Syntactic Salt and Sugar Presentation
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Syntactic Salt and Sugar James Gould Alex Holmes Verisign 205
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Transcript of Syntactic Salt and Sugar Presentation
Syntactic Salt and Sugar
James Gould
Alex Holmes
Verisign
205
Alex
2
Jim
3
Introduction
4
Format> Discuss 5 Syntactic Elements
> Lead discussion of each Element
– Introduce newer Elements
– Identify Good
– Identify Bad
> Participation is encouraged!
5
6
AGENDA
> DSL
> Project Lambda
> AOP
> CDI
> Grab Bag
2
7
AGENDA
> DSL
> Project Lambda
> AOP
> CDI
> Grab Bag
2
omain specific language
Noun: a computer programming language of limited expressiveness focused on a particular domain.
Rich languages
Domain specific language
DSL examples
ELECT * FROM STATION WHERE LAT_N > 39.7;
Domain model
Grammatical Elements of a DSL
deposit
withdraw
account
amount
verbs nounsoperators +
separators
() {} [] . -> => =
< > ! ~ ? : ==
++ || -- *=
<<< % ^ ; ,
%= && >= -1
>>>= // #
Internal DSL
An internal DSL is a DSL
represented within the syntax of
a general-purpose language.
It's a stylized use of that
language for a domain-specific
purpose.
Excerpt from Martin Fowler’s book “Domain Specific Languages”, published by Addison-Wesley
Java internal DSL
15
Java internal DSL
External DSL
An external DSL is a domain-
specific language represented in a
separate language to the main
programming language it's
working with. This language may
use a custom syntax, or it may
follow the syntax of another
representation such as XML.
Excerpt from Martin Fowler’s book “Domain Specific Languages”, published by Addison-Wesley
External DSL for ATM
d -> :a(0.95) :chk(12345)
What do “d”, “a” and “chk” represent?
What’s with the obfuscated syntax?
Where is the language documented?
YALTL – Yet another language to learn
Just call me Sherlock
Re-worked DSL grammar
deposit amount 0.95 into checking 12345
DSL Sugar
21
diomatic way to communicate with domain experts
an be used by non-programmers
elf-documenting
DSL Salt
22
SL syntax can quickly become salty
o you really need a DSL?
upporting a DSL is labor-intensive
23
AGENDA
> DSL
> Project Lambda
> AOP
> CDI
> Grab Bag
2
24
Project Lambda : Introduction
> Included in Java 8
> Defined in JSR-335
– Lambda Expressions
– Default Methods
Project Lambda : Lambda Expressions
25
ublic class Calculator {
static interface Calculate {
int calc(int op1, int op2);
}
public static void main(String... args) {
Calculate addition = new Calculate() {
public int calc(int op1, int op2) {
return op1 + op2;}};
System.out.println("Addition = " + addition.calc(10, 20));
Calculate multiply = new Calculate() {
public int calc(int op1, int op2) {
return op1 * op2;}};
System.out.println("Multiply = " + multiply.calc(10, 20));
}
public class Calculator {
static interface Calculate {
int calc(int op1, int op2);
}
public static void main(String... args) {
Calculate addition = (op1, op2) -> op1 + op2;
System.out.println("Addition = " + addition.calc(10, 20));
Calculate multiply = (op1, op2) -> op1 * op2;
System.out.println("Multiply = " + multiply.calc(10, 20));
}
}
26
Project Lambda : Type Targeting
> How “Calculate addition = (op1, op2) -> op1 + op2;” works?
– Type expression is inferred by type expected in context
– Calculate is a Functional Interface
– Expression compatible to Function Interface Interface is Functional Interface Expression has same number of parameters Expression return is compatible Expression exception thrown is allowed by Interface
> Lambda’s are strongly typed
Project Lambda : Type Targeting Sample
27
ublic class HelloWorld {
public static void main(String... args) throws Exception {
Callable<Void> helloCall =
() -> {System.out.println("Hello World!"); return null;};
Runnable helloRun =
() -> {System.out.println("Hello World!");};
helloCall.call();
helloRun.run();
}
Lambda’s and Collections
raditional iteration:
or (Car c : cars) {
c.setColor(RED);
28
ewritten for lambda’s:
ars.forEach(c -> c.setColor(RED));
arallelized:
ars.parallel()
.forEach(c -> c.setColor(RED));
Project Lambda : Lambda Expression Sugar
29
nonymous Inner Classes done in a clean way
Calculate addition = new Calculate() {
public int calc(int op1, int op2) {
return op1 + op2;
}};
atches feature of other languages
C#, C++, Ruby, Python, JavaScript, …
Take advantage of multicore processors
Mark Reinhold – “the real reason is multicore processors; the best way to handle them is with Lambda”
Calculate addition = (op1, op2) -> op1 + op2;
Project Lambda : Lambda Expression Salt
30
ark Reinhold – “Some would say adding Lambda expressions is just to keep up with the cool kids, and there’s some truth in that”
ava as a Object Oriented language
o you want Anonymous Inner Classes on steroids?
