response（向客户端写入数据、对相应进行设置（状态码、响应头））

一、向客户端写入数据

1、写入文字

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");//设置服务器的编码，默认是ISO-8859-1
        response.setContentType("text/html; charset = utf-8");//告诉浏览器服务器的编码格式
        response.getWriter().write("你好，JAVA");
    }

 2、图片

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletOutputStream out=response.getOutputStream();
        File file=new File("图片路径");
        FileInputStream fi = new FileInputStream(file);
        byte[] buf = new byte[1024];
        int len = 0;
        while ((len = fi.read(buf)) != -1) {
            out.write(buf, 0, len); // 将数组中的指定长度的数据写入到输出流中。
        }
        fi.close();
        out.close();
    }

采用了缓冲数组读入图片数据，减少了时间的消耗。创建ServletOutputStream对象，将数据输出到了客户端。

二、response对响应的设置

1、response对象设置响应行状态码：

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setStatus(404);
    }

 2、response对象添加响应头：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Date date=new Date(121344444);
response.addHeader("zzz","I love JAVA.");
response.addIntHeader("myself",22);
response.addDateHeader("Time:",date.getTime());
}

 3、response对象设置响应头：

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    Date date=new Date(121344444);
    response.addHeader("zzz","I love JAVA.");
    response.addIntHeader("myself",22);
    response.addDateHeader("Time:",date.getTime());
    response.setIntHeader("myself",23);
    }