HttpServletResponse的学习
关于Response对象的一些方法和属性可以查看官方文档：https://javaee.github.io/javaee-spec/javadocs/
比如里面定义了许多常量：
这些都是服务器向浏览器返回的一些状态码，我们把它定义成常量，之后就不要写数字！
还有一些方法：
1、示例：向浏览器输出中文：
package test; import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Properties; import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub大小写要注意好了
response.setHeader("Content-type", "text/html;charset=UTF-8"); //要告诉浏览器以什么编码打开
String s = "中国";
OutputStream out = response.getOutputStream();
out.write(s.getBytes("UTF-8")); //为了兼容性，我们设置字符编码为utf-8
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
还可以：
package test; import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Properties; import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String s = "中国";
OutputStream out = response.getOutputStream();
//使用html的meta标签模拟一个http响应头，来控制浏览器行为
out.write("<meta http-equiv='content-type' content='text/html;charset=UTF-8'>".getBytes());
out.write(s.getBytes("UTF-8")); //为了兼容性，我们设置字符编码为utf-8
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
注意：下面这种方式对于谷歌浏览器不可以，对于IE浏览器可以
package test; import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Properties; import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String s = "中国";
response.setCharacterEncoding("UTF-8"); //设置response的默认编码，控制response以什么码表像浏览器输出数据
response.setHeader("Content-type", "text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write(s); //通过字符方式写数据
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
//下面两个语句一样的效果
response.setHeader("Content-type", "text/html;charset=UTF-8");
response.setContentType("text/html;charset=UTF-8"); 这样也可以
2、文件下载
package test; import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Properties; import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String path = this.getServletContext().getRealPath("/download/1.txt");
String file_name = path.substring(path.lastIndexOf("\\")+1);
response.setHeader("content-disposition", "attachment;filename="+file_name);
//文件写入response
InputStream in = null;
OutputStream out = null;
try {
in = new FileInputStream(path);
int len=0;
byte buffer[] = new byte[1024];
out = response.getOutputStream();
while((len = in.read(buffer))>0) {
out.write(buffer,0,len);
}
}finally {
if(in!=null) {
try {
in.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
如果文件名是中文的需要经过URL编码
package test; import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.util.Properties; import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String path = this.getServletContext().getRealPath("/download/你好.txt");
String file_name = path.substring(path.lastIndexOf("\\")+1);
response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(file_name,"UTF-8"));
//文件写入response
InputStream in = null;
OutputStream out = null;
try {
in = new FileInputStream(path);
int len=0;
byte buffer[] = new byte[1024];
out = response.getOutputStream();
while((len = in.read(buffer))>0) {
out.write(buffer,0,len);
}
}finally {
if(in!=null) {
try {
in.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
2、生成随机验证图片，并向浏览器输出
目录为：
ServletContextDemo2.Java内容：
package test; import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.util.Properties;
import java.util.Random; import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
public static final int WIDTH = 120;
public static final int HEIGHT = 35;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
//背景色
setBackGround(g);
//边框
setBorder(g);
//干扰线
drawRandomLine(g);
//画随机数\字体旋转
drawRandomNum((Graphics2D)g); //图形写给浏览器
response.setContentType("image/jpeg");
//控制浏览器不要缓存随机图片
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
ImageIO.write(image, "jpg", response.getOutputStream());
} private void drawRandomNum(Graphics2D g) {
// TODO Auto-generated method stub
g.setColor(Color.red);
//设置字体为加粗宋体，高度20
g.setFont(new Font("宋体",Font.BOLD,20));
//在UTF-8码表中，所有汉字都在[4e00-9fa5]这个区间内
//char c = '\u4e00'; Java内内置编码为UTF-8 ，所以\u4e00就相当于一个汉字
//常用汉字编码utf-8编码
String data = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";
int x=5;
for(int i=0;i<4;++i)
{
int degree = new Random().nextInt()%30; //生成-30-30的随机数
String ch = data.charAt(new Random().nextInt(data.length()))+"";
//degree*Math.PI/180角度变弧度,设置旋转角度
g.rotate(degree*Math.PI/180,x,20); //基于(x,20)点旋转
g.drawString(ch, x, 20);
g.rotate(-degree*Math.PI/180,x,20); //调回旋转角度
x+=30;
}
} private void drawRandomLine(Graphics g) {
