Top 50 java ee 7 best practices [con5669]

TOP 50 JAVA EE 7 BEST
PRACTICES
Ryan Cuprak
Michael Remijan

About Us
Ryan
• @ctjava
• rcuprak@gmail.com
• http://www.cuprak.info
• https://www.linkedin.com/in/rcuprak
Michael
• @mjremijan
• mjremijan@yahoo.com
• http://mjremijan.blogspot.com
• http://linkedin.com/in/mjremijan

EJB 3 In Action 2nd Edition
Updated For
• EE 7
• EJB 3.2

Java EE 7
Concurrency
Utilities
Batch
Applications
Java
API for
JSON
Java API for
WebSocket
JSF 2.2
JSX-WS
2.2
JAX-RS
2
EL 3
Servlet 3.1
Common
Annotations 1.2
Interceptors 1.2 CDI 1.1
Managed Beans 1.0 EJB 3.2
Connector
1.7
JPA 2.1 JTA 1.2 JMS 2
JSP 2.3
JAXB

#1 JAX-RS: API Versioning
Version your JAX-RS with one of two approaches:
1. URL
http://ctjava.org/v2/meetings
http://ctjava.org/v1/meetngs
2. Media Content or Header Param
curl -H "Content-Type:application/srv-v4+json” …
Return HTTP Status Codes for services moved/changed:
• 301 Moved Permanently
• 302 Found

#1 JAX-RS: API Versioning (Continued…)
Approach 1: URL
Approach 2: Media Types

#1 JAX-RS: API Versioning (Continued…)
Service Moved Permanently

#2 JAX-RS: Error Handling
Provide ExceptionMappers to handle and process errors.

#2 JAX-RS: Error Handling (Continued…)
HTML content is hardly a friendly response for an API!

#2 JAX-RS: Error Handling (Continued…)

#3 JAX-RS: Caching
Tell clients to cache data!

#4 JAX-RS + Bean Validation
Use Bean Validation to check data.

#5 JAX-RS: Compress Responses
Use gzip compression for responses to reduce bandwidth.

#6 Securing RESTful Services
• Use tokens with RESTful Web Services (OWASP).
• Leverage JASPIC to setup JAAS environment.

#7 JAX-RS + EJB
• Use @Stateless and @Path together
• Pooled, thread safe, monitored

#7 JAX-RS + EJB (Continued…)
• http://localhost:4848/monitoring/domain/server/applications/WebApp
lication1/StatelessResource/bean-methods/getText[.json]

#8 JAX-RS: Asynchronous API Gateway
• Gateway calls multiple microservices asynchronously
• Combines results into a DTO

#8 JAX-RS: Async…(Continued…)
• Gateway calls multiple microservices asynchronously
• Combines results into a DTO

#9 JPA: Pagination
Use pagination for potential large result sets.

#9 JPA: Pagination (Continued…)

#10 JPA: Lazy Relationships
Avoid unnecessary queries – use Fetch on Lazy
relationships.

#10 JPA: Lazy Relationships (Continued…)
1. SELECT MEETINGID, DATE, MEETINGABSTRACT, TITLE FROM MEETING WHERE (MEETINGID
= ?)
2. SELECT t1.SPEAKERID, t1.BIOGRAPHY, t1.FIRSTNAME, t1.LASTNAME FROM meeting_speakers
t0, SPEAKER t1 WHERE ((t0.meetingid = ?) AND (t1.SPEAKERID = t0.speakerid))

#10 JPA: Lazy Relationships (Continued…)
1. SELECT t1.MEETINGID, t1.DATE, t1.MEETINGABSTRACT, t1.TITLE, t0.SPEAKERID, t0.BIOGRAPHY,
t0.FIRSTNAME, t0.LASTNAME FROM SPEAKER t0, meeting_speakers t2, MEETING t1 WHERE
((t1.MEETINGID = ?) AND ((t2.meetingid = t1.MEETINGID) AND (t0.SPEAKERID = t2.speakerid)))
1 Query Not TWO!

