1, HTML+CSS

2, JavaScript

3, JQuery, BootStrap framework

4, XML

5, Web overview and Tomcat server

5.1 preparation before using tomcat

• Install and configure jdk
• Download and unzip Tomcat
• Configure environment variables
  Variable name: CATALINA_HOME
  Variable value: path just installed

5.2 directory structure of Tomcat

Directory name	effect
bin	Executable program specially used to store Tomcat server
conf	Store the configuration file of Tomcat
lib	jar package for storing Tomcat
logs	Store the log output by Tomcat server during operation
temp	Store temporary data generated by Tomcat runtime
webapps	Store the deployed Web project
work	Tomcat's working time directory

5.3 starting and shutting down Tomcat server

Start Tomcat server

• Find the startup. In bin under Tomcat directory DAT, double-click to start.

• Open the command line, cd to bin, and the catalina run command

Shut down Tomcat server

• Close the command window

• Find the shutdown. Under bin Bat execution

• Put the Tomcat service window on the current page, ctrl+c

Test Tomcat

• http://locathost:8080

• http://127.0.0.1:8080

• http: / / real IP: 8080

5.4 other settings of Tomcat

• Modify port number

  Find the conf directory under the Tomcat directory and find the server XML modify port number
  

• Configure host name

  ![Insert picture description here](https://img-blog.csdnimg.cn/20210622084342992.png)
  

• Deploy web project

  hold Web Copy project directory to Tomcat Directory webapps in
  

• The difference between the way of hand holding and accessing at http:ip port number / project name

  The file: / / protocol is used
  Enter http: / / in the browser using the HTTP protocol

  When we enter the access address in the browser address bar and there is no project name, the default access is the root project
  When we enter the access address in the browser address bar and there is no resource name, the index file is accessed by default

Principles of website access
1. Enter the domain name and press enter
2. Is there a domain name mapping under the local c:/windows/System32/drivers/Etc/Hosts configuration file
Return the corresponding ip address
Did not go to the dns server to find it and put it back

5.5 Web overview

• What is java web?

      JavaWeb Is dynamic Web Resource development technology, All pass Java General name of programs written in language that can be accessed through browser, be called JavaWeb
      JavaWeb It is developed based on request and response
  

• What is a request?

      request(Request)It refers to that the client sends data to the server.
  

• What is response?

      response(Response)It refers to the data returned by the server to the client.
  

• The connection between the two?

      When there is a request, there is a response!
  

• Classification of Web resources

  Web resources can be divided into static resources and dynamic resources according to the implementation technology and presentation effect
  Static resources: html css js txt MP4 jpg
  Dynamic resources: jsp page Servlet program

• Common Web servers

   Tomcat  jboss  GlassFish  Resin  WebLogic.....
  

5.6 dynamic Web project directory

6, Servlet program

6.1 introduction to Servlet

• Servlet is one of the specifications of Java EE, and the specification is the interface.
• Servlet is one of the three components of Java Web. The three components are: servlet program, listener, listener and filter.
• Servlet is a java applet running on the server side. It can receive requests from the client and respond to data.

6.2 implementation of Servlet

• Method 1: implement Servlet interface

   1. Write class implementation Servlet Interface
   2. realization Service method, Process requests and respond to data
   3. stay Web.xml Medium configuration Servlet Access address of the program
  

• Method 2: inherit HttpServlet

    1. Write class inheritance httpServlet 
    2. rewrite doGet  doPost Method( Service Method is distributed)
            note: If rewritten init Method needs to be added to the first line super.init(config);
    3. reach web.xml Medium configuration Servlet Access address for
  

Web.xml execution process
Configure web xml

Configuration of Mapping

• Mapping can specify multiple resource paths (specify more servlet mapping)

• mapping can specify a generic path (*)

• mapping can customize the suffix
  *.xxx

6.3 Servlet inheritance system

6.4 Servlet life cycle

1. Class loading,Then execute Servlet Construction method
2. web Container execution init()Initialization method initialization Servlet container
           First two steps, Is created for the first time Servlet Called when the program
3. implement service method
      Called every time
4. implement destroy Destruction method
      Called when the project stops

6.5 implementation principle of Servlet

  1.The browser sends a message to the server GET request(Request server ServletA)

