2016년 8월 16일 화요일

11day JSP

servlet 실행순서

  • init()
    서블릿 시작
  • 요청
    • service()
      무조건 요청이 생겼을 경우  (사용하는 것 지양)
    • doGet()
      get 방식의 요청이 생겼을 경우
    • doPost()
      post방식의 요청이 생겼을 경우
  • destroy()
    서블릿 종료
  • 선택적으로 필요한 기능을 구현


1.서블릿
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx01</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- 서블릿 클래스에 서블릿 이름정함, 서블릿 이름으로 URL을 정함 -->
  <servlet>
      <servlet-name>ServletEx01</servlet-name>
    <servlet-class>servlet1.ServletEx01</servlet-class>      
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx01</servlet-name>
      <url-pattern>/servlet01</url-pattern>
  </servlet-mapping>
</web-app>


package servlet1;

import java.io.IOException;

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

public class ServletEx01 extends HttpServlet {

 @Override
 protected void service(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("service 호출");
 }

 @Override
 public void destroy() {
  // TODO Auto-generated method stub
  System.out.println("destroy 호출");
 }

 @Override
 public void init(ServletConfig config) throws ServletException {
  // TODO Auto-generated method stub
  System.out.println("init 호출");
 }

}
init 메서드는 최초 클라이언트에 의해 한번 수행됨
이후에 서버는 켜진채로 유지되며 다른 클라이언트요청이 오면 service 메서드만 사용

2. doGet
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx01</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- 서블릿 클래스에 서블릿 이름정함, 서블릿 이름으로 URL을 정함 -->
  <servlet>
      <servlet-name>ServletEx01</servlet-name>
    <servlet-class>servlet1.ServletEx01</servlet-class>      
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx01</servlet-name>
      <url-pattern>/servlet01</url-pattern>
  </servlet-mapping>
</web-app>

package servlet1;

import java.io.IOException;

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

public class ServletEx01 extends HttpServlet {

 //@Override
 //protected void service(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
  // TODO Auto-generated method stub
 // System.out.println("service 호출");
 //}

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("doGet 호출");
 }

 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("doPost 호출");
 }

 @Override
 public void destroy() {
  // TODO Auto-generated method stub
  System.out.println("destroy 호출");
 }

 @Override
 public void init(ServletConfig config) throws ServletException {
  // TODO Auto-generated method stub
  System.out.println("init 호출");
 }

}


3.클래스마다 서블릿 등록
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx01</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- 서블릿 클래스에 서블릿 이름정함, 서블릿 이름으로 URL을 정함 -->
  <servlet>
      <servlet-name>ServletEx01</servlet-name>
    <servlet-class>servlet1.ServletEx01</servlet-class>      
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx01</servlet-name>
      <url-pattern>/servlet01</url-pattern>
  </servlet-mapping>
  <!-- 클래스 하나당 각각 서블릿등록  -->
  <servlet>
      <servlet-name>ServletEx02</servlet-name>
    <servlet-class>servlet1.ServletEx02</servlet-class>      
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx02</servlet-name>
      <url-pattern>/servlet02</url-pattern>
  </servlet-mapping>
</web-app>

package servlet1;

import java.io.IOException;

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

public class ServletEx02 extends HttpServlet {

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("doGet 호출");
 }

 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("doPost 호출");
 }
 
}


4.JSP파일에서 서블리 호출
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="ko">
<head>
<meta name="viewport" content="width=device-width,initial-scale=1.0,minimum-scale=1.0,maximum-scale=1.0">
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<!-- JSP 파일에서 서블릿 get, post방식 호출 -->
<form action="./servlet02" method="post">
    아이디 : <input type="text" name="id" />
    <input type="submit" value="전송" />
</form>

