Javaweb

发送错误页面

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 AServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.sendError(404, "不给你！！");
    }

}

显示图片

import java.io.FileInputStream;
import java.io.IOException;

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

import org.apache.commons.io.IOUtils;


public class BServlet extends HttpServlet {


    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        /*String s = "Hellow outputStream";
        byte[] bytes = s.getBytes();
        response.getOutputStream().write(bytes);*/
        String path = "F:/521宿舍线上点单.png";
        /*
         * 响应字节数据
         * 把一张图片读到数组中
         */
        FileInputStream in = new FileInputStream(path);
        byte[] bytes = IOUtils.toByteArray(in);//读取输入流的字节到字节数组中
        response.getOutputStream().write(bytes);
        
        
    }

}

重定向

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 CServlet extends HttpServlet {

    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("CServlet");
        /*
         * 重定向     1、设置Localhost  2、发送302状态码
         */
        /*response.setHeader("Localhost", "DServlet");
        response.setStatus(302);*/
        
        /*
         * 快捷重定向
         */
        response.sendRedirect("www.baidu.com");
    }

}

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 DServlet extends HttpServlet {


    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("DServlet");
    }

}

	/**
	 * 路径 
	 * web.xml中<url-pattern>路径（它是Servlet路径）
	 * 	要么以"*"开头 要么以"/"开头
	 * 不以"/"开头：相对当前Servlet路径
	 * 
	 * 转发和包含路径 
	 * ***以"/"开头 相对于当前路径  例如httpL//localhost:8080/项目名   request.getRequestdispacher("/Bservlet").for..();  
	 * 不以"/"开头相当于Servlet路径  
	 * 
	 * 重定向路径（客户端路径）
	 * 以 "/" 开头相对当前主机  例如"http://localhost:8080"  所以需要自己手动添加项目名   reponse.sendRedirect("/day10_1/Servlet")
	 * 
	 * 页面中超链接和表单路径  
	 * 		与重定向相同都是客户端路径，需要添加项目名
	 * 
	 * 建议使用"/" 开头的路径  即绝对路径
	 * 
	 * ServletContext获取资源路径（）
	 * 相当于项目目录  即当然index.jsp所在目录
	 * 
	 * ClassLoader获取资源路径
	 * 相对classes路径
	 * 
	 * class获取资源路径
	 * 以"/"开头相对classes目录
	 * 不以"/"开头相对于当前.class文件所在目录
	 */