Learning about Web Technology

Servlet

1:Tomcat 's directory structure

2: Publish first project

Under the webapps directory, create a directory that must be created according to the Java EE architecture:

Project

Index.html

Web-inf

Xml

Classes

Lib

1: The Way of publishing 1

Put it in the webapps directory .

2: Release mode 2

Put it in a separate directory, referenced in the server.xml file:

3: Stand-alone configuration file

4: Configure the Virtual host

To configure the above project City:www.inkeeper.com

Configure DNS

To configure a virtual host:

Unpackwars= "true" autodeploy= "true" >

</Host>

The default main project in Tomcat is ROOT

3: integration with Eclipse Step 1: Add the Tomcat server

After adding is complete:

Step 2: Add a project-server project

Start:

4: Development of the first helloword web project in Eclipse Step 1: Create a Web project

Step 2: View the structure of the created project

Directly right-click to run as:

5: three major components in Javaweb development

Filter- Highest level

Listener Level Second

Servlet level third - "learn from here."

The three components above are interfaces that require programmers to implement them. The Servlet container is also called by tomcat/ to instantiate this class.

Time to display the server:

JS script: No, because JS runs on the client side, it shows the customer's time .

When the server is displayed, you must use Java code.

6:Servlet

a Servlet is a component

Used to generate dynamic pages

Receives a user's request to output a response to the user.

A Servlet is a combination of Server+let that refers to a small program on a service.

1: View the servlet API

Jdk.chm was developed by javase .

Servlets are javase developed. So check another set of APIs, and there is no Servlet in the JDK class.

View:

Javax.servlet
Interface Servlet

Defines methods that all servlets must implement. Some methods are defined, and all subclasses must implement these methods.

A servlet is a small the Java program, that runs within a WEB server. Servlets receive and respond to requests from WEB clients, usually across

A Servlet is a Java applet that runs on a javaweb server , such as Tomcat . Receives a response request through the client. Often through the HTTP protocol.

HTTP, the hypertext Transfer Protocol. (Hypertext Transfer Protocol HTML)

HTTP Protocol - text Format:

Agreement for instructions:

GET ( request type get|post)/index.html ( Consult resource ) http/1.1--> request first line

Host: There are many www.baidu.com:80 request headers.

...

..

[ blank line ]

Request Body GET mode There is no data here,POST means there's data here .

Response protocol

http/1.1 (Response code ) OK

Response header

Server: ...

Blank Line

Body

The HTTP protocol is a stateless protocol

Step 1: Develop a class implementation interface

Public class Oneservlet implements Servlet {

/**

* This method is the initialization method when this class, instantiated, is called by the Tomcat container to the party <br>

* will only be called once

*/

@Override

Public void init (servletconfig config) throws servletexception {

System. err. println (" initialized :" + this) ;

}

/**

* methods to provide service to users, each time the user calls, will execute this method

*/

@Override

Public void Service (servletrequest req, servletresponse Res) throws Servletexception, IOException {

set the type of response to

Res.setcontenttype ("Text/html;charset=utf-8");

get output to the browser output stream

PrintWriter out = Res.getwriter ();

String str = new simpledateformat ("Yyyy-mm-dd HH:mm:ss"). Format (new Date ());

output to

System. err. println ("Service this:" + this);

Out.print ("<b> current time is :</b>" + str);

}

@Override

Public void Destroy () {

a method called by Tomcat to clean up some resources when Tomcat is closed

will only be called once

System. err. println ("destory:" + this);

}

Step 2: Configure it to Web. XML

<!-- configuration of the first Servlet --

<servlet>

<!-- Declare any name--

<servlet-name>one servlet</servlet-name>

<!-- The name of the specified class--

<servlet-class>cn.inkeeper.OneServlet</servlet-class>

</servlet>

< how!--configuration is accessed --

<servlet-mapping>

<!-- reference the name of the above declaration--

<servlet-name>one servlet</servlet-name>

<!-- configuration access URL--

<url-pattern>/one.html</url-pattern>

</servlet-mapping>

Step 3: Access

Http://localhost/helloworld/one.html

7:theServlet 's access process

8: instantiation time and number of instantiations of Servlet

Instantiation time

All of the default servlets are not instantiated when the project starts.

Instantiated and initialized the first time a user accesses.

Number of instantiations:

The Servlet defaults to a single instance, which is instantiated by Tomcat through reflection and called by Tomcat to initialize the method.

9: The life cycle approach of the Servlet

The life cycle initialization method must be called the following name, and must receive the following types of parameter classes:

This method will only be called once:

@Override

Public void init (servletconfig config) throws servletexception {

System. err. println (" initialized :" + this) ;

}

Here's how the service is provided in the lifecycle, which is called every time a user requests a server:

@Override

Public void Service (servletrequest req, servletresponse Res) throws Servletexception, IOException {

a method called by Tomcat to clean up some resources when Tomcat is closed -it will only execute once

@Override

Public void Destroy () {

a method called by Tomcat to clean up some resources when Tomcat is closed

will only be called once

System. err. println ("destory:" + this);

}

Ten: Through the above explanation

Two points:

1:theServlet is a singleton. This class is instantiated by the Tomcat container, and the Serv Let instance is maintained by the Tomcat server .

2: The life cycle of the Servlet:

Init (ServletConfig)

Service (REQ,RESP)

Destory ();

How to configure:

1: Declaring a class implements an interface

2: Configure this class in Web . XML <servlet><servlet-mapping>

3: Access by <url-pattern>/one is .../one

One: quick example

User Registration function:

Thought:

1: Develop a registered page. <form>

2: receiving data in the background development a Servlet receives the data passed by the user.

Step 1: Develop a registered page

<form method="POST" action="Reg">

<p> Please register </p>

<table>

Step 2: Develop the servlet to receive the user's registration

Public class Regiestservlet implements Servlet {

@Override

Public void Service (servletrequest req, servletresponse Res) throws Servletexception, IOException {

1: Set the encoding type

Req.setcharacterencoding ("UTF-8");

2: receive user's parameters <input type= "text" name= "name" in /> "Name"

String name = Req.getparameter ("name");

String pwd = req.getparameter ("pwd");

String sex = req.getparameter ("Sex");

String major = Req.getparameter ("major");

3: Display

Res.setcontenttype ("Text/html;charset=utf-8");// Set the format of the response

get Output Object

PrintWriter out =

Res.getwriter ();

Out.print (" name is :"+name+ "

Out.print (" password is :"+pwd+ "

Out.print (" Gender is :"+sex+ "

Out.print (" Education :"+major+ "

}

Step 3: Configure

<!-- Configure a second servlet --

<servlet>

<servlet-name>regServlet</servlet-name>

<servlet-class>cn.inkeeper.RegiestServlet</servlet-class>

</servlet>

< how!--configuration is accessed --

<servlet-mapping>

<servlet-name>regServlet</servlet-name>

<url-pattern>/Reg</url-pattern>

</servlet-mapping>

<form method="POST" action="Reg">

<p> Please register </p>

<table>

Learning about Web Technology