Java 4 WEB

Август 2, 2022

Содержание

2. Lesson goals Client-Server Static vs dynamic content Java Servlet Tomcat
3. Client-Server architecture A person enters a URL string into the browser. The browser generates HTTP-request. The
4. Client-Server architecture • Web-server for static content (popular): Apache, nginx, GWS, IIS, ... • Software for
5. CGI - Common Gateway Interface Standard used to communicate of the web server with an external
6. CGI - Common Gateway Interface Shortcomings of CGI technology: ● Start an OS process for each
7. Http Servlet service(HttpServletRequest, HttpServletResponse) doGet(HttpServletRequest, HttpServletResponse) doPost(HttpServletRequest, HttpServletResponse)
8. Java Servlet @WebServlet(name = "helloServlet", urlPatterns = {"/hello"}) public class HelloServlet extends HttpServlet { public void
9. Java Servlet 4.0 HTTP /2 Request/Response multiplexing Stream Prioritization Server Push Upgrade from HTTP 1.1
10. Servlet Lifecycle Loads the servlet class Creates an instance of the servlet class Initializes the servlet
11. HttpServletRequest Container creates HttpServletRequest object and passes it as argument to Servlet's service methods (doGet, doPost,
12. HttpServletRequest Methods: - getHeader (String) - getParameter (String) - getInputStream () - getSession () - getServletContext
13. HttpServletResponse Container creates HttpServletResponse object and passes it to Servlet's service methods (doGet, doPost, etc.) HttpServletResponse
14. HttpServletResponse Methods: - addHeader (String, String) - setStatus (int) - sendError (int) - sendRedirect (String) -
15. HttpSession HttpSession session = request.getSession(); Main methods: - invalidate () - getAttributeNames () - getAttribute (String)
16. ServletContext Servlet uses ServletContext to communicate with its servlet container, access the servlet container. ServletContext sc
17. Filter @WebFilter(urlPatterns = {"/*"}) public class HelloFilter implements Filter { public void init(FilterConfig cfg) { }
18. Error Handling @WebServlet("/error") public class ErrorHandler extends HttpServlet { private static final long serialVersionUID = 1L;
19. Error Handling Web Project java.lang.RuntimeException /error
20. Web (servlet) container A Web server - component that interacts with Java Servlets. Primary responsibilities are:
21. Java EE & Servlet (Web) Container Most popular Servlet (Web) Containers • Apache Tomcat • Jetty
22. Apache Tomcat
23. WAR Web application ARchive - is a JAR file used to distribute a collection of JavaServer
24. WAR
25. Literature Building Java Web Applications Servlets (by Baeldung) Servlets (by Tutorialspoint) How to Install Apache Tomcat
26. Homework Task 1 Implement a servlet with interface: `/session?action=[add/update/remove/invalidate]&name=...&value=...` 1. The servlet generates a form with
28. Скачать презентацию

Слайд 2

Lesson goals
Client-Server
Static vs dynamic content
Java Servlet
Tomcat

Слайд 3

Client-Server architecture
A person enters a URL string into the browser.
The browser

generates HTTP-request.
The server receives a request, processes, and sends an HTTP response.
The browser receives a response and displays it.

Слайд 4

Client-Server architecture
• Web-server for static content (popular): Apache, nginx, GWS, IIS,

...
• Software for dynamic content: CGI programs & modules, PHP AS,
MS IIS AS, Java EE, ...

Слайд 5

CGI - Common Gateway Interface
Standard used to communicate of the web

server with an external program for generating dynamic web content.
CGI-script - a program that works on the CGI-interface. Web-server is configured to redirect certain URL requests for CGI scripts.

Слайд 6

CGI - Common Gateway Interface
Shortcomings of CGI technology:
● Start an OS

process for each request
● A lot of low-level coding
● No sharing resources across requests
● No session state

Слайд 7

Http Servlet
service(HttpServletRequest, HttpServletResponse)
doGet(HttpServletRequest, HttpServletResponse)
doPost(HttpServletRequest, HttpServletResponse)

Слайд 8

Java Servlet
@WebServlet(name = "helloServlet", urlPatterns = {"/hello"}) public class HelloServlet extends HttpServlet

{ public void doGet( HttpServletRequest request, HttpServletResponse response ) throws IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("

Hello World

"); } }

Слайд 9

Java Servlet 4.0
HTTP /2
Request/Response multiplexing
Stream Prioritization
Server Push
Upgrade from HTTP 1.1

Слайд 10

Servlet Lifecycle
Loads the servlet class
Creates an instance of the servlet class
Initializes

the servlet instance by calling the init() method
Does all work
When the container needs to remove the servlet, it calls the servlet’s destroy() method

Слайд 11

HttpServletRequest
Container creates HttpServletRequest object and passes it as argument to Servlet's

service methods (doGet, doPost, etc.)
HttpServletRequest provides client request info to Servlet.
Passed to the service(...) method, doGet (...), doPost (...), do ... ().

Слайд 12

HttpServletRequest
Methods:
- getHeader (String)
- getParameter (String)
- getInputStream ()
-

getSession ()
- getServletContext ()
- etc

Слайд 13

HttpServletResponse
Container creates HttpServletResponse object and passes it to Servlet's service methods

(doGet, doPost, etc.)
HttpServletResponse assists a servlet in sending a response to the client.
As well as HttpServletRequest is passed in service(...) and do...(...)