#11 JPA: Cascade
• Don’t forget cascade levels to handle child data
• cascade=ALL is equivalent to cascade={PERSIST,
MERGE, REMOVE, REFRESH, DETACH}

#13 JPA + DAO
Put CRUD operations into DAOs.

#14 JPA: hashcode() & equals()
The equals and hashcode are required for:
• Entity is added to a collection
• When re-attaching entities to a new persistence context.
Important points:
• Do not use generated identifiers
• Use business key equality

#14 JPA: hashcode() & equals() Continued…

#15 JPA: Optimistic Locking
• Don’t roll your own
• Use @Version for optimistic locking: Integer

#15 JPA: Optimistic Locking (Continued…)
• Timestamp

#16 JPA: Pessimistic Locking
• PESSIMISTIC_READ, PESSIMISTIC_WRITE
• Lock timeout
HINT

#17 JPA: Mapping Inheritance
• Inheritance can have a big impact upon performance.
• Three approaches:
• Single table
• Joined-tables
• Table-per-class
• Denormalize for better performance

#18 JPA L2 Cache
JPA 2 introduced the L2 Cache, use this cache for:
• Entities that are frequently read
• Entities that are modified infrequently
• Not critical if stale
• L2 cache can consume large amounts of memory
• ALL
• NONE
• ENABLE_SELECTIVE
• DISABLE_SELECTIVE
Are you using a default setting?

#18 JPA L2 Cache (Continued…)
Mark entity for L2 cache
Bypass L2 cache

#19 JPA: Persisting ENUM
• ENUM is a good case of converting data types
• Use a @Converter

#19 JPA: Persisting ENUM (Continued…)
• @Converter
• AttributeConverter<X,Y>
• X is my application, Y is the database

#20 EJB: Transaction Handling
• EJBs exist to handle transactions. Keep them at the right layer
• Don’t ignore transactions. Default: REQUIRED
• JAX-RS endpoints, database reads & performance

#21 EJB: Stateless Thread Safety
• Stateless beans are a pooled, managed resource
• Pools configurable by the application server

#22 EJB: Asynchronous
• @Asynchronous runs in container-managed thread
• Return Future<> to get results later
• Ideal for wrapping JAX-RS calls
• Good way to avoid any of your own threading

#23 EJB: Security
• Use declarative security and let the container handle it
• Avoid programmatic security
• EE servers trust principal/roles passed between
containers.

#23 EJB: Security (Continued…)
• EE Configuration
• web.xml
• @DeclaredRoles
• @RolesAllowed
• Custom Configuration
• EE Server Realm
• glassfish-web.xml

#24 EJB: Avoid Lengthy Initialization
Don’t abuse startup – @PostConconstruct delays
You delay initialization of the container!

#24 EJB: Avoid Lengthy Initialization

#25 CDI: Observers
• In-memory event processing
• Very “reactive”
• Decouple work to be done, avoids unnecessary
dependencies
• Create an event to fire

#25 CDI: Observers (Continued…)
• Fire the event
• Observers process the event

#26 CDI: Producer + Cache
• Use a producer to customize creation of an object
• Producer method is always called, so cache the instance

#27 CDI: Interceptors
• Limit to cross-cutting concerns
• Do not use to change business logic
• Create an annotation

• Create the interceptor

• Apply the interceptor

#28 CDI: Decorators
• Use to enhance or decorate existing code
• Open-close principle
• Do not use for cross-cutting concerns

#28 CDI: Decorators (Continued…)
• /WEB-INF/beans.xml
• /META-INF/beans.xml

#29 CDI: Transactions
Java EE introduced @Transactional for non-EJBs.
Pro: Easier to utilize transactions outside of EJB.
Con: Mixes layers – transactions & rest etc.

#30 CDI: Bean Discovery
• Java EE 7 CDI is enabled by default.
• beans.xml is no longer required as in EE 6
• Bean discovery mode:
• Annotated – only annotated classes
• All – includes beans that are not annotated
• None – CDI disabled
• Default mode is ‘annotated’

#31 Batch: Java EE not SE
• Think Java EE for batch, not SE
• Batch API
• Cron like schedule on EJB methods
• META-INF/batch-jobs/processInvoices.xml

#32: Batch Best Practices
• Package/deploy batch jobs separately
• Implement logic to cleanup old jobs
• Implement logic for auto-restart
• Test restart and checkpoint logic
• Configure database to store jobs
• Configure thread pool for batch jobs
• Only invoke batch jobs from logic that is secured (@Role
etc.)

