自己在WEB学习过程中遇到的问题
问题一:
下面这两段代码差别不大,为何test1结果不同:
代码1:
1 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 2 test(response); 3 test1(response); 4 } 5 6 //这样写会乱码,返回两个? 原因是外国人默认用ISO8859码表,当数据存到response中时,ISO8859中没有汉字对应的码表,所以返回?所以解决乱码的关键在于码表的更换, 7 public void test(HttpServletResponse response) throws IOException{ 8 String data = "中国"; 9 PrintWriter out = response.getWriter(); 10 out.write(data); 11 12 } 13 //解决test里面的乱码问题 14 public void test1(HttpServletResponse response) throws IOException{ 15 //设置response用的码表是UTF-8,以控制response以什么码表像浏览器写出数据 16 response.setCharacterEncoding("UTF-8"); 17 //因为浏览器默认GB2312,所以现在必须控制浏览器打开数据的码表为UTF-8 18 response.setHeader("content-type","text/html;charset=UTF-8"); 19 String data = "中国"; 20 PrintWriter out = response.getWriter(); 21 out.write(data); 22 }
代码2:
1 public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 2 doGet(request,response); 3 } 4 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 5 //test(response); 6 test1(response); 7 } 8 9 //这样写会乱码,返回两个? 原因是外国人默认用ISO8859码表,当数据存到response中时,ISO8859中没有汉字对应的码表,所以返回?所以解决乱码的关键在于码表的更换, 10 public void test(HttpServletResponse response) throws IOException{ 11 String data = "中国"; 12 PrintWriter out = response.getWriter(); 13 out.write(data); 14 15 } 16 //解决test里面的乱码问题 17 public void test1(HttpServletResponse response) throws IOException{ 18 //设置response用的码表是UTF-8,以控制response以什么码表像浏览器写出数据 19 response.setCharacterEncoding("UTF-8"); 20 //因为浏览器默认GB2312,所以现在必须控制浏览器打开数据的码表为UTF-8 21 response.setHeader("content-type","text/html;charset=UTF-8"); 22 String data = "中国"; 23 PrintWriter out = response.getWriter(); 24 out.write(data); 25 }
两段代码区别在于:第一段test和test1方法同时调用,输出结果是????
第二段只调用了test1方法,结果输出 “中国”
为什么?????
问题二:
下列代码,想从浏览器访问对应位置的图片,为什么总显示NullPointException
1 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 2 //1、先设置浏览器要以什么方式打开 3 response.setHeader("Content-type","image/jpeg"); 4 //2、再把目标文件加载成一个输入流 输入流才有读的方法 F://10.jpg这样写是错误的 5 InputStream in = this.getServletContext().getResourceAsStream("F://10.jpg"); 6 //3、定义字符数组长度的中间变量 7 int len = 0; 8 //4、定义一个字符数组 9 byte by[] = new byte[1024]; 10 //5、先定义好一个输出到浏览器的流 11 //6、把输入流里的东西读入到字符数组中 12 OutputStream out = response.getOutputStream(); 13 while((len = (in.read(by)))!=-1){ 14 15 out.write(by,0,len); 16 out.flush(); 17 } 18 out.close(); 19 in.close(); 20 }
当把"F://10.jpg"改成“10.jpg”就对了???是不能指定图片所在路径吗?(F盘下有10.jpg,web应用下也有10.jpg)