ServletConfig, ServletContext

http://noritersand.tistory.com/129

ServletConfig, ServletContext

web.xml 문서를 조작하여 서블릿에 정보를 전달하기 위한 용도로 사용되는 인터페이스.

특징과 설정방법은 다음과 같다 :

구 분	적용	범위 설정
ServletConfig	해당 서블릿에서만 사용할 수 있다. * 필터에서도 사용 가능	<servlet>   <servlet-name>    </servlet-name>   <servlet-class>    </servlet-class>   <init-param>     <param-name>   </param-name>     <param-value>   </param-value>   </init-param> </servlet>
ServletContext	동일 웹 애플리케이션 내 모든 서블릿(또는  JSP)에서 사용 할 수 있다.	<context-param>     <param-name>   </param-name>     <param-value>   </param-value> </context-param>

만약 서버의 설정을 변경해야 할 때라고 치자. 

해당 값이 자바파일에 명시되어 있다면 그 클래스를 수정하여 다시 컴파일하고 배포도 다시 해야한다.

하지만 ServletConfig나 ServletContext 인터페이스를 이용해 작성하면 xml 수정 후 서버만 리셋하면 된다. 

어느것이 더 편한지는 개발자 쓰기 나름

MVC2 패턴 구현에도 사용되는 듯 하다. 바로가기

● 예제

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<servlet>     <servlet-name>test</servlet-name>     <servlet-class>com.test1.TestServlet</servlet-class>     <init-param>         <param-name>name</param-name>         <param-value>han</param-value>     </init-param>     <init-param>         <param-name>age</param-name>         <param-value>20</param-value>     </init-param> </servlet>   <servlet-mapping>     <servlet-name>test</servlet-name>     <url-pattern>/test</url-pattern> </servlet-mapping>   <context-param>     <param-name>city</param-name>     <param-value>seoul</param-value> </context-param>

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protected void process(HttpServletRequest req, HttpServletResponse resp)         throws ServletException, IOException {     ServletConfig config = getServletConfig(); //해당 서블릿에서만 사용가능     ServletContext context = getServletContext(); //동일한 웹어플리케이션 어디서든 접근가능               String name = config.getInitParameter("name");     String age = config.getInitParameter("age");               String city = context.getInitParameter("city");             //로그설정     context.log("로그를 출력합니드아");       resp.setContentType("text/html;charset=utf-8");     PrintWriter out = resp.getWriter();               out.print("name:" + name + "<br/>");     out.print("age:" + age + "<br/>");     out.print("city:" + city + "<br/>"); }

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http://noritersand.tistory.com/65#j_3

servlet MVC2 구현예제

목차

config.properties
web.xml
CONTROL
MODEL
VIEW

WebContent/WEB-INF/config.properties

/bbs.do=com.mvc.bbs.BoardAction

/guest.do=com.mvc.guest.GuestAction

WebContent/WEB-INF/web.xml

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<servlet>    <servlet-name>my</servlet-name>    <servlet-class>com.mvc.MyServlet</servlet-class>    <init-param>        <param-name>config</param-name>        <param-value>/WEB-INF/config.properties</param-value>    </init-param>  </servlet>

CONTROL

● com.mvc.MyServlet.java  

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public class MyServlet extends HttpServlet {       private static final long serialVersionUID = 1L;       private Map<String, Object> map = new Hashtable<String, Object>();       public void init(ServletConfig config) throws ServletException {           super.init(config);           ServletContext context = getServletContext();         // web.xml 의 servlet 태그안의 init-param 값 읽어오기         String pathname = config.getInitParameter("config");           if (pathname == null)             return;           pathname = context.getRealPath(pathname);           try {             // properties 파일에 저장된 내용을 Properties 객체에 저장             Properties prop = new Properties();             FileInputStream fis = null;               fis = new FileInputStream(pathname);               // 파일의 내용을 읽어 Properties 객체에 저장             prop.load(fis);             fis.close();               // Properties 객체에 저장된 클래스의 객체를 생성 map에 저장             Iterator<Object> it = prop.keySet().iterator();               while (it.hasNext()) {                 String key = (String) it.next();                 String className = prop.getProperty(key);                   Class<?> cls = Class.forName(className);                 Object ob = cls.newInstance();                   map.put(key, ob);             }           } catch (Exception e) {             System.out.println(e);         }     }       public void destroy() {     }       protected void doGet(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException {           process(req, resp);     }       protected void doPost(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException {           process(req, resp);     }       protected void process(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException {           MyAction action = null;           try {             String uri = req.getRequestURI();               if (uri.indexOf(req.getContextPath()) == 0) {                 uri = uri.substring(req.getContextPath().length());                 action = (MyAction) map.get(uri);                 action.execute(req, resp);             }           } catch (Exception e) {             System.out.println(e);         }     } }

MODEL

● com.mvc.MyAction.java

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public abstract class MyAction {       public abstract void execute(HttpServletRequest req,             HttpServletResponse resp) throws ServletException, IOException;       public void forward(HttpServletRequest req, HttpServletResponse resp,             String path) throws ServletException, IOException {           RequestDispatcher rd = req.getRequestDispatcher(path);         rd.forward(req, resp);     } }

● com.mvc.BoardAction.java

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public class BoardAction extends MyAction {     public void execute(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException {           String mode = req.getParameter("mode");           if (mode == null || mode.equals("list")) {             forward(req, resp, "/mvc/bbs/list.jsp");         } else if (mode.equals("created")) {             forward(req, resp, "/mvc/bbs/created.jsp");         }     } }

● com.mvc.GuestAction.java

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public class GuestAction extends MyAction {     public void execute(HttpServletRequest req, HttpServletResponse resp)             throws ServletException, IOException {           String mode = req.getParameter("mode");           if (mode == null || mode.equals("guest")) {               forward(req, resp, "/mvc/guest/guest.jsp");         }     } }

VIEW

● root/mvc/bbs/list.jsp

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<body>   <a href="<%=cp%>/bbs.do">게시판</a> <a href="<%=cp%>/guest.do">방명록</a><br/>   게시판 리스트입니다.<br/> <a href="<%=cp%>/bbs.do?mode=created">글쓰기</a>   </body>     root/mvc/bbs/created.jsp <body>   <a href="<%=cp%>/bbs.do">게시판</a> <a href="<%=cp%>/guest.do">방명록</a><br/> 게시판 글쓰기입니다.<br/>   </body>

● root/mvc/guest/guest.jsp

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<body>   <a href="<%=cp%>/bbs.do">게시판</a> <a href="<%=cp%>/guest.do">방명록</a><br/> 방명록입니다.<br/>   </body>