서블릿 컨텍스트

• 어플리케이션을 대표하는 객체
• 서블릿 프로그램이 컨테이너와 정보를 주고받기 위한 메서드를 제공한다. (ex) 파일의 MIME TYPE 정보 가져오기, 요청정보 보내기, 로깅 등
  
• 웹 애플리케이션당 1개씩 생성된다 (자동)
• 서블릿 컨텍스트 객체는 서블릿이 초기화 될 때 ServletConfig객체를 통해서 얻을 수 있다.
• 애플리케이션 종료까지 계속 살아있음 (전역변수 st로 어디서든지 쓸 수 있다)

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class T07_ServletContextTest extends HttpServlet{
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		
		ServletContext ctx = req.getServletContext();
		
		System.out.println("서블릿 컨텍스트의 기본경로 : "+**ctx.getContextPath()**);
		System.out.println("서블릿 컨텍스트의 기본경로 : "+req.getContextPath()); //같은거임
		System.out.println("서버정보 : "+ctx.getServerInfo());
		System.out.println("서블릿 API의 메이저버전 정보 : "+ctx.getMajorVersion());
		System.out.println("서블릿 API의 마이너버전 정보 : "+ctx.getMinorVersion());
		System.out.println("배포기술자에 기술된 컨텍스트명 : "+ctx.getContextPath());
		System.out.println("리소스 경로목록 : "+ctx.getServletContextName());
		System.out.println("모든 등록된 서블릿 목록 맵 : "+ctx.getServletRegistrations().toString());
		System.out.println("파일에 대한 MIME타입 정보 : "+ctx.getMimeType("a.mp3"));
		System.out.println("파일시스템상의 실제경로 : "+ctx.getRealPath("/"));
		
		// 로깅(로그파일)
		ctx.log("서블릿 컨텍스트를 이용한 로깅작업중입니다");
		
		// 속성값 설정
		ctx.setAttribute("attr1", "속성1");
		// 속성값 변경
		ctx.setAttribute("attr1", "속성2");
		//속성값 가져오기
		System.out.println("attr1 : " +ctx.getAttribute("attr1"));
		// 속성값 지우기
		ctx.removeAttribute("attr1");
	}
	
	
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doGet(req, resp);
	}

}

<servlet>
		<servlet-name>T07</servlet-name>
		<servlet-class>kr.or.ddit.basic.T07_ServletContextTest</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>T07</servlet-name>
		<url-pattern>/T07</url-pattern>
	</servlet-mapping>

리스너

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionAttributeListener,HttpSessionListener {
	@Override
	public void attributeAdded(HttpSessionBindingEvent event) {
		System.out.println("[MyHttpSessionListener]" + event.getName() + "추가됨");
	}

	@Override
	public void attributeRemoved(HttpSessionBindingEvent event) {
		System.out.println("[MyHttpSessionListener]" + event.getName() + "삭제됨");		
	}

	@Override
	public void attributeReplaced(HttpSessionBindingEvent event) {
		System.out.println("[MyHttpSessionListener]" + event.getName() + "대체됨");		
	}

	@Override
	public void sessionCreated(HttpSessionEvent se) {
		System.out.println("[MyHttpSessionListener]" + "세션이 생성됨. 세션ID => "+se.getSession().getId());				
	}

	@Override
	public void sessionDestroyed(HttpSessionEvent se) {
		System.out.println("[MyHttpSessionListener]" + "세션이 소멸됨. 세션ID => "+se.getSession().getId());				
	}
	
}

<listener>
		<listener-class>kr.or.ddit.basic.MyHttpSessionListener</listener-class>
	</listener>

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class T_09SessionListnerTest extends HttpServlet{
	
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// HttpSession 객체 생성 및 소멸
		HttpSession session = req.getSession(); //true가 디폴트
		//session.invalidate(); // 세션 삭제
		
		session.setAttribute("ATTR1", "속성1");
		session.setAttribute("ATTR1", "속성11");
		session.setAttribute("ATTR2", "속성2");
		session.removeAttribute("ATTR1");
		
		session.invalidate(); // 세션삭제
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doGet(req, resp);
	}

}

<servlet>
		<servlet-name>T09</servlet-name>
		<servlet-class>kr.or.ddit.basic.T_09SessionListnerTest</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>T09</servlet-name>
		<url-pattern>/T09</url-pattern>
	</servlet-mapping>

http://localhost/ServletTest/T09 접속

또다른 예제

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyServletContextListener implements ServletContextListener, ServletContextAttributeListener{

	@Override
	public void contextDestroyed(ServletContextEvent sce) {
		System.out.println("[MyServletContextListener] 소멸자 호출됨.");
	}

	@Override
	public void contextInitialized(ServletContextEvent sce) {
		System.out.println("[MyServletContextListener] 생성자 호출됨.");
	}

	@Override
	public void attributeAdded(ServletContextAttributeEvent event) {
		System.out.println("[MyServletContextListener] 속성 추가됨. => " + event.getName());
	}

	@Override
	public void attributeRemoved(ServletContextAttributeEvent event) {
		System.out.println("[MyServletContextListener] 속성 삭제됨. => "+event.getName());
	}

	@Override
	public void attributeReplaced(ServletContextAttributeEvent event) {
		System.out.println("[MyServletContextListener] 속성 변경됨. => "+event.getName());
	}

}

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class T10_ServletContextListenerTest extends HttpServlet{
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		req.getServletContext().setAttribute("ATTR1", "속성1"); //ATTR1 속성을 추가
		req.getServletContext().setAttribute("ATTR1", "속성11"); //ATTR1 속성을 변경
		req.getServletContext().setAttribute("ATTR2", "속성2"); //ATTR2 속성을 추가
		
		this.getServletContext().removeAttribute("ATTR1"); //ATTR1속성을 삭제
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doGet(req, resp);
	}
	
	

}

<listener>
		<listener-class>kr.or.ddit.basic.MyServletContextListener </listener-class>
	</listener>
	
	
	<servlet>
		<servlet-name>T10</servlet-name>
		<servlet-class>kr.or.ddit.basic.T10_ServletContextListenerTest</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>T10</servlet-name>
		<url-pattern>/T10</url-pattern>
	</servlet-mapping>

서버 시작시 이런 콘솔이 찍히는데, 서블릿 콘텍스트가 만들어졌다는것! 이제 갖다 쓰면돼

http://localhost/ServletTest/T10 << 접속하면

서버 종료시키면

톰캣 중지시 어플리케이션 종료..... 호출