  2.The container logic on the server received the message url,According to this url Judged as Servlet At this time, the container logic will produce two objects: the request object(HttpServletRequest)And response objects(HttpServletResponce)

  3.Container logic basis url Find the target Servlet(The goal of this example Servlet by ServletA),And create a thread A

  4.The container logic passes the request object and response object just created to the thread A

  5.Container logical call Servlet of service()method

  6.service()Method depends on the request type(This example is GET request)call doGet()(This example calls doGet())or doPost()method

  7.doGet()After execution, the result is returned to the container logic

  8.thread  A Destroyed or placed in the process pool

be careful:

• In principle, there is only one instance of each Servlet in the container
• Each request corresponds to one thread
• Multiple threads can act on the same Servlet (which is the root cause of unsafe Servlet threads)
• Once each thread completes its task, it is destroyed or placed in the thread pool for recycling

6.6 common classes of Servlet

6.6.1 ServletConfig

 ServletConfig In visit Servlet Program by Tomcat establish, yes Servlet Configuration file for

Role of ServletConfig

• Get alias
  this.getServletConfig().getServletName();
• Get the initialization parameter init param (need to be configured under servlet)
  this.getServletConfig().getInitParameter("root");
• Get ServletContext context object
  this.getServletConfig().getServletContext();

6.6.2 ServletContext

• Introduction to ServletContext

  1. ServletContext Is an interface, It means Servlet Context object for
  2. One Web There is only one project ServletContext Object instance(Global uniqueness)
  3. ServletContext Is a domain(Operating range of accessing data)object    similar map object
        Save operation         setAttribute() 
        Fetch operation         getAttribute()
        Delete operation     removeAttribute()
  4. ServletContext stay web Start on project deployment, Destroy on cessation of work
  

• The role of ServletContext

  1. Share data (domain object), request forwarding, get context parameter context param
     getServletConfig().getServletContext().getInitParameter("String s")
  2. Get the current project path, format: / Project path
     getContextPath()
     Get the absolute path on the server hard disk after project deployment
     getRealPath("/")
     Note: / the address resolved by the server is: http://ip:port/ Project name / map to IDEA code web directory
  3. Access data like map
     setAttribute/getAttribute/removeAttribute
  4. Read resource file (read Properties)

• Three ways to get ServletContext
  this.getServletContext()
  this.getServletConfig().getServletContext()
  req.getSession().getServletContext()

6.6.3 HttpServletRequest

 Every time there is a request to enter Tomcat The server, Tomcat The server will send the request HTTP The protocol information is parsed and encapsulated Request Object. Then pass it to Service method(doGet/doPost)In, we can pass HttpServletRequest object, Get all requested information.
 effect:
      Get client information
      Get client parameters and request headers
      Realize request forwarding and data sharing


common method
  getRequestURL()                             Get the requested resource path(resources url)
  getRemoteURL()                             Gets the absolute path of the request(complete url)
  getQueryString()                              Returns the parameter part of the request line
  getRemoteHost()                             Gets the host name of the client
  getRemoteAddr()                             Get client's ip address
  getRemotePort()                              Get the port number of the client
  getHeader(String s)                         Get request header
  getParameter()                                Get request parameters
  getParameterValue()                           Get request group     
  getMethod()                                   Get request type
  setAttribute(key,value)                       Set domain data
  getAttribute(key)                             Get domain data
  getRequestDispatcher()                        Get request forwarding object

 solve post Chinese garbled code:    req.setCharacterEncoding("char")

6.6.4 HttpServletResponse

 and httpServletRequest Same class, Every time you ask to come in, Tomcat The server will create one Response Object passed to Servlet Program to use, If we need to set the information returned to the client, Can pass HttpServletResponse Object(Download File, Write data to the client, Write response header, redirect)
 effect:  Write data to the client
           Byte stream         getOutputStream()                 For download
           Character stream         getWriter()                       Used to return string
    notes: Only one of two streams can be used at the same time
 Write response header
          resp.setHeader();
 redirect
         resp.setHeader("Refresh","5; url= xxxx ");
         resp.sendRidect("");

Logic for downloading files
1. Get the absolute path of the file this getServletContext(). Getrealpath ("/ img / related instruction. PNG");
2. Get the file name realpath subString(realPath.lastIndexOf("//")+1)
3. Modify the response header resp setHeader(“content-disposition”, “attachment;filename=”+fileName);
4. io stream operation

When downloading Chinese files, it should be noted that the Chinese file name should use urlencoder Encode with the encode method (URLEncoder.encode(fileName, "character encoding")), otherwise the file name will be garbled.

