HttpServletRequest、request常用方法、request常见应用、请求转发、RequestDispatcher .

HttpServletRequest对象代表客户端的请求，当客户端通过HTTP协议访问服务器时，HTTP请求头中的所有信息都封装在这个对象中，开发人员通过这个对象的方法，可以获得客户这些信息。


request常用方法

获得客户机信息

getRequestURL方法返回客户端发出请求时的完整URL。

getRequestURI方法返回请求行中的资源名部分。

getQueryString 方法返回请求行中的参数部分。

getRemoteAddr方法返回发出请求的客户机的IP地址

getRemoteHost方法返回发出请求的客户机的完整主机名

getRemotePort方法返回客户机所使用的网络端口号

getLocalAddr方法返回WEB服务器的IP地址。

getLocalName方法返回WEB服务器的主机名

getMethod得到客户机请求方式


package com.hbsi.request;


import java.io.IOException;


import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;


public class Request1 extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

System.out.println(request.getRequestURI());

System.out.println(request.getRequestURL());

System.out.println(request.getQueryString());

System.out.println(request.getMethod());

System.out.println(request.getRemoteAddr());

System.out.println(request.getRemoteHost());

System.out.println(request.getRemotePort());

System.out.println(request.getLocalAddr());



}


public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


doGet(request, response);

}


}



获得客户机请求头

getHead(name)方法

getHeaders(String name)方法

getHeaderNames方法

获得客户机请求参数(客户端提交的数据)

getParameter(name):获取指定名称的参数值。这是最为常用的方法之一。

getParameterValues（String name）:获取指定名称参数的所有值数组。它适用于一个参数名对应多个值的情况。如页面表单中的复选框，多选列表提交的值。

getParameterNames():返回一个包含请求消息中的所有参数名的Enumeration对象。通过遍历这个Enumeration对象，就可以获取请求消息中所有的参数名。

getParameterMap():返回一个保存了请求消息中的所有参数名和值的Map对象。Map对象的key是字符串类型的参数名，value是这个参数所对应的Object类型的值数组。


package com.hbsi.request;


import java.io.IOException;

import java.util.Enumeration;


import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;


public class Request2 extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//String value = request.getHeader("Accept");

//System.out.println(value);


Enumeration e = request.getHeaderNames();

while(e.hasMoreElements()){

String name = (String) e.nextElement();

String value = request.getHeader(name);

System.out.println(name+":"+value);

}


}


public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


doGet(request, response);

}


}


request常见应用


各种表单输入项数据的获取

text、password、radio、checkbox、

file、select、textarea、 hidden、

image、button给js编程用


下面是request代码

package com.hbsi.request;


import java.io.IOException;


import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;


public class Reqeust3 extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

System.out.println(request.getParameter("name"));


}


private void test1form(HttpServletRequest request) {

String name = request.getParameter("username");

String password = request.getParameter("password");

String sex = request.getParameter("sex");

String city = request.getParameter("city");

String [] likes = request.getParameterValues("likes");

String likeString="";

for(int i=0;likes!=null && i<likes.length;i++){

String like = likes[i];

likeString +=like;

}

String memo = request.getParameter("memo");

System.out.println(name+","+password+","+sex+","+city+","+likeString+","+memo);

}


public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


doGet(request, response);

}


}


请求参数的中文乱码问题

URL地址的编码


package com.hbsi.request;


import java.io.IOException;

import java.io.UnsupportedEncodingException;


import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;


public class Request4 extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


String value = request.getParameter("name");

System.out.println(new String(value.getBytes("iso8859-1"),"UTF-8"));


}


private void test2(HttpServletRequest request)

throws UnsupportedEncodingException {

//get方式

String name = request.getParameter("username");

name = new String(name.getBytes("iso8859-1"),"UTF-8");

System.out.println(name);

}


private void test1(HttpServletRequest request)

throws UnsupportedEncodingException {

request.setCharacterEncoding("UTF-8");//只对post方式起作用

System.out.println(request.getParameter("username"));

}


public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


doGet(request, response);

}


}


防盗链


package com.hbsi.request;


import java.io.IOException;


import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;


public class Request5 extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


String referer = request.getHeader("referer");


if(referer==null || !referer.startsWith("http://localhost")){

response.sendRedirect("/servletdemo/index.jsp");

return;

}

response.setContentType("text/html;charset=utf-8");

String data = "秘密！！！！";

response.getWriter().write(data);


}


public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


doGet(request, response);

}


}


request对象实现请求转发：请求转发指一个web资源收到客户端请求后，通知服务器去调用另外一个web资源进行处理。


请求转发

Servlet API中定义了一个RequestDispatcher接口，俗称请求分派器。它定义了如下两个方法：

public void forward(ServletRequest request, ServletResponse response)


public void include(ServletRequest request, ServletResponse response)

获取RequestDispatcher实例的方式主要有两种：

调用ServletContext接口提供的getRequestDispatcher(String url)方法。

调用ServletRequest接口提供的getRequestDispatcher(String url)方法。


RequestDispatcher


include方法：

RequestDispatcher.include方法用于将RequestDispatcher对象封装的资源内容作为当前响应内容的一部分包含进来，从而实现可编程的服务器端包含功能。

被包含的Servlet程序不能改变响应消息的状态码和响应头，如果它里面存在这样的语句，这些语句的执行结果将被忽略。


package com.hbsi.request;


import java.io.IOException;


import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;


public class Request6 extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

request.getRequestDispatcher("/header.html").include(request, response);

response.getOutputStream().write("aaaaaaaaaaaa".getBytes());

request.getRequestDispatcher("/footer.html").include(request, response);


}


public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {


doGet(request, response);

}


}