Java Request(域物件+請求轉發+原理)詳解
阿新 • • 發佈:2020-08-02
Java Request詳解
request物件和respose物件的原理
request物件
request物件和response物件都是由伺服器建立的,我們是來使用他們
request物件是用來獲取請求訊息的,response物件是用來設定響應訊息的
本篇文章我們先來講解request
request的繼承體系
request的功能
1. 獲取請求訊息資料
1. 獲取請求行資料
-
GET /day14/demo1?name=zhangsan HTTP/1.1
-
方法:
1. 獲取請求方式 :GET
* String getMethod()
2. (*)獲取虛擬目錄:/day14
* String getContextPath()
3. 獲取Servlet路徑
* String getServletPath()
4. 獲取get方式請求引數:name=zhangsan
* String getQueryString()
5. (*)獲取請求URI:/day14/demo1
* String getRequestURI(): /day14/demo1
* 6.獲取url
* StringBuffer getRequestURL() :http://localhost/day14/demo1* URL:統一資源定位符 : http://localhost/day14/demo1 中華人民共和國 * URI:統一資源識別符號 : /day14/demo1 共和國 **6. 獲取協議及版本**:HTTP/1.1 * String getProtocol() **7. 獲取客戶機的IP地址**: * String getRemoteAddr() **2. 獲取請求頭資料** * **方法**: * (*)String getHeader(String name):通過請求頭的名稱獲取請求頭的值 * Enumeration<String> getHeaderNames():獲取所有的請求頭名稱 **3. 獲取請求體資料**: * 請求體:只有POST請求方式,才有請求體,在請求體中封裝了POST請求的請求引數 * 步驟: **1. 獲取流物件** * BufferedReader getReader():獲取字元輸入流,只能操作字元資料 * ServletInputStream getInputStream():獲取位元組輸入流,可以操作所有型別資料 * 在檔案上傳知識點後講解 **2. 再從流物件中拿資料** **2. 其他功能**: **1. 獲取請求引數通用方式**:不論get還是post請求方式都可以使用下列方法來獲取請求引數 1. String getParameter(String name):根據引數名稱獲取引數值 username=zs&password=123 2. String[] getParameterValues(String name):根據引數名稱獲取引數值的陣列 hobby=xx&hobby=game 3. Enumeration<String> getParameterNames():獲取所有請求的引數名稱 4. Map<String,String[]> getParameterMap():獲取所有引數的map集合 * **中文亂碼問題**: * **get方式**:tomcat 8 已經將get方式亂碼問題解決了 * **post方式**:會亂碼 * **解決**:在獲取引數前,設定request的編碼request.setCharacterEncoding("utf-8");
請求轉發
什麼是請求轉發?
請求轉發是伺服器內部資源跳轉的一種方式
步驟
- 通過request物件獲取請求轉發器物件:RequestDispatcher getRequestDispatcher(String path)
- 使用RequestDispatcher物件來進行轉發:forward(ServletRequest request, ServletResponse response)
2. 特點:
- 瀏覽器位址列路徑不發生變化
- 只能轉發到當前伺服器內部資源中。
- 轉發是一次請求
請求轉發圖解:
程式碼
這個案例是以index.jsp頁面向Servletimp請求,然後Servletimp跳轉到Bservlet
Servletimp
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/Servletimp")
public class Servletimp extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
RequestDispatcher requestDispatcher = req.getRequestDispatcher("/Bservlet");
requestDispatcher.forward(req,resp);
System.out.println("Servletimp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doGet(req,resp);
}
}
Bservlet
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/Bservlet")
public class Bservlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
System.out.println("Bservlet");
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}
<%--
Created by IntelliJ IDEA.
User: 86151
Date: 2020/7/29
Time: 11:00
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<FORM action="/Servletimp" method="post">
<input name="username">
<input type="submit" value="提交">
</FORM>
</body>
</html>
共享資料
我們先來了解什麼是域物件?
域物件:一個有作用範圍的物件,可以在範圍內共享資料
request:代表一次請求的範圍,一般用於請求轉發中多個資源的共享資料
方法
- void setAttribute(String name,Object obj):儲存資料
- Object getAttitude(String name):通過鍵獲取值
- void removeAttribute(String name):通過鍵移除鍵值對
獲取ServletContext
ServletContext getServletContext
簡單的程式碼實現
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/Servletimp")
public class Servletimp extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
RequestDispatcher requestDispatcher = req.getRequestDispatcher("/Bservlet");
req.setAttribute("id",1);//存入鍵名為id值為1的資料
requestDispatcher.forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/Bservlet")
public class Bservlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
Object id = req.getAttribute("id");//獲取鍵名為id的鍵值
System.out.println(id);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}