Request和Response
1.创建request对象,封装数据到request对象里
2.创建response对象
3.调用servlet的service方法传递这两个参数
一、Response
1.response概述
response是Servlet.service方法的一个参数,类型为javax.servlet.http.HttpServletResponse。在客户端发出每个请求时,服务器都会创建一个response对象,并传入给Servlet.service()方法。response对象是用来对客户端进行响应的,这说明在service()方法中使用response对象可以完成对客户端的响应工作。
response对象的功能分为以下四种:
设置响应头信息;
发送状态码;
设置响应正文;
重定向;
2.response响应正文
response是响应对象,向客户端输出响应正文(响应体)可以使用response的响应流,repsonse一共提供了两个响应流对象:
PrintWriter out = response.getWriter():获取字符流;
ServletOutputStream out = response.getOutputStream():获取字节流;
如果响应为字符,则使用字符流,如果响应为字节,使用字节流,在同一个响应中,不能使用两个流,否则抛出IllegalStateException异常。
字符响应流
字符编码
在使用response.getWriter()时需要注意默认字符编码为ISO-8859-1,如果希望设置字符流的字符编码为utf-8,可以使用response.setCharaceterEncoding(“utf-8”)来设置。这样可以保证输出给客户端的字符都是使用UTF-8编码的!
但客户端浏览器并不知道响应数据是什么编码的!如果希望通知客户端使用UTF-8来解读响应数据,那么还是使用response.setContentType("text/html;charset=utf-8")方法比较好,因为这个方法不只会调用response.setCharaceterEncoding(“utf-8”),还会设置content-type响应头,客户端浏览器会使用content-type头来解读响应数据。
缓冲区
response.getWriter()是PrintWriter类型,所以它有缓冲区,缓冲区的默认大小为8KB。也就是说,在响应数据没有输出8KB之前,数据都是存放在缓冲区中,而不会立刻发送到客户端。当Servlet执行结束后,服务器才会去刷新流,使缓冲区中的数据发送到客户端。
如果希望响应数据马上发送给客户端:
1.向流中写入大于8KB的数据;
2.调用response.flushBuffer()方法来手动刷新缓冲区;
设置响应头
可以使用response对象的setHeader()方法来设置响应头!使用该方法设置的响应头最终会发送给客户端浏览器!
1.response.setHeader(“content-type”, “text/html;charset=utf-8”):设置content-type响应头,该头的作用是告诉浏览器响应内容为html类型,编码为utf-8。而且同时会设置response的字符流编码为utf-8,即response.setCharaceterEncoding(“utf-8”);
2.response.setHeader("Refresh","5; URL=http://localhost:8080/test3/AServlet"):5秒后自动跳转。
package cn.forcoldplay.itcast1;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class AServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("doGet()...");
ServletContext application = this.getServletContext();
Integer count = (Integer)application.getAttribute("count");
if(count == null){
count = 1;
} else {
count++;
}
//设置响应头
response.setContentType("text/html;charset=utf-8");
//设置响应正文
response.getWriter().print(" <style>");
response.getWriter().print(" .black-background {");
response.getWriter().print(" background-color: black;");
response.getWriter().print(" }");
response.getWriter().print(" p {");
response.getWriter().print(" font-size: 26px;");
response.getWriter().print(" font-family: monospace;");
response.getWriter().print(" color: white;");
response.getWriter().print(" }");
response.getWriter().print(" </style>");
response.getWriter().print(" <!DOCTYPE encoding=\"utf-8\" html>");
response.getWriter().print(" <html>");
response.getWriter().print(" <head>");
response.getWriter().print(" <meta charset=\"UTF-8\">");
response.getWriter().print(" <title>隐藏页面</title>");
response.getWriter().print(" </head>");
response.getWriter().print(" <body bgcolor= black>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <p align = \"center\">THIS PROGRAM WAS</p>");
response.getWriter().print(" <p align = \"center\">WRITTEN BY</p>");
response.getWriter().print(" <p align = \"center\">OPEN-REACH</p>");
response.getWriter().print(" <p align = \"center\">WHO LOVES NORIKO</p>");
response.getWriter().print(" <p align = \"center\">...</p>");
response.getWriter().print(" </body>");
response.getWriter().print(" </html>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <br> </br>");
response.getWriter().print(" <br> </br>");
response.getWriter().print("<p size=3>访问次数:" + count + "</p>");
application.setAttribute("count", count);
response.setHeader("Refresh","2; URL=http://localhost:8080/test3/AServlet");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print(" This is ");
out.print(this.getClass());
out.println(", using the POST method");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
设置状态码及其他方法
