JavaWeb15.4【response：ServletContext物件的獲取方式和功能】
阿新 • • 發佈：2021-07-01
1 package com.haifei.servletcontext; 2 3 import javax.servlet.ServletContext; 4 import javax.servlet.ServletException; 5 import javax.servlet.annotation.WebServlet; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse;9 import java.io.IOException; 10 11 /** 12 * ServletContext物件的獲取方式 13 * 1. 通過request物件獲取 14 * request.getServletContext(); 15 * 2. 通過HttpServlet獲取 16 * this.getServletContext(); 17 */ 18 @WebServlet("/servletContextDemo1") 19 public class ServletContextDemo1 extends HttpServlet {20 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 21 ServletContext context1 = request.getServletContext(); 22 ServletContext context2 = this.getServletContext(); 23 System.out.println(context1); //org.apache.catalina.core.ApplicationContextFacade@501082b224 System.out.println(context2); //org.apache.catalina.core.ApplicationContextFacade@501082b2 25 System.out.println(context1 == context2); //true 26 } 27 28 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 29 this.doPost(request, response); 30 } 31 }
1 package com.haifei.servletcontext; 2 3 import javax.servlet.ServletContext; 4 import javax.servlet.ServletException; 5 import javax.servlet.annotation.WebServlet; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 import java.io.IOException; 10 11 /** 12 * ServletContext物件的功能1：獲取MIME型別 13 * * MIME型別:在網際網路通訊過程中定義的一種檔案資料型別 14 * * 格式： 大型別/小型別 text/html image/jpeg 15 * * 檢視：D:\Program Files\apache-tomcat-8.5.31\conf\web.xml 16 * * 獲取：String getMimeType(String file) 17 */ 18 @WebServlet("/servletContextDemo2") 19 public class ServletContextDemo2 extends HttpServlet { 20 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 21 ServletContext context = this.getServletContext(); 22 23 //定義檔名稱 24 String fileName = "a.jpg"; 25 //獲取檔案的MIME型別 26 String mimeType = context.getMimeType(fileName); 27 System.out.println(mimeType); //image/jpeg 28 29 } 30 31 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 32 this.doPost(request, response); 33 } 34 }
1 package com.haifei.servletcontext; 2 3 import javax.servlet.ServletContext; 4 import javax.servlet.ServletException; 5 import javax.servlet.annotation.WebServlet; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 import java.io.IOException; 10 11 /** 12 * ServletContext物件的功能2：域物件-共享資料 13 * 14 * 1. setAttribute(String name,Object value) 15 * 2. getAttribute(String name) 16 * 3. removeAttribute(String name) 17 * 18 * * ServletContext物件範圍：所有使用者所有請求的資料，即最大範圍 19 */ 20 @WebServlet("/servletContextDemo3") 21 public class ServletContextDemo3 extends HttpServlet { 22 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 23 ServletContext context = this.getServletContext(); 24 25 context.setAttribute("msg", "哈哈"); 26 } 27 28 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 29 this.doPost(request, response); 30 } 31 }
1 package com.haifei.servletcontext; 2 3 import javax.servlet.ServletContext; 4 import javax.servlet.ServletException; 5 import javax.servlet.annotation.WebServlet; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 import java.io.IOException; 10 11 /** 12 * ServletContext物件的功能2：域物件-共享資料 13 * 14 * 1. setAttribute(String name,Object value) 15 * 2. getAttribute(String name) 16 * 3. removeAttribute(String name) 17 * 18 * * ServletContext物件範圍：所有使用者所有請求的資料 19 */ 20 @WebServlet("/servletContextDemo4") 21 public class ServletContextDemo4 extends HttpServlet { 22 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 23 ServletContext context = this.getServletContext(); 24 25 Object msg = context.getAttribute("msg"); 26 System.out.println(msg); 27 /* 28 http://localhost:8080/day15/servletContextDemo3 29 http://localhost:8080/day15/servletContextDemo4 30 31 哈哈 32 */ 33 } 34 35 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 36 this.doPost(request, response); 37 } 38 }
1 package com.haifei.servletcontext; 2 3 import javax.servlet.ServletContext; 4 import javax.servlet.ServletException; 5 import javax.servlet.annotation.WebServlet; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 import java.io.File; 10 import java.io.IOException; 11 12 /** 13 * ServletContext物件的功能3：獲取檔案的真實(伺服器[tomcat])路徑 14 * 15 * 方法：String getRealPath(String path) 16 * 17 */ 18 @WebServlet("/servletContextDemo5") 19 public class ServletContextDemo5 extends HttpServlet { 20 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 21 ServletContext context = this.getServletContext(); 22 23 String realPath = context.getRealPath("/b.txt"); //web目錄下資源的訪問 24 System.out.println(realPath); 25 // D:\Workspace-java\idea\Workspaces\itheima-javaweb\out\artifacts\day15_war_exploded\b.txt 26 // "/b.txt"中的/代表D:\Workspace-java\idea\Workspaces\itheima-javaweb\out\artifacts\day15_war_exploded\，即web目錄 27 File file = new File(realPath); 28 29 String realPath1 = context.getRealPath("/WEB-INF/c.txt"); //WEB-INF目錄下資源的訪問 30 System.out.println(realPath1); 31 //D:\Workspace-java\idea\Workspaces\itheima-javaweb\out\artifacts\day15_war_exploded\WEB-INF\c.txt 32 33 String realPath2 = context.getRealPath("/WEB-INF/classes/a.txt"); //src目錄下資源的訪問 34 System.out.println(realPath2); 35 //D:\Workspace-java\idea\Workspaces\itheima-javaweb\out\artifacts\day15_war_exploded\WEB-INF\classes\a.txt 36 } 37 38 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 39 this.doPost(request, response); 40 } 41 }