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>