</body>
</html>


5.서블릿 매핑
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx01</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
      <servlet-name>ServletEx01</servlet-name>
    <servlet-class>servlet1.ServletEx01</servlet-class>      
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx01</servlet-name>
      <url-pattern>/servlet01</url-pattern>
  </servlet-mapping>
  <!-- 호출 패턴의 변경  -->
  <!-- 서블릿 URL 두개적을 수 있음 -->
  <!-- 확장자를 뒤에 적어줘서 실제파일이 아니라 가상의 파일임을 암시할 수 있음 
           웹상에서 URL실제 파일이 없을때 실제파일을 찾으려면 설정파일 web.xml을 봐야한다-->
  <!-- 가상의 디렉토리를 표시할 수있음 -->
  <!-- *.daum 어느파일이름을 써도 뒤에 확장자가daum을 붙이면 서블릿이 다 받음 -->
  <servlet>
      <servlet-name>ServletEx02</servlet-name>
    <servlet-class>servlet1.ServletEx02</servlet-class>      
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx02</servlet-name>
      <url-pattern>/servlet02.do</url-pattern>
      <url-pattern>/servlet03.naver</url-pattern>
      <url-pattern>/dir/servlet03.naver</url-pattern>
      <url-pattern>*.daum</url-pattern>
  </servlet-mapping>
</web-app>

package servlet1;

import java.io.IOException;

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

public class ServletEx02 extends HttpServlet {

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("doGet 호출");
 }

 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  System.out.println("doPost 호출");
 }
 
}


ex

6.톰캣에서 해주는 서블릿 제작을 직접하기
package servlet1;

import java.io.IOException;
import java.io.PrintWriter;

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

public class ServletEx01 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doProcess(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doProcess(req, resp);
    } 
    
    //doGet, doPost 같이 받는 메소드 만듦
    protected void doProcess(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        PrintWriter out =resp.getWriter();
        out.println("<html>");
        out.println("<head>");
        out.println("</head>");
        out.println("<body>");
        out.println("Hello Servlet");
        out.println("</body>");
        out.println("</html>");
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx02</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- 서블릿 등록 -->
  <servlet>
      <servlet-name>ServletEx01</servlet-name>
      <servlet-class>servlet1.ServletEx01</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx01</servlet-name>
      <url-pattern>/servlet01</url-pattern>
  </servlet-mapping>
</web-app>


7. 서블릿 간의 요청, 응답
package servlet1;

import java.io.IOException;
import java.io.PrintWriter;

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

public class ServletEx01 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doProcess(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doProcess(req, resp);
    } 
    
    //클라이언트 get or post 요청시 실행
    protected void doProcess(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        //서블릿 응답 한글인코딩 ◀JSP에서 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
        resp.setContentType("text/html; charset=utf-8");
        
        PrintWriter out =resp.getWriter();
        out.println("<html>");
        out.println("<head>");
        out.println("<meta charset='UTF-8'>"); //HTTP 한글 페이지 인코딩
        out.println("</head>");
        out.println("<body>");
        out.println("<form action='servlet02' method='post'>");
        out.println("아이디 : <input type='text' name='id' />");
        out.println("<input type='submit' value='전송' />");
        out.println("</form>");
        out.println("</body>");
        out.println("</html>");
    }

}


package servlet1;

import java.io.IOException;
import java.io.PrintWriter;

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

public class ServletEx02 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doProcess(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doProcess(req, resp);
    } 
    
    //
    protected void doProcess(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        req.setCharacterEncoding("utf-8");
        
        String id = req.getParameter("id");
        resp.setContentType("text/html; charset=utf-8");
        PrintWriter out = resp.getWriter();
        out.println("<html>");
        out.println("<head>");
        out.println("<meta charset='UTF-8'>");
        out.println("</head>");
        out.println("<body>");
        out.println("아이디 :" +id);
        out.println("</body>");
        out.println("</html>");
    }
    
