Hello2源码解析

hello2应用程序是一个Web模块，它使用Java Servlet技术来显示问候语和响应，源代码位置在_tut-install_/examples/web/servlet/hello2/

虽然该hello2应用程序的表现几乎相同的hello1 应用程序，但它使用Java Servlet技术，而不是JavaServer Faces技术实现的

cd到该目录，命令行打包（可参见上一篇博客步骤）

打开eclipse，点击GreetingServlet.java Run as Run on server

1.选择hello2文件夹并单击“打开项目”

2.点击pom.xml打开网页如图所示：

可见，跟hello1 不一样的是hello2是servlet的。
3.

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">//此标签可告知浏览器文档使用哪种HTML规范；DTD一套文本类型的定义；标准原文的链接

//语言使用英文；xml采用名字空间声明，允许你通过一个网址来识别你的标记；jcp是java社区的执行委员会 Facelets Hello Greeting //作为资源形式出现的；alt加载不出来就进行替换

Hello, my name is Duke. What's yours?

展开“源包”节点，然后展开javaeetutorial.hello2节点。双击该Hello.java文件以查看它。如图所示

点开两个后可参看代码：

greetingservelet.java

/**

Copyright © 2014 Oracle and/or its affiliates. All rights reserved.
You may not modify, use, reproduce, or distribute this software except in
compliance with the terms of the License at:
https://github.com/javaee/tutorial-examples/LICENSE.txt
*/
package javaeetutorial.hello2;

import java.io.IOException;
import java.io.PrintWriter;
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;

/**

This is a simple example of an HTTP Servlet. It responds to the GET method of

the HTTP protocol.
*/
@WebServlet("/greeting")
public class GreetingServlet extends HttpServlet {

@Override
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {

 response.setContentType("text/html");
 response.setBufferSize(8192);
 try (PrintWriter out = response.getWriter()) {
     out.println("<html lang=\"en\">"
             + "<head><title>Servlet Hello</title></head>");
     
     // then write the data of the response
     out.println("<body  bgcolor=\"#ffffff\">"
             + "<img src=\"resources/images/duke.waving.gif\" "
             + "alt=\"Duke waving his hand\">"
             + "<form method=\"get\">"
             + "<h2>Hello, my name is Duke. What's yours?</h2>"
             + "<input title=\"My name is: \" type=\"text\" "
             + "name=\"username\" size=\"25\"/>"
             + "<p></p>"
             + "<input type=\"submit\" value=\"Submit\"/>"
             + "<input type=\"reset\" value=\"Reset\"/>"
             + "</form>");
     
     String username = request.getParameter("username");
     if (username != null && username.length() > 0) {
         RequestDispatcher dispatcher =
                 getServletContext().getRequestDispatcher("/response");
         
         if (dispatcher != null) {
             dispatcher.include(request, response);
         }
     }
     out.println("</body></html>");
 }

}

@Override
public String getServletInfo() {
return “The Hello servlet says hello.”;

}
}

这个servlet覆盖了doGet方法，实现了HTTP的GET方法。servlet显示一个简单的HTML问候表单，它的Submit按钮，就像hello1那样，为其操作指定一个响应页面。下面的摘录从@WebServlet注释开始，它指定了相对于上下文根的URL模式:

responseservlet.java

/**

You may not modify, use, reproduce, or distribute this software except in
compliance with the terms of the License at:
https://github.com/javaee/tutorial-examples/LICENSE.txt
*/
package javaeetutorial.hello2;

/**

This is a simple example of an HTTP Servlet. It responds to the GET method of

the HTTP protocol.
*/
@WebServlet("/greeting")
public class GreetingServlet extends HttpServlet {

@Override
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {

 response.setContentType("text/html");
 response.setBufferSize(8192);
 try (PrintWriter out = response.getWriter()) {
     out.println("<html lang=\"en\">"
             + "<head><title>Servlet Hello</title></head>");
     
     // then write the data of the response
     out.println("<body  bgcolor=\"#ffffff\">"
             + "<img src=\"resources/images/duke.waving.gif\" "
             + "alt=\"Duke waving his hand\">"
             + "<form method=\"get\">"
             + "<h2>Hello, my name is Duke. What's yours?</h2>"
             + "<input title=\"My name is: \" type=\"text\" "
             + "name=\"username\" size=\"25\"/>"
             + "<p></p>"
             + "<input type=\"submit\" value=\"Submit\"/>"
             + "<input type=\"reset\" value=\"Reset\"/>"
             + "</form>");
     
     String username = request.getParameter("username");
     if (username != null && username.length() > 0) {
         RequestDispatcher dispatcher =
                 getServletContext().getRequestDispatcher("/response");
         
         if (dispatcher != null) {
             dispatcher.include(request, response);
         }
     }
     out.println("</body></html>");
 }

}

@Override
public String getServletInfo() {
return “The Hello servlet says hello.”;

}
}

Hello, my name is Duke. What's yours?

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