1.response.setContentType("text/html;charset=utf-8"):等同与调用response.setHeader(“content-type”, “text/html;charset=utf-8”);
2.response.setCharacterEncoding(“utf-8”):设置字符响应流的字符编码为utf-8;
3.response.setStatus(200):设置状态码;
4.response.sendError(404, “您要查找的资源不存在”):当发送错误状态码时,Tomcat会跳转到固定的错误页面去,但可以显示错误信息。
package cn.forcoldplay.itcast1;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class BServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.sendError(404,"你查找的资源不存在,测试response.sendError()");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
3.重定向
当你访问http://www.sun.com时,你会发现浏览器地址栏中的URL会变成http://www.oracle.com/us/sun/index.htm,这就是重定向了。
重定向是服务器通知浏览器去访问另一个地址,即再发出另一个请求。
完成重定向
响应码为200表示响应成功,而响应码为302表示重定向。所以完成重定向的第一步就是设置响应码为302。
因为重定向是通知浏览器再第二个请求,所以浏览器需要知道第二个请求的URL,所以完成重定向的第二步是设置Location头,指定第二个请求的URL地址。
package cn.forcoldplay.itcast1;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setStatus(302);
response.setHeader("Location", "http://www.forcoldplay.com/");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
便捷的重定向方式
package cn.forcoldplay.itcast1;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.sendRedirect("http://www.forcoldplay.com");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
response.sendRedirect()方法会设置响应头为302,以设置Location响应头。
如果要重定向的URL是在同一个服务器内,那么可以使用相对路径,例如:
package cn.forcoldplay.itcast1;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class EServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.sendRedirect("/test3/DServlet");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
4.重定向小结
- 重定向是两次请求;
- 重定向的URL可以是其他应用,不局限于当前应用;
- 重定向的响应头为302,并且必须要有Location响应头;
- 重定向就不要再使用response.getWriter()或response.getOutputStream()输出数据,不然可能会出现异常;
二、Request对象
1.Request概述
request是Servlet.service()方法的一个参数,类型为javax.servlet.http.HttpServletRequest。在客户端发出每个请求时,服务器都会创建一个request对象,并把请求数据封装到request中,然后在调用Servlet.service()方法时传递给service()方法,这说明在service()方法中可以通过request对象来获取请求数据。
request的功能可以分为以下几种
- 封装了请求头数据;
- 封装了请求正文数据,如果是GET请求,那么就没有正文;
- request是一个域对象,可以把它当成Map来添加获取数据;
- request提供了请求转发和请求包含功能
1.request域对象和方法
request是域对象!在JavaWeb中一共四个域对象,其中ServletContext就是域对象,它在整个应用中只创建一个ServletContext对象。request其中一个,request可以在一个请求中共享数据。
一个请求会创建一个request对象,如果在一个请求中经历了多个Servlet,那么多个Servlet就可以使用request来共享数据。
- void setAttribute(String name, Object value):用来存储一个对象,也可以称之为存储一个域属性,例如:servletContext.setAttribute(“xxx”, “XXX”),在request中保存了一个域属性,域属性名称为xxx,域属性的值为XXX。请注意,如果多次调用该方法,并且使用相同的name,那么会覆盖上一次的值,这一特性与Map相同;
- Object getAttribute(String name):用来获取request中的数据,当前在获取之前需要先去存储才行,例如:String value = (String)request.getAttribute(“xxx”);,获取名为xxx的域属性;
- void removeAttribute(String name):用来移除request中的域属性,如果参数name指定的域属性不存在,那么本方法什么都不做;
- Enumeration getAttributeNames():获取所有域属性的名称;
package cn.forcoldplay.itcast1;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class FServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setAttribute("name1", "laozhang");
request.setAttribute("name2", "laowang");
request.setAttribute("name3", "laoli");
String ans1 = (String)request.getAttribute("name1");
System.out.println(ans1);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
2.request获取请求头数据
request与请求头相关的方法有:
- String getHeader(String name):获取指定名称的请求头;
- Enumeration getHeaderNames():获取所有请求头名称;
- int getIntHeader(String name):获取值为int类型的请求头。
request获取请求其它相关的方法
- int getContentLength():获取请求体的字节数,GET请求没有请求体,没有请求体返回-1;
- String getContentType():获取请求类型,如果请求是GET,那么这个方法返回null;如果是POST请求,那么默认为application/x-www-form-urlencoded,表示请求体内容使用了URL编码;
- String getMethod():返回请求方法,例如:GET
- Locale getLocale():返回当前客户端浏览器的Locale。java.util.Locale表示国家和言语,这个东西在国际化中很有用;
- String getCharacterEncoding():获取请求体编码,如果没有setCharacterEncoding(),那么返回null,表示使用ISO-8859-1编码;
- void setCharacterEncoding(String code):设置请求编码,只对请求体有效!注意,对于GET而言,没有请求体!!!所以此方法只能对POST请求中的参数有效!
