Build a Web environment & get to know JSP

1. Program structure

B/S architecture program (Broswer/server)

Access the application through a browser, such as Taobao browser page
is more convenient to maintain and update the software
usingRequest/responseMode to interact

C/S architecture program (Client/server)

Access the server through the client, such as QQ.
Note: URL-the only naming convention that can identify the location of a specific computer, directory or folder on the Internet, Uniform Resource Locator, which is also a web address, generally consists of a protocol

2. Web server

• It is a program that can provide documents to the requesting browser
• Provide online information browsing service

Tomcat server

Features

• Open source project of Apache Jakarta
• Lightweight application server
• Open source, stable, low resource usage

Configure the environment variable


Tomcat directory to

start Tomcat.
Click the bin directory under the apache-tomcat-8.5.45 file and click startup.bat to start the server. At this time, enter http://localhost:8080 in the web page to access Tomcat Homepage
stop Tomcat
bin\shutdown.bat
Note : localhost is the machine, 8080 is the default port number of Tomcat, you can modify the Tomcat port number through the configuration file server.xml
. Deploy the static website in Tomcat
Copy the project to the webapps folder

三.JSP(Java Server Pages)

1. Concept

• Java page running on the server

• Use HTML nested Java code to achieve

2. Working principle

3. Use JSP to achieve output

Note: The syntax is the same as HTML, see the article "Forms" for details

The first

The second

Use out.print to output statements

4. Grammar

• Use to <%%>declare local variables,% is used to write java code

• Use to <%!%>declare global variables
  

• <%@page%>Used to set the properties of a JSP page

• <%out.print();%>Or <%out.println(); %>realize page output

Comments that JSP can add

• HTML comments:<!--HTML注释-->
• JSP notes:<%--JSP注释--%>
• Comment in the JSP script:<%//单行注释%><%/*多行注释*/%>

5. JSP execution process

6. Summary

• Declare and use variables in JSP. Such as: <%String title="Talking about the spirit of Beijing";%>
• <%=%> Realize page output. Such as: <%=title%>

Common mistakes:

• <%=title; %>, Do not write semicolons when using variables

• Use <%@page%>guide package. Such as:<%@page import="java.util.Date"%>

• Output escape characters. Such as:<%="谈\"北京精神\""%>

Four. Web program debugging and troubleshooting

Common errors in web programs:

404 error-the visited page or resource could not be found

• URL input error during runtime

• Put the page under WEB-INF

• Start Tomcat externally without deploying the project

500 error-wrong JSP page code

• There is an error in the JSP page code

The page cannot be displayed

• Tomcat is not started