ack of code clarity
Project Lambda : Default Methods
nterface A {
void execute() default {
System.out.println("A.execute()");
}
lass ClassA implements A {
lassA classA = new ClassA();
lassA.execute();
A.execute()”
31
Project Lambda : Default Methods
nterface A {
void execute() default {
System.out.println("A.execute()");
}
nterface B extends A {
void execute() default {
System.out.println(“B.execute()");
}
nterface C extends A {}
lass ClassHuh implements C, B {}
new ClassHuh()).execute();
B.execute()”
32
Project Lambda : Default Methods
nterface A {
void execute() default {
System.out.println("A.execute()");
}
nterface B {
void execute() default {
System.out.println(“B.execute()");
}
lass ClassHuh implements A, B {
void execute() {
A.super.execute();
}
new ClassHuh()).execute();
rror: reference to execute is ambiguous
A.execute()”
33
Project Lambda : Default Methods and Lambda
nterface A {
void execute() default {
System.out.println("A.execute()");
}
nterface B extends A {
void execute() default {
System.out.println(“B.execute()");
}
void execute2();
nterface C extends A, B {}
lambdaC = () -> {System.out.println(“Lambda Expression”);};
ambdaC.execute();
ambdaC.execute2();
B.execute()”
Lambda Expression”
34
Project Lambda : Default Methods Sugar
35
inally able to add code to interfaces!
Project Lambda : Default Methods Salt
36
dding multiple inheritance to Java
ixing Default Methods and Lambda Expressions adds more confusion
37
AGENDA
> DSL
> Project Lambda
> AOP
> CDI
> Grab Bag
2
38
AOP : Introduction2
spect Oriented Programming (AOP)
OP
2
nnotation Oriented Programming (AOP)
39
> When should aspects be used?
– By container?
– Extraneous functions?
– Semantics of the language? A = B?
> When should aspects be used?
By container?
Extraneous functions?
Semantics of the language? A = B?
AOP : Aspect Oriented Programming2
40
> Annotations designed in similar goals as AOP
– Special markers to classes, methods, and fields
– Processed by libraries and tools
> Everything seems to be annotated now!
AOP : Annotation Oriented Programming2
41
Sample sample = new Sample(21, “James”); assert ( sample.getAge() == 21);assert ( sample.getName().equals(“James”));sample.setName(“Jim”);System.out.println(“sample = “ + sample);
“sample = Sample(age=21, name=Jim)
RequiredArgsConstructor
EqualsAndHashCode
ToString
ublic class Sample {
@Getter private final int age;
@NonNull @Getter @Setter private String name;
@Datapublic class Sample { private final int age; @NonNull private String name;}
AOP : Annotation Oriented Programming Sample2
42
Communication with compiler
@Override, @Deprecated, @SuppressWarnings
Communication with frameworks
Java Persistence API, Spring
AOP : Annotations Sugar2
43
Configuration
Added Dependencies
Used for code generation
AOP : Annotations Salt2
44
> Annotations and aspects together is a natural fit
– Annotations provide meta-data
– Aspects to drive cross-cutting logic based on Annotations
AOP : AOP 2 2
45
ublic class PrintInterceptor {
@AroundInvoke
public Object execute(InvocationContext ctx) throws Exception {
System.out.println("Intercepting method " +
ctx.getMethod().getDeclaringClass().getName() + ":" +
ctx.getMethod().getName());
Object result = ctx.proceed();
return result;
}
Interceptors(PrintInterceptor.class)
ublic void targetMethod() {
…
AOP : Java EE Interceptors2
46
Procedure(name = "Account.deposit")
ublic void deposit (
@In(Types.NUMERIC) final Long accountId,
@In(Types.NUMERIC) final Long locationId,
@In(Types.NUMERIC) final BigDecimal amount,
@In(Types.TIMESTAMP) final Date transactionDate,
@Out(Types.NUMERIC) Ref<BigDecimal> balance) {
throw new IllegalStateException(
"This method invocation was not intercepted" );
AOP : What is This?2
47
AGENDA
> DSL
> Project Lambda
> AOP
> CDI
> Grab Bag
2
Changing Landscape of Dependency Injection
Huh?
JSR-330 + JSR-299 Compared
JSR-330 Annotations
• @Inject
• @Named
• @Provider
• @Qualified
• @Scope
• @Singleton
Basic Injection
Named Injections
Qualifiers
Pop Quiz
55
Question: Do both garage instances refer to the same object?
Answer: No, the default scoping in JSR-330 is “@Dependent”
Scopes
JSR-299 – Context Dependency Injection
• Uses JSR-330 as foundation• Adds Java EE-specific extensions
• Producers
• Decorators
• Interceptor enhancements
JSR-299 – Additional Scopes
built-in scopes:
RequestScoped
SessionScoped
ApplicationScoped
ConversationScoped
Pop Quiz
CDI Extensions
CDI Sugar
62
tandards for Dependency Injection
nnotation-driven injection, decorators, interceptors
xtensible SPI
CDI Salt
63
hy are there 2 standards?
ack of Java SE DI support
o dynamic DI injection
64
AGENDA
> DSL
> Project Lambda
> AOP
> CDI
> Grab Bag
2
Binary Literals and Underscores
Handling multiple exceptions
Multi-Catch
Resource cleaning
Try-with-resources
Strings in switch
Diamonds (are a geek’s best friend)
Java 7 Language Enhancements: Sugar or Salt?
72
James Gould verisigninc.com
Verisign [email protected]
Alex Holmes verisign.com
Verisign [email protected]
