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

发布于：2023-09-27 ⋅ 阅读:(78) ⋅ 点赞:(0) 
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;

public class BServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println(request.getAttribute("date"));
        request.getRequestDispatcher("/Welcome.html").forward(request,response);
    }
}

package com.powernode.javaweb.servlet;

import jakarta.servlet.*;
import jakarta.servlet.http.*;

import java.io.IOException;
import java.io.PrintWriter;

public class BServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println(request.getAttribute("date"));
        request.getRequestDispatcher("/Welcome.html").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);
    }

}

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>
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