响应数据

响应字符数据：

@WebServlet("/servletDemo3")
public class HttpServletDemo3 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置响应编码格式
        resp.setContentType("text/html;charset=UTF-8");
        //获取字节输出流
        ServletOutputStream os = resp.getOutputStream();
        //写数据
        os.write("你好".getBytes("UTF-8"));
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

响应图片：

@WebServlet("/servletDemo3")
public class HttpServletDemo3 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取图片绝对路径
        String realPath = getServletContext().getRealPath("/img/1.png");
        System.out.println(realPath);

        //1、获取字节输出流
        ServletOutputStream os = resp.getOutputStream();
        //2、创建字节输入流
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(realPath));
        //3、读取图片并写出
        int len;
        byte[] bytes = new byte[1024];
        while ((len = bis.read(bytes)) != -1) {
            os.write(bytes, 0, len);
        }
        bis.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}