Servlet消耗http發佈參數

Question

我完全不熟悉JAVA。我需要編寫一個將使用從客戶端發送的http post參數的servlet。我已經有一個Java應用程序平臺服務器，可以在那裏部署我的應用程序我需要的是寫一個servlet，它會對發佈的參數做出反應。

顯然我需要在Servlet中公開這些變量？我做了谷歌，並且遇到了建議使用REST框架來實現這一目標的結果。如果不使用任何額外的框架，就不可能寫平面java代碼（例如運行Tomcat）？樣本或教程的鏈接也會有所幫助。

謝謝

Answer 1

不，你不需要一個REST框架。

只需編寫一個擴展HttpServlet並實施doPost()的servlet。

開始與Sun/Oracle的教程：

http://java.sun.com/developer/onlineTraining/Programming/BasicJava1/servlet.html

下面是父類的javadoc：

http://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html

Answer 2

如果你想建立與JAX-RS應用程序，在部署到Tomcat之前，您只需在項目中包含幾個jar。您的IDE可能會在構建戰爭文件時爲您做這件事。如果您希望在部署時減少上載的大小，可以將這些jar移動到Tomcat lib文件夾中。但你當然不需要使用REST來訪問請求參數。

實際上，所有傳統的Web應用程序都需要捕獲http post參數。我編寫了一個小實用程序servlet來列出所有參數，以幫助我防止在HTML中使用一個名稱和servlet中的另一個名稱調用參數的愚蠢錯誤。這段代碼演示瞭如何獲取請求和會話參數：（見HttpServletRequest docs）

import java.io.IOException; 
import java.io.PrintWriter; 
import javax.servlet.ServletException; 
import javax.servlet.annotation.WebServlet; 
import javax.servlet.http.*; 

/** 
* This Servlet contains some helpful debugging methods. 
    * @author Leon LaSpina 
*/ 
@WebServlet(name = "UtilityServlet", urlPatterns = {"/dev/Utility"}) 
public class UtilityServlet extends HttpServlet { 

    /** 
    * This is a utility method for displaying the list of all request parameters 
    * sent to a Servlet or JSP. 
    * @param request - The HTTP request sent to the Servlet or JSP 
    * @param out The stream so that the method may write directly to the web page. 
    */ 
    public static void printMap(HttpServletRequest request, PrintWriter out) { 
     java.util.Map<String, String[]> paramMap = request.getParameterMap(); 
     out.println("<h3>From Data</h3>"); 
     out.println("<table border='1'><tr>"); 
     out.print("<td>attribte name</td><td>Attribute Data</td></tr>"); 
     String[] attribute; 
     for (String name : paramMap.keySet()) { 
      out.print("<tr>"); 
      out.println("<td>" + name + "</td><td>"); 
      attribute = paramMap.get(name); 
      if (attribute.length == 1) { 
       out.print(attribute[0]); 
      } else { 
       for (String s : attribute) { 
        out.print(s + ", "); 
       } 
      } 
      out.println("</td></tr>"); 
     } 
     out.println("</table>"); 
    } 

    /** 
    * This is a simple utility method for displaying the list of all Session 
    * Objects in a simple table. 
    * @param request - sent to servlet or JSP 
    * @param out the OutputStream so that we may write directly to the web page 
    */ 
    public static void printSessionMap(HttpServletRequest request, PrintWriter out) { 
     HttpSession session = request.getSession(); 
     printSessionMap(session, out); 
    } 

    /** 
    * This is a simple utility method for displaying the list of all Session 
    * Objects in a simple table. 
    * @param request - sent to servlet or JSP 
    * @param out the OutputStream so that we may write directly to the web page 
    */ 
    public static void printSessionMap(HttpSession session, PrintWriter out) { 
     java.util.Enumeration<String> names = session.getAttributeNames(); 
     out.println("<h3>Session Objects</h3>"); 
     out.println("<table border='1'><tr>"); 
     out.print("<td>attribte</td><td>DataType</td><td>Object Data</td></tr>"); 
     while (names.hasMoreElements()) { 
      out.print("<tr><td>"); 
      String attribute = names.nextElement(); 
      out.print(attribute + "</td><td>"); 
      out.print(session.getAttribute(attribute).getClass().getName()); 
      out.print("</td><td>"); 
      out.println(session.getAttribute(attribute)); 
      out.println("</td></tr>"); 
     } 
     out.println("</table>"); 
    } 

    /** 
    * Handles the HTTP <code>POST</code> method. 
    * @param request servlet request 
    * @param response servlet response 
    * @throws ServletException if a servlet-specific error occurs 
    * @throws IOException if an I/O error occurs 
    */ 
    @Override 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
     response.setContentType("text/html;charset=UTF-8"); 
     PrintWriter out = response.getWriter(); 
     //HttpSession theSession = request.getSession(); 
     try { 
      out.println("<html><head>"); 
      out.println("<title>UtilityServlet</title></head>"); 
      out.println("<body><h1>UtilityServlet for development</h1>"); 
      printMap(request, out); 
      printSessionMap(request, out); 
      out.println("</body></html>"); 
     } finally { 
      out.close(); 
     } 
    } 
}