【web기본】2021 11 01 am : JSP & Servlet - 데이터 공유 : ServletContext 와 액션 태그(forward/include)

데이터 공유 : ServletContext
여러 Servlet에서 공통적으로 사용할 데이터를 공유할 경우,
context parameter를 이용하여 web.xml 문서에 기술...

<context-param>
<param-name>공유 파라미터 이름</param-name>
<param-value>공유 값</param-value>
</context-param>

공유 데이터 추출 : context 영역 데이터
String 변수 = getServletContext().getInitParameter("공유 파라미터 이름");

*** WEB-INF 폴더 내부는 외부에서 접근 못하도록 차단된 폴더!!!!!
web.xml
~~.jsp / ~~.html 파일들은 반드시 WebContent 영역에 존재해야 한다!!!!!

WebContent => index.html
WebContent/html => html 파일들
WebContent/js => js 파일들
WebContent/jsp => jsp 파일들
WebContent/css => css 파일들

WebContent/member/html
WebContent/member/js
WebContent/member/jsp
WebContent/member/css

WebContent/order/html
WebContent/order/js
WebContent/order/jsp

WebContent/order/css

WebContent/notice/html
WebContent/notice/js
WebContent/notice/jsp
WebContent/notice/css

옥션 / 쿠팡 /~~~ 장터들
Tomcat
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Tomcat
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Tomcat
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jsp 또는 서블릿으로 바로 이동 : response.sendRedirect()
response.sendRedirect("page.jsp?no=1&search=spring");

response.sendRedirect() 사용 시, 주의사항
response.sendRedirect()를 기준으로 위, 아래에는 화면 출력코드를 사용하지 않는다!!!
이유 : response.sendRedirect()를 만나면 해당 페이지로 바로 이동하기 때문에..

액션 태그 : JSP 페이지 내에서 어떤 동작을 하도록 지시하는 내장 태그
다른 페이지로 이동 / 다른 페이지를 내장
자바 코드를 HTML 태그 사용할 경우....
(JSTL : 별도의 라이브러리가 필요!!! <%@ tablib ~~ %> )

1. forward : 다른 페이지로 이동할 때 사용
<jsp:forward page="이동할 페이지(~~.jsp)" />

2. include : 다른 페이지를 현재 페이지에 내장(삽입) 할 때
<jsp:include page="내장(삽입)할 페이지(~~.jsp)" flush="true" />

3. param : forward / include 태그 내에서 전달할 값을 설정할 때 사용..
<jsp:forward page="이동할 페이지(~~.jsp)" >
<jsp:param name="파라미터명" value="전달값" />
<jsp:param name="파라미터명" value="전달값" />
</jsp:forward>

<jsp:include page="이동할 페이지(~~.jsp)" >
<jsp:param name="파라미터명" value="전달값" />
<jsp:param name="파라미터명" value="전달값" />

</jsp:include>