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx02</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- 서블릿 등록 -->
  <servlet>
      <servlet-name>ServletEx01</servlet-name>
      <servlet-class>servlet1.ServletEx01</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx01</servlet-name>
      <url-pattern>/servlet01</url-pattern>
  </servlet-mapping>
  <!-- 서블릿 등록 -->
  <servlet>
      <servlet-name>ServletEx02</servlet-name>
      <servlet-class>servlet1.ServletEx02</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>ServletEx02</servlet-name>
      <url-pattern>/servlet02</url-pattern>
  </servlet-mapping>
</web-app>


8. annotation기법: 서블릿을 만들고 web.xml에 일일적어주는 것을 개량


자동 생성됨 
package servlet1;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ServletEx01
 */
@WebServlet("/servlet01")
public class ServletEx01 extends HttpServlet {
 private static final long serialVersionUID = 1L;

 /**
  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  doProcess(request, response);
 }

 /**
  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  doProcess(request, response);
 }

 protected void doProcess(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  
 }
 
}


9
package servlet1;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class ServletEx01
 */
@WebServlet("/servlet01")
public class ServletEx01 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doProcess(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doProcess(request, response);
    }

    protected void doProcess(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        
        ServletContext context = getServletContext();
        String serverInfo = context.getServerInfo();
        int majorVersion = context.getMajorVersion();
        String path1 = context.getContextPath();  //프로젝트 경로를 알기위해서 자주 사용함
        String path2 = context.getRealPath("/text.html");
        
        PrintWriter out =response.getWriter();
        //서블릿 정보 출력
        out.println("<html>");
        out.println("<head>");
        out.println("<meta charset='UTF-8'>");
        out.println("</head>");
        out.println("<body>");
        out.println("웹서버 : "+ serverInfo + "<br>");
        out.println("버전 : "+ majorVersion+ "<br>");
        out.println("경로1 : "+ path1 + "<br>");
        out.println("경로2 : "+ path2 + "<br>");
        out.println("</body>");
        out.println("</html>");
    }
    
}


10.서블릿 구구단
서블릿명 : gugudan.java URL명: /gugudan 
package servlet1;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class gugudan
 */
@WebServlet("/gugudan")
public class gugudan extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }
    
    protected void doProcess(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        //서블릿 응답 한글인코딩 ◀JSP에서 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
        resp.setContentType("text/html; charset=utf-8");
        
        PrintWriter out =resp.getWriter();
        out.println("<html>");
        out.println("<head>");
        out.println("<meta charset='UTF-8'>"); //HTTP 한글 페이지 인코딩
        out.println("</head>");
        out.println("<body>");
        out.println("<form action='gugudan_ok' method='post'>");
        out.println("시작단 : <input type='text' name='startdan' />");
        out.println("끝단 : <input type='text' name='enddan' />");
        out.println("<input type='submit' value='전송' />");
        out.println("</form>");
        out.println("</body>");
        out.println("</html>");
    }
}


서블릿명 : gugudanok.java URL명: /gugudan_ok 
package servlet1;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class gugudanok
 */
@WebServlet("/gugudan_ok")
public class gugudanok extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }
    
    protected void doProcess(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        request.setCharacterEncoding("utf-8");
        int startdan = Integer.parseInt((request.getParameter("startdan")== null || request.getParameter("startdan").equals(""))?"1":request.getParameter("startdan"));
        int enddan = Integer.parseInt((request.getParameter("enddan")== null || request.getParameter("startdan").equals(""))?"2":request.getParameter("enddan"));
        
        response.setContentType("text/html; charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<html>");
        out.println("<head>");
        out.println("<meta charset='UTF-8'>");
        out.println("</head>");
        out.println("<body>");
        out.println("구구단 :<br>");
        out.print("<table border='1'>");
            for(int i=startdan; i<=enddan; i++){
                out.print("<tr>");
                for(int j=1;j<=9;j++){
                    out.print("<td>"+i+" X "+j+" = "+i*j+"</td>");
                }
                out.print("</tr>");
            }
        out.print("</table>");
        out.println("</body>");
        out.println("</html>");
    }
}


