필터

• 사용목적
  • 클라이언트의 요청을 수행하기 전에 가로채 필요한 작업을 수행할 수 있다
  • 클라이언트에 응답정보를 제공하기 전에 응답정보에 필요한 작업을 수행할 수 있다
• 사용 예
  • 인증필터
  • 데이터압축필터
  • 인코딩 필터
  • 로깅 및 감사처리
  • 이미지 변환 필터 등
• 인코딩 같은거... 매번 쓰기 귀찮았으니까 필터 쓰면 편하겠지!
• 사용자가 게시판 등록할때 로그인한 사람인지 체크하는 필터 등 (세션을 뒤져서 아이디 꺼내보고 있으면 로그인했단거니까 ㅇㅋ해주고 아니면 로그인화면에... )

import java.io.IOException;
import java.util.Date;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class T08_ServletFilter  implements Filter{
	
	

	@Override
	public void destroy() {
		// 필터객체가 컨테이너에의해 서비스로부커 제거되기 전에 호출됨
		System.out.println("T08_ServletFilter => destroy() 호출됨");
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("T08_ServletFilter => doFilter() 시작...");
		
		// 클라이언트 IP주소 가져오기
		String ipAddr = req.getRemoteAddr();
		// 클라이언트 포트번호 가져오기
		int port = req.getRemotePort();
		
		System.out.println("IP주소 : "+ipAddr+"\n 포트번호 : "+port+"\n 현재시간 : "+new Date().toString());
		
		// 필터체인(필터여러개)을 실행한다
		chain.doFilter(req, resp);
		
		// 필터체인 아래는 나가는 부분이래
		System.out.println("T08_ServletFilter => doFilter() 끝... ");
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		System.out.println("T08_ServletFilter => init() 호출됨");
		
		// 초기화 파라미터 정보 가져오기
		String initParam = filterConfig.getInitParameter("init-param");
		
		System.out.println("init-param : "+initParam);
	}

}

<filter>
		<filter-name>T08</filter-name>
		<filter-class>kr.or.ddit.basic.T08_ServletFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>T08</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

<servlet>
		<servlet-name>T01_SLC</servlet-name>
		<servlet-class>kr.or.ddit.basic.T01_ServletLifeCycle</servlet-class>
		**<load-on-startup>1</load-on-startup>**
	</servlet>

<filter>
		<filter-name>T08_ServletFilter</filter-name>
	</filter>
	<filter-mapping>
		<filter-name>T08_ServletFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

필터두개

import java.io.IOException;
import java.util.Date;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class T08_ServletFilter2  implements Filter{
	
	

	@Override
	public void destroy() {
		// 필터객체가 컨테이너에의해 서비스로부커 제거되기 전에 호출됨
		System.out.println("T08_ServletFilter2 => destroy() 호출됨");
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("T08_ServletFilter2 => doFilter() 시작...");
		
		// 서블릿 수행시간 계산하기
		long startTime = System.currentTimeMillis();
		
		
		// 필터체인(필터여러개)을 실행한다
		chain.doFilter(req, resp);
		
		System.out.println("서블릿 수행시간(ms) : "+(System.currentTimeMillis() - startTime));
		
		System.out.println("T08_ServletFilter2 => doFilter() 끝... ");
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		System.out.println("T08_ServletFilter2 => init() 호출됨");
		
		// 초기화 파라미터 정보 가져오기
		String initParam = filterConfig.getInitParameter("init-param");
		
		System.out.println("init-param : "+initParam);
	}

}

<filter>
		<filter-name>T08_2</filter-name>
		<filter-class>kr.or.ddit.basic.T08_ServletFilter2</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>T08_2</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

http://localhost/ServletTest/T01_SLC 에 접속하면,

initparam

<filter>
		<filter-name>T08</filter-name>
		<filter-class>kr.or.ddit.basic.T08_ServletFilter</filter-class>
		<init-param>
			<param-name>init-param</param-name>
			<param-value>파라미터값입니다</param-value>
		</init-param>
	</filter>

서블릿도 가능!

<servlet>
		<servlet-name>T01_SLC</servlet-name>
		<servlet-class>kr.or.ddit.basic.T01_ServletLifeCycle</servlet-class>
		<init-param>
			<param-name>init-param</param-name>
			<param-value>서블릿 초기화</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>T01_SLC</servlet-name>
		<url-pattern>/T01_SLC</url-pattern>
	</servlet-mapping>

인코딩을 필터로 해보자

public class T03_ServletParameterTest extends HttpServlet {
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
	//인코딩 주석처리
		//req.setCharacterEncoding("UTF-8");

인코딩을 주석처리 했으니 이렇게 한글이름이 오류가 나게됨

인코딩 필터를 만들어서 넣어주기!

import java.io.IOException;
import java.security.spec.ECField;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class CharacterEncodingFilter implements Filter {
	private String encoding; //인코딩정보
	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("인코딩 설정 정보"+ encoding);
		req.setCharacterEncoding(encoding);
		resp.setCharacterEncoding(encoding);
		
		chain.doFilter(req, resp);
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		if(filterConfig.getInitParameter("endoing") == null) {
			this.encoding = "UTF-8";
		} else {
			this.encoding = filterConfig.getInitParameter("encoding");
		}
	}

}

<filter>
		<filter-name>CEF</filter-name>
		<filter-class>kr.or.ddit.util.CharacterEncodingFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>CEF</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>