Overview Choosing the Environment Two-Tier Advantages

Transcription

1 Overview Choosing the Environment Two-Tier Advantages Case study: Oracle Extensions Middleware Checklist Application Development The Bet is on Java JServer Examples: Applications build on Oracle using Java 3-tier architecture with fat clients 3-tier architecture with thin clients 2-tier architecture with thin clients Performance Comparison Summary 1

2 Multi-vendor middleware applications are not always the best solution, e.g. If the expected amount of data and number of users is relatively small If the necessary infrastructure for a full fledged n-tier approach is missing All major database vendors offer now middleware extensions, such as TP-Monitors Persistent queuing and Message Broker Object Request Brokers and EJB/DCOM compliant application services Generalized programming interfaces, such as JDBC, ODBC, http, POP3,... Vertical market functionality To the outside such so-called TP-Light applications appear as 2-tier systems As a concrete example we will take a look at Oracle Largest enterprise database vendor Expands agressively its range of products and services Many/most of the observations apply to the other database vendors Less components to integrate and interface A single provider can offer some integration guarantees The components/ modules should have little overlap Less communication overhead Smaller, faster applications Less development environments to master Single programming language possible 2

3 Development (o) Various language and APIs Tools, libraries + complete o some - minimal Services (o) Connection logic Standard wrappers Transactional interfaces Control (-) System monitors Communication tools Load balancing, priority scheduling Storage (+) Persistent queues, buffering Replication, distribution Backups 3

4 PL/SQL is here to stay Still the fastest for data access (20x), native datatypes Huge amounts of legacy code Limited functionality Cumbersome development environments Available Java APIs Call Java from PL/SQL and vice versa Stored Procedures, Triggers (intern) CORBA, EJB (multi-tier applications) JDBC/SQLJ (extern) Java Development: e.g. JDeveloper 3.1 Free from Modern environment Many libraries (XML, Infobus,..) Complete Java integration on the way Most extension API s directly callable (DBMS Libraries, vertical market extensions, Java Message Service ) New extensions are written in Java (e.g. 8i FileSystem) Object services available (Visigenics 3.2 Corba ORB, EJB 1.1, replication through IIOP) Service tools are ported to Java (DBA management pack, database administration, replication manager) What are the goals? Java programming on all tiers Middleware functionality is either used implicitly (e.g. connection balancing) or explicitly through interfaces Code base compatibility among oracle server released for different platforms 4

5 Compatibility of internal Java VM Up to Java 1.2.1, JDBC 2.0 Some limitations; e.g. no GUI code Distributed transactions (8.1.7) Performance compared to external JVM Poor responsiveness (8.1.6) Slow execution of java code in general Good scalability: low memory usage - 30KB per user versus 1MB Fast data processing Solution 1: New Connection Logic Apache now the Oracle Listener Direct pl/sql calls through http Solution 2: Native Compilation Translation of JDBC to native calls Java- or byte- code translated to C, then compiled to binaries, e.g. core Three-tier architecture Fat Java client with local data and connection libraries Link to middle layer through RMI JDBC connection to databases with some stored procedures Advantages in development Complete control Common Java codebase possible Easy deployment Disadvantages in development Complex program environments Integration of other middleware services difficult -> best for larger projects 5

6 Three-tier architecture Thin clients access through browsers Java servlets are the application logic Database services through JDBC Advantages in development Professional, exchangeable, full featured products available Superior scalability Industry standard connections to other middleware Disadvantages in development Higher transfer overhead Complex installation and interfaces -> typical web-based database solution Two-Tier architecture Thin clients access through browsers The webserver is implemented in Java and loaded as stored procedures Advantages in development Binary code calling native Oracle methods is fast One data transfer Less components to worry about Disadvantages in development Stored procedures have limitations (e.g. no GUI code) Loading and debugging is slow -> currently best as glue code 6

7 What was measured Demo: External Webserver Demo: Internal Webserver Oracle nicely showcases current middleware trends It strives to become the global internet application platform (8 i == internet) Middleware extensions are added at a fast pace Compared to established middleware services, such as TP-Monitors, the provided functionality is still light The choice of services to be used in the application determines its architecture Nevertheless, there are many benefits for application developers Java is Oracle s language of choice to tie the pieces together Using Java it is possible to develop for all tiers in one language 7