#33 JAXB Primitive Data Types
anySimpleType
decimal
integer
long
int
short
byte
float double
nonPositiveInteger
negativeInteger
nonNegativeInteger
unsigneLong positiveInteger
unsignedInt
unsignedInt
unsignedByte

#34 JAXB: Date & Time Representation
• Use XMLGregorianCalendar for dates
• Avoid java.util.Date and java.util.Calendar
• XMLGregorianCalendar
• Handles long fractions of seconds – important to .NET
interoperability

#35 JAXB: Annotate
Don’t let JAXB generate everything!

#36 JAX-WS: RPC vs. Document
• Four different possibilities:
• RPC/Literal
• RPC/Encoded
• Document/Literal
• Document/Encoded
• Encoded is not supported by WS-I
• Default and most commonly used is Document/Literal
• Use Document/Literal
• RPC/Literal:
• Limited to basic XSD types
• WSDL will not include types section to constrain parameters

#37 JAX-WS: JAXB Gotcha
• JAXB will serialize an entire object graph.
Oops!
Use either:
• DTO – Data Transfer Object
• @XmlTransient

#38 JAX-WS Interoperable Services
• Design service starting with the WSDL
• Create data types using XSD
• Keep data types SIMPLE
• Avoid xsd:anyType
• Avoid sending Null values
• Use byte[] instead of String when character encoding is
unknown

#39 SOAP Faults
• Types of SOAP faults:
• Modeled – exception explicitly thrown by business logic.
• Mapped to wsdl:fault in WSDL file
• Unmodeled – RuntimeException, represented as generic
SOAPFaultException

#40 JAX-WS Input/Output Processing
Use SOAP message handlers to pre/post process
messages and handle SOAP faults.

#40 JAX-WS Input/Output Processing

#41 JAX-WS Security
Specify Roles

#42 JAX-WS Large Files
Use W3C Message Transmission Optimization Mechanism
(MTOM) to handle large files.

#43 Deployment Classpath
• Are you pulling in third-party JAR files?
• Do these JAR files include Java EE annotated classes?
• Are you accidently deploying web services, MDBs etc.?
• Are you including container dependencies?
BAD!

#44 Threading
• Never create create threads.
• Container manages resources.

#44 Threading…
Thread Factory

#45 Distributed Caches
• Don’t treat @Singleton as a “global” singleton!
• Use JCache implementation (ex. HazelCast)
Java EE Server #1
app.war
SingletonBean
Java EE Server #2
app.war
SingletonBean

#46 Testing: Load
Load testing always at 100%?
Scenario:
• Message Driven Bean with a connection to a remote
resource.
• Standing pool size: 3
Oops!

#46 Testing Load (Continued…)
Oops, resource only leak as bean instances fluctuate!
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8 9
Leak
Bean
Returning to standing pool size leaks resources.

#47 Testing: Integration
Use Arquillian:

#48 Java EE Tutorial Table of Contents
• What’s in Java EE?
• 918 pages
• TOC is a great summary
• 30+ pages
• Highlights just how much is
in EE

#49 There are no “small” applications
• Don’t fall into these traps:
• “It’s just a simple application”
• “It only needs to do…”
• “Code it up real quick…”
• EE Specification exists for a reason
• Multiple users
• Concurrency
• Multi-threading
• Transaction management
• External resources
• Messaging

#50 Start with an EE Server
• Because there are no “small” applications
• Start with an EE Server
Avoid filling yourWAR with
“EE Features”
because you are not using an EE server
• But Servers are “heavy-weight”?
• Payara
• WildFly
• TomEE
• Benefits
• “Light-weight”
• Regular updates
• Great online community support

Join Us!
https://javaee-guardians.io

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