11. 웹실행시 초기값을 주고싶을때

package servlet1;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(
  //초기화 데이터 생성됨
  urlPatterns = { "/ServletEx01" }, 
  initParams = { 
    @WebInitParam(name = "user", value = "tester"), 
    @WebInitParam(name = "password", value = "1234")
  })
public class ServletEx01 extends HttpServlet {
 private static final long serialVersionUID = 1L;
 private String user;
 private String password;

 @Override
 public void init() throws ServletException {
  // 서버실행시 초기화
  user = getInitParameter("user");
  password = getInitParameter("password");

 }
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.getWriter().append("Served at: ").append(request.getContextPath());
  response.getWriter().append("user : "+user);
  response.getWriter().append("password: "+password);
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  doGet(request, response);
 }

}


12. 톰캣 서버시작시에 초기화
package servlet1;

import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//톰캣이 가동되었을때 미리 init()을 메모리에 올려둠 loadOnStartup, 빠른속도로 데이터에 접근할 수있음
//올려지는 순서 =1
@WebServlet(urlPatterns = "/ServletEx01", loadOnStartup=1)
public class ServletEx01 extends HttpServlet {
 private static final long serialVersionUID = 1L;
       
    public ServletEx01() {
        super();
    }

 public void init(ServletConfig config) throws ServletException {
  System.out.println("ServletEx01 init()");
 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.getWriter().append("Served at: ").append(request.getContextPath());
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  doGet(request, response);
 }

}


package servlet1;

import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//톰캣이 가동되었을때 미리 init()을 메모리에 올려둠 loadOnStartup, 빠른속도로 데이터에 접근할 수있음
//올려지는 순서 =2
@WebServlet(urlPatterns = "/ServletEx02", loadOnStartup=2)
public class ServletEx02 extends HttpServlet {
 private static final long serialVersionUID = 1L;
       
    public ServletEx02() {
        super();
    }

 public void init(ServletConfig config) throws ServletException {
  System.out.println("ServletEx02 init()");
 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.getWriter().append("Served at: ").append(request.getContextPath());
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  doGet(request, response);
 }

}


package servlet1;

import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//톰캣이 가동되었을때 미리 init()을 메모리에 올려둠 loadOnStartup, 빠른속도로 데이터에 접근할 수있음
//올려지는 순서 =3
@WebServlet(urlPatterns = "/ServletEx03", loadOnStartup=3)
public class ServletEx03 extends HttpServlet {
 private static final long serialVersionUID = 1L;
       
    public ServletEx03() {
        super();
    }

 public void init(ServletConfig config) throws ServletException {
  System.out.println("ServletEx03 init()");
 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.getWriter().append("Served at: ").append(request.getContextPath());
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  doGet(request, response);
 }

}


13. 서블릿은 이미지 전송 가능함
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>부부 클리닉</title>
</head>
<body>
<center>
<h3>이부부의 이혼에 찬성하십니까? 반대하십니까</h3>
    <form action="ServletEx01" method="post">
        <input type="radio" name="choice" value="yes" />찬성이에요.<br>
        <input type="radio" name="choice" value="no" />반대입니다.<br>
        <input type="submit" value="투표하기" />
    </form>
</center>
</body>
</html>


package servlet1;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

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

public class ServletEx01 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //파일저장하는 실제경로, 초기화 매개변수 파일 이름 획득
        String path = this.getServletContext().getRealPath("/data");
        String file_name = this.getInitParameter("result");
        
        //디렉토리만듦, 파일객체 만듦
        File dir = new File(path);
        if(!dir.exists())dir.mkdir();
        File file= new File(dir,file_name);
        
        //파일있으면 읽어와서 기존 찬성반대수 입력받음
        int agree =0;
        int disagree = 0;
        if(file.exists()){
            DataInputStream f_in = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));
            try{
                agree=f_in.readInt();
                disagree =f_in.readInt();
            }catch(Exception e){
                agree = 0;
                disagree = 0;
            }
            f_in.close();
        }
        
