InterConnect 2016, OpenJPA and EclipseLink Usage Scenarios (PEJ-5303)
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The document discusses the usage scenarios for OpenJPA and EclipseLink in JPA applications, highlighting their key features, differences, and migration considerations. It advises users to continue with OpenJPA for existing applications while recommending EclipseLink for new developments, and provides insights into the migration process along with available tools. Additionally, it addresses potential challenges encountered during migration and suggests best practices for leveraging both frameworks effectively.
InterConnect 2016, OpenJPA and EclipseLink Usage Scenarios (PEJ-5303)
- 1. PEJ-5303 OpenJPA and EclipseLink Usage Scenarios Explained Kevin Sutter, STSM WebSphere Java EE and JPA Architect Twitter: @kwsutter LinkedIn: https://www.linkedin.com/in/kevinwsutter Cindy High, Senior Software Engineer WebSphere Migration Toolkit Twitter: @CTHigh LinkedIn: http://www.linkedin.com/in/cindyhigh
- 2. Please Note: 2 • IBM’s statements regarding its plans, directions, and intent are subject to change or withdrawal without notice at IBM’s sole discretion. • Information regarding potential future products is intended to outline our general product direction and it should not be relied on in making a purchasing decision. • The information mentioned regarding potential future products is not a commitment, promise, or legal obligation to deliver any material, code or functionality. Information about potential future products may not be incorporated into any contract. • The development, release, and timing of any future features or functionality described for our products remains at our sole discretion. • Performance is based on measurements and projections using standard IBM benchmarks in a controlled environment. The actual throughput or performance that any user will experience will vary depending upon many factors, including considerations such as the amount of multiprogramming in the user’s job stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be given that an individual user will achieve results similar to those stated here.
- 3. Agenda • OpenJPA and EclipseLink • JPA version comparisons • OpenJPA to EclipseLink Migration • High level concepts • OpenJPA to EclipseLink Investigation • Specific differences • Migration Toolkit • Summary • Q & A 3
- 5. OpenJPA and EclipseLink • Apache OpenJPA • Basis for WebSphere’s JPA solution for JPA 1.0 and JPA 2.0 • EclipseLink • JPA Reference Implementation – “gospel” • Basis for WebSphere Liberty’s JPA solution for JPA 2.1 • Moving forward… • OpenJPA will continue to be supported in WebSphere for many, many years • At least until JPA 2.0 is deprecated… • Both WebSphere traditional and Liberty 5
- 6. Multiple JPA Providers • Do I have to switch providers? • Absolutely not! • If you are happy with the current OpenJPA offering, there is no need to move to EclipseLink • If you want to use the JPA 2.1 features, you may need to change… • Many of the JPA 2.1 features have corresponding OpenJPA proprietary solutions • Apache OpenJPA (ie. JPA 2.0) is compatible with other Java EE 7 features • Allows for an easier, more gradual JPA migration 6
- 7. Key JPA 2.1 Features available in OpenJPA • Schema Generation (JPA 2.1 Spec, Section 9.4) • Generates DDL or interacts directly with database to define table schemas based on JPA Entity definitions • Similar functionality provided by OpenJPA’s schema mapper • Entity Graphs (JPA 2.1 Spec, Section 3.7) • Allows for specified fetching or processing of a graph of Entity objects • Similar functionality provided by OpenJPA’s FetchPlan and FetchGroup • Stored Procedure Queries (JPA 2.1 Spec, Section 3.10.17) • Ability to invoke database stored procedures • Similar functionality provided by OpenJPA’s Query invocation 7