Слайд 14

HttpServletResponse
Methods:
- addHeader (String, String)
- setStatus (int)
- sendError (int)

- sendRedirect (String)
- setHeader (String, String)
- getWriter ()
- etc

Слайд 15

HttpSession
HttpSession session = request.getSession();
Main methods:
- invalidate ()
- getAttributeNames ()

- getAttribute (String)
- removeAttribute (String)
- setAttribute (String, Object)
- etc

Слайд 16

ServletContext
Servlet uses ServletContext to communicate with its servlet container, access the

servlet container.
ServletContext sc = request.getServletContext();
Main methods:
- getAttributeNames ()
- getAttribute (String)
- removeAttribute (String)
- setAttribute (String, Object)
- etc

Слайд 17

Filter
@WebFilter(urlPatterns = {"/*"}) public class HelloFilter implements Filter { public void init(FilterConfig

cfg) { } public void doFilter(
ServletRequest req, ServletResponse resp, FilterChain chain ) throws ServletException, IOException { chain.doFilter(req, resp); } public void destroy() { } }

Слайд 18

Error Handling
@WebServlet("/error") public class ErrorHandler extends HttpServlet { private static final long

serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException { resp.setContentType("text/html; charset=utf-8"); try (PrintWriter writer = resp.getWriter()) { writer.write("Error description"); writer.write("

Error description

"); writer.write("

" + e + ":" + req.getAttribute(e) + "

"); writer.write(""); } } }

Слайд 19

Error Handling
Web Project

java.lang.RuntimeException

/error

Слайд 20

Web (servlet) container
A Web server - component that interacts with Java

Servlets.
Primary responsibilities are:
- Management of servlets and their life cycle
- Mapping the URL to a specific servlet.
- Check access rights

Слайд 21

Java EE & Servlet (Web) Container
Most popular Servlet (Web) Containers
• Apache

Tomcat
• Jetty
• JBoss Application Server (WildFly)
• …

Слайд 22

Apache Tomcat

Слайд 23

WAR
Web application ARchive - is a JAR file used to distribute

a collection of JavaServer Pages, Java Servlets, Java classes, XML files, libraries, static web pages (HTML, JS, CSS, etc) and other resources…

Слайд 24

WAR

Слайд 25

Literature
Building Java Web Applications
Servlets (by Baeldung)
Servlets (by Tutorialspoint)
How to Install Apache

Tomcat
What is servlet container
Servlets (by Jetbrains)

Слайд 26

Homework Task 1
Implement a servlet with interface:
`/session?action=[add/update/remove/invalidate]&name=...&value=...`
1. The servlet generates

a form with input fields "action", "name", "value" and button "Submit". Below print is a list of all attributes of the user session.
action - depending on the value, the servlet adds, updates, or removes an attribute in/from a session;
name - the name of the attribute;
value - is the value of the attribute.
2. If any error happens – log and redirect user to custom error page
3. Add request blocking filter, when user browser is ‘Microsoft Edge’ – block request and show error page. Use
4. Add separate request logging filter. Log endpoints path and total execution time. Should measure all actions (even when request blocked)
5. Add separate request blocking filter. When today is weekend – deny all operations. Microsoft Edge users should never come here and be stopped by user-agent filter.
6. Attributes lists should not be shared between two browsers

Java 4 WEB

Содержание

Lesson goalsClient-ServerStatic vs dynamic contentJava ServletTomcat

Client-Server architectureA person enters a URL string into the browser.The browser

Client-Server architecture• Web-server for static content (popular): Apache, nginx, GWS, IIS,

CGI - Common Gateway Interface Standard used to communicate of the web

CGI - Common Gateway InterfaceShortcomings of CGI technology:● Start an OS

Http Servletservice(HttpServletRequest, HttpServletResponse)doGet(HttpServletRequest, HttpServletResponse)doPost(HttpServletRequest, HttpServletResponse)

Java Servlet@WebServlet(name = "helloServlet", urlPatterns = {"/hello"}) public class HelloServlet extends HttpServlet

Hello World

Java Servlet 4.0 HTTP /2Request/Response multiplexingStream PrioritizationServer PushUpgrade from HTTP 1.1

Servlet LifecycleLoads the servlet classCreates an instance of the servlet classInitializes

HttpServletRequestContainer creates HttpServletRequest object and passes it as argument to Servlet's

HttpServletRequestMethods: - getHeader (String) - getParameter (String) - getInputStream () -

HttpServletResponseContainer creates HttpServletResponse object and passes it to Servlet's service methods

HttpServletResponseMethods: - addHeader (String, String) - setStatus (int) - sendError (int)

HttpSessionHttpSession session = request.getSession();Main methods: - invalidate () - getAttributeNames ()

ServletContextServlet uses ServletContext to communicate with its servlet container, access the

Filter@WebFilter(urlPatterns = {"/*"}) public class HelloFilter implements Filter { public void init(FilterConfig

Error Handling@WebServlet("/error") public class ErrorHandler extends HttpServlet { private static final long