ServletContext共享資料
阿新 • • 發佈：2020-06-29
今天觀看視訊複習得時候學到了ServletContext相關知識，發現它可以實現servlet之間得資料共享，可以在servlet中傳遞資料，我還記得原來做老師佈置的專案的時候因為這個問題，我把資料都存在session域再在需要的servlet取用，那樣特別麻煩，還是源於自己之前學的不踏實。
所有的servlet都共用一個servletcontext的物件，利用它存取資料：
下面我貼一下我使用其的例子：
<html> <body> <h2>Hello World!</h2> <form action="servlet_01"> <index.jspinput type="submit" value="queding"> </form> </body> </html>
import java.io.IOException; import java.io.Writer; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest;servlet-01.javaimport javax.servlet.http.HttpServletResponse; /** * Servlet implementation class servlet_01 */ public class servlet_01 extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public servlet_01() { super();// TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Writer writer = response.getWriter(); writer.append("hello servlet"); ServletContext context = this.getServletContext(); context.setAttribute("username", "一個程式猿！"); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }
package frist_test; import java.io.IOException; import java.io.Writer; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class servlet_02 */ public class servlet_02 extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public servlet_02() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ServletContext context = this.getServletContext(); // response.setHeader("utf-8", "text/html"); response.setContentType("text/html"); response.setCharacterEncoding("utf-8"); String name = (String)context.getAttribute("username"); response.getWriter().append(name); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }servlet-02.java