- 8. Additional JPA 2.1 Features available in OpenJPA • Basic Attribute Type Conversion (JPA 2.1 Spec, Section 3.8) • Similar functionality support provided by OpenJPA’s Externalizer feature • @Index and @ForeignKey annotations (JPA 2.1 Spec, Sections 11.1.19 and 11.1.23) • Similar functionality provided by OpenJPA’s annotations • Unwrap utility methods for EntityManager, Cache, etc (JPA 2.1 Spec Sections 3.1.1 and 7.10) • Similar functionality provided by OpenJPA’s implementation -- EntityManagerImpl.unwrap() and OpenJPAPersistence.cast() • Object construction when mapping results from native SQL (JPA 2.1 Spec, Section 3.10.16.2.2) • Similar functionality provided by OpenJPA’s internal ResultShape object 8
- 9. Additional JPA 2.1 Features NOT available in OpenJPA • Criteria API Updates (JPA 2.1 Spec, Sections 6.5.15 and 6.5.7) • Bulk update/delete • Support for TREAT, ON, and FUNCTION operators • Unsynchronized Persistence Contexts (JPA 2.1 Spec, Section 7.6.1) • Provides more control over when Persistence Contexts are synchronized with a transaction. Useful for mobile applications. • EntityListeners and CDI (JPA 2.1 Spec, Section 3.5.1) • EntityListeners can now use CDI for injection of objects • JPQL Updates for JPA 2.1 (JPA 2.1 Spec, Chapter 4) • Several extensions to JPQL in support of the other features • OpenJPA’s JPQL will stay at the JPA 2.0 level 9
- 10. Feature Comparison Chart 10 Key JPA 2.1 Features Available in current OpenJPA solution? Schema Generation Yes, SynchronizeMappings Entity Graphs Yes, FetchPlans and FetchGroups Stored Procedures Yes, Query interface Basic Attribute Type Conversion Yes, Externalizer (and Factory) @Index and @ForeignKey annotations Yes, proprietary @Index and @ForeignKey annotations Unwrap utility functions Yes, EntityManagerImpl.unwrap() and OpenJPAPersistence.cast() Object construction when mapping results with native SQL Yes, ResultShape (internal OpenJPA implementation) Criteria API updates No Unsynchronized PersistenceContexts No EntityListeners and CDI No JPQL Updates in support of JPA 2.1 No
- 11. Bottom Line • YOU DO NOT NEED TO MIGRATE • Our Advice • Continue using OpenJPA for your existing applications • Use EclipseLink for your new applications • But… If you want to use EclipseLink with existing applications, the following slides will discuss what to look out for when migrating existing applications 11
- 13. Cache • DataCache • OpenJPA's L2 cache is disabled out of the box. EclipseLink's L2 cache is enabled by default. • If you are migrating an application that isn't using the OpenJPA cache, it is highly recommended to disable the EclipseLink cache using: <shared-cache-mode>NONE</shared-cache-mode> • Query (Results) Cache • If QueryCache is enabled for OpenJPA, it will cache all Named Queries and JPQL Statement Results • EclipseLink only caches Named Queries Results • More information on EclipseLink QueryCache here 13
- 14. Weaving/enhancement/transformation • OpenJPA: Entities must be enhanced • EclipseLink: Entities do not have to be enhanced • Documented missing features (lazy loading, performance gains, etc) • WebSphere container automatically weaves/enhances Entities for both OpenJPA and EclipseLink • Applications packaged with entities pre-enhanced by OpenJPA must be recompiled and repackaged • Removes OpenJPA specific enhancement bytecode 14
- 16. Investigation • Goal • Find differences in behavior between OpenJPA and EclipseLink • OpenJPA → EclipseLink migration issues • Data • Entities from OpenJPA's testing framework (>700 entities) • Process • Auto generate databases tables using both providers • Use tables created by OpenJPA for verification • Database: DB2 • Results • Errors (fix EclipseLink) • Table differences 16
- 17. Private Accessor Methods • JPA 2.1 Spec: property accessor methods must be public or protected • OpenJPA: ignores “private” fields • EclipseLink: persists “private” fields • Migrating issue: missing database column error • Solution: Add @Transient to the method • Forces EclipseLink to ignore the field 17 Add @Transient
- 18. Getter/Setter accessor methods • Annotated getter method with no corresponding setter • OpenJPA: silently ignores the field • EclipseLink: throws an error during entity validation • Solution: remove annotation 18 Missing setVersion method