        //방금 투표한 값을 찬반수에 더해줌
        String choice = request.getParameter("choice");
        if(choice != null && choice.equalsIgnoreCase("yes")) agree++;
        else if(choice != null && choice.equalsIgnoreCase("no")) disagree++;
        
        //투표로 변경된 찬반수를 파일로 다시 저장함
        DataOutputStream f_out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
        f_out.writeInt(agree);
        f_out.writeInt(disagree);
        f_out.close();
        
        //이미지 형태의 서블릿을 HTML출력
        response.setContentType("text/html; charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<html><head><title>결과</title></head>");
        out.println("<body><center>");
        out.println("<h3>찬반투표결과!</h3>");
        out.println("<img src='ServletEx01_Sub?agree=" +agree);
        out.println("&disagree="+disagree +"'/>");
        out.println("</center></body></html>");
    }
}

package servlet1;

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;

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

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class ServletEx01_Sub extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //서블릿으로 전달된 파라매터 받음
        int agree = Integer.parseInt(request.getParameter("agree"));
        int disagree = Integer.parseInt(request.getParameter("disagree"));
        int tot = agree+disagree;
        
        //차트그림
        Graphics2D g = null;
        try{
            int width = 300;
            int height = 200;
            //그림판 생성
            BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            //그림판에 그래픽객체 생성
            g= img.createGraphics();
            
            int x_start = 30;
            int agree_y_start = height*1/4;
            int disagree_y_start = height*3/5;
            int g_height =25;
            int space =5;
            int y_space = 20;
            
            //배경
            g.setColor(Color.LIGHT_GRAY);
            g.fillRect(0, 0, width, height);
            //좌표
            g.setColor(Color.BLACK);
            g.drawLine(x_start, space, x_start, height-y_space);
            g.drawLine(x_start, height-y_space, width-space, height-y_space);
            g.drawString("찬성", space, height*1/3);
            g.drawString("반대", space, height*2/3);
            g.drawString("0%", x_start, height-space);
            g.drawString("50%", x_start+(width-(x_start+space))/2, height-space);
            g.drawString("100%", width-30, height-space);
            //찬성막대그래프
            g.setColor(Color.RED);
            g.fillRect(x_start, agree_y_start, (width-(x_start+space))*agree/tot, g_height);
            //반대막대그래프
            g.setColor(Color.GREEN);
            g.fillRect(x_start, disagree_y_start, (width-(x_start+space))*disagree/tot, g_height);
            
            //응답유형 정함
            response.setContentType("image/jpeg");
            //이미지처리 1바이트 출력 스트림 생성
            ServletOutputStream out = response.getOutputStream();
            //인코딩 객체 생성
            JPEGImageEncoder encode = JPEGCodec.createJPEGEncoder(out);
            //인코딩 후 출력
            encode.encode(img);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            if(g !=null) g.dispose();
        }
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletEx00</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- 서블릿 등록, 초기값 지정 -->
  <servlet>
      <servlet-name>MyServlet</servlet-name>
      <servlet-class>servlet1.ServletEx01</servlet-class>
      <init-param>
          <param-name>result</param-name>
          <param-value>result.dat</param-value>
      </init-param>
  </servlet>
  <servlet-mapping>
      <servlet-name>MyServlet</servlet-name>
      <url-pattern>/ServletEx01</url-pattern>
  </servlet-mapping>
  <!-- 서블릿 등록 -->
  <servlet>
      <servlet-name>MyServlet_Sub</servlet-name>
      <servlet-class>servlet1.ServletEx01_Sub</servlet-class>
  </servlet>
    <servlet-mapping>
      <servlet-name>MyServlet_Sub</servlet-name>
      <url-pattern>/ServletEx01_Sub</url-pattern>
  </servlet-mapping>
</web-app>


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