The Web Application Developer s. Red Hat Database. View. October 30, Webcast. Patrick Macdonald, Fernando Nasser. Red Hat Database Engineering

Transcription

1 Red Hat Database The Web Application Developer s View Webcast October 30, 2001 Patrick Macdonald, Fernando Nasser Liam Stewart, Neil Padgett Red Hat Database Engineering

2 Agenda Red Hat Database Web Interaction Patrick Macdonald Programming Interfaces Overview Fernando Nasser Demonstration / Examples Overview Liam Stewart Interaction with PHP Neil Padgett Interaction with Java Liam Stewart Future Enhancements: GUI Tools Neil Padgett Q&A

3 Red Hat Database Web Interaction

4 Database as a Web Server Backend Simplified View Client Server Client Server Browser http Web Server Database Inside the Server is another Client / Server hierarchy

5 Red Hat Database as a Web Server Backend PostgreSQL ORDBMS SQL92 Transactional ACID compliant

6 Red Hat Database as a Web Server Backend Multiple supported programming languages and interfaces for clients Data indexing for retrieval Online backups Multi-Version Concurrency Control (MVCC)

7 URLs of Interest Red Hat Database - PostgreSQL - Apache - Tomcat - jakarta.apache.org PHP - Java/JDBC - java.sun.com/products jdbc.postgresql.org

8 Programming Interfaces Overview

9 Database Client-Server Architecture Client Server Client Application Database Backend Code written in supported frontend programming interface Code written in supported backend programming interface

10 Database Client-Server Architecture Client Server Client Application Database Backend C/C++, Embedded SQL in C, Tcl, Python, Perl, Emacs LISP Perl DBI, ODBC, JDBC SQL, PL/pgSQL, PL/Tcl, PL/Perl, C

11 Database as a Web Server Backend Client Server Client Server Browser http Web Server HTML Database Scripting Languages Perl, PHP, JSP

12 Programming Interfaces Summary Frontend Languages Web Scripting C/C++ Embedded SQL in C Tcl Python (incl. DB-API) PHP Perl JSP Apache mod or CGI interpreter (with Tomcat or similar W.A.S.) Perl (incl. Perl DBI) Emacs LISP JDBC ODBC (C/C++, Perl, Tcl )

13 Programming Interfaces Summary Backend Languages Language SETOF TRIGGER SQL s PL/pgSQL t PL/Tcl t PL/Perl C s t

14 Perl, C etc. Cohabitation with Other DBMS ODBC Driver PG ODBC Driver API Mngr ODBC Driver DB/2 ODBC Driver Oracle

15 Perl Script Cohabitation with Other DBMS DBD:Pg PG DBI DBD:DB2 DB/2 DBD:Oracle Oracle

16 Demonstrations / Example Overview

17 PHP / Java Demo Application Simple news site similar to Slashdot and Linux Today Visitors can read articles posted by moderators, post comments about articles, and read comments posted by other visitors Design follows the web client-server model Implemented in both PHP and Java with Red Hat Database as the database backend

18 PHP / Java Demo Application

19 PHP / Java Demo Application

20 Database Schema Users id: integer (primary key) handle: string string name: string image: blob Categories id: integer (primary key) name: string img_type: string Articles Comments id: integer (primary key) category: integer poster: integer date: timestamp headline: string summary: string story: string comments: integer id: integer (primary key) article: integer poster: string comments: string date: timestamp

21 Demonstrations / Example Interaction with PHP

22 Using PHP with Red Hat Database Similar to using PHP with other popular databases Minor changes in access functions PHP supports a number of useful features when used with Red Hat Database (PostgreSQL) Connection Pooling (Persistent Connections) Large Objects

23 Connecting to the Database Open a persistent connection if(!( $connection = pg_pconnect( "host=myhost ". "dbname=webcastdemo ". Connection Index "user=webcastdemo ". "password=mypassword" ))) { echo "<B>Error:</B>"; echo "Could not establish connection to database server."; echo "<BR> ; exit; } Connection String

24 Performing a Query // Article lookup query Result Index $query = "SELECT headline FROM articles"; Connection Index // Query for all of the articles Query String if(!( $result $query))) { echo "<B>Error:</B>"; echo "Could not execute article lookup query:"; echo "<PRE>", pg_errormessage($connection), "</PRE>"; exit; }

25 Working With Results A number of relevant functions pg_result(int result_id, int row_number, mixed fieldname) Index into result by row and field pg_fetch_row(int result, int row) Work with a result row at a time as an enumerated array pg_fetch_array(int result, int row [, int result_type]) Index into result as an enumerated array like pg_fetch_row() Enhancement: Index by field number or field name (associative array) pg_fetch_object(int result, int row [, int result_type]) Creates an object with properties named as the fields Like working with a populated C struct

26 Working With Results: An Example <? // Output a list of all of the article headlines?> <UL> Iterate over all results <? for( $row = 0; $data $result, $row); $row++) {?> Get the current row as an object <LI> <?=$data->headline?> </LI> <? } Echo the headline?> </UL>

27 Working With Transactions Managed by sending SQL to the backend Relevant SQL statements: BEGIN Start a transaction COMMIT Commit the current transaction to the database ROLLBACK Back out of the current transaction

