050_Servlet详解
目录
Servlet
package com.qing.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
public class HelloServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException {
//响应的类型：html
response.setContentType("text/html");
//响应的编码
response.setCharacterEncoding("utf-8");
//获取响应的输出流
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head>");
out.println("<title>Hello World!</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Hello World!</h1>");
out.println("</body>");
out.println("</html>");
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<!--web.xml中配置web的核心应用-->
<!--注册Servlet-->
<servlet>
<!--名称，可以随意写-->
<servlet-name>helloServlet</servlet-name>
<servlet-class>com.qing.servlet.HelloServlet</servlet-class>
</servlet>
<!--映射：一个Servlet对应一个mapping-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<!--请求路径，可以随意写-->
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
Servlet简介
- Servlet是sun公司开发动态web的一门技术
- sun公司在这些API中提供一个接口：Servlet，如果想开发一个Servlet程序，只需要完成两个步骤
- 编写一个类，实现Servlet接口
- 把开发好的java类部署到web服务器中
- 我们把实现了Servlet接口的java程序叫做Servlet
- Servlet接口sun公司有两个默认的实现类：HttpServlet和GenericServlet
HelloServlet
- 构建一个普通maven项目，删掉src目录，这个空的工程就是Maven主工程，可以在里面建立Module；
- 配置pom.xml，添加依赖；
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.qing</groupId>
<artifactId>javaweb-03-servlet</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
</dependencies>
</project>
- 在父工程中新建子模块Module；
- 关于父子工程的理解：父项目中的jar包子项目可以直接使用；
- 父项目中会有
- 子项目中会有
<modules>
<module>servlet-01</module>
</modules>
<parent>
<artifactId>javaweb-03-servlet</artifactId>
<groupId>com.qing</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
- Maven环境优化：
- 修改web.xml为最新版本：修改子工程web.xml中的版本；
- 将maven的结构搭建完整：子工程添加java和resources目录；
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
</web-app>
- 编写一个Servlet程序；
- 编写一个普通类
- 实现Servlet接口，这里继承HttpServlet
package com.qing.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
public class HelloServlet extends HttpServlet {
//由于get或者post只是请求实现的不同方式，可以相互调用，业务逻辑都一样
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("进入doGet方法");
PrintWriter writer = resp.getWriter();//响应流
writer.print("hello,servlet");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
- 在web.xml中编写Servlet的映射
为什么需要映射？
我们写的是Java程序，但是要通过浏览器访问，而浏览器需要连接web服务器，所以我们需要在web服务中注册我们写的Servlet，还需要给他一个浏览器可以访问的路径
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<!--注册Servlet-->
<servlet>
<servlet-name>helloServlet</servlet-name>
<servlet-class>com.qing.servlet.HelloServlet</servlet-class>
</servlet>
<!--Servlet的请求路径-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
- 配置Tomcat
- 启动测试
Servlet原理
Servlet是由web服务器调用，web服务器收到浏览器请求后，会：
servlet-mapping Servlet请求路径
- 一个Servlet指定一个映射路径
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
- 一个Servlet指定多个映射路径
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello1</url-pattern>
</servlet-mapping>
- 一个Servlet指定通用映射路径
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/hello/*</url-pattern>
</servlet-mapping>
- 默认请求路径，会跳过index.jsp，直接进Servlet
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
- 指定后缀
<!--可以自定义后缀实现请求映射，注意：*前面不能加任何字符，否则会报错-->
<servlet-mapping>
<servlet-name>helloServlet</servlet-name>
<url-pattern>*.qing</url-pattern>
</servlet-mapping>
- 优先级问题：指定固定映射路径优先级最高，如果找不到就会走默认请求路径
<!--404-->
<servlet>
<servlet-name>error</servlet-name>
<servlet-class>com.qing.servlet.ErrorServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>error</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
ServletContext Servlet上下文
web容器在启动的时候，会为每个web程序都创建一个对应的ServletContext对象，它代表了当前web应用
ServletContext的应用
共享数据：在一个Servlet设置的数据，可以在另一个Servlet获取到
package com.qing.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class HelloServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("hello");
//Servlet上下文
ServletContext context = this.getServletContext();
//设置数据
String username = "清风";
context.setAttribute("username", username);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
package com.qing.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class GetServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("get");
ServletContext context = this.getServletContext();
