Java-web-http protocol and Tomcat server

HTTP protocol and Tomcat server

HTTP protocol1. What is the HTTP protocol

HTTP, Hypertext Transfer Protocol (hypertext Transfer Protocol) is one of the most widely used network protocols on the Internet. All WWW documents must comply with this standard. HTTP was originally designed to provide a way to publish and receive HTML pages

2. The composition of the HTTP protocol

The HTTP protocol consists of HTTP requests and HTTP responses, and when a Web site is entered in a browser, your browser encapsulates your request to a server site, and the server receives a request that organizes the response data into an HTTP response that is returned to the browser. That is, there is no response without a request.

　　　　　　　　　　　　　　　　　　　　　　　　

1. HTTP request

Edit a form.html form page as follows:

Click the Submit button to grab the package as follows

1) Request Line

Request method: POST, GET

Requested resource:/demoee/form.html

Protocol version: http/1.1

http/1.0, send a request, create a connection, get a Web resource, disconnect the connection.

http/1.1, sends a request, creates a connection, obtains multiple Web resources, and remains connected.

2) Request Header

The request header is some information that the client sends to the server, using a key-value pair to represent the Key:value

Common Request Headers	Description (Red master, other understanding)
Referer	The browser notifies the server where the current request is coming from. If it is direct access, there will be no such header. Commonly used: anti-theft chain
If-modified-since	The browser notifies the server of the last change time of the local cache. Controls the caching of browser pages with a combination of another response header.
Cookies	Session-related techniques for storing cookie information cached by the browser.
User-agent	Browser notification server, client browser and operating system related information
Connection	Keep the connection state. Keep-alive connection, Close is closed
Host	The requested server host name
Content-length	The length of the request body
Content-type	If it is a POST request, it will have this header, the default value is Application/x-www-form-urlencoded, which indicates that the request body content uses URL encoding
Accept:	The MIME types that the browser can support. A description of the file type. MIME format: Large type/small type [; parameter] For example: text/html, HTML file TEXT/CSS,CSS file Text/javascript,js file image/*, all picture files
Accept-encoding	The browser notifies the server that the browser supports the data compression format. such as: gzip compression
Accept-language	The browser notifies the server that the browser supports the language. Languages of the World (international i18n)

3) Request body

When the request mode is post, the request realizes the requested parameter, in the following format:

Username=zhangsan&password=123

If the request method is get, then the request parameter will not appear in the request body, will be stitched behind the URL address

Http://localhost:8080...?username=zhangsan&password=123

HTTP Response

1) Response Line

HTTP protocol

Status code:

The usual status codes are as follows:

200: The request was successful.

302: Request redirection.

304: The request resource has not changed to access the local cache.

404: The request resource does not exist. This is usually a user path write error, or the server resource has been deleted.

500: Server internal error. Usually the program throws an exception.

Status information: status information is changed according to the status code change

2) Response Head

The response is also a key-value pair, and the server returns the information to the client in the form of a key-value pair

Common Request Headers	Describe
Location	Specifies the path of the response, which needs to be used in conjunction with status Code 302 to complete the jump.
Content-type	Type of response body (MIME type) Value: Text/html;charset=utf-8
Content-disposition	Parse the body by browser download method Value: Attachment;filename=xx.zip
Set-cookie	Session-related technologies. Server writes cookies to browser
Content-encoding	Compression format used by the server Value: gzip
Content-length	Length of response body
Refresh	Timed refresh, Format: number of seconds; url= path. The URL can be omitted, and the default value is the current page. Value: 3;url=www.itcast.cn//Three seconds Refresh page to www.itcast.cn
Server	Refers to the server name, default value: apache-coyote/1.1. Modifications can be made through the Conf/server.xml configuration. <connector port= "8080" ... server= "Itcast"/>
Last-modified	The server notifies the browser of the last modified time of the file. Used in conjunction with If-modified-since.

3) Response body

The response body is the page body that the server writes back to the client, the browser loads the body into memory, and then parses the render display page content

Tomcat ServerCommon concepts in web development(1) b/s system and C/s system

Brower/server: Browser Server System-----Web site

Client/server: Client Server System-----QQ, Fei Qiu, large game

(2) Web application Server

Server Software for external publishing of Web resources

　　　　　　　　　　　　　　　　　　　　　　

Web Resources

The resources that exist in the Web application server that are accessible to the outside world are Web resources

For example: HTML, Css, JS, pictures, videos, etc. that exist inside the Web application server

Static resources: Data that is accessible to people in a Web page is always the same. For example: HTML, CSS, JS, pictures, multimedia.

Dynamic resources: Refers to the Web page for people to browse the data is generated by the program, at different points in time to access the content of the Web page can be seen differently. For example: Jsp/servlet, ASP, PHP

Javaweb Domain: Dynamic resources think Java code to dynamically generate HTML

Requests and Responses

　　　　　　　　　　　　　　　　

the requested URL address

Web Application server commonly used in web development

1) weblogic:oracle Company's large toll Web server supports all Java EE specifications

2) WEBSPHERE:IBM Company's large toll Web server supports all Java EE specifications

3) Open source free small and medium Web application server under Tomcat:apache Open Source support servlet and JSP specifications in Java EE

2. Download and installation of TomcatDownload Tomcat

Website address: http://tomcat.apache.org/whichversion.html

Installing Tomcat

Tomcat has installed version and press release (green version)

Installation version in the form of an. exe installation package, double-click Install to our computer, with less

Decompression version, that is, the green version, extracted directly after use, with more

Tomcat's directory structure

Bin: Script Directory

Startup script: Startup.bat

Stop script: Shutdown.bat

Conf: Configuration file directory (config/configuration)

Core configuration file: Server.xml

User Rights profile: Tomcat-users.xml

All Web project default profiles: XML

LIB: Dependent libraries, Tomcat, and jar packages needed in Web projects

Logs: Log file.

Localhost_access_log.*.txt Tomcat Records user access information, and Star * represents time.

Example: Localhost_access_log.2016-02-28.txt

Temp: Temporary file directory, folder contents can be arbitrarily deleted.

WebApps: The directory where the Web project is published by default.

Work:tomcat handles the working directory of the JSP.

tomcate Start-up and Operation

Double-click Startup.bat under the bin under Tomcat to start Tomcat

　　　　　　

Enter http://localhost:8080 in the address bar of the browser and see the following page to prove the successful start

Cause analysis for Tomcat startup unsuccessful:

1) If you do not configure the JAVA_HOME environment variable, when you double-click the "Startup.bat" file to run Tomcat, the Flash is turned off immediately. and must be configured correctly, and Java_home point to the JDK's installation directory

2) port conflict

Java.net.BindException:Address already in Use:jvm_bind <null>:8080

Modify Tomcat/conf/server.xml

directory structure for Web apps

Note: The Web-inf directory is protected and cannot be accessed directly by the outside world

use Eclipse to bind Tomcat and publish your app

Step 1: Get the server run environment configuration, Window/preferences/server/runtime Environmen

Java-web-http protocol and Tomcat server