java servlet的执行流程

1、先附上代码如下

Servlet1.java

public class Servlet1 implements Servlet {
    @Override
    public void init(ServletConfig config) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    @Override
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        //返回到浏览器
        res.getWriter().write("hello servlet");

    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
         xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name>

<servlet>
  <!--定义一个serlvet-->
  <servlet-name>servlet1</servlet-name>
  <servlet-class>com.rookie.bigdata.Servlet1</servlet-class>
</servlet>

  <!--对servlet进行映射-->
  <servlet-mapping>
    <servlet-name>servlet1</servlet-name>
    <url-pattern>/servlet1</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

2、整体流程图如下：

3、针对上面代码的详细流程如下

1、启动tomact加载应用和web.xml文件

2、http访问程序 http://localhost:8080/servlet1,最终通过web.xml文件映射为com.rookie.bigdata.Servlet1

3、实例化Servlet1对象

4、调用Servlet1中的init方法

5、调用service方法接受浏览器请求