- String getContextPath():返回上下文路径,例如:/hello
- String getQueryString():返回请求URL中的参数,例如:name=zhangSan
- String getRequestURI():返回请求URI路径,例如:/hello/oneServlet
- StringBuffer getRequestURL():返回请求URL路径,例如:http://localhost/hello/oneServlet,即返回除了参数以外的路径信息;
- String getServletPath():返回Servlet路径,例如:/oneServlet
- String getRemoteAddr():返回当前客户端的IP地址;
- String getRemoteHost():返回当前客户端的主机名,但这个方法的实现还是获取IP地址;
- String getScheme():返回请求协议,例如:http;
- String getServerName():返回主机名,例如:localhost
- int getServerPort():返回服务器端口号,例如:8080
package com.forcoldplay.itcast;
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 BServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public BServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
System.out.println( request.getContentLength() ); //获取请求体字节数
System.out.println( request.getContentType() ); // 获取请求体类型
System.out.println( request.getMethod() ); //获取请求方法
System.out.println( request.getLocale() ); //获取当前客户端浏览器的Local
System.out.println( request.getCharacterEncoding()); // 获取请求体编码
System.out.println( request.getContextPath()); //获取上下文路径
System.out.println( request.getServletPath()); //返回Servlet路径
System.out.println( request.getRemoteAddr()); //获取当前IP地址
System.out.println( request.getRemoteHost()); //获取当前主机名
System.out.println( request.getScheme()); //获取http请求协议
System.out.println( request.getServerName()); //获取服务器主机名
System.out.println( request.getServerPort()); //获取服务器端口号
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
3.IP被封案例
package com.forcoldplay.itcast;
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 BServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public BServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String Ip = request.getRemoteAddr();
if("0:0:0:0:0:0:0:1".equals(Ip)) {
System.out.println(Ip + "被封了");
}else {
System.out.println("正常IP");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
4.request获取请求参数
最为常见的客户端传递参数方式有两种:
- 浏览器地址栏直接输入:一定是GET请求;
- 超链接:一定是GET请求;
- 表单:可以是GET,也可以是POST,这取决与<form>的method属性值;
5.get和post的区别
- get
参数在地址栏中显示,相对不安全,参数长度限制在了1K之内
get方法没有请求体,无法通过request.setCharacterEncoding()来设置请求体参数。
- post
参数不在地址栏中显示,相对安全,参数长度没有限制。
String getParameter(String name):通过指定名称获取参数值;
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>test page</h1>
<a href="/test1/CServlet?p1=v1&p2=v2">超链接</a>
<hr/>
<form action="/test1/CServlet" method="post">
账号:<input type="text" name="p1" /> <br/>
密码:<input type="text" name="p2" /> <br/>
提交:<input type="submit" value="提交"/>
</form>
</body>
</html>
package com.forcoldplay.itcast;
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 CServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public CServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//response.getWriter().append("Served at: ").append(request.getContextPath());
String str1 = request.getParameter("p1");
String str2 = request.getParameter("p2");
System.out.println("p1: " + str1);
System.out.println("p2: " + str2);
response.getWriter().println("p1: " + str1);
response.getWriter().println("p2: " + str2);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//doGet(request, response);
String name = request.getParameter("p1");
String password = request.getParameter("p2");
System.out.println("name: " + name);
System.out.println("passwd: " + password);
response.getWriter().println("name: " + name);
response.getWriter().println("passwd: " + password);
}
}
package com.forcoldplay.itcast;
import java.io.IOException;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sun.xml.internal.bind.v2.runtime.unmarshaller.XsiNilLoader.Array;
import sun.security.krb5.internal.EncKDCRepPart;
public class CServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public CServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//response.getWriter().append("Served at: ").append(request.getContextPath());
String str1 = request.getParameter("p1");
String str2 = request.getParameter("p2");
System.out.println("p1: " + str1);
System.out.println("p2: " + str2);
