Java-Servlet技术入门笔记-3

  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置服务器字符集
        response.setCharacterEncoding("UTF-8");
        //设置浏览器字符集
        response.setHeader("Content-Type","text/html;charset=UTF-8");
        PrintWriter writer = response.getWriter();
        writer.write("哈哈");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("txt/html;charset=utf-8")
        PrintWriter writer = response.getOutputStream();
        //获取字符串的字节数组
        writer.write("哈哈".getBytes("utf-8"));
        //默认编码是本机编码，也可以自己设置编码
    }

public class Response1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //第一种方法
        /*
            System.out.println("我曾来过");
            //设置状态码302，表示重定向（已搬迁）
            response.setStatus(302);
            //设置响应头，说明新的地址在哪
            response.setHeader("Location","http://localhost:8080/myfirst/response2");
        */
        //第二种方法（推荐使用）
        response.sendRedirect("https://www.baidu.com");
    }
}

@WebServlet("/checkcode")
public class CheckCode extends HttpServlet {
    int width = 100;
    int height = 50;
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //创建验证码图片对象
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
        //美化图片
        //填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0,0,width,height);
        //画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width-1,height-1);
        String str="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
        Random random = new Random();
        for(int i = 1; i <= 4; i++){
            int index = random.nextInt(str.length());
            //获取随机字符
            char ch = str.charAt(index);
            //生成验证码
            g.drawString(ch+"",width/5*i,height/2);
        }
        //画干扰线
        for(int i = 0; i < 6; i++){
            int x1 = random.nextInt(width);
            int x2 = random.nextInt(width);
            int y1 = random.nextInt(height);
            int y2 = random.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }
        //将图片输出到页面展示
        ImageIO.write(image,"jpg",resp.getOutputStream());
    }
}

@WebServlet("/download")
public class DownloadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取请求参数，文件名称
        String filename = req.getParameter("filename");
        //获取servletContext对象以获取文件的真实路径
        ServletContext servletContext = this.getServletContext();
        String realPath = servletContext.getRealPath("/jpg/" + filename);
        //用字节流关联文件
        FileInputStream in = new FileInputStream(realPath);
        //获取文件对应的MIME类型以设置响应头类型
        String mimeType = servletContext.getMimeType(filename);
        resp.setHeader("content-type",mimeType);
        //设置响应头的打开方式
        resp.setHeader("content-disposition","attachment;filename=" + filename);
        //将输入流的数据写出到输出流中
        ServletOutputStream outputStream = resp.getOutputStream();
        byte[] buff = new byte[1024 * 8];
        int len = 0;
        //read()读取一个字节，read(byte b[])读取b.length个字节的数据到b数组中，并返回读取到的字节数，如果没有字节可读了，即read（）督导文件末尾了，则返回-1
        while((len = in.read(buff)) != -1){
            //public void write(byte b[ ], int off, int len) ：将参数b的从偏移量off开始的len个字节写到输出流
            outputStream.write(buff,0,len);
        }
        in.close();
    }
}