String username = (String) context.getAttribute("username");
System.out.println(username);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>com.qing.servlet.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>get</servlet-name>
<servlet-class>com.qing.servlet.GetServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>get</servlet-name>
<url-pattern>/get</url-pattern>
</servlet-mapping>
</web-app>
获取初始化参数
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<context-param>
<param-name>url</param-name>
<param-value>127.0.0.1</param-value>
</context-param>
<servlet>
<servlet-name>get</servlet-name>
<servlet-class>com.qing.servlet.GetServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>get</servlet-name>
<url-pattern>/get</url-pattern>
</servlet-mapping>
</web-app>
package com.qing.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class GetServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("get");
ServletContext context = this.getServletContext();
String url = context.getInitParameter("url");
resp.getWriter().println(url);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
请求转发
package com.qing.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class GetServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("get");
ServletContext context = this.getServletContext();
//转发到/hello
context.getRequestDispatcher("/hello").forward(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
读取Properties文件
username=root
password=123456
package com.qing.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
public class PropertiesServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取流，根路径为打包后target下的项目名称
InputStream in = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");
Properties properties = new Properties();
properties.load(in);
String user = properties.getProperty("username");
String pwd = properties.getProperty("password");
resp.getWriter().print(user + ":" + pwd);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<servlet>
<servlet-name>prop</servlet-name>
<servlet-class>com.qing.servlet.PropertiesServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>prop</servlet-name>
<url-pattern>/prop</url-pattern>
</servlet-mapping>
</web-app>
HttpServletResponse
- web服务器接收到浏览器的http请求，针对这个请求，分别创建一个代表请求的HttpServletRequest对象和一个代表响应的HttpServletResponse对象
- 如果要获取浏览器请求过来的参数：找HttpServletRequest
- 如果要给浏览器响应一下信息：找HttpServletResponse
- 简单分类
- 负责向浏览器发送数据的方法
ServletOutputStream getOutputStream() throws IOException;
PrintWriter getWriter() throws IOException;
- 负责向浏览器发送响应头的方法
void setCharacterEncoding(String var1);
void setContentLength(int var1);
- 响应的状态码
int SC_OK = 200;
int SC_CREATED = 201;
- 常见应用
- 向浏览器输出消息
下载文件
- 获取下载文件的路径
- 获取文件名
- 设置浏览器支持下载
- 文件下载的消息头和编码问题 [https://www.cnblogs.com/hackxiyu/p/9046247.html](https://www.cnblogs.com/hackxiyu/p/9046247.html)
response.setHeader("Content-Disposition", "attachment;filename="+new String(AREA_FILE.getBytes("gb2312"), "ISO-8859-1"));
- 获取下载文件的输入流
- 创建缓冲区
- 获取OutputStream对象
- 将输入流写入buffer缓冲区，使用输出流将缓冲区中的数据输出到客户端
package com.qing.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;
public class FileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取下载文件的路径
String realPath = this.getServletContext().getRealPath("/WEB-INF/classes/静.jpg");
System.out.println("下载文件的路径为：" + realPath);
//获取文件名
String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
System.out.println("文件名为：" + fileName);
//设置浏览器支持下载
resp.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
//获取下载文件的输入流
FileInputStream fileInputStream = new FileInputStream(realPath);
//创建缓冲区
int len = 0;
byte[] buffer = new byte[1024];
//获取OutputStream对象
ServletOutputStream outputStream = resp.getOutputStream();
//将输入流写入buffer缓冲区，使用输出流将缓冲区中的数据输出到客户端
while ((len=fileInputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, len);
}
fileInputStream.close();
outputStream.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<servlet>
<servlet-name>fileDown</servlet-name>
<servlet-class>com.qing.servlet.FileServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>fileDown</servlet-name>
<url-pattern>/fileDown</url-pattern>
</servlet-mapping>
</web-app>
验证码功能