// TODO Auto-generated method stub
g.setColor(Color.GREEN);
for(int i=0;i<5;++i) {
int x1 = new Random().nextInt(WIDTH); //生成[0,WIDTH)的随机数
int y1 = new Random().nextInt(HEIGHT); int x2 = new Random().nextInt(WIDTH); //生成[0,WIDTH)的随机数
int y2 = new Random().nextInt(HEIGHT);
g.drawLine(x1, y1, x2, y2);
}
} private void setBorder(Graphics g) {
// TODO Auto-generated method stub
g.setColor(Color.BLUE);
g.drawRect(1, 1, WIDTH-2, HEIGHT-2);
} private void setBackGround(Graphics g) {
// TODO Auto-generated method stub
g.setColor(Color.WHITE);
g.fillRect(0, 0, WIDTH, HEIGHT);
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
还有html内容：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="">
用户名：<input type="text" name="username">
密码：<input type="password" name="password">
认证码：<input type="text" name="checkcode"><img src="/day02/ServletContextDemo2"><br/>
<input type="submit" value="注册">
</form>
</body>
</html>
实现点验证图片之后换一张图片只需要改一下html内容：
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
function changeimage(img){
//img.src = img.src 后面的src是获取html里面img的src属性，赋值给img.src就代表重新访问
//但是上面的语句不可行是因为浏览器会默认从缓存里面找图片，所以你应该把图片地址换一下
//这样浏览器在缓存里面找不到就会向服务器发送请求
img.src=img.src+"?"+new Date().getTime();
}
</script>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="">
用户名：<input type="text" name="username">
密码：<input type="password" name="password">
认证码：<input type="text" name="checkcode">
<img src="/day02/ServletContextDemo2" onclick="changeimage(this)" alt="换一张" style="cursor:hand"><br/>
<input type="submit" value="注册">
</form>
</body>
</html>
3、控制浏览器定时刷新
package test; import java.io.IOException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setHeader("refresh", "3"); //3秒刷新一次
String data = new Random().nextInt(1000000)+"";
response.getWriter().write(data); //以字符形式输出数据
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
3秒之后跳转到指定页面
package test; import java.io.IOException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setHeader("Content-type", "text/html;charset=utf-8");
//3秒之后刷新，并跳转到register.html页面
response.setHeader("refresh", "3;url='/day02/register.html'");
response.getWriter().write("本浏览器在3秒后跳转，若没有跳转，点击<a href=''>超链接</a>"); //以字符形式输出数据
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
使用expries控制浏览器缓存
package test; import java.io.IOException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//控制浏览器缓存，浏览器缓存截止于1小时后不可用
//1000代表一秒，乘于3600就是一小时。System.currentTimeMillis()代表当前时间
response.setDateHeader("expries", System.currentTimeMillis()+1000*3600);
String data = "aaaaaa";
response.getWriter().write(data);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
重定向：
package test; import java.io.IOException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
//重定向会发送两次请求，每一次请求都是不同的servlet处理
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//重定向
response.setStatus(302);
response.setHeader("location", "/day02/register.html"); //下面也是重定向
response.sendRedirect("/day02/register.html");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
getWriter和getOutputStream不能用同一个servlet处理，就比如你使用转发，这个时候是一个servlet处理两次请求，所以即使在两个文件却不能同时出现两种输出数据方式，示例：
ServletContextDemo2
package test; import java.io.IOException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo2
*/
@WebServlet("/ServletContextDemo2") //注意有了这个就不需要往web.xml文件里面添加路径映射
public class ServletContextDemo2 extends HttpServlet {
private static final long serialVersionUID = 1L; /**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
//重定向会发送两次请求，每一次请求都是不同的servlet处理
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.getOutputStream();
this.getServletContext().getRequestDispatcher("/ServletContextDemo1").forward(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
ServletContextDemo1
package test; import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; /**
* Servlet implementation class ServletContextDemo1
*/
@WebServlet("/ServletContextDemo1")
public class ServletContextDemo1 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.getWriter();
} /**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
} }
上面这样就会报错，但是换成重定向就没有问题，因为重定向的两次请求不是一个servlet处理的。
HttpServletResponse的学习的更多相关文章
- HttpServletResponse对象 学习
Web服务器收到客户端的http请求,会针对每一次请求,分别创建一个用于代表请求的request对象.和代表响应的response对象.request和response对象即然代表请求和响应,那我们要 ...
- HttpServletResponse类学习
/*//2) 乱码的解决. //设置服务器输出的编码为UTF-8---在BaseServlet处已经已经进行了设置 response.setCharacterEncoding("UTF-8& ...