Solve the problem of garbled code
resp.setContentType("text/html; charset=UTF-8");

6.6.5 request and redirection

• Request forwarding

  What is request forwarding?
  Request forwarding means that after receiving the request, the server operates the request. When the business logic is complex, it needs to transfer the result of Servlet1 to another Servlet program for operation, and finally return to the client. This is request forwarding.
  

• redirect

  It refers to sending a request to the client and the server, and the server returns some addresses of the client to redirect the client (because the addresses between them may be discarded)

• The difference between request forwarding and request redirection

1. Same point

       The page will jump
   

2. difference

       When requesting forwarding, url No change, Redirect and vice versa.
       Request forwarding share Request Data for the domain.
       Request forwarding can be forwarded to WEB-INF Resources under.
       Request forwarding cannot access resources outside the project.
       Request forwarding is a request.
   

6.7 Http protocol

What is HTTP protocol?

        Rules to be followed for data sent during communication between client and server, HTTP The data in the protocol is also called message.

HTTP protocol format of the request

       GET
             Request line 
                      - Request mode
                      - Requested resource path[+?+Request parameters]
                      - Requested protocol version number
             Request header
                     key:value  Form different key value pairs, Different meanings

  POST
            The request line and header are basically the same GET(POST Empty line in request header)
            POST Request body  == >  Data sent to the server

Common request header
Accept: indicates the data type that the client can receive
Accept language: indicates the language type that the client can receive
User agent: represents the information of the client browser
Host: indicates the requested server IP and port number

    Responsive HTTP Protocol format
             Response line
                   (1) Protocol and version number of response
                   (2) Response status
                   (3) Response state descriptor
             Response header
                   (1) key:value      Different response headers, It has different meanings
                   Empty line
             response  -->  Data returned to the client

Description of common response codes
         200               Request succeeded
         302               request redirections 
         404               The request has been received by the server, But the data does not exist
         500               Request server received, But there was an internal error in the server

7, JSP page, EL expression, JSTL tag library

7.1 introduction to JSP

   -  JSP(Java server pages)  Java Service page for
   -  JSP The main function of is to replace Servlet Program return html Page data
   -  because Servlet Program return HTML Page data is a very cumbersome thing, High development and maintenance costs
   -  JSP Is essentially a Servlet program(HttpJspBase Class inherits HttpServlet class)
   -  When we first visited JSP Page time, Tomcat The server will help us jsp The page is translated into a java source file, And compile and generate.class Bytecode program.

7.2 Jsp instruction

   1.Page instructions
       <%@ page content Type="text/html;charset=utf-8" language="java" %>
       JSP of page Instructions can be modified jsp Some important properties in the page, Or behavior

        - language                                     express jsp What language file is it after translation
        - contentType                                  jsp What is the data type returned, Also in the source code response.setContentType("xxx");This sentence                       
        - pageEncoding                                 jsp Character set of the page                     
        - import                                       Follow java Same as in the source code, Used to guide packages and classes
        - autoFlush(Out Output stream dedicated)                      Set when out When the output stream buffer is full,Whether to refresh buffer automatically
        - buffer(Out Output stream dedicated)                         Set buffer size
        - errorPage                                    Set when jsp An error occurred while the page was running, Automatically jump to the wrong page
        - isErrorPage                                  Set current jsp Is the page an error message page, Default is false
        - session                                      Set access current jsp page,Will it be created HttpSession object,Default is true          
        - extends                                      set up jsp Who does the translated class inherit by default
      note: Except for special cases, it is basically the default

  2.include instructions
       -  JSP Static include label
                <%@ include file=""%>
                characteristic:     1. Static inclusion will not translate the included jsp page 
                          2. Static inclusion is actually the inclusion of jsp Copy the code of the page to the included location
        
