JAVA-EE请求request对象的常用API方法------计算机网络经典

傷城~ 2024-02-29 04:22 5阅读 0赞

>     Request对象实际上是一个域对象,请求域对象
>     应用域对象是什么ServletContext对象,即servlet上下文对象
>     全局都使用的,全局(webapp)共享的,内容较小,修改较少的我们就绑定在应用域之中
>     可以提高我们程序的执行效率
>     如果这个数据查询完毕后,放到了我们的servletContext中,就可以不用每次查询都去连接数据库实现查找数据
>     大大提升了查询效率(连接数据库需要从硬盘中取文件),实际上我们针对高并发的系统做法也是一样的
>     就是利用了缓存这个机制实现的提高查询效率,减少了IO的操作,大大提升了系统性能
>     线程池,字符串常量池,连接池,整数型常量池,redis,MongoDB
>     域都有这三个方法
>     void setAttribute(String name,Object obj);向域中绑定数据
>     Object setAttribute(String name);//获取域中的数据
>     void removeAttribute(String name);//将域当中的指定的数据移除
>     请求域只在一次请求内有效,尽可能使用请求域,保证这个内存占用尽可能早被清除
>     一个请求对象对应一个请求域对象,
> 
>     Request对象实际上是一个域对象,请求域对象
>     应用域对象是什么ServletContext对象,即servlet上下文对象
>     全局都使用的,全局(webapp)共享的,内容较小,修改较少的我们就绑定在应用域之中
>     可以提高我们程序的执行效率
>     如果这个数据查询完毕后,放到了我们的servletContext中,就可以不用每次查询都去连接数据库实现查找数据
>     大大提升了查询效率(连接数据库需要从硬盘中取文件),实际上我们针对高并发的系统做法也是一样的
>     就是利用了缓存这个机制实现的提高查询效率,减少了IO的操作,大大提升了系统性能
>     线程池,字符串常量池,连接池,整数型常量池,redis,MongoDB
>     域都有这三个方法
>     void setAttribute(String name,Object obj);向域中绑定数据
>     Object setAttribute(String name);//获取域中的数据
>     void removeAttribute(String name);//将域当中的指定的数据移除
>     请求域只在一次请求内有效,尽可能使用请求域,保证这个内存占用尽可能早被清除
>     一个请求对象对应一个请求域对象,

>     <?xml version="1.0" encoding="UTF-8"?>
>     <web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_6_0.xsd"
>              version="6.0">
>         <servlet>
>             <servlet-name>RTS</servlet-name>
>             <servlet-class>com.powernode.javaweb.servlet.RequestTestServlet</servlet-class>
>         </servlet>
>         <servlet-mapping>
>             <servlet-name>RTS</servlet-name>
>             <url-pattern>/RTS</url-pattern>
>         </servlet-mapping>
>         <servlet>
>             <servlet-name>AServlet</servlet-name>
>             <servlet-class>com.powernode.javaweb.servlet.AServlet</servlet-class>
>         </servlet>
>         <servlet-mapping>
>             <servlet-name>AServlet</servlet-name>
>             <url-pattern>/AServlet</url-pattern>
>         </servlet-mapping>
>         <servlet>
>             <servlet-name>BServlet</servlet-name>
>             <servlet-class>com.powernode.javaweb.servlet.BServlet</servlet-class>
>         </servlet>
>         <servlet-mapping>
>             <servlet-name>BServlet</servlet-name>
>             <url-pattern>/BServlet</url-pattern>
>         </servlet-mapping>
>         <welcome-file-list>
>             <welcome-file>RTS</welcome-file>
>         </welcome-file-list>
>     </web-app>
> 
>     <?xml version="1.0" encoding="UTF-8"?>
>     <web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_6_0.xsd"
>              version="6.0">
>         <servlet>
>             <servlet-name>RTS</servlet-name>
>             <servlet-class>com.powernode.javaweb.servlet.RequestTestServlet</servlet-class>
>         </servlet>
>         <servlet-mapping>
>             <servlet-name>RTS</servlet-name>
>             <url-pattern>/RTS</url-pattern>
>         </servlet-mapping>
>         <servlet>
>             <servlet-name>AServlet</servlet-name>
>             <servlet-class>com.powernode.javaweb.servlet.AServlet</servlet-class>
>         </servlet>
>         <servlet-mapping>
>             <servlet-name>AServlet</servlet-name>
>             <url-pattern>/AServlet</url-pattern>
>         </servlet-mapping>
>         <servlet>
>             <servlet-name>BServlet</servlet-name>
>             <servlet-class>com.powernode.javaweb.servlet.BServlet</servlet-class>
>         </servlet>
>         <servlet-mapping>
>             <servlet-name>BServlet</servlet-name>
>             <url-pattern>/BServlet</url-pattern>
>         </servlet-mapping>
>         <welcome-file-list>
>             <welcome-file>RTS</welcome-file>
>         </welcome-file-list>
>     </web-app>

