Java第四十二天，Servlet系列（五），Servlet 体系

一、Servlet 体系

Servlet

GenericServlet ===> 实现 Servlet 接口的抽象类

HttpServlet ===> 继承 GenericServlet 抽象类的子抽象类

二、GenericServlet

GenericServlet 实现了 Servlet 接口，而且将除了 service 方法外的其他方法都进行了空实现，即我们的自定义 Servlet 如果继承该抽象类，仅需实现 service 方法即可

package web.servlet;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;

@WebServlet(urlPatterns = {"/first"})
public class FirstServlet extends GenericServlet {
    
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("this is my first servlet!");
    }
}

三、HttpServlet （推荐）

默认实现了判断 get 和 post 的逻辑，如果是 get，则执行 doGet()；如果是 post，则执行 doPost()；因此我们继承该类时需要复写 doPost() 方法

package web.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(urlPatterns = {"/first"})
public class FirstServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doGet......");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doPost......");
    }
}

四、urlPatterns 命名规则

• /xxx
• /xxx/xxx
• 结合通配符（ /* ，*.[后缀]）

package web.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(urlPatterns = {"/first", "/first/one", "*.info", "/*"})
public class FirstServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doGet......");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doPost......");
    }
}