       -  JSP Dynamic inclusion label
                <jsp:include page=""></jsp:include>
                characteristic:     1. Dynamic inclusion will include jsp Page translation java code
                          2. The underlying code of dynamic inclusion uses the following code to call the included jsp Page execution output
                              JspRuntimeLibrary.include(request,response,"",out,false)
                           3. Parameters can be passed
  3.Taglib instructions
    - introduce jstl Tag library

Custom error page
When an error occurs on a page, use errorPage to jump to the error page

7.3 Jsp common scripts

• Declaration script
  <%! Declare java code% >
  Function: define attributes and methods for java classes translated from jsp, even static code blocks or internal classes
  note: the member variables declared in the declaration script are executed once when the jsp is run for the first time, while the code script is executed every time
• Expression script
  <% = expression% >
  Function: output data on jsp page
  Features: 1 All expression scripts will be translated into_ jspService method.
  2. All expression scripts will become out Print () is output to the page.
  3. Because the content of expression script translation is_ jspService method, so_ All objects in the jspService method can be used directly.
  4. Expressions in expression scripts cannot end with semicolons
• Code script
  <% Java statement% >
  Function: we can write our own functions (written java statements) in jsp pages
  Features: 1 After the code script is translated_ jspService method
  2. Code script due to translation to_ In the jspService method_ All objects in jspService can be used
  3. The code script can also complete a complete java statement due to the composition of multiple code script blocks
  4. Code script can also be combined with expression script

7.4 JSP comments

 html notes    <!--Note Content -->
 Java notes    //   /* */
 JSP notes    <%--Note Content --%>

7.5 JSP built-in objects

  -  jsp Built in objects in, Refers to Tomcat In Translation jsp Page becomes Servlet After source code, Nine objects provided internally. 
       request                                    Request object
       response                                   Response object
       PageContext                                jsp Context object for
       session                                    Session object
       application                                ServletContext object
       config                                     ServletConfig object
       out                                        jsp Output stream object  
       page                                       Point to current jsp Object of
       exception                                  Exception object

  -  JSP Four domain objects
    -  PageContext(PageContextImpl class)          current jsp Valid within page range
    -  Request(HttpServletRequest class)           Valid within one request
    -  Session(HttpSession class)                  Valid within a session scope(Shopping cart, login)
    -  application(ServletContext class)           whole Web Effective within the project
  
   note: 1. Domain objects are similar to map The same object that accesses data, The functions of the four domain objects are the same, The difference is that they have different ranges.
              Priority of use:  pageContext >> requset >> session >> application
         2. Out Output and getWriter Differences in output :
        because jsp After translation, The underlying source code is used out To output, Therefore, we should unify to avoid disrupting the order of page output content

7.6 JSP action instructions

jsp:useBean       Find or instantiate a JavaBean
jsp:setProperty   set up JavaBean Properties of
jsp:getProperty   Output a JavaBean Properties of
jsp:forward       Forward the request to a new page
 Common properties: id(Can pass PageContext call),scope(Define lifecycle)
 Use example 
    jsp:useBean   id=""   class=""
        jsp:setProperty name="id" Property="" value=""                                              
          Called here bean of set method
    /jsp:userBean
    jsp:getProperty name=  Property  
          Called here bean of get method

7.7 JavaBean

JavaBean It's a kind of Java Reusable components written in.
 javaBean，It refers to those that meet the following standards Java Class:
   Serializable
   Class is public
   There is a public constructor without parameters(Through reflection mechanism)
   There is Privatization attribute and corresponding get,set method

Users can use JavaBeans to package functions, processing, values, database access and any other objects that can be created with Java code, and other developers can use these objects through internal JSP pages, servlets, other JavaBeans, applet programs or applications. Users can think that JavaBeans provide a function of copying and pasting anytime, anywhere, without caring about any changes.

7.8 EL expression

• EL expression language is the expression language

  1. It mainly replaces the expression script in the jsp page to output data in the jsp page
  2. Output data, perform operations and obtain objects

• Format of EL expression: ${expression}
  Note: when EL expression outputs null value, empty string will be output.