- Servlet（六）：Cookie
Cookie 学习:问题: HTTP 协议是没有记忆功能的,一次请求结束后,相关数据会被销毁.如果第二次的请求需要使用相同的请求数据怎么办呢?难道是让用户再次请求书写吗?解决: 使用 Cookie 技 ...
- java攻城师之路--复习java web之request_respone
Servlet技术 两条主线1.HTTP协议 2.Servlet生命周期 init() 方法中参数 ServletConfig 对象使用通过ServletConfig 获得 ServletContex ...
- Java第三阶段学习（十二、HttpServletRequest与HttpServletResponse）
一.HttpServletRequest 1.概述: 我们在创建Servlet时会覆盖service()方法,或doGet()/doPost(),这些方法都有两个参数,一个为代表请求的request和 ...
- [原创]java WEB学习笔记09：ServletResponse & HttpServletResponse
本博客为原创:综合 尚硅谷(http://www.atguigu.com)的系统教程(深表感谢)和 网络上的现有资源(博客,文档,图书等),资源的出处我会标明 本博客的目的:①总结自己的学习过程,相当 ...
- java web学习总结(八) -------------------HttpServletResponse对象(二)
一.HttpServletResponse常见应用--生成验证码 1.1.生成随机图片用作验证码 生成图片主要用到了一个BufferedImage类,
- java web学习总结(七) -------------------HttpServletResponse对象(一)
Web服务器收到客户端的http请求,会针对每一次请求,分别创建一个用于代表请求的request对象.和代表响应的response对象.request和response对象即然代表请求和响应,那我们要 ...
- JAVAWEB学习总结 HTTPSERVLETRESPONSE对象（二）
一.HttpServletResponse常见应用--生成验证码 1.1.生成随机图片用作验证码 生成图片主要用到了一个BufferedImage类 步骤: 1. 在内存中创建一张图片 2.得到图片 ...
随机推荐
- Linux下安装Oracle11g服务器【转】
安装环境 Linux服务器:oracle linux 6.6 64位 Oracle服务器:Oracle11gR2 64位 系统要求 Linux安装Oracle系统要求 系统要求 说明 内存 必须高于1 ...
- uber_go_guide解析(二)
前言 接上回 正文 错误消息 Go中声明错误有几种方式 errors.New() 简单的声明静态字符串信息的错误 fmt.Errorf 可以格式化插入信息的错误 自己实现 Error() 方法 使用e ...
- vue 侦听器watch 之 深度监听 deep
<template> <div> <p>FullName: {{person.fullname}}</p> <p>FirstName: &l ...
- APPIUM-Android自动化元素定位方式
一.常用元素定位方法 appium从selenium中继承了所有的元素定位方法, 并且增加了一些自己的元素定位方式,下方截图分别为selenium和MobileBy包源码: 但是从继承selenium ...
- Git软件安装过程
Git程序安装过程 官网: https://git-scm.com/ 下载: https://git-scm.com/downloads 我的操作系统是 Windows + 64位的 https:// ...
- 【Linux】 多个会话同时执行命令后history记录不全的解决方案
基本认识 linux默认配置是当打开一个shell终端后,执行的所有命令均不会写入到~/.bash_history文件中,只有当前用户退出后才会写入,这期间发生的所有命令其它终端是感知不到的. 问题场 ...
- 视图V_160M和表T_160M的维护
今天发现一个视图,通过SM30居然无法维护,这个视图就是V_160M,表为T_160M,是采购相关的系统消息, 不过别着急,有办法维护的,呵呵,看下面: 试一试OMCQ这个事物代码吧! 分享出来,给需 ...
- 发票校验BAPI_INCOMINGINVOICE_CREATE
CALL FUNCTION 'BAPI_INCOMINGINVOICE_CREATE' EXPORTING headerdata = headerdata ...
- kafka（二）基本使用
一.Kafka线上集群部署方案 既然是集群,那必然就要有多个Kafka节点机器,因为只有单台机器构成的kafka伪集群只能用于日常测试之用,根本无法满足实际的线上生产需求. 操作系统: kafka由S ...
- 1.5V转3.3V升压电路图和1.5V转3.3V的电源芯片
1.5V转3.3V的电路图需要材料:PW5100芯片,2个贴片电容,1个贴片电感.即可组成一个DC-DC同步升压高效率电路图,可提供稳定的3.3V输出电压. 1.5V转3.3V的电源芯片 1.5V转3 ...