-Dynamic Web Pages

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-Dynamic Web Pages

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Product

• HTML is static but CGI and Web server APIs arent
• Using HTML, The text and the format of its
  display remain constant and cannot be changed at
  run time
• Using CGI and major Web server APIs, you can
  execute a server program from an input HTML form
  and then generate an output HTML report based on
  the result of that program execution
• CGI is portable but it can be slow
• The Web-server unique APIs are fast but they are
  not portable
• Net.Data as a Web gateway tool
• Net.Data does most of the grunt work for you and
  makes your job much easier when creating dynamic
  Web pages
• Net.Data supports major Web server APIs in
  addition to CGI, provides access to a rich set of
  databases
• Net.Data includes some important performance
  enhancement features
• Net.Data serves as a good case study that
  illustrates many of the major issues one faces
  when designing and implementing a dynamic Web
  page generation tool

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CGI(1)

• CGI allows you to invoke a program from a Web
  server that normally only knows how to process
  HTML documents
• This can be done
• through a URL directly from a Web browser
• as an HTML anchor reference
• as an action attribute of a HTML form
• http//server-name/cgi-directory-name/cgi-program
• When receiving such a URL
• The Web server set up some environment variables
  and invokes the CGI program
• The CGI program then reads the environment
  variables and starts executing
• The CGI program further reads input data from the
  Web server through the standard input pipe, and
  it writes result data to the Web server through
  the standard output pipe
• The Web server treats the results as a normal
  HTML document and returns it to the Web browser
  for display

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CGI(2)

• The common architecture for Web data access using
  CGI involves two passes
• In the first pass
• From a Web browser, the user downloads an HTML
  form using a URL
• The user then fills in the input data
• In the second pass
• The user submits the HTML form whose action
  attribute contains a URL that specifies the name
  of a CGI program
• The Web server invokes the program that contains
  a SQL query on a database
• The CGI program collects the query results and
  generates a standard HTML report to be returned
  by the Web server for display to the user
• Fg 11-1.Web Data Access Using CGI

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CGI(3)

• Fg 11-2. HTTP Process Flow Calling CGI

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CGI(4)

• As a developer of a CGI-based data access
  application
• You must develop or handle
• the input HTML form
• the CGI program that accesses databases
• the passing of input data from the HTML form to
  the CGI program
• The generation of an HTML report based on the
  data access results
• gt All these are tailored for the specific
  application
• If another application comes along, you must
  repeat the whole cycle again for that application
• CGI can be slow so you will have to worry about
  replacing CGI with Web server unique APIs and so
  on

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NET.DATA(1)

• Net.Data is a Web gateway tool
• It provides a robust and scalable framework for
  creating dynamic Web pages with data originating
  from a variety of sources
• Multiple platform HP, LINUX, OS/2, SUN, WinNT
• Multiple datasource DB2, Oracle, ODBC data
  sources
• Multiple language environments Java, REXX,
  Perl, C
• It is easy to use, extendable, and fast
• Fg 11-3. Web Data Access Using Net.Data

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NET.DATA(2)

• The development of Net.Data followed the
  evolution of Web data access
• Net.Data was first introduced in 1995 to enable
  Web-based, server-side applications
• It used static CGI processes and provided access
  to mainly DB2 databases (it was called DB2 WWW
  Connection)
• In 1996, it added support for access to multiple
  data sources, Web server APIs, live connections,
  the use of Java applets and JavaScript on the
  client, and server-side JDBC processing
• Major action items planned for future releases
  include visual programming tools, Fast CGI
  support, Java servlets(server-side includes),
  performance improvements, additional data
  sources, and additional platforms

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The Net.Data Architecture(1)

• Net.Data applications have a 3-tier architecture
• Fg 11-5. The Net.Data 3-Tier Architecture

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The Net.Data Architecture(2)

• Net.Data applications have a 3-tier architecture
• Net.Data itself resides on Tier 2, a Web server
• Net.Data is a Web server program that can be
  invoked through CGI, a Web-server specific API,
  or as Java servlets
• Net.Data applications appear in the form of macro
  files, which contain HTML forms, SQL queries, and
  optional function calls(in Java, REXX, Perl, or
  C)
• The user of an application invokes it from the
  client, Tier 1, by using a URL that specifies the
  Net.Data executable, the name of a macro file,
  and the input HTML form
• When the user submits the form, its action causes
  a certain SQL query to be executed on the
  database server, Tier 3
• The result of the query is used to generate an
  output HTML report for display to the user

