COMP9321 Web Application Engineering

Transcription

1 COMP9321 Web Application Engineering Wrap-up Dr. Basem Suleiman Service Oriented Computing Group, CSE, UNSW Australia Semester 1, 2016, Week

2 Course Core Components This course consists of: 12 weeks of lectures 1 individual assignment 10 marks 1 group assignment 25 marks 1 group assignment 15 marks 1 final exam (50 marks) 2

3 Assignments Assignment 1 GradeBook Assignment 2 Week 13 (GradeBook) Assignment 3 Due Wednesday, June 1, 2016, 23:59:59 3

4 Assignments Assignment 1 Individual web application development XML, Servlet and JSP Assignment 2 Group Hotel Management Web Application JSP, Java objects, JDBC, others Design patters, MVC, other frameworks Teamwork skills Assignment 3 Performance Evaluation of Web application Group performance of Hotel Management Application Performance testing JMeter, Queuing theory and laws, Analysis and reporting 4

5 Final Exam 5

6 Final Exam 2 hours exam (+10 minutes reading time) Total marks 50 6 Main questions (Answer only 5) No multiple choice questions First 5 answers will be marked Questions cover both technical and conceptual understanding on the core topics Concepts, explanation, design principles, comparisons Short, factual and essay question, technical knowledge concepts Topics/Lectures Week1- Week10 To make both our life easier, please Write to the point, use diagrams wherever is helpful, provide examples especially if the question asks for it Write legibly and clearly quality not quantity 6

7 Final Exam 7

8 Final Exam The following topics from the lectures will not be asked in the final exam: TCP and DNS from Web Essentials Queueing Theory and Performance Modeling in Performance Measurement Lecture Service Oriented Architecture (SOA)/Web Services NoSQL database Introduction to Cloud Computing Architecting Web Applications for the Cloud 8

9 General Review Week 1 10 Warning: this review covers some topics only. For the final exam, study all topics and slides covered in weeks 1-10, excluding topics specified in the previous slide. 9

10 Different Layers in an Application 10

11 Presentation Layer HTML <form> method attribute specifies how to send form-data as URL variables (with method="get"), or HTTP post transaction (with method="post"). Method? Get/Post 11

12 Static vs. Dynamic Web Page A static web page is delivered to the user exactly as stored, in contrast to dynamic web pages which are generated by a web application, and on demand! is-a web page whose construction is controlled by an application server processing server-side scripts. is-a e.g. software framework that provides both facilities to create web applications and a server environment to run them. Java application servers It's core set of API and features are defined by Java EE. The Web modules include Java Servlets and Java Server Pages. 12

13 Java Servlets

14 A Lifecycle of a Servlet The Web container controls the lifecycle of a servlet class: initialisation ServletConfig ServletContext 14

15 Attributes and Sharing Attributes 15

16 Who has access to the board and how long does it live? COMP9321, 16s1, Week 2 16

17 RequestDispatcher in Servlet The RequestDispatcher interface provides the facility of dispatching the request to another resource, e.g., servlet, jsp, or html. This interface can also be used to include the content of another resource also. It is one of the way of servlet collaboration. The RequestDispatcher interface provides two methods: forward and include Forward: Forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server. public void forward(servletrequest request,servletresponse response) 17

18 RequestDispatcher in Servlet The RequestDispatcher interface provides the facility of dispatching the request to another resource, e.g., servlet, jsp, or html. This interface can also be used to include the content of another resource also. It is one of the way of servlet collaboration. The RequestDispatcher interface provides two methods: forward and include Include: Includes the content of a resource (servlet, JSP page, or HTML file) in the response. public void include(servletrequest request,servletresponse response) 18

19 Session Management COMP9321, 16s1, Week 2 19

20 Session Management COMP9321, 16s1, Week 2 20

21 Managing the User State A problem in HTTP request/response: HTTP is a stateless protocol. A single request/response; Nothing is remembered 'between requests' from the same user; Web applications need to maintain users + their data. It is a programmer's responsibility: The term "session" is used to represent the data associated with one user while she navigates around a Web application. Session is a conversional state between client and server. Session can consists of multiple request and response between client and server. Since HTTP is stateless, the only way to maintain a session is when some unique information about the session (session id) is passed between server and client in every request and response. 21

22 Cookies Cookies are text files stored on the client computer and they are kept for various information tracking purpose. Java Servlets transparently supports HTTP cookies. There are three steps involved in identifying returning users: Server script sends a set of cookies to the browser. e.g. session id Browser stores this information on local machine for future use. Next time, browser sends request + those cookies to the server and server uses that information to identify the user. 22

