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Walkthrough of Java APIs

Walkthrough of Java APIs. Presented By Tracy Engwirda. 28 September, 2005. Overview. Background Walk through of Java APIs High level review of packages, patterns Building Block Overview. Audience. Knowledge of Java programming

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Walkthrough of Java APIs

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  1. Walkthrough of Java APIs Presented By Tracy Engwirda 28 September, 2005

  2. Overview • Background • Walk through of Java APIs • High level review of packages, patterns • Building Block Overview

  3. Audience • Knowledge of Java programming • People who want an overview of the entire range of functionality exposed • (without resorting to reading the docs) • Thinking of building, don’t know what to look at first…

  4. Design Goals – High Level • Decouple persistence from data objects • XML and Database • Originally targeted for import/export • Database abstraction • Iterative functionality • Start with simple objects, mapped to the legacy schema • Managed extensibility • System extensions and deployment model

  5. A Little History… Import/Export Building Blocks Module Developer Kit R6 Gradebook R6 Assessment R6 Portal

  6. Security Session Context Plug-ins Log Config Persistence I18N VXI Building Blocks Architecture Business Layer (JSP, Servlet, Struts) View Layer (JSP, Servlet, Tag Library) Data Objects Core Services

  7. Road Map • Data objects and packages • What data can I see? • Persistence objects and packages • How do I get to the data? • Service objects and packages • How do I log it, authenticate it, etc.?

  8. Which API is that? • blackboard.* Building Block API • blackboard.admin.* Release 6 Admin API • com.blackboard.event.* Bb 5.5 Event API (deprecated)

  9. Building Block API Packages announcement navigation blackboard.data. calendar role content course gradebook user announcement navigation blackboard.persist. calendar role content course gradebook user

  10. Building Block API Packages blackboard.platform. context filesystem session log persistence plugin blackboard.portal. blackboard.base. blackboard.util.

  11. Data Objects blackboard.data • Object view of the schema • Typed to wrap legacy database constructs • Type-safe enumerations for constrained database columns • User.Role.SYSTEM_ADMIN

  12. Data Objects – BbObject • Base object for all data objects • Common attributes – Primary Key (Id), dates, etc. • “Smart” attributes • Properties stored in an internal map, instead of member variables • Smart load, dirty flag • Id attribute helps define lifecycle • Id.UNSET_ID – default id for new objects

  13. Data Objects – Content blackboard.data.content • Content is the root object that can be used in the “content” areas of a course • All other objects are simple subclasses of Content that over-ride specific values • Custom content types should create and manipulate Content objects; not CourseDocument objects. • CourseDocument can be used to manipulate the base “Item” type

  14. Data Objects – Content • ContentHandler • Ties content to URI-based “handlers” • This is really the B2 “glue” for custom content • IsFolder • Can the object contain other objects • IsLesson • Should the contents be displayed sequentially • Plus many more added in Bb 6.3

  15. Data Objects – Content

  16. Data Objects – Course blackboard.data.course • Course and Organization • Organization overrides course for specific attributes • Course Enrolment • CourseMembership • Enumerated roles • CourseMembership.Role.INSTRUCTOR • Course Groups and Group Enrolment

  17. Data Objects – Gradebook blackboard.data.gradebook • LineItem • Defines the “columns” in a course gradebook • Score • Wraps the actual outcome for a given line item

  18. Data Objects – Misc. • Announcement • Wraps announcements • Can be system or course level • Calendar • Wrap entries in the calendar • Course and System level

  19. Persistence Objects • Intended to be decoupled from data objects • Interfaces allow replaceable persistence implementations • Currently proprietary to Blackboard • BbPersistenceManager • Ties together different aspects of persistence • Loader/Persister broker • Container

  20. Persistence Objects – Id • Used to encapsulate the unique identifier for each data object • Primary key, and more… • Data type • Container (database) • GUIDs are not used, so keys can collide

  21. Persistence Objects – Loaders • Base interface to get at data • Roughly one-to-one correspondence to data objects • All type-specific loaders are geared towards known predicates • loadById() • loadByUserIdandType() • Performance. Ad hoc queries can kill the system… • Schema stability

