servlet和http请求协议
Servlet的体系结构
HttpServlet --抽象类
| 继承
GenericServlet --抽象类
| 实现
Servlet --接口
GenericServlet :将Servlet接口中的其他方法变成了默认空实现,只有将service()方法作为抽象
如果将来定义servlet类时不用实现Servlet接口而是去继承GenericServlet类时,不用重写其他的方法,只用重写service()方法即可
ServletDemo2(继承GenericServlet类) :
package wtf.servlet; import javax.servlet.GenericServlet; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.annotation.WebServlet; import java.io.IOException; @WebServlet("/demo2") public class ServletDemo2 extends GenericServlet { @Override public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException { System.out.println("GenericServlet"); } }
HttpServlet:对http协议的一种封装,简化操作
如果将来定义servlet类时不用实现Servlet接口而是去继承HttpServlet类时,不用重写其他的方法,而只需根据请求类型来重写doGet或者是doPost方法即可
HttpServlet图解:
ServletDemo3(继承HttpServlet类) :
package wtf.servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/demo3") public class ServletDemo3 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("use get"); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("use post"); } }
login.html(分别使用doGet和doPost方法):
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>登录</title> </head> <body> <!--这里method如果是get,控制台会输出的是use get,method如果是post,控制台会输出的是use post--> <form action="/demo3" method="post"> <input name="username"> <input type="submit" value="提交"> </form> </body> </html>