Domain Specific Languages (EclipseCon 2012)

DOMAIN-SPECIFIC
LANGUAGES
@svenefftinge

DOMAIN-SPECIFIC
LANGUAGE

A Domain Speciﬁc Language (DSL) is
a computer programming language
focused on a particular domain.

DOMAIN-SPECIFIC
LANGUAGE

Or just a hip term for a very
readable and expressive
programming interface
(aka API)

IT IS NOT! A WAY TO LET
BUSINESS PEOPLE WRITE SOFTWARE

ABSTRACTION
"THE ABILITY TO SIMPLIFY MEANS
TO ELIMINATE THE UNNECESSARY
SO THAT THE NECESSARY MAY SPEAK"
(HANS HOFMANN)

A TYPICAL WEB APPLICATION

Request

Response


Http Routing


Http Routing Controller


Http Routing Controller Domain Model



Data Access



Templates for HTML, CSS and JS Data Access


?
Http Routing
?
Controller ?
Domain Model

?
Templates for HTML, CSS and JS
?
Data Access

HTTP-ROUTING WITH
SERVLET API

HTTP-ROUTING WITH
JAX-RS

Java / Xtend

HTTP-ROUTING WITH
PLAY!

HTTP-ROUTING WITH
PLAY!
Static Typing ?

HTTP-ROUTING WITH
PLAY!
Static Typing ?

Viewpoint Speciﬁc Analysis?


Http Routing
?
Controller ?
Domain Model

?
?
Data Access

Controller

Use a General Purpose Language:
Java, ..., Xtend, ...


Http Routing Controller ?
Domain Model

?
?
Data Access

<%@ page language="java" import="captchas.CaptchasDotNet" %>

<html>
  <head>
    <title>Sample JSP CAPTCHA Query</title>
  </head>
  <h1>Sample JSP CAPTCHA Query</h1>
<% CaptchasDotNet captchas = new captchas.CaptchasDotNet(
  request.getSession(true),     // Ensure session
  "demo",                       // client
  "secret"                      // secret
  );%>
  <form method="get" action="<%=response.encodeUrl("check.jsp")%>">
    <table>
      <tr>
        <td><input name="message" size="60" />
        </tr>
      <tr>
        <td>
          <input name="password" size="16" />
        </td>
      </tr>
      <tr>
        <td>
          <%= captchas.image() %><br>
          <a href="<%= captchas.audioUrl() %>">Phonetic spelling (mp3)</a>
        </td>
      </tr>
      <tr>
        <td>
          <input type="submit" value="Submit" />
        </td>
      </tr>
    </table>
  </form>
</html>

<%@ page language="java" import="captchas.CaptchasDotNet" %>

<html>
  <head>

  </head> Java Server Pages
    <title>Sample JSP CAPTCHA Query</title>

  <h1>Sample JSP CAPTCHA Query</h1>

Velocity
<% CaptchasDotNet captchas = new captchas.CaptchasDotNet(
  request.getSession(true),     // Ensure session
  "demo",                       // client

Freemarker
  "secret"                      // secret
  );%>
  <form method="get" action="<%=response.encodeUrl("check.jsp")%>">

Hamlets
    <table>
      <tr>
        <td><input name="message" size="60" />

Scalate
        </tr>
      <tr>
        <td>
          <input name="password" size="16" />
        </td>
      </tr>
      <tr>
StringTemplate
        <td>
Thymeleaf
          <%= captchas.image() %><br>
          <a href="<%= captchas.audioUrl() %>">Phonetic spelling (mp3)</a>

Jamon
        </td>
      </tr>
      <tr>

WebMacro
        <td>
          <input type="submit" value="Submit" />
        </td>
      </tr>
    </table>
  </form>
</html>
...

html [
head [
title [$("XML encoding with Xtend")]
]
body [
h1 [$("XML encoding with Xtend")]
p [$("this format can be used as an alternative to XML")]

// an element with attributes and text content
a("http://www.xtend-lang.org") [$("Xtend")]

// mixed content
p [
$("This is some")
b[$("mixed")]
$("text. For more see the")
a("http://www.xtext.org")[$("Xtext")]
$("project")
]
p [$("some text")]

// content generated from arguments
p [
for (arg : args)
$(arg)
]
]
]


Domain Model

?
Data Access

DATA ACCESS WITH
JPA QUERY LANGUAGE

.NET LINQ

val namesWithFiveCharacters = from name in names
where name.Length < 5
select name;

SCALA QUERY

val q1 = for(u <- Users if u.first === "Stefan")
yield u.id ~ u.last


Domain Model

Templates for HTML, CSS and JS Data Access

@Entity
public class Customer implements Serializable {
private Long id;
private String name;
private Address address;
private Collection<Order> orders = new HashSet<Order>();
private Set<PhoneNumber> phones = new HashSet<PhoneNumber>();

public Customer() {}
@Id
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
@OneToMany
public Collection<Order> getOrders() {
return orders;
}
public void setOrders(Collection<Order> orders) {
this.orders = orders;
}
@ManyToMany
public Set<PhoneNumber> getPhones() {
return phones;
}
public void setPhones(Set<PhoneNumber> phones) {
this.phones = phones;
}
}

entity Customer {
id Long id
String name
Address address
onetomany Collection<Order> orders
manytomany Set<PhoneNumber> phones
}

com.springsource.roo.pizzashop roo> entity --class ~.domain.Topping --testAutomatically
~.domain.Topping roo> field string --fieldName name --notNull --sizeMin 2
~.domain.Topping roo> entity --class ~.domain.Base --testAutomatically
~.domain.Base roo> field string --fieldName name --notNull --sizeMin 2
~.domain.Base roo> entity --class ~.domain.Pizza --testAutomatically
~.domain.Pizza roo> field string --fieldName name --notNull --sizeMin 2
~.domain.Pizza roo> field number --fieldName price --type java.lang.Float
~.domain.Pizza roo> field set --fieldName toppings --type ~.domain.Topping
~.domain.Pizza roo> field reference --fieldName base --type ~.domain.Base
~.domain.Pizza roo> entity --class ~.domain.PizzaOrder --testAutomatically
~.domain.PizzaOrder roo> field string --fieldName name --notNull --sizeMin 2
~.domain.PizzaOrder roo> field string --fieldName address --sizeMax 30
~.domain.PizzaOrder roo> field number --fieldName total --type java.lang.Float
~.domain.PizzaOrder roo> field date --fieldName deliveryDate --type java.util.Date
~.domain.PizzaOrder roo> field set --fieldName pizzas --type ~.domain.Pizza

Know your toolbox, be creative and have fun!
Thank you!

Domain Specific Languages (EclipseCon 2012)

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