23 JavaServer Pages (JSP) Technology JavaServer Pages (JSP) technology allows you to easily create web content that has both static and dynamic components. JSP technology makes available all the dynamic capabilities of Java Servlet technology; but provides a more natural approach to creating static content. JSP is similar to PHP, but it uses the Java programming language. To deploy and run JavaServer Pages, a compatible web server with a servlet container, such as Apache Tomcat, is required. 23

24 JSP 24

25 JSP Basics Scripting Elements Traditional Modern Scriptlet Expression Declaration Comments EL Scripting ${ } JSP Page JSP Elements Directive Elements Page Include Taglib Action Elements Template Text (HTML bits ) custom Standard <abc:mytag> <jsp:usebean> <jsp:getproperty> <jsp:setproperty> <jsp:include> <jsp:forward> <jsp:param> 25

26 Extensible Markup Language (XML) XML originally designed to meet the challenges of large-scale electronic publishing. XML separates presentation issues from the actual data. XML plays an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere. Needs a communication protocol? e.g. SOAP stands for Simple Object Access Protocol SOAP is based on XML SOAP is a W3C recommendation SOAP uses XML Information Set for its message format. 26

27 JSP Elements: JSP Actions (usebean) COMP9321, 16s1, Week 3 27

28 The XML Family XML: a markup language used to describe information. DOM: a programming interface for accessing and updating documents. DTD and XML Schema: describes the structure and content of XML documents. XSLT: a language for transforming XML documents XPath: a query language for navigating XML documents. XPointer: for identifying fragments of a document. XLink: generalises the concept of a hypertext link. XInclude: for merging documents. XQuery: a language for making queries across documents. RDF: a language for describing resources. 28

29 XML Document Type Definition An XML document with correct syntax is called "Well Formed Errors (incorrect syntax) application processing will trigger errors Well Formed XML document it has valid XML syntax rules Well formed XML document valid XML document? A valid XML document must be: Well formed AND Conform to Document Type Definition (DTD) Document Type Definition (DTD) Defines the structure and the legal elements and attributes of an XML document DTD or XML Schema (XML alternative to DTD) Internal DTD declaration or external DTD declaration (.dtd) COMP9321, 16s1, Week 4 29

30 Well-formedness and Validity of XML COMP9321, 16s1, Week 4 30

31 Limitations of DTD COMP9321, 16s1, Week 4 31

32 The XML Family XML Schema XML Schema (or SML Schema Definition XSD) is an XML-based alternative to DTD. describes the structure of an XML document. defines elements and attributes that can appear in a document defines data types for elements and attributes defines default and fixed values for elements and attributes defines the child elements, their orders, etc. XML Schemas are much more powerful than DTDs. The XML Schema language is also referred to as XML Schema Definition (XSD). COMP9321, 16s1, Week 4 32

33 XML Namespaces COMP9321, 16s1, Week 4 33

34 Simple Types COMP9321, 16s1, Week 4 34

35 Constraint enumeration Description Type Restrictions Defines a list of acceptable values fractiondigits Specifies the maxi number of decimal places allowed. Must be equal to or greater than zero length Specifies the exact number of characters or list items allowed. Must be >= than zero maxexclusive Specifies the upper bounds for numeric values (the value must be less than this value) maxinclusive Specifies the upper bounds for numeric values (the value must be <= to this value) maxlength Specifies the Max number of characters or list items allowed. Must be >= zero minexclusive Specifies the lower bounds for numeric values (the value must be greater than this value) mininclusive Specifies the lower bounds for numeric values (the value must be>= to this value) minlength Specifies the minimum number of characters or list items allowed. Must be >= 0 pattern totaldigits whitespace Defines the exact sequence of characters that are acceptable Specifies the exact number of digits allowed. Must be greater than zero Specifies how white space (line feeds, tabs, spaces, and carriage returns) is handled COMP9321, 16s1, Week 4 More examples : 35

36 Complex Types COMP9321, 16s1, Week 4 36

37 Persistence Persistence is a fundamental concept in application development In an object-oriented applications, persistence allows an object to outlive the process that created it The state of the object may be stored to disk and an object with the same state re-created at some point in the future. Sometimes entire graphs of interconnected objects may be made persistent and later re-created in a new process. (Hibernate, pp.5-29) COMP9321, 16s1, Week 5 37

38 Data Persistence When you work with a relational database in a Java application, the Java code issues SQL statements to the database via the JDBC API. The Java Database Connectivity (JDBC) API provides universal data access from the Java programming language. Using the JDBC API, you can access virtually any data source, from relational databases to spreadsheets and flat files. The JDBC API is comprised of two packages: java.sql javax.sql (Hibernate, pp.5-29) 38

39 JDBC Interfaces COMP9321, 16s1, Week 5 39

40 Accessing DB from an Application 40

41 PreparedStatement object A more realistic case is that the same kind of SQL statement is processed over and over (rather than a static SQL statement). In PreparedStatement, a place holder (?) will be bound to an incoming value before execution (no recompilation). 41

