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//通过响应对象重定向页面 resp.sendRedirect("404.jsp");
例一，通过ServletContext对象读取网站配置文件
1，新建一个database.properties文件
driver=com.mysql.jdbc.Driver username=root password=123456 url=jdbc:mysql://localhost:3306/smbms
2，编写servlet类
package com.kuang.servlet; import javax.servlet.ServletException; 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.util.Properties; //读取properties配置文件 public class ServletDemo03 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req,resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //读取配置文件 //1.获得配置文件的路径 String realPath = this.getServletContext().getRealPath("/WEB-INF/classes/resources/database.properties"); System.out.println("取得的路径为："+realPath); Properties properties = new Properties(); FileInputStream is = new FileInputStream(realPath); properties.load(is);//把文件流加载到配置文件的对象中； String driver = properties.getProperty("driver"); String username = properties.getProperty("username"); String password = properties.getProperty("password"); String url = properties.getProperty("url"); //响应到网页 resp.getWriter().println(driver); resp.getWriter().println(username); resp.getWriter().println(password); resp.getWriter().println(url); //======================================= System.out.println(driver); System.out.println(username); System.out.println(password); System.out.println(url); } }
3，配置web.xml
<servlet>
<servlet-name>Demo03</servlet-name>
<servlet-class>com.kuang.servlet.ServletDemo03</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Demo03</servlet-name>
<url-pattern>/q3</url-pattern>
</servlet-mapping>
4，网页打开
locallhost:8080/demo02/q3
5，网页显示
${pageContext.request.contextPath}
package com.kuang.servlet; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class RequestDemo01 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //查看request对象的方式 System.out.println(request.getContextPath()); //获得web项目路径 System.out.println(request.getRequestURI()); //请求的URL路径 //Remote 远程 System.out.println(request.getRemoteUser()); //获得远程的用户名 System.out.println(request.getRequestedSessionId()); //获得SessionId； System.out.println(request.getServletPath()); //请求servlet的url System.out.println(request.getLocalAddr()); //获得本地地址 防火墙 System.out.println(request.getLocalName()); //获得本地名字 System.out.println(request.getLocalPort()); //获得访问的端口号 } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } }
IDEA运行结果
1，写前端注册页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>注册</title> </head> <body> <%-- JSP的注释 --%> <%-- Form表单 action：代表要提交的路径，表单要提交到哪里 ，可以提交到一个Servlet //提交到Servlet需要，获取到Web项目的路径下的Servlet method: 提交表单的方式 --%> <h1>注册</h1> <form action="${pageContext.request.contextPath}/r2" method="post"> <p>用户名：<input type="text" name="username"></p> <p>密码：<input type="password" name="password"></p> <p> <input type="submit"> <input type="reset"> </p> </form> </body> </html>
2，写处理前端提交信息的Servlet
1 package com.kuang.servlet; 2 import javax.print.attribute.HashPrintRequestAttributeSet; 3 import javax.servlet.ServletException; 4 import javax.servlet.http.HttpServlet; 5 import javax.servlet.http.HttpServletRequest; 6 import javax.servlet.http.HttpServletResponse; 7 import java.io.IOException; 8 9 //处理前端提交过来的数据 10 public class RequestDemo02 extends HttpServlet { 11 @Override 12 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 13 doPost(req,resp); 14 } 15 @Override 16 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 17 18 //通过HttpServletRequest获取前端用户提交的信息 19 //req.getParameterValues(); 获得前端传递的控件信息，通过控件的name；但是可以接受多个参数的控件，比如（多选框....） 20 //req.getParameter(); 获得前端传递的控件信息，通过控件的name； 21 22 req.setCharacterEncoding("utf-8"); 23 resp.setCharacterEncoding("utf-8"); 24 25 String username = req.getParameter("username"); 26 String password = req.getParameter("password"); 27 28 //连接数据库，比较数据库中的信息是否匹配 29 30 if (username.equals("admin")&&password.equals("1234567")){ 31 System.out.println("登录成功！"); //跳转到成功页面 32 }else { 33 System.out.println("登录失败！"); //提示重新注册 34 } 35 36 System.out.println(username); 37 System.out.println(password); 38 } 39 }
3,配置web.xml
配置对应的XML文件
<servlet> <servlet-name>RequsetDemo02</servlet-name> <servlet-class>com.kuang.servlet.RequestDemo02</servlet-class> </servlet> <servlet-mapping> <servlet-name>RequsetDemo02</servlet-name> <url-pattern>/r2</url-pattern> </servlet-mapping>
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原文：https://www.cnblogs.com/like-lry/p/11198219.html