  22. Persistence Objects – Persisters • Perform any action that manipulates data • Again, one-to-one correspondence with data objects • “Smart” update • Id object state determines insert vs. update

  23. Accessing Persisters and Loaders • They’re interfaces, not directly instantiated by callers • BbPersistenceManager is the broker • Most have a Default object for direct access ContentDbLoader loader = ContentDbLoader.Default.getInstance()

  24. Putting It Together Content content = new Content(); content.setTitle(); // etc. . . ContentDbPersister contentPersister = ContentDbPersister.Default.getInstance(); contentPersister.persist( content );

  25. Putting It Together – v2 Content content = new Content(); content.setTitle(); // etc. . . // new reflection-based persistence methods content.persist();

  26. Services • Infrastructure for common utility functions • Exposed as interfaces (mostly) • Lookup via BbServiceManager

  27. Service Lookups LogService logService = BbServiceManager.getLogService(); LocaleManager locMgr = BbServiceManager.getLocaleManager(); ContextManager ctxMgr = (ContextManager)BbServiceManager .lookupService( ContextManager.class );

  28. Services – Context blackboard.platform.context • Critical entry point that all code must call • Context wraps information about current request to get the correct database connection • Interact via ContextManager.setContext() and ContextManager.releaseContext()

  29. Services – Session blackboard.platform.session • State for the current browser-based client • Stores authentication status • Cookie-based session management • Database persistent to share between Perl and Java processes • Some assembly required • Not all HTTP-clients (e.g., media plugins for browsers) honor the host browser’s cookies

  30. Services – Filesystem blackboard.platform.filesystem • FileSystemService - Broker different file system locations • Course and content • E.g., getContentDirectory()

  31. Services – Log blackboard.platform.log • Simple write-only log implementation • Supports configurable levels • Written before log4j and JDK 1.4

  32. Services – Security blackboard.platform.security • Authentication and Authorization • AccessManagerService

  33. Package Base • Mix of utility objects • List functionality • BbList – should use List instead though • GenericFieldFilter • GenericFieldComparator • Comparator implementation that can sort based on arbitrary properties • Works with String, Boolean, Dates, and Comparable

  34. Package Base • BbEnum – base class for all type-safe enumerations • FormattedText – encapsulation of text data entered via standard Text boxes • Defines enumeration for Smart, Plain, and HTML text • NestedRuntimeException/NestedException – pre-JDK 1.4 facility for chaining exceptions

  35. Portal blackboard.portal.external • CustomData is all you’ll need… • getModuleData() • getModulePersonalizationData() • Store name/value • Value can be string, or binary object

  36. Administrative API Packages blackboard.admin.data. user course category datasource blackboard.admin.persist. user course category datasource

  37. Administrative APIs blackboard.admin.* • APIs geared towards data integration • Formerly called the “Event” APIs • Repackaged to be more consistent with B2 APIs • Compatibility layer supported • Base classes used in Snapshot

  38. Administrative APIs • Follows IMS Data Model • Person, Course (Group), and Membership • Additional objects for Blackboard usage • Category • Data Source • Defines logically related entities that can be managed independently via Snapshot

  39. Beyond APIs – UI Integration • Tag Libraries • Encapsulate re-usable UI components to capture the Blackboard look and feel • Tag Library Descriptors • Re-use within individual web applications • .tld files

  40. Beyond APIs - Deployment • Not an API, per se • Critical aspect of extension development • XML manifest used to generate records in the database that define navigation, content brokering

  41. Tying It All Together • A Building Block may require touching several different APIs • Set context • Authorize current User • Load content object • Access Gradebook data • Perform custom calculation • Log result • Render results (bracketed via tags) • Release context

  42. Thoughts • There are a lot of classes to look at… • Focus on the type of Building Block you need to build • Take it methodically, iteratively. What’s your first goal? Second goal? • Think of combining functions • What can I do using Content with Gradebook?

  43. Questions?

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