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The Net.Data Architecture(3)

• Net.Data consists of the major components
• Fg 11-6. The Net.Data Component Architecture

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The Net.Data Architecture(4)

• Net.Data consists of the major components
• Macro processor
• It processes macro files, invokes function calls,
  links to language environments, and generates
  HTML pages
• Macro files
• These are Net.Data applications written by users
• Function library
• This contains Net.Datas built-in functions
• Language environments
• These are Net.Datas backends or databases
• Live connection
• It can be used to maintain and manage live
  connections to databases and Java virtual
  machines

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Macro Processing(1)

• A Net.Data macro file is processed twice by the
  macro processor during a user session
• In the first pass
• From a Web browser, the user invokes the macro
  processor using a URL that specifies the macro
  processor, the name of the macro file, and the
  name of an HTML section that defines the input
  HTML form
• The macro processor processes the macro
  file-specifically, the named HTML section
• The macro processor generates a standard HTML
  form to be returned by the Web server for display
  to the user
• In the second pass
• The user submits the HTML form, whose action
  attribute contains a URL
• The macro processor again processes the macro
  file-specifically, the named HTML section-that
  contains a function call executing a SQL query on
  a database or invoking a procedure on other
  backends
• The macro processor makes the function call,
  collects the result, and generates a standard
  HTML report to be returned by the Web server for
  display to the users

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Macro Processing(2)

• Fg 11-7. Net.Data Macro Processing Report
  Generation

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The Macro Processor(3)

• The macro processor can be invoked by a Web
  server via a URL
• This can be done directly by a user, as an HTML
  anchor reference, or as an action attribute of an
  HTML form
• When invoked as a CGI or ICAPI(IBMs Internet
  Connection API) application,
• http//server-name/cgi-directory-name/db2www.exe/m
  acro-filename/macro-block-name
• When invoked as an NSAPI(Netscape Server API) or
  ISAPI(Microsofts Internet Server API)
  application,
• http//server-name/macro-filename/macro-block-name
  
• The macro processor processes macro file and
  performs the following tasks
• Includes files, defines variable, and defines
  functions
• Resolves variable references and invokes function
  calls
• Loads in appropriate (language environment)
  libraries
• Generates standard HTML pages

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The Macro File(1)

• The macro file provides you with the means to add
  logic, variables, function calls, and reports to
  otherwise static HTML
• A macro file consists of macro statements which
  are denoted by a special macro symbol( or _at_)
• The major type of macro statements
• Blocks
• These are used to define HTML forms and reports,
  variables, functions and their reports
• block-type()
• Function calls
• These are used to invoke functions
• _at_function-name()
• Control statements
• These can be used to control the flow of macro
  execution
• if elif else endif
• Comments

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The Macro File(2)

• Three major type of macro blocks
• Define
• This can be used to define variables
• HTML
• This is used to define input HTML forms and
  output HTML reports
• Function
• This can be used to define language-environment
  specific functions
• Function block may include a Report block and
  Message block
• Report block
• This is used to define the report to be generated
• Message block
• This is used to define the message to be
  displayed in case an error occurs
• The macro file provides three major expressive
  capabilities
• Variable definition and passing
• Function definition and invocation
• Report definition

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The Macro File(3)

• Net.Data variables
• can be used to pass values within a macro file or
  between a macro file and a language environment
• All variables are character strings (they have no
  data types)
• The major kinds of variables
• Implicit
• These contain data returned from SQL queries and
  from function calls
• Report
• These can be used to customize report format
• SQL
• These can be used to tailor access to databases
• User-defined
• These are user-defined variables
• User-defined variables can be defined in the
  Define block, defined in an HTML forms INPUT or
  SELECT statement, or passed in as URL data
• Once defined, user-defined variables can be
  referenced as (variable-name) anywhere in the
  macro file

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The Macro File(4)