• The order in which EL expressions search for domain data
  Search for value from the smallest range of key s

7.8.1 EL calculation

 -  Relational operation
   ==      eq
   >       gt
   <       lt
   >=      ge
   <=      le
   !=      ne
 -  Logical operation
   and  or  not  
   &&    ||  !
 -  arithmetic operation 
   + -  * / /div  %/mod
 -  empty operation
    empty You can judge whether a data is empty, Output Boolean
 The following cases are empty
        1. Value is null value
        2. Empty string
        3. Object Class array, Length is 0
        4. list aggregate, The number of elements is zero
        5. map aggregate, The number of elements is zero

7.8.2 11 implicit objects of EL expression (defined by EL expression itself)

    pageContext                                PageContextLmpl                             It can get jsp Nine built-in objects in

    pageScore                                  Map<String,Object>                          It can get pageContext Data in domain
    requestScope                               Map<String,Object>                          It can get Request Data in domain
    sessionScope                               Map<String,Object>                          It can get Session Data in domain
    applicationScope                           Map<String,Object>                          It can get ServletContext Data in domain
    
    param                                      Map<String,String>                          It can get the value of the request parameter
    paramValues                                Map<String,String[]>                        It can get the value of the request parameter, Used when getting multiple values
   
    header                                     Map<String,String>                          It can get the information of the request header
    headerValues                               Map<String,String[]>                        It can get the information of the request header, It can get multiple values
    
    cookie                                     Map<String,cookie>                          It can get the current request Cookie
    initParam                                  Map<String,String>                          It can be obtained in web.xml Configured in context-param Context parameters

7.9 JSTL tag library

7.9.1 introduction to JSTL tag library

   -  JSTL Tag library(JSP Standard Tag Library) JSP Standard label Library, It is a continuously improving open source system JSP Tag library, EL Expressions are mainly used to replace jsp Expression script in, The tag library is to replace the code script,  This makes the whole jsp The page becomes more brief

   -  JSTL It is composed of five tag libraries with different functions(Database and xml Basically not used) 
         Core tag library(c)
         format(fmt)
         function(fn)
   -  stay jsp Use in tag library taglib Instruction introduction label Library
        <%@ taglib prefix="c" url="http://java.sun.com/jsp/jstl/core" %>
        <%@ taglib prefix="fmt" url="http://java.sun.com/jsp/jstl/fmt" %>
        <%@ taglib prefix="fn" url="http://java.sun.com/jsp/jstl/functions" %>
   -  Use steps
        1. Guide package import jstl Label Library jar package(Import to WEB-INF Lower lib package, Then copy the package to Tomcat of lib lower)
        2. use taglib Instruction introduction label Library(IDEA Automatically generated)
        3. Use label    

7.9.2 common labels

Use of core library

1. <c:set var="" value=""/>
   Function: set tag can save data to the domain
   Domain object setAttribute(key,value);

     attribute: scope(Set domain)  var(set up key)   value
              - page express PageContext field
              - request express Request field
              - session express Session field
              - application express ServletContext field
   

2. < C: if test = "judgment condition" var = "assign to new variable" scope = "domain range" / >

3. <c:choose>
   < C: when test = "judgment condition" > output 1 < / C: when >
   < C: otherwise > similar to default in switch < / C: otherwise >
   </c:choose>

4. <c:forEach>
   -var variable output each time
   -Set / array of item output
   -begin/end sets the start and end positions
   -Step step

7.10 MVC three-tier architecture

MVC architecture

• What is MVC? Model view controller

• Model

  • Business processing: business logic (Service)
  • Data persistence layer: CURD operation (DAO)

• View

  • Display data
  • Provide link to initiate Servlet request (a,form,img)

• Controller

  • Accept the user's request (req: request parameters, Session information)
  • Give it to the business layer to process the corresponding code
  • Control view jump

8, Listener introduction, Cookie, Session and Session Technology

8.1 session and status session

• It is a session from the user opening the browser to accessing Web resources and finally closing the browser.
• When a user visits a web page for the first time and then visits it again, some settings do not need to be set again. They can access directly. This is called state session.

