Analysis of Hello2 source code
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，使用的是 Java Servlet 技术。
该应用程序源代码在 tutorial-examples\web\servlet\hello2\src\main\java\javaeetutorial\hello2 下，分别为：GreetingServlet.java和ResponseServlet.java
此 servlet 重写该 doGet 方法，实现 GET HTTP 方法。servlet 显示一个简单的HTML问候表单
GreetingServlet.java
@WebServlet("/greeting") //将 URL 指定为/greeting
public class GreetingServlet extends HttpServlet {
@Override
public void doGet(HttpServletRequest request, //重写 httpservlet 的 doget 方法，实现覆盖并用来处理 get 请求
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html"); // 设置响应类型为 HTML
response.setBufferSize(8192);
try (PrintWriter out = response.getWriter()) {
out.println("<html lang=\"en\">" //设置 HTML 语言
+ "<head><title>Servlet Hello</title></head>"); // 网页标题
// 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>"); // HTML 源代码，以显示页面
String username = request.getParameter("username");
//获取传来的参数值。
//通过容器传递给当前 httpservlet
if (username != null && username.length() > 0) { //判断用户输入的值是否有效
RequestDispatcher dispatcher =
getServletContext().getRequestDispatcher("/response"); //获取url为/response的servlet作为一个dispatcher资源
if (dispatcher != null) {
dispatcher.include(request, response);
}
}
out.println("</body></html>");
}
}
//dispatcher 中通过 request 获得 username，在response中添加了hello这几句话，dispatcher 就是开始获得的 /response 对应的httpservlet。
ResponseServlet.java
@WebServlet("/response") // 将 URL 配置为 /response
public class ResponseServlet extends HttpServlet {
@Override
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
try (PrintWriter out = response.getWriter()) { //获取输出对象，用于向页面写数据。返回一个 PrintWriter 对象
String username = request.getParameter("username"); //获取用户的字符串或字符
if (username != null && username.length() > 0) { //判断输入值是否有效，有效则执行
out.println("<h2>Hello, " + username + "!</h2>"); //在页面输出一句话。
}
}
}
@Override
public String getServletInfo() {
return "The Response servlet says hello.";
}
}
在本地部署servlet时，可以使用以下URL访问它：
http://localhost:8080/hello2/greeting
参考链接：
https://blog.csdn.net/X_Teddy/article/details/88785624
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