>     package com.powernode.javaweb.servlet;
>     
>     import jakarta.servlet.ServletContext;
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.http.*;
>     
>     import java.io.IOException;
>     import java.io.PrintWriter;
>     import java.util.Enumeration;
>     import java.util.Iterator;
>     import java.util.Map;
>     import java.util.Set;
>     
>     public class RequestTestServlet extends HttpServlet
>     {
>         @Override
>         protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
>             resp.setContentType("text/html;charset=UTF-8");
>             PrintWriter out = resp.getWriter();
>             //获取客户端的IP地址
>             String remoteAddr = req.getRemoteAddr();
>             out.println(remoteAddr);
>             System.out.println(remoteAddr);
>             //设置请求体的字符集
>             //get在请求行上提交数据,post在请求体上提交数据,这个设置是针对post的
>             req.setCharacterEncoding("UTF-8");
>         }
>         //    @Override
>     //    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
>     //        response.setContentType("text/html;charset=UTF-8");
>     //        PrintWriter out = response.getWriter();
>     //        out.println(request);
>     //        out.println("<br>");
>     //        out.println(response);
>     //        out.println("<br>");
>     //        Map<String, String[]> parameterMap = request.getParameterMap();
>     //        Set<String> strings = parameterMap.keySet();
>     //        Iterator<String> iterator = strings.iterator();
>     //        while (iterator.hasNext())
>     //        {
>     //            String next = iterator.next();
>     //            out.println(next);
>     //            String[] strings1 = parameterMap.get(next);
>     //            for (int i = 0; i < strings1.length; i++) {
>     //                out.println(strings1[i]);
>     //            }
>     //            out.println("<br>");
>     //        }
>     //        Enumeration<String> parameterNames = request.getParameterNames();
>     //        while(parameterNames.hasMoreElements())
>     //        {
>     //            String s = parameterNames.nextElement();
>     //            String[] strings1 = parameterMap.get(s);
>     //            for (int i = 0; i < strings1.length; i++) {
>     //                out.println(strings1[i]);
>     //            }
>     //            out.println("<br>");
>     //        }
>     //        String username = request.getParameter("username");
>     //        String password = request.getParameter("password");
>     //        String[] interests = request.getParameterValues("interest");
>     //        for (int i = 0; i < interests.length; i++) {
>     //            out.println(interests[i]);
>     //        }
>     //    }
>     }
> 
>     package com.powernode.javaweb.servlet;
>     
>     import jakarta.servlet.ServletContext;
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.http.*;
>     
>     import java.io.IOException;
>     import java.io.PrintWriter;
>     import java.util.Enumeration;
>     import java.util.Iterator;
>     import java.util.Map;
>     import java.util.Set;
>     
>     public class RequestTestServlet extends HttpServlet
>     {
>         @Override
>         protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
>             resp.setContentType("text/html;charset=UTF-8");
>             PrintWriter out = resp.getWriter();
>             //获取客户端的IP地址
>             String remoteAddr = req.getRemoteAddr();
>             out.println(remoteAddr);
>             System.out.println(remoteAddr);
>             //设置请求体的字符集
>             //get在请求行上提交数据,post在请求体上提交数据,这个设置是针对post的
>             req.setCharacterEncoding("UTF-8");
>         }
>         //    @Override
>     //    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
>     //        response.setContentType("text/html;charset=UTF-8");
>     //        PrintWriter out = response.getWriter();
>     //        out.println(request);
>     //        out.println("<br>");
>     //        out.println(response);
>     //        out.println("<br>");
>     //        Map<String, String[]> parameterMap = request.getParameterMap();
>     //        Set<String> strings = parameterMap.keySet();
>     //        Iterator<String> iterator = strings.iterator();
>     //        while (iterator.hasNext())
>     //        {
>     //            String next = iterator.next();
>     //            out.println(next);
>     //            String[] strings1 = parameterMap.get(next);
>     //            for (int i = 0; i < strings1.length; i++) {
>     //                out.println(strings1[i]);
>     //            }
>     //            out.println("<br>");
>     //        }
>     //        Enumeration<String> parameterNames = request.getParameterNames();
>     //        while(parameterNames.hasMoreElements())
>     //        {
>     //            String s = parameterNames.nextElement();
>     //            String[] strings1 = parameterMap.get(s);
>     //            for (int i = 0; i < strings1.length; i++) {
>     //                out.println(strings1[i]);
>     //            }
>     //            out.println("<br>");
>     //        }
>     //        String username = request.getParameter("username");
>     //        String password = request.getParameter("password");
>     //        String[] interests = request.getParameterValues("interest");
>     //        for (int i = 0; i < interests.length; i++) {
>     //            out.println(interests[i]);
>     //        }
>     //    }
>     }

