序言
當我們繼承HttpServlet類的時候，其實我們只需要重寫servlet中的doGet方法，和doPost方法，無需再進行重寫service方法。
打開httpservlet的源碼文件，查看大概在第658行處service函數的定義，在這裏可以看到service函數無論如何最終都是要進行doGet或者是doPost的調用，所以我們在繼承Httpservlet類的時候，可以直接對doGet和doPost進行重寫
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod();
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
doGet(req, resp);
} else {
long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
if (ifModifiedSince < lastModified) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
}
} else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else if (method.equals(METHOD_POST)) {
doPost(req, resp);
} else if (method.equals(METHOD_PUT)) {
doPut(req, resp);
} else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp);
} else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp);
} else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp);
} else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
//
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
測試
創建客戶端提交表單
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="http://localhost:8080/Demo_03/my_http_servlet" method="get">
ID:<input type="text" name="IdNumber">
Pw:<input type="password" name="pw">
使用get方法提交<input type="submit" name = "GetSubmit">
</form>
</br>
<form action="http://localhost:8080/Demo_03/my_http_servlet" method="post">
ID:<input type="text" name="IdNumber">
Pw:<input type="password" name="pw">
使用get方法提交<input type="submit" name = "GetSubmit">
</form>
</body>
</html>
創建對應類
package com.demo03_httpServlet;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.Executor;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sun.net.httpserver.HttpContext;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
public class MyHttpServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String MethodName = req.getMethod();
System.out.println("當前使用的請求方法：" + MethodName);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String MethodName = req.getMethod();
System.out.println("當前使用的請求方法：" + MethodName);
}
}
配置文件
<!-- HttpServlet獲取請求的演示 -->
<servlet>
<servlet-name>MyHttpServlet</servlet-name>
<servlet-class>com.demo03_httpServlet.MyHttpServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyHttpServlet</servlet-name>
<url-pattern>/my_http_servlet</url-pattern>
</servlet-mapping>
運行測試