- 19. No-arg Constructor • JPA 2.1 Spec: an entity must have a no-arg constructor • OpenJPA: if missing, generates a no-arg constructor. • EclipseLink: throws an error only if the no-arg constructor is missing, but other constructors exist. • Solution: Add an empty no-arg constructor 19 Add no-arg constructor
- 20. Unannotated Collections • Unannotated fields of type java.util.Collection or any of it’s subinterfaces (List<E>, Queue<E>, Set<E>, etc) • OpenJPA: ignores fields • EclipseLink: persists fields • Solution: Add @javax.persistence.Transient 20 Add @Transient
- 21. @javax.persistence.ElementCollection • @ElementCollection generates a Separate table • Two columns: id, value • Different value column name • OpenJPA: 'element’ • CREATE TABLE EntityA_LISTOFSTRINGS (ENTITYA_ID INTEGER, element VARCHAR(254)) • EclipseLink: field name • CREATE TABLE EntityA_LISTOFSTRINGS (EntityA_ID INTEGER, LISTOFSTRINGS VARCHAR(255)) • Solution: Add @javax.persistence.Column 21 Add @Column
- 22. Behavior Mismatch: @GeneratedValue • Generate values for primary keys • Strategies: TABLE, SEQUENCE, IDENTITY, AUTO • No Strategy or 'AUTO': JPA provider picks the strategy • Good news: OpenJPA and EclipseLink default to 'TABLE' strategy • Bad news: different table schemas are created • Solution • Change entity to explicitly use 'TABLE' strategy • Map to existing OpenJPA table 22
- 23. Java Persistence Query Language (JPQL) • @NamedQuery: specify named query in JPQL • OpenJPA: ignores invalid unused JPQL statements • EclipseLink: validates all JPQL statement by default • Solutions • Solution 1: fix JPQL statements • Solution 2: set eclipselink's invalid JPQL tolerance property to true 23
- 24. Unique Names • Tables, NamedQuery, SQLResultSetMapping must have unique names • OpenJPA behavior is undefined • Example: tables with same name are combined • EclipseLink throws an error during entity validation • Solution: review entities (manual process) 24
- 25. Summary
- 26. Summary • Do I want to utilize my existing database tables? • Modifications to the entities may be necessary • Database tables previously created (by OpenJPA) may not match EclipseLink’s generated tables • OpenJPA may have been more lenient with spec violations than Eclipselink is • Recommendation • Continue using OpenJPA for existing applications • Migrate to EclipseLink only for new applications 26
- 28. Do you need to migrate? Best practice is to • Use OpenJPA for your existing applications • Use EclipseLink for your new applications But… If you need to migrate, we have tools to assist. 28
- 29. An Overview of WebSphere Migration Tools A set of tools help you: - Migrate from third-party application servers to WebSphere Application Server - Migrate between versions of WebSphere Application Server - Migrate to WebSphere Application Server to the Cloud 29 Migration discovery Binaries analysis Source migration Config migration On-line tool that helps you • Estimate the effort required to migrate your application to WebSphere Application Server from third-party application servers • Select the IBM cloud platform suited to host your application and estimate migration to that platform Command-line analysis of application binaries that provides • High level evaluation report showing the Java EE technologies your application uses • Detailed analysis for migration between versions of WebSphere traditional, Liberty, and Liberty Core • Cloud migration for instant runtimes differences • Java EE 7 differences • Cloud connectivity analysis Eclipse plugins that scans application source to provide • High level evaluation report • A line-by-line analysis of code changes required • Detailed analysis for migrating from third-party applications servers • Detailed analysis for migration between versions of WebSphere traditional, Liberty, and Liberty Core • Java EE 7 differences • Cloud migration for instant runtimes differences • Cloud connectivity analysis Eclipse plugin that helps migrate server configuration • From third-party application servers to WebSphere Application Server • Between versions of WebSphere Application Server including WebSphere traditional to Liberty.