>     package com.powernode.javaweb.servlet;
>     
>     import jakarta.servlet.*;
>     import jakarta.servlet.http.*;
>     
>     import java.io.IOException;
>     import java.io.PrintWriter;
>     import java.util.Date;
>     
>     public class AServlet extends HttpServlet {
>         @Override
>         protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
>             Date date = new Date();
>             request.setAttribute("date",date);
>     //        response.setContentType("text/html;charset=UTF-8");
>     //        PrintWriter out = response.getWriter();
>     //        out.println(request.getAttribute("date"));
>             //Servlet对象不能由程序员创建,没有放进tomcat容器内
>             //第一步获取请求转发器对象
>     //        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/BServlet");
>             //把下一个跳转的资源包装为一个对象告知tomcat服务器
>     //        requestDispatcher.forward(request,response);
>             request.getRequestDispatcher("/BServlet").forward(request,response);
>         }
>     
>     }
> 
>     package com.powernode.javaweb.servlet;
>     
>     import jakarta.servlet.*;
>     import jakarta.servlet.http.*;
>     
>     import java.io.IOException;
>     import java.io.PrintWriter;
>     import java.util.Date;
>     
>     public class AServlet extends HttpServlet {
>         @Override
>         protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
>             Date date = new Date();
>             request.setAttribute("date",date);
>     //        response.setContentType("text/html;charset=UTF-8");
>     //        PrintWriter out = response.getWriter();
>     //        out.println(request.getAttribute("date"));
>             //Servlet对象不能由程序员创建,没有放进tomcat容器内
>             //第一步获取请求转发器对象
>     //        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/BServlet");
>             //把下一个跳转的资源包装为一个对象告知tomcat服务器
>     //        requestDispatcher.forward(request,response);
>             request.getRequestDispatcher("/BServlet").forward(request,response);
>         }
>     
>     }

>     <!DOCTYPE html>
>     <html lang="en">
>     <head>
>         <meta charset="UTF-8">
>         <title>Title</title>
>     </head>
>     <body>
>       <h1>注册页面</h1><br>
>       <form action="/RTS" method="post">
>         名字:<input type="text" name="name"><br>
>         密码:<input type="password" name="password"><br>
>         aihao:<input type="checkbox" name="aihao" value="a"><br>
>         <input type="checkbox" name="aihao"value="i"><br>
>         <input type="checkbox" name="aihao" value="h"><br>
>         <input type="submit" value="submit"><br>
>       </form>
>     </body>
>     </html>
> 
>     <!DOCTYPE html>
>     <html lang="en">
>     <head>
>         <meta charset="UTF-8">
>         <title>Title</title>
>     </head>
>     <body>
>       <h1>注册页面</h1><br>
>       <form action="/RTS" method="post">
>         名字:<input type="text" name="name"><br>
>         密码:<input type="password" name="password"><br>
>         aihao:<input type="checkbox" name="aihao" value="a"><br>
>         <input type="checkbox" name="aihao"value="i"><br>
>         <input type="checkbox" name="aihao" value="h"><br>
>         <input type="submit" value="submit"><br>
>       </form>
>     </body>
>     </html>

>     <!DOCTYPE html>
>     <html lang="en">
>     <head>
>         <meta charset="UTF-8">
>         <title>Welcome</title>
>     </head>
>     <body>
>       <h1>welcome</h1>
>     </body>
>     </html>
> 
>     <!DOCTYPE html>
>     <html lang="en">
>     <head>
>         <meta charset="UTF-8">
>         <title>Welcome</title>
>     </head>
>     <body>
>       <h1>welcome</h1>
>     </body>
>     </html>