Servlet 使用 PrintWriter

2025 iThome 鐵人賽

DAY 21

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從0開始學習Java系列第 21 篇

17th鐵人賽

ingrchen

2025-09-01 23:58:18

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package web.demo;

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("/hello")
public class HelloServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        
        // 設定回應的內容型態 (告訴瀏覽器要用UTF-8顯示HTML)
        response.setContentType("text/html; charset=UTF-8");

        // 建立 PrintWriter，回應給前端
        PrintWriter out = response.getWriter();

        // 輸出 HTML 內容
        out.println("<!DOCTYPE html>");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Hello Servlet</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>哈囉！這是我的第一個Servlet輸出</h1>");
        
        // 可以接收 request 的參數
        String name = request.getParameter("name");
        if (name != null && !name.isEmpty()) {
            out.println("<p>你好, " + name + "！</p>");
        } else {
            out.println("<p>你沒有傳入 name 參數</p>");
        }

        out.println("</body>");
        out.println("</html>");

        // 結束 PrintWriter
        out.close();
    }
}