- 30. How can the migration toolkit help? • Scan for OpenJPA to EclipseLink differences • The Eclipse-based, source scanning migration tool • Contains 19 Java rules with 9 quick fixes • Contains 5 XML rules with 2 quick fixes • Focuses on annotated JPA applications • Provides some configuration support • The binary scanning tool • Detects Entities enhanced for OpenJPA • Contains 2 Java rules • Contains 5 XML rules 30
- 31. Where can I get the migration tools? • http://wasdev.net 31 • Eclipse Marketplace
- 32. How do I use the Eclipse migration tool? Select Run > Analysis… to configure the JPA related rules. • Choose the OpenJPA to EclipseLink JPA Migration rule set if you are only interested in the JPA rules. 32
- 33. How do I use the Eclipse migration tool? • Select Run > Analysis to configure JPA related rules. • Choose the WebSphere Application Server Version Migration rule set if you want to do more analysis. • Select Java EE 7 as the target Java EE version • Select JPA 33
- 34. 34 See the code to change • After running Analysis, use the Software Analyzer Results view to interpret the scan.
- 35. 35 See the proposed fix before applying the change
- 36. When you need more help 36 • Each rule has help that you can view from the results or from the configuration dialog.
- 37. 37 What can I expect? -- Java rules
- 38. 38 What can I expect? -- XML rules Note: The rule Mapping files are not processed during OpenJPA to EclipseLink migration is a reminder that most of the rules are Java annotation rules. If define your Entities in mapping files rather than using JPA annotations, you will need to make manual mapping file changes.
- 39. What if I don’t have source code? The binary scanner detects • Enhanced Java code – only in the binary scanner • the XML issues • org.apache.openjpa packages in use 39
- 40. How do I use the binary scanner? • java -jar binaryAppScanner.jar --help 40
- 41. Resources
- 42. Other Tools: Integrity Checker • EclipseLink provides a way to verify descriptor's metadata against database metadata • Setup the integrity checker using a session customizer (link) • Catches missing tables or columns without having to persist • Example: private getter methods • setShouldCatchExceptions(true) - find all entities with missing columns • Cons: doesn't catch everything or maybe anything… • Failed to catch @ElementColumn resulting in a different column name in the separate table, @GeneratedValue looking for a different table • Doesn't compare column types • Better than nothing, but it missed many common issues 42
- 43. Useful Links • EclipseLink JPA provider for Liberty profile article https://developer.ibm.com/wasdev/blog/2014/05/28/ eclipselink-jpa-provider-liberty-profile/ • EclipseLink Migration Wiki Page https://wiki.eclipse.org/EclipseLink/Examples/JPA/Migration/ OpenJPA 43
- 44. Useful Links • WebSphere Application Server Migration Toolkit • wasdev.net download and links to the documentation • https://developer.ibm.com/wasdev/downloads/#asset/tools-WebSphere_Application_Server_Migration_Toolkit • Eclipse Marketplace • https://marketplace.eclipse.org/content/ibm-websphere-application-server-migration-toolkit • Migration Toolkit for Application Binaries • wasdev.net download and links to the documentation • https://developer.ibm.com/wasdev/downloads/#asset/tools-Migration_Toolkit_for_Application_Binaries 44
