@WebServlet("/ajaxLab")
public class AjaxLab extends HttpServlet {
	
	@Override
	protected void service(HttpServletRequest request, 
    HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
		String param = request.getParameter("param");	
        // ajax로 전송된 매개변수 가져옴
		System.out.println("From Client : "+param);
		
		PrintWriter out = response.getWriter();
		out.print("안녕하세요. 서버가 보낸 메세지입니다.");	
        // 브라우저(클라이언트)에 응답 메세지 보냄
	}
}

@WebServlet("/ajaxLab02")
public class AjaxLab02 extends HttpServlet {
	
	@Override
	protected void service(HttpServletRequest request, 
    HttpServletResponse response) throws ServletException, IOException {
		
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html; charset=utf-8");
		
		String result = "";
		PrintWriter out = response.getWriter();
		
		// 도서정보를 xml로 작성한 후 클라이언트로 전송
		result = "<main><book>" +
				"<title><![CDATA[Spring Securit 3/e]]></title>" +
				"<writer><![CDATA[믹 넛슨]]></writer>" +
				"<image><![CDATA[http://localhost:8080/chap14_Ajax/image/
                image2.jpg]]></image>" +
				"</book>"+
				"<book>"+
				"<title><![CDATA[함수형 코틀린]]></title>" +
				"<writer><![CDATA[마리오 아리아스]]></writer>" +
				"<image><![CDATA[http://localhost:8080/chap14_Ajax/image/
                image.jpg]]></image>" +
				"</book>"+
				 "</main>";
		System.out.println(result);
		out.print(result);
	}
}

package kr.co.ezenac.ajax;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

public class MemberDAO {
	private Connection con;
	private PreparedStatement pstmt;
	private DataSource dataFactory;
	
	public MemberDAO() {
		try {
			Context ctx = new InitialContext();
			Context envContext =(Context) ctx.lookup("java:/comp/env");
			dataFactory =(DataSource) envContext.lookup("jdbc/oracle");
			
			
		}catch(NamingException e) {
			e.printStackTrace();
		}
	}
	
	// 아이디 중복체크 메서드
	public boolean isDuplicated(String id) {
		boolean result = false;
		
		try {
			con = dataFactory.getConnection();
			String query="SELECT DECODE(COUNT(*),1,'true','false') AS result FROM T_MEMBER WHERE id= ?";
			pstmt = con.prepareStatement(query);
			pstmt.setString(1, id);
			ResultSet rs = pstmt.executeQuery();
			
			rs.next();
			result = Boolean.parseBoolean(rs.getString("result"));
			
		}catch(SQLException E) {
			E.printStackTrace();
			System.out.println("ID 중복 여부 체크 중 에러 발생");
		}
		return result;
	}
}

package kr.co.ezenac.ajax;

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;

@WebServlet("/mem")
public class MemberServlet extends HttpServlet {
	@Override
	protected void service(HttpServletRequest request,HttpServletResponse 
	response) throws ServletException, IOException {
		
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html; charset=utf-8");
		
		PrintWriter out = response.getWriter();
		
		String id = request.getParameter("id");
		System.out.println("id = "+id);
		
		MemberDAO dao = new MemberDAO();
		boolean isDuplicated = dao.isDuplicated(id);
		
		if(isDuplicated == true) {
			out.print("not_usable");	// true면 중복된 아이디
		}
		else {
			out.print("usable");
		}
	}
}

@WebServlet("/json")
public class JsonServlet extends HttpServlet {
	
	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html; charset=utf-8");
		
		// 문자열로 전송된 JSON 데이터를 가져옴
		String jsonInfo = request.getParameter("jsonInfo");
		
		// JSON데이터를 처리하기위해 JSONParser객체 생성
		JSONParser jsonParser = new JSONParser();
		try {
			//전송된 JSON 데이터를 파싱
			JSONObject jsonObject =(JSONObject) jsonParser.parse(jsonInfo);
			
			System.out.println("회원 정보");
			// JSON 데이터의 name속성들을 get()전달해 value 출력함.
			System.out.println(jsonObject.get("name"));
			System.out.println(jsonObject.get("age"));
			System.out.println(jsonObject.get("gender"));
			System.out.println(jsonObject.get("nickname"));
		} catch (ParseException e) {
			
			e.printStackTrace();
		}
	}
}