Response基础（下）
Response对象（下）
一、服务器输出字符数据到浏览器步骤如下
1.获取字符流输出 2.输出数据 新建Servlet“ResponseDemo4”@WebServlet("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1、获取字符输出流
PrintWriter printWriter = response.getWriter();
// 2、输出数据
printWriter.write("hello response");
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}测试结果：
如果想让输出字符变成一级标题加粗，则在输出中加标签
@WebServlet("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1、获取字符输出流
PrintWriter printWriter = response.getWriter();
// 2、输出数据
printWriter.write("hello response
");
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
测试结果：
注意：
但是出现输出中文有乱码怎么办？
一般出现乱码的原因：编解码使用的字符集不一致
printWriter.write("
你好， response
");
解决：
在获取流对象之前，设置流的默认编码：ISO-8859-1 设置为：GBK
@WebServlet("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 获取流之前，要将流的默认编码：ISO-8859-1，设置为GBK
response.setCharacterEncoding("GBK");
// 1、获取字符输出流
PrintWriter printWriter = response.getWriter();
// 2、输出数据
printWriter.write("你好， response
");
}输出结果：
仅仅是这一步还不行，需要告诉浏览器，服务器发送的消息体数据的编码，建议浏览器使用该编码解码.
@WebServlet("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 获取流之前，要将流的默认编码：ISO-8859-1，设置为GBK
response.setCharacterEncoding("utf-8");
// 告诉浏览器，服务器发送的消息体数据的编码，建议浏览器使用该编码解码
response.setHeader("content-type","text/html;charset=utf-8");// 不区分大小写，告诉浏览器，我使用的是"utf-8"
// 1、获取字符输出流
PrintWriter printWriter = response.getWriter();
// 2、输出数据
printWriter.write("你好， response
");
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
测试结果：
或者用简单的格式:
@WebServlet("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 获取流之前，要将流的默认编码：ISO-8859-1，设置为GBK// 使用更简单的形式，设置编码
response.setContentType("text/html;charset=utf-8");
// 1、获取字符输出流
PrintWriter printWriter = response.getWriter();
// 2、输出数据
printWriter.write("你好吗？ response
");
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
测试结果:
二、服务器输出字节数据到浏览器
步骤如下：
1.获取字节流输出
2.输出数据
@WebServlet("/ResponseDemo5")
public class ResponseDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1.获取字节输出流
ServletOutputStream servletOutputStream = response.getOutputStream();
// 2.输出数据
servletOutputStream.write("hello
".getBytes());
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}测试结果:
同样出现乱码情况的解决
@WebServlet("/ResponseDemo5")
public class ResponseDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 告诉浏览器，服务器发送的消息体数据的编码，建议浏览器使用该编码解码
response.setContentType("text/html;charset=utf-8");
// 1.获取字节输出流
ServletOutputStream servletOutputStream = response.getOutputStream();
// 2.输出数据
servletOutputStream.write("你现在怎么样？
".getBytes("utf-8"));
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
三、验证码
1.本质：图片
@WebServlet("/checkCodeServlet")
public class checkCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
// 1.创建对象，在内存中画图（验证码的图片对象）
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
// 2.美化图片
// 2.1 填充背景
Graphics g = image.getGraphics();// 画笔对象
g.setColor(Color.PINK);// 设置笔画颜色
g.fillRect(0,0,width,height);
// 3.图片输出
ImageIO.write(image,"jpg",response.getOutputStream());
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}测试结果：
进一步设置：
@WebServlet("/checkCodeServlet")
public class checkCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
// 1.创建对象，在内存中画图（验证码的图片对象）
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
// 2.美化图片
// 2.1 填充背景
Graphics g = image.getGraphics();// 画笔对象
g.setColor(Color.PINK);// 设置笔画颜色
g.fillRect(0,0,width,height);
// 2.2 画边框
g.setColor(Color.BLUE);
g.drawRect(0,0,width-1,height-1);
// 2.3 写验证码
g.drawString("A",20,25);
g.drawString("B",40,25);
g.drawString("c",60,25);
g.drawString("d",80,25);
// 3.图片输出
ImageIO.write(image,"jpg",response.getOutputStream());
}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
测试结果：
如何让验证码随机生成？
在原来代码的基础上加上以下代码:
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; // 列出验证码所有可能出现的情况// 生成随机角标
Random ran = new Random();
for(int i = 0 ; i < 4;i++){
int index = ran.nextInt(str.length());
// 获取字符
char ch = str.charAt(index); // 随机字符
// 2.3 写验证码
g.drawString(ch+"",width/5*i,height/2);// 验证码字母的位置 20/40/60/80
}
加上干扰：
// 画干扰线
g.setColor(Color.GREEN);
// 随机生成坐标点
for(int i = 0 ;i< 10;i++){
int i0 = ran.nextInt(width);
int i1 = ran.nextInt(width);
int i2 = ran.nextInt(width);
int i3 = ran.nextInt(width);
g.drawLine(i0,i1,i2,i3);
}
2.验证码的切换
新建register.html
Title
看不清换一张？
以下，点击即可切换验证码
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