• Net.Data variables
• Implicit variables include
• (Nn),(N_columnName),(NLIST) contain column
  names
• (Vn),(V_columnName),(VLIST) contain column
  values in the current row
• (ROW_NUM) contains the row number of the current
  row
• (NUMBER_COLUMN) contains the number of columns
  in the result table
• (TOTAL_ROWS) contains the number of rows in the
  result table
• (RETURN_CODE) contains the return code for use
  in the Message block
• SQL variables include
• DATABASE specifies the database to connect to
• LOGIN specifies the user id
• PASSWORD specifies the password to be used with
  the user id
• TRANSACTION_SCOPE specifies the transaction scope
  for SQL statements

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The Macro File(5)

• Net.Data functions
• can be used to add logic, access databases, or
  interact with external programs during macro
  execution
• The major types of functions
• Math, String manipulation, Table, User-defined
• User-defined function contains the following
  information
• Language environments, Name (Required)
• IN, OUT, and INOUT parameters (Optional)
• Return variable, Executable statements (Optional)
• Report block, Message block (Optional)
• Net.Data reports
• Within a Function block you can use the Report
  block and Message block to define the report and
  message to be generated
• The report block consists of the following
• Header, ROW block, Footer
• The Row block displays HTML formatted data once
  for each row of data returned from the function
  call
• The Message block allows you to associate a
  message with each return code value generated by
  the function call and to specify the action for
  Net.Data

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Language Environments(1)

• Net.data provides a rich set of language
  environments
• SQL/DB2, Oracle, and Sybase with native access
• ODBC
• Java Applet and Java Application
• REXX and Perl
• System (C)
• Users can also build and plug in their own
  language environment
• You simply specify the SQL statement to be
  executed within a function body and then call the
  function
• If you want to have more control over data
  access, you can use the Java Applet (from the
  client side) or the Java Application (from the
  server side) language environment
• The Java Applet language environment can
  dynamically generate the following parameter
  specifications for an applet
• NUMBER_OF_TABLES, TABLE_ltigt_NAME,
  NUMBER_OF_COLUMNS, NUMBER_OF_ROWS,
  COLMUMN_NAME_ltigt, ltcolumn_namegt_VALUE_ltigt
• Net.Data Java Applet Interfaces
• getNumberOfTables(), getTableNames(),
  getNumberOfColumns(String tableName),
  getNumberOfRows(String tableName),
  getColumnNames(String tableName), getTable(String
  tableName)

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Language Environments(2)

• Fg 11-9. Client-Side Application with Java Applet

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Language Environments(3)

• Fg 11-10. Server-Side Application with Java
  Application

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Live Connection

• Only one database connection per macro execution
• Net.Data establishes a connection to a database
  at the beginning of macro execution
• Net.Data closes the connection at the end of
  macro execution
• Live connection allows you to create and maintain
  persistent connections
• Live connection consists of a connection manager
  and cliettes
• The connection manager is a separate executable
  from Net.Data
• Cliettes are single-threaded processes that the
  connection manager starts, and they run
  continuously to service requests
• Cliettes are
• made to handle specific language environments
• pre-started at Web server initialization
• configurable with a minimum and maximum number of
  processes
• pre-connected to specified databases or backends
• reusable for the same type of connection
• Live connection provides two major advantages
• Improved performance
• Multiple database access

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Conclusion

• Net.Data takes the grunt work out of CGI
  programming and makes life much easier for you in
  generating dynamic Web pages based on live data
• Reference sites
• http//www-4.ibm.com/software/data/net.data/
• http//www-4.ibm.com/software/data/net.data/docs/i
  ndex.html
• ??
• DB2 Universal DB V7
• Packages which include Net.Data
• DB2 Universal Developer's Edition
• DB2 Universal Database Workgroup Edition
• DB2 Universal Database Enterprise Edition (EE)
• DB2 Universal Database Enterprise-Extended
  Edition (EEE)
• DB2 Connect Enterprise Edition
• Fee download package (you can get it from IBM Web
  site)
• DB2 Personal Developer's Edition
• DB2 Universal DB V5 (you can get it from CD)
• DB2 Universal Database Workgroup Edition
• DB2 Universal Database Enterprise Edition