookie: myCookie=good; Max-Age=600;
//response.setHeader("Set-Cookie", "myCookie=good; Max-Age=600");
Cookie cookie = new Cookie("myCookie", "good");
cookie.setMaxAge(600); //600초
response.addCookie(cookie);
}
private void redirect(HttpServletResponse response) throws IOException {
//Status Code 302
//Location: /basic/hello-form.html
// response.setStatus(HttpServletResponse.SC_FOUND); //302
// response.setHeader("Location", "/basic/hello-form.html");
response.sendRedirect("/basic/hello-form.html");
}
}
HTTP 응답 데이터
단순 텍스트 : wirter.println("ok")
html
package hello.servlet.basic.response;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
@WebServlet(name="responseHtmlServlet", urlPatterns = "/response-html")
public class ResponseHtmlServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// Content-Type: text-html;charset=utf-8
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.println("<html>");
writer.println("<body>");
writer.println("<div style='color:pink'>안녕!</div>");
writer.println("</body>");
writer.println("</html>");
}
}
package hello.servlet.basic.response;
import com.fasterxml.jackson.databind.ObjectMapper;
import hello.servlet.basic.HelloData;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet(name="responseJsonServlet", urlPatterns = "/response-json")
public class ResponseJsonServlet extends HttpServlet {
private ObjectMapper objectMapper = new ObjectMapper();
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// Content-Type
response.setContentType("text/plain;applicaiton/json;charset=utf-8");
HelloData helloData = new HelloData();
helloData.setUsername("sek");
helloData.setAge(28);
// {"username":"sek", "age":28}
String result = objectMapper.writeValueAsString(helloData);
response.getWriter().write(result);
}
}
🙋♀️참고
application/json 은 스펙살 utf-8 형식을 사용하도록 정의되어 있기 때문에 charset=utf-8과 같은 추가 파라미터를 지원하지 않음
response.getWriter() 를 사용하면 추가 파라미터를 자동으로 추가해버리는데 이때 response.getOutputStream() 으로 출력하면 그런 문제가 없다