Servlet详细介绍

<?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>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <servlet>
        <servlet-name>date</servlet-name>
        <servlet-class>date.DateDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>date</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>
</web-app>

package date;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@SuppressWarnings("serial")
public class DateDemo extends HttpServlet {


    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter p=response.getWriter();
        Date now=new Date();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        String time=sdf.format(now);
        p.write(time);
        p.close();
    }

}

1）Servlet实际上就是一个容器，Tomcat就是一个Servlet，它提供了Servlet运行的环境

2）关于Servlet路径的认识---Servlet是如何运行的

 2.1比如在浏览器中输入: http://localhost:8080/Servlet2/hi

   1,浏览器通过ip,port与Servlet建立连接

   2,浏览器将请求参数打包发送给Servlet容器。

   3,Servlet解析请求数据，并将该数据放到request对象上，同时创建response对象

   4,Servlet会通过配置(Servlet2/hi)找到配置文件，然后创建对应的Servlet对象。

   5,Servlet容器自动调用service方法，处理request对象，并且返回给response对象

   6,Servlet容器打包resopnse数据，返回给浏览器。

   7,浏览器给句数据展示给用户。

Java代码：

package date;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@SuppressWarnings("serial")
public class DateDemo extends HttpServlet {

@Override
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter p=response.getWriter();
Date now=new Date();
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
String time=sdf.format(now);
p.write(time);
p.close();
}

}

web.xml配置

<?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>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>

<servlet>
<servlet-name>date</servlet-name>
<servlet-class>date.DateDemo</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>date</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
</web-app>