package com.qing.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
public class ImageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//设置浏览器3秒自动刷新一次
resp.setHeader("refresh", "3");
//在内存中创建一个图片
BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
//得到画笔
Graphics2D g = (Graphics2D) image.getGraphics();
//设置画笔颜色，画矩形背景
g.setColor(Color.WHITE);
g.fillRect(0,0,80,20);
//设置画笔颜色和字体，画随机数
g.setColor(Color.BLUE);
g.setFont(new Font(null,Font.BOLD,20));
g.drawString(makeRandom(),0,20);
//告诉浏览器，这个请求用图片的方式打开
resp.setContentType("image/jpeg");
//网站存在缓存，不让浏览器缓存
resp.setDateHeader("expires",-1);
resp.setHeader("Cache-Control","no-cache");
resp.setHeader("Pragma","no-cache");
//把图片写给浏览器
ImageIO.write(image,"jpg",resp.getOutputStream());
}
//生产随机数
private String makeRandom() {
Random random = new Random();
String num = random.nextInt(9999999) + "";
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 7 - num.length(); i++) {
sb.append(0);
}
num = sb.toString() + num;
return num;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<servlet>
<servlet-name>imageServlet</servlet-name>
<servlet-class>com.qing.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>imageServlet</servlet-name>
<url-pattern>/image</url-pattern>
</servlet-mapping>
</web-app>
重定向
一个web资源收到客户端请求后，他会通知客户端去访问另外一个web资源，这个过程叫重定向。
常见场景：用户登录
package com.qing.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class RedirectServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
/*
重定向相当于
resp.setHeader("Location","/resp/image");
resp.setStatus(302);
*/
//重定向
resp.sendRedirect("/resp/image");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<servlet>
<servlet-name>imageServlet</servlet-name>
<servlet-class>com.qing.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>imageServlet</servlet-name>
<url-pattern>/image</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>redirectServlet</servlet-name>
<servlet-class>com.qing.servlet.RedirectServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>redirectServlet</servlet-name>
<url-pattern>/redirect</url-pattern>
</servlet-mapping>
</web-app>
重定向和转发的区别
- 相同点
- 页面都会实现跳转
- 不同点
- 请求转发的时候，URL不会发生变化 状态码：307
- 重定向的时候，URL会发生变化 状态码：302
登录demo
- pom.xml添加jsp依赖：javax.servlet.jsp
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.qing</groupId>
<artifactId>javaweb-03-servlet</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
<module>servlet-01</module>
<module>servlet-02</module>
<module>response</module>
</modules>
<dependencies>
<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
</dependency>
</dependencies>
</project>
- 编辑登录页，${pageContext.request.contextPath}代表当前项目
<html>
<body>
<h2>Hello World!</h2>
<%--这里提交的路径，需要寻找到项目的路径--%>
<%--${pageContext.request.contextPath}代表当前项目--%>
<form action="${pageContext.request.contextPath}/login" method="get">
用户名：<input type="text" name="username">
密码：<input type="password" name="password">
<input type="submit">
</form>
</body>
</html>
- 编辑登录成功页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Success</title>
</head>
<body>
<h1>Success</h1>
</body>
</html>
- 处理登录请求，重定向到成功页面
package com.qing.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("进入登录请求");
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println(username + ":" + password);
//重定向
resp.sendRedirect("/resp/success.jsp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
- 在web.xml中添加Servlet映射
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
<servlet>
<servlet-name>loginServlet</servlet-name>
<servlet-class>com.qing.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>loginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
HttpServletRequest
HttpServletRequest代表客户端的请求，用户通过http协议访问服务器，http请求中的所有信息都会被封装到HttpServletRequest，通过HttpServletRequest的方法，可以获得客户端的所有信息。
获取浏览器传递的参数
String contextPath = req.getContextPath();//项目路径
String servletPath = req.getServletPath();//Servlet路径
String requestURI = req.getRequestURI();//请求路径
String name = req.getParameter("name");
String[] names = req.getParameterValues("name");
请求转发
//请求转发
//这里的/代表当前的web应用，即contextPath
req.getRequestDispatcher("/success.jsp").forward(req,resp);
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