42 Data Access Objects (DAO) COMP9321, 16s1, Week 5 42

43 Object-Relational Impedance Mismatch Problems 43

44 Object-Relational Impedance Mismatch Problems 44

45 Impedance (or Paradigm) Mismatch Problem Subtypes (Hibernate, pp.5-29) The problem of subtypes COMP9321, 16s1, Week 5 45

46 Hibernate - ORM Framework Hibernate is an open source ORM solution for JAVA which provides Object-Relational Persistence and Query service for any Java Application Improve development efficiency by relieving the developer from majority of common data persistence related programming tasks Hibernate maps Java classes to database tables and from Java data types to SQL data types Hibernate sits between traditional Java objects and database server to handle all the work in persisting those objects based on the appropriate O/R mechanisms and patterns Supports major RDBMS including MySQL, MS SQL, Oracle, DB2, HSQL COMP9321, 16s1, Week 5 46

47 Design Patterns A pattern is a proven solution to a problem in a context. Each pattern expresses a relation between a certain context, a problem, and a solution. A design pattern represents a solutions to problems that arise when developing a software. Design pattern are granular and applied at different levels such as: Frameworks Subsystems Sub-subsystems Categories include: Design Architectural Analysis Creational Structural Behavioral 47

48 J2EE Design Patterns 48

49 Servlet design guidelines: When to use Servlets COMP9321, 16s1, Week 6 49

50 JSP Design Guidelines COMP9321, 16s1, Week 6 50

51 General Guideline for Servlet/JSP/JavaBeans 51

52 Model 1 Architecture COMP9321, 16s1, Week 6 52

53 Model 2 Architecture = MVC pattern COMP9321, 16s1, Week 6 53

54 Model 2 Architecture = MVC pattern COMP9321, 16s1, Week 6 54

55 Command Design Pattern COMP9321, 16s1, Week 6 55

56 Securing your Web Application: Threats! 56

57 Securing your Web Application: Threats! 57

58 CSRF Attacks Mechanisms GET scenario Using GET method, the money transfer operation might be reduced to a request like GET HTTP/1.1 Maria decides to exploit this web application vulnerability using Alice as her victim. Maria first constructs the following exploit URL which will transfer $100,000 from Alice's account to her account. She takes the original command URL and replaces the beneficiary name with herself, raising the transfer amount significantly at the same time GET The attack that tricks Alice into loading this URL when she's logged into the bank application Sending an unsolicited with HTML content Planting an exploit URL or script on pages that are likely to be visited by the victim while they are also doing online banking The exploit URL can be disguised as an ordinary link, encouraging the victim to click it <a href=" my Pictures!</a> More CSRF Attacks Examples: COMP9321, 16s1, Week 8 58

59 Cross Site Scripting (XSS): Summary! COMP9321, 16s1, Week 8 59

60 Cross Site Scripting (XSS): Prevention!! COMP9321, 16s1, Week 8 60

61 Cross Site Scripting (XSS): Prevention!! More on XSS prevention rules and examples COMP9321, 16s1, Week 8 61

62 Session Management 62

63 Transport Layer Security (e.g. HTTPS) 63

64 Performance 64

65 Scalability 65

66 Architectural Considerations - Network COMP9321, 16s1, Week 10 66

67 General Techniques for Improving Performance and Scalability 1. Caching and Replication 2. Parallelism 3. Redundancy 4. Asynchrony 5. Resource Pooling COMP9321, 16s1, Week 10 67

68 Improving Performance using HTTP features COMP9321, 16s1, Week 10 68

69 Improving Database Access 69

70 Improving Database Access COMP9321, 16s1, Week 10 70

71 Improving Database Access JOINT queries COMP9321, 16s1, Week 10 71

72 Improving Database Access COMP9321, 16s1, Week 10 72

73 Scaling & Request Load Balancing COMP9321, 16s1, Week 10 73

74 Scaling & Request Load Balancing COMP9321, 16s1, Week 10 74

75 Scaling & Request Load Balancing Application-Level Load Balancing with Stateless Logic COMP9321, 16s1, Week 10 75

76 Scaling & Request Load Balancing Scaling Databases - Replication COMP9321, 16s1, Week 10 76

77 COMP9322!! from building a web site (cs9321) to building web services (cs9322)... context: global/distributed/complex business applications Goals: understand the concept of services and business processes articulate the motivation behind web service-based technologies apply the knowledge in practical situations COMP9322 course aims: provide students with a deep understanding of SOA, service-orientation paradigm, business processes and Web services as an implementation technology. 77

78 Good Luck! 78

79 79