response.getWriter().println("p1: " + str1);
response.getWriter().println("p2: " + str2);
// 获取所有名为name的参数值
String[] names1 = request.getParameterValues("name");
System.out.println(Arrays.toString(names1));
//Map getParameterMap():获取所有参数封装到Map中,其中key为参数名,value为参数值,
//因为一个参数名称可能有多个值,所以参数值是String[],而不是String。
Map<String, String[]> paramMap = request.getParameterMap();
for(String name1 : paramMap.keySet()) {
String[] values = paramMap.get(name1);
System.out.println(name1 + ": " + Arrays.toString(values));
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//doGet(request, response);
String name = request.getParameter("p1");
String password = request.getParameter("p2");
System.out.println("name: " + name);
System.out.println("passwd: " + password);
response.getWriter().println("name: " + name);
response.getWriter().println("passwd: " + password);
//
//Enumeration getParameterNames():获取所有参数的名字;
Enumeration<String> names = request.getParameterNames();
System.out.println(names==null);
while(names.hasMoreElements()) {
System.out.println(names.nextElement());
}
//String[] getParameterValues(String name):当多个参数名称相同时,可以使用方法来获取;
// 获取所有名为name的参数值
String[] names1 = request.getParameterValues("name");
System.out.println(Arrays.toString(names1));
//Map getParameterMap():获取所有参数封装到Map中,其中key为参数名,value为参数值,
//因为一个参数名称可能有多个值,所以参数值是String[],而不是String。
Map<String, String[]> paramMap = request.getParameterMap();
for(String name1 : paramMap.keySet()) {
String[] values = paramMap.get(name1);
System.out.println(name1 + ": " + Arrays.toString(values));
}
}
}
6.请求转发与请求包含
无论是请求转发还是请求包含,都表示由多个Servlet共同来处理一个请求。例如Servlet1来处理请求,然后Servlet1又转发给Servlet2来继续处理这个请求。
7.请求转发
DServlet
package com.forcoldplay.itcast;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public DServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("this is DServlet");
RequestDispatcher rd = request.getRequestDispatcher("EServlet");
rd.forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
EServlet
package com.forcoldplay.itcast;
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 EServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public EServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//response.getWriter().append("Served at: ").append(request.getContextPath());
System.out.println("this is EServlet");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
输出结果
this is DServlet
this is EServlet
8.请求包含
package com.forcoldplay.itcast;
import java.io.IOException;
import javax.security.auth.message.callback.PrivateKeyCallback.Request;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class GServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public GServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//response.getWriter().append("Served at: ").append(request.getContextPath());
System.out.println("this is GServlet");
RequestDispatcher rd = request.getRequestDispatcher("/HServlet");
rd.include(request, response);
System.out.println("this is end ....");
response.getWriter().println("<h1>333........</h1>");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
package com.forcoldplay.itcast;
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 HServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public HServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//response.getWriter().append("Served at: ").append(request.getContextPath());
System.out.println("this is HServlet");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
9.请求转发与请求包含比较
- 如果在AServlet中请求转发到BServlet,那么在AServlet中就不允许再输出响应体,即不能再使用response.getWriter()和response.getOutputStream()向客户端输出,这一工作应该由BServlet来完成;如果是使用请求包含,那么没有这个限制;
- 请求转发虽然不能输出响应体,但还是可以设置响应头的,例如:response.setContentType(”text/html;charset=utf-8”);
- 请求包含大多是应用在JSP页面中,完成多页面的合并;
- 请求大多是应用在Servlet中,转发目标大多是JSP页面;
10.请求转发与重定向比较
- 请求转发是一个请求,而重定向是两个请求;
- 请求转发后浏览器地址栏不会有变化,而重定向会有变化,因为重定向是两个请求;
- 请求转发的目标只能是本应用中的资源,重定向的目标可以是其他应用;
- 请求转发对AServlet和BServlet的请求方法是相同的,即要么都是GET,要么都是POST,因为请求转发是一个请求;
- 重定向的第二个请求一定是GET;