8.2 two techniques for saving sessions

- Cookie(client)
       1.One Cookie Only one information can be saved(Key value pair)
       2.One Cookie Size up to 4 kb
       3.The server can send 20 messages to the browser cookie
    
  Get client's Cookie
       req.getCookie();
  Cookie operation
       getName() getValue();  
  delete Cookie  
        1. Set the validity period to 0    cookie.setMaxAge(0)
        2. No validity period is set, Close browser auto clear Cookie
  Respond to clients Cookie
       resp.addCookie(cookie);
       cookie.setMaxAge( ns );
  
  Cookie Two parameters of the constructor(key and value)All String

- Session(The server)
       1.The server will give each user(browser)Create a Session object
       2.One Session Exclusive browser, As long as the browser doesn't close, Sesson Has always existed
       3.After user login, The entire website is accessible, Save user information, Shopping cart information.....

       -  session of id Will take cookie Send to the client, Value is session of id
           
       obtain Session 
             getSession()     return HttpSession
       Session operation
             set/get/removeAttribute                   Domain object
             getID                                     obtain SessionID
             isNew                                     judge Session Is it newly created
     
       Manual logoff Session 
             session.invalidate()
       send Session invalid(web.xml Medium configuration)
        <session-config>
                <session-timeout>In seconds</session-timeout>   
        </sessin-config>

8.3 difference between cookie and Session

  1.Cookie Is to write the user's data to the user's browser, Browser save(Multiple can be saved)
  2.Session It is to write the user's data to the user's exclusive session in, Server side save(Save important information, Reduce server-side resource waste)
  3.Session It was created by the server

9, Filter filter

9.1 introduction to filter

Filter: filter, Used to filter the data of the website, JavaWeb One of the three components
   - Filter yes JavaEE One of the norms
   - Intercept request, Filter response

9.2 using Filter

  1.realization Filter Interface(javax.servlet)
  2.rewrite iniit,destroy,doFilter Method in which the request is intercepted, Filter response)

9.3 filter life cycle

• Execution sequence
  1. Constructor method (automatically executed when the Web project starts)
  2. Initialize init method (automatically executed when the Web project starts)
  3. doFilter filtering method (it will be executed every time a request is intercepted)
  4. destroy destruction method (the Filter will be destroyed when the Web project is stopped)

9.4 filter common classes

9.4.1 filterConfig

Filter Filter profile class
   Tomcat Every time you create Filter When, One will also be created FilterConfig class, This includes Filter Configuration information for
  effect: obtain Filter Configuration content of filter
      1. obtain Filter Name of filter-name
      2. Get in Filter Initialization parameters in init-param
      3. obtain ServletContext object

9.4.2 filterChain filter chain

• Multiple Filter filters form a chain
  FilterChain. The role of the dofilter () method
  -Execute target resource (no Filter)
  -Execute the next filter (with Filter)

Multiple Filter filters are executed in the order of web Configuration order execution in XML
.
On the web Configuration in XML

• Multiple Filter execution features
  1. All filter s and target resources are in the same thread by default
  2. When multiple filter s are executed together, they all use the same Request object

9.4.3 three ways to intercept paths

 -- Exact match
     url-pattern    /target.jsp
 -- Directory matching
     url-pattern    /admin/*
 -- Suffix matching
     *suffix.xxxxx    with xxxx The end can be intercepted

10, Maven project management, GIT & GitHub usage

10.1 Maven automated build tool

10.1.1 Maven's core concepts

10.1.1.1 introduction to maven

10.1.1.2 agreed directory structure and pom file

10.1.1.3 coordinate, dependency and packing type

10.1.1.4 warehouse

10.1.1.5 life cycle, plug-ins and commands

10.1.2 IDEA integrated Maven environment

1) Configure local Maven in IDEA

Click file - > settings

2) Use the old Maven settings for newly imported or newly created projects

3) Create a Java se project under Maven

4) Maven's work window

5) Configure POM in idea XML file to implement dependency

6) Import Maven project in idea

10.1.3 Maven configuration and dependency management

10.1.3.1 dependency management

Scope of dependency: use scope Indicates the scope of the dependency
 Range representation: This dependency works at that stage of project construction
scope Optional value
       compile: default, Participate in all phases of the build project
       test: Testing phase
       provided: When a provider project is deployed to a server, There is no need to provide this dependency jar, But by the server jar package

10.1.3.2 Maven configuration

10.2 Git & Github

11, File upload and download

12, Ajax, JSON

13, Smbms supermarket order management system