- 45. Sampling of Related Sessions… • PEJ-5296: Java EE 7 Overview – Monday, 10:30am-11:30am, Mandalay Bay North, South Pacific Ballroom A • PEJ-2876: Configuring WebSphere Application Server for Enterprise Messaging Needs – Monday, 12:00pm-1:00pm, Mandalay Bay North, Islander Ballroom G • PEJ-2139: Technical Deep Dive into IBM WebSphere Liberty – Monday, 3:00pm-4:00pm, Mandalay Bay North, South Pacific Ballroom A • PEJ-1603: IBM WebSphere Liberty in the Wild – Tuesday, 1:15pm-2:15pm, Mandalay Bay North, South Pacific Ballroom A • PEJ-6480: Don’t Wait! Developing Responsive Applications with Java EE 7 – Tuesday, 1:15pm-2:15pm, Mandalay Bay North, Islander Ballroom G • PEJ-1979: Hands-On with the IBM WebSphere Application Server Migration Toolkit (LAB) – Tuesday, 01:15 PM - 02:15 PM, MGM Grand - Room 320 • PEJ-2151: Agile Development Using Java EE 7 with WebSphere Liberty Profile (LAB) – Wednesday, 8:30am-9:30am, MGM Grand Room 306 • PEJ-1973: WAS Migration: Benefits, Planning, and Best Practices – Wednesday, 12:00pm-1:00pm, Mandalay Bay North, South Pacific Ballroom A • PEJ-1902: Migrate Java EE Applications to Cloud with Cloud Migration Toolkit – Wednesday, 2:30pm-12:15pm, Mandalay Bay North, Islander Ballroom G • PEJ-5303: OpenJPA and EclipseLink Usage Scenarios Explained – Thursday, 11:30am-12:15pm, Mandalay Bay North, South Pacific Ballroom A 45 45
- 46. Notices and Disclaimers 46 Copyright © 2016 by International Business Machines Corporation (IBM). No part of this document may be reproduced or transmitted in any form without written permission from IBM. U.S. Government Users Restricted Rights - Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM. Information in these presentations (including information relating to products that have not yet been announced by IBM) has been reviewed for accuracy as of the date of initial publication and could include unintentional technical or typographical errors. IBM shall have no responsibility to update this information. THIS DOCUMENT IS DISTRIBUTED "AS IS" WITHOUT ANY WARRANTY, EITHER EXPRESS OR IMPLIED. IN NO EVENT SHALL IBM BE LIABLE FOR ANY DAMAGE ARISING FROM THE USE OF THIS INFORMATION, INCLUDING BUT NOT LIMITED TO, LOSS OF DATA, BUSINESS INTERRUPTION, LOSS OF PROFIT OR LOSS OF OPPORTUNITY. IBM products and services are warranted according to the terms and conditions of the agreements under which they are provided. Any statements regarding IBM's future direction, intent or product plans are subject to change or withdrawal without notice. Performance data contained herein was generally obtained in a controlled, isolated environments. Customer examples are presented as illustrations of how those customers have used IBM products and the results they may have achieved. Actual performance, cost, savings or other results in other operating environments may vary. References in this document to IBM products, programs, or services does not imply that IBM intends to make such products, programs or services available in all countries in which IBM operates or does business. Workshops, sessions and associated materials may have been prepared by independent session speakers, and do not necessarily reflect the views of IBM. All materials and discussions are provided for informational purposes only, and are neither intended to, nor shall constitute legal or other guidance or advice to any individual participant or their specific situation. It is the customer’s responsibility to insure its own compliance with legal requirements and to obtain advice of competent legal counsel as to the identification and interpretation of any relevant laws and regulatory requirements that may affect the customer’s business and any actions the customer may need to take to comply with such laws. IBM does not provide legal advice or represent or warrant that its services or products will ensure that the customer is in compliance with any law
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- 49. Backup
- 50. Differences in Column Types • Mapping fields to columns • Example: java.lang.String fields • OpenJPA: VARCHAR(254) • EclipseLink: VARCHAR(255) • Mostly non-problematic • Exception: java.util.Locale fields • OpenJPA: VARCHAR(254) • EclipseLink: BLOB(64000) • Solution • Use a type converter (introduced in JPA 2.1) • BLOB (object) ↔ VARCHAR (database) 50