hello2 source analysis
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hello2 source analysis
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Hello2 應用程序是一個 Web 模塊，它使用 Java Servlet 技術來顯示問候語和響應，使用的是 Java Servlet 技術。
該應用程序源代碼在 tutorial-examples\web\servlet\hello2\src\main\java\javaeetutorial\hello2 下，分別為：GreetingServlet.java和ResponseServlet.java
此 servlet 重寫該 doGet 方法，實現 GET HTTP 方法。servlet 顯示一個簡單的HTML問候表單，GreetingServlet.java：
@WebServlet("/greeting")????? //將 URL 指定為/greeting
public class GreetingServlet extends HttpServlet { @Override
??? public void doGet(HttpServletRequest request,? //重寫 httpservlet 的 doget 方法，實現覆蓋并用來處理 get 請求
??????????? HttpServletResponse response)
??????????? throws ServletException, IOException { response.setContentType("text/html");? // 設置響應類型為 HTML
??????? response.setBufferSize(8192);?
??????? try (PrintWriter out = response.getWriter()) {
??????????? out.println("<html lang=\"en\">"?????? //設置 HTML 語言
??????????????????? + "<head><title>Servlet Hello</title></head>");?? // 網頁標題
???????????
??????????? // 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 源代碼，以顯示頁面
???????????
??????????? String username = request.getParameter("username");
?????????? //獲取傳來的參數值。
?????????? //通過容器傳遞給當前 httpservlet
??????????
??????????? if (username != null && username.length() > 0) { ?//判斷用戶輸入的值是否有效
??????????????? RequestDispatcher dispatcher =
??????????????????????? getServletContext().getRequestDispatcher("/response");??? //獲取url為/response的servlet作為一個dispatcher資源
???????????????
??????????????? if (dispatcher != null) {
??????????????????? dispatcher.include(request, response);
??????????????? }
??????????? }
??????????? out.println("</body></html>");
??????? }
??? }
??? //dispatcher 中通過 request 獲得 username，在response中添加了hello這幾句話，dispatcher 就是開始獲得的 /response 對應的httpservlet。
12345678910111213141516171819202122232425262728293031323334353637383940414243
編輯器打開 ResponseServlet.java ：
@WebServlet("/response")?? ?// 將 URL 配置為 /response
public class ResponseServlet extends HttpServlet { @Override
??? public void doGet(HttpServletRequest request,
??????????? HttpServletResponse response)
??????????? throws ServletException, IOException {
??????? try (PrintWriter out = response.getWriter()) {??? //獲取輸出對象，用于向頁面寫數據。返回一個 PrintWriter 對象
??????????? String username = request.getParameter("username"); //獲取用戶的字符串或字符
??????????? if (username != null && username.length() > 0) { ?//判斷輸入值是否有效，有效則執行
??????????????? out.println("<h2>Hello, " + username + "!</h2>");? //在頁面輸出一句話。
??????????? }
??????? }
??? } @Override
??? public String getServletInfo() {
??????? return "The Response servlet says hello."; }
}
123456789101112131415161718192021
以上就是 Hello2 的基本代碼實現，整體來講實現代碼不多，也有很高的可讀性，代碼清晰，學習起來也沒那么困難。
在本地部署servlet時，可以使用以下URL訪問它：
http://localhost:8080/hello2/greeting
該應用程序源代碼在 tutorial-examples\web\servlet\hello2\src\main\java\javaeetutorial\hello2 下，分別為：GreetingServlet.java和ResponseServlet.java
此 servlet 重寫該 doGet 方法，實現 GET HTTP 方法。servlet 顯示一個簡單的HTML問候表單，GreetingServlet.java：
@WebServlet("/greeting")????? //將 URL 指定為/greeting
public class GreetingServlet extends HttpServlet { @Override
??? public void doGet(HttpServletRequest request,? //重寫 httpservlet 的 doget 方法，實現覆蓋并用來處理 get 請求
??????????? HttpServletResponse response)
??????????? throws ServletException, IOException { response.setContentType("text/html");? // 設置響應類型為 HTML
??????? response.setBufferSize(8192);?
??????? try (PrintWriter out = response.getWriter()) {
??????????? out.println("<html lang=\"en\">"?????? //設置 HTML 語言
??????????????????? + "<head><title>Servlet Hello</title></head>");?? // 網頁標題
???????????
??????????? // 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 源代碼，以顯示頁面
???????????
??????????? String username = request.getParameter("username");
?????????? //獲取傳來的參數值。
?????????? //通過容器傳遞給當前 httpservlet
??????????
??????????? if (username != null && username.length() > 0) { ?//判斷用戶輸入的值是否有效
??????????????? RequestDispatcher dispatcher =
??????????????????????? getServletContext().getRequestDispatcher("/response");??? //獲取url為/response的servlet作為一個dispatcher資源
???????????????
??????????????? if (dispatcher != null) {
??????????????????? dispatcher.include(request, response);
??????????????? }
??????????? }
??????????? out.println("</body></html>");
??????? }
??? }
??? //dispatcher 中通過 request 獲得 username，在response中添加了hello這幾句話，dispatcher 就是開始獲得的 /response 對應的httpservlet。
12345678910111213141516171819202122232425262728293031323334353637383940414243
編輯器打開 ResponseServlet.java ：
@WebServlet("/response")?? ?// 將 URL 配置為 /response
public class ResponseServlet extends HttpServlet { @Override
??? public void doGet(HttpServletRequest request,
??????????? HttpServletResponse response)
??????????? throws ServletException, IOException {
??????? try (PrintWriter out = response.getWriter()) {??? //獲取輸出對象，用于向頁面寫數據。返回一個 PrintWriter 對象
??????????? String username = request.getParameter("username"); //獲取用戶的字符串或字符
??????????? if (username != null && username.length() > 0) { ?//判斷輸入值是否有效，有效則執行
??????????????? out.println("<h2>Hello, " + username + "!</h2>");? //在頁面輸出一句話。
??????????? }
??????? }
??? } @Override
??? public String getServletInfo() {
??????? return "The Response servlet says hello."; }
}
123456789101112131415161718192021
以上就是 Hello2 的基本代碼實現，整體來講實現代碼不多，也有很高的可讀性，代碼清晰，學習起來也沒那么困難。
在本地部署servlet時，可以使用以下URL訪問它：
http://localhost:8080/hello2/greeting
轉載于:https://www.cnblogs.com/sclerx/p/10624723.html
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