28 Working With Transactions: An Example (Slide 1/2) "BEGIN"); Begin our transaction $query = "INSERT INTO comments(article,poster,subject,comment)". "VALUES (". $article. ", ". "'". $poster. "', ". "'". $subject. "', ". "'". $comments. "')"; First, post the comment if(!@pg_exec( $connection, $query)) "ROLLBACK"); echo "<br> <i>unable to process request.</i>"; exit; } In case of failu abort and rollb

29 Working With Transactions: An Example (Slide 2/2) $query = "UPDATE articles SET comments = comments + 1 WHERE id = ". $article; Now, update the comment count if(!@pg_exec($connection, $query)) "ROLLBACK"); echo "<br> <i>unable to process request.</i>"; exit; } In case of failure, abort and rollback (repeated code could use a $connection, "COMMIT");?> Commit the transaction <p><i>your comment has been submitted.</i></p> Report success to the user

30 Using Large Objects: Image Database Example $query = "SELECT image FROM images WHERE id=". $id; Lookup the OID of the large object $result $query); header("content-type: image/gif"); Send the content type to the "BEGIN"); Open the large object using the $image = pg_loopen($connection, pg_result($result, 0, "image" "r"); pg_loreadall($image); File "COMMIT"); Send the large object to the browser

31 Demonstrations / Example Interaction with Java

32 Java and JDBC Java is an object-oriented language developed by Sun Microsystems JDBC: Java's database access API Provides Java programmers with a large set of classes for working with databases Code written using JDBC can be used against multiple databases with little or no change Red Hat Database provides drivers for both JDBC 1 and JDBC 2 Updated drivers available from PostgreSQL s JDBC web page

33 Implementation Overview Java Servlets and Java Server Pages (JSP) used: JSP for main index, story page, and comment submission page Servlet that retrieves an image from the categories table Several support classes All use JDBC for database access

34 Communication Pathway Client web-browser Apache web-server Tomcat application server Java Servlets and Server Pages Red Hat Database server

35 Connecting to the Database A Connection object represents a connection to a database Request connection after loading appropriate driver <% %> Dynamically load and register the driver Class.forName( org.postgresql.driver ); Connection con = DriverManager.getConnection( jdbc:postgresql://demobox/webcastdemo, webcastdemo, mypassword ); Request connection fro driver manager

36 Performing a Query Create a Statement or a PreparedStatement object and use its executequery method to execute a query Results stored in a ResultSet object and data can be accessed via accessor methods <% %> <% %> Statement stmt = con.createstatement(); ResultSet rs = stmt.executequery( SELECT headline FROM articles ); while (rs.next()) { Loop through results } <LI> <%= rs.getstring( headline ); %> </LI> Retrieve headline field Send query to database

37 Performing an Update Similar to performing a query except use executeupdate method of Statement or PreparedStatement object Also used for SQL statements such as CREATE, DROP, etc. If applicable, returns number of rows changed (zero otherwise)

38 Working With Transactions By default every SQL statement is a complete transaction Use the setautocommit, commit, rollback methods of Connection objects when working with multi-statement transactions: setting auto-commit mode to false enters multi-statement transaction mode first SQL statement after turning off auto-commit or after a commit/rollback is start of transaction commit commits all changes since start of transaction rollback undoes all changes since start of transaction

39 Working With Transactions: An Example <% %> <% %> <% %> Statement stmt = con.createstatement(); con.setautocommit(false); Turn off auto-commit try { stmt.executeupdate( INSERT INTO comments + VALUES(10, 1, foo, bar, now() ); stmt.executeupdate( UPDATE articles SET + con.commit(); comments = comments + 1 WHERE article=1 ); <P><I>Your comment has been submitted.</i></p> } catch (Exception ex) { con.rollback(); <P><I>Unable to process request.</i></p> } Commit all changes Any errors will be caught and transaction will be rolled back

40 Using Large Objects JDBC supports input and output of large objects Can use standard Java I/O functionality (streams) when inserting and pulling out large objects Enclose all large object operations in a transaction

41 Using Large Objects: An Example Statement stmt = con.createstatement(); con.setautocommit(false); ResultSet rs = stmt.executequery( SELECT img_type, image + FROM categories WHERE id = 3 ); if (rs.next()) { resp.setcontenttype(rs.getstring( img_type )); InputStream in = rs.getbinarystream( image ); ServletOutputStream out = resp.getoutputstream(); int b; Retrieve while ((b = in.read())!= -1) { large obj out.write(b); and send } to client in.close(); out.close(); } con.commit(); con.setautocommit(true);

42 Disconnecting from the Database Call the close method of Connection object: <% con.close(); %>

43 Red Hat Database Future Enhancements Preview GUI Tools

44 Red Hat Database GUI tools Suite of GUI tools for database management, access, administration, and configuration Designed to allow cross-platform use Initial release of tools for Red Hat Linux Support for other popular OS s planned Provide enhanced ease-of-use, and allow faster administration

45 Red Hat Database GUI tools (continued) Today s Preview: Red Hat Database Administrator GUI Administration Tool Manage database objects Users, Groups, Indexes, Tables, etc. Goal is to accelerate typical administrative tasks Add / Drop / Create objects Grant / Revoke user permissions etc.

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51 Thank you! Visit the Red Hat website to learn more about Red Hat Database: Coming early November, Red Hat Database Community Project Pages: sources.redhat.com/rhdb Upcoming Training: Dec 4-7, Durham, N.C. RDB147 Red Hat Database Essentials Contact Red Hat Sales 866-2REDHAT - Option 2444 sales@redhat.com

52 Questions and Answers All participants are on mute. Please submit your questions via the chat feature