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Best Practices in Java Development
JA-SIG Summer Conference
Denver, CO
June 24 – 27, 2007
Best Practices in Java Development
Who am I?
• I’m Scott Battaglia!
• Application Developer @ Rutgers
• Java Developer for 5+ Years
• Lead Developer/Architect on JA-SIG CAS
• Committer to Acegi Security
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Agenda
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Methodologies
Language Features
Non Language Specific
Tool Chest
Discussion
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
1.
Methodologies
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Test Driven Development
• Writing a test case and implementing only
code necessary to pass test
• A method of designing software, not merely a
method of testing
• Can still produce crappy code
• Unit vs. Integration Tests
• Useful when used judiciously
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Test Driven Development
• Three rules from “Uncle Bob”
– You are not allowed to write any production code unless it is
to make a failing unit test pass.
– You are not allowed to write any more of a unit test than is
sufficient to fail; and compilation failures are failures.
– You are not allowed to write any more production code than is
sufficient to pass the one failing unit test.
• http://butunclebob.com/ArticleS.UncleBob.TheThreeR
ulesOfTdd
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Test Driven Development
• What makes a good unit test?
– Run fast (they have short setups, run times, and break
downs).
– Run in isolation (you should be able to reorder them).
– Use data that makes them easy to read and to understand.
– Use real data (e.g. copies of production data) when they need
to.
– Represent one step towards your overall goal.
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Domain Driven Design
• The premise of domain-driven design is two-fold:
– For most software projects, the primary focus should be on the
domain and domain logic; and
– Complex domain designs should be based on a model.
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Domain Driven Design
• Business people talk naturally in Business terms
(using ubiquitous language):
- Open grading period, Pending class roster, Student
eligible for grading, Course grading policy, etc.
• Objects shift language from data to behavior
- Away from flags and if conditions
- Toward responsibilities and naming
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Domain Driven Design
• Models the business domain concepts
• Maps to Screens and DB
• Easier to test, and change
• Reusable (different application clients)
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Domain Driven Design
• Business logic can be complex
- Rules in Domain Model (DM) describe the many
cases & variations
• DM creates a web of interconnected objects where
each represents a meaningful concept some as large
as an entire company or as small as a person’s name
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Iterative Development
• Cyclic/incremental
• Milestones, Release
Candidates…
• Feedback before its too
late!
• Allows you to take
advantage of previously
gained knowledge
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Code Reviews
• Systematic examination of course code
• Goals
– Improve quality of code
– Share knowledge
• Ideally…
– Short
– Focused on code
• Many ways of doing it
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Aspect Oriented Programming
• Deals with the separation of concerns (cross-cutting
concerns)
• Breaking down a program into distinct parts that
overlap in functionality as little as possible
• Examples
– Transactions, logging, security, ContractByDesign
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
2.
Language Features
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
“final” Keyword
• Used as follows:
– final Object o = new Object();
• Advantages:
–
–
–
–
Prevents accidental assigning of variables
Turns logical errors into compile errors
JVM can optimize final constants
Limit Scope of Variables
• Gotchas:
– Final primitives and Strings are substituted at compile-time
– Final means no variable re-assignment
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
StringBuilder
• Usage:
– final StringBuilder builder = new StringBuilder(50);
– builder.append(“myString”);
– builder.append(“moreOfMyString”);
• StringBuilder vs. StringBuffer vs String
• “Best Guess” StringBuilder size
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Enumerations
• Traditional Enumerations:
– public final int ENUM_VALUE_1 = 1
– public final int ENUM_VALUE_2 = 2
– …
• Type Safe Enums:
– Implementation of Java classes
• Java 5 Enumerations
– enum COLOR {BLACK, WHITE, RED, GREEN, BLUE, YELLOW}
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
JPA
• JPA is
– Java Persistence API
– -Entities
– Java Persistence Query Language
• Advantages
– Pluggable backend (TopLink, Hibernate, etc.)
– Database agnostic DAO layer
– No complex mapping files
• Disadvantages
– Difficult to retrofit “legacy” tables
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
PreparedStatements
• Statements vs. PreparedStatements
• Advantages:
– Compiled
– Correctly escape characters
– As of JDBC 3, can be pooled
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Annotations
• Extra information associated with Class, Method,
Variables
• Most useful for non-frequently changing information
• Keeps meta data and object together
• Examples:
– Spring Transactions
– CAS Property Validation
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
3.
Non-Language Specific
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Design Patterns
• Recurring solutions to common problems
• Solve design problems not computational problems
• Five types of Patterns
• Benefits:
– Easy to understand code
– General solutions
– Allow people to communicate using the same language
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Model-View-Controller
• Division of Labor into the following parts:
– Those responsible for business logic (the Model -- often
implemented using Enterprise JavaBeans™ or plain old Java
objects).
– Those responsible for presentation of the user interface (the
View).
– Those responsible for application navigation (the Controller -usually implemented with Java servlets or associated classes like
Struts controllers).
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Interfaces
• Interface vs. Abstract Class
• Coding to Interfaces
• Examples
– Collections Framework
– CAS
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Logging
• Makes debugging easier
• Everywhere you would have put a System.out, put a
logger statement
• log.isXXXXEnabled() vs. log.XXXX(“data”)
• Logging via AOP
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Exception vs. Runtime Exception
• Two types of Exceptions in Java
– Exception (checked)
– Runtime Exception (unchecked)
• Checked Exceptions indicate something that can be
handled.
• Unchecked Exceptions indicate something that can’t
be.
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Don't Re-Invent the Wheel
• Use Common well know frameworks
– Spring, Hibernate, Web Flow, Acegi...
• Don't fall for “not invented here” syndrome
• Balance needs of application vs. library
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Documentation & Comments
• Documentation is pretty much the bane of all
developer’s existences
• Be sure to place comments in code, but don’t put too
much
– // send the mail message
– javaMailSender.send(message);
• You never know when you need to revisit your code
– Document methods, classes, configuration
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Unit Testing
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•
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Use a Code Coverage tool
Don't Mandate 100% test coverage
Add tests when you see they don't exist
Add tests to prove a bug
Run your tests frequently
Make sure the tests execute quickly
Don’t let the tests become out of date
Don’t throw them away when they stop passing - fix
them!
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
4.
Tool Chest
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Build Tools
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Wiki
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Issue Tracking
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Continuous Integration
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Version Control
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Integrated Development Environment
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
5.
Discussion
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
Further Reading..
• Thinking in Java by Bruce Eckel
• J2EE Design and Development by Rod Johnson
• Refactoring: Improving the Design of Existing Code by
Martin Fowler
• Effective Java by Joshua Bloch
• Domain Driven Design by Eric Evans
JA-SIG Summer Conference – June 24 – June 27, 2007
Best Practices in Java Development
?
What are Your “Best Practices?”
JA-SIG Summer Conference – June 24 – June 27, 2007