Mapping a Design to Code

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Mapping design to code 🔗

UML artifacts created during design, such as interaction diagrams and design class diagrams (DCDs), serve as inputs to code generation.

Implementation model

All implementation artifacts:
- Source code, database definitions, JSP/XML/HTML pages, and so on.

When implementing a design in an object-oriented language, write source code for:

Class and interface definitions.
Method definitions.

Converting a UML design to code

From class diagrams to
class definitions
.
From interaction diagrams to
method bodies
.

Creating class definitions from a DCD 🔗

A DCD contains enough information to create basic class definitions in an object-oriented language.

Defining attributes as Java fields

Declare the attributes in the DCD as Java fields.

For example, quantity: Integer maps to private int quantity;.
For example, description: ProductDescription maps to private ProductDescription description;.

Method signatures

Declare the operations in the DCD as Java methods.

For example, getSubtotal(): Money maps to public Money getSubtotal() { ... }.

Creating method bodies from interaction diagrams 🔗

The message sequence in an interaction diagram becomes a sequence of statements in a method definition.

Extracting messages from an interaction diagram

An enterItem message is sent to a Register instance, so the enterItem method is defined in the Register class.
Follow the message sequence to implement the method's behavior in code.

Message sequence

Message 1: Send getProductDescription to the ProductCatalog object to retrieve a product description.
Message 2: Send makeLineItem to the Sale object to create a sales line item.

Java implementation

Convert the messages into code statements to implement the enterItem method.

예시 코드

public class Register {
		private ProductCatalog catalog;
		private Sale currentSale;
		public Register(ProductCatalog catalog) {
				this.catalog = catalog;
				this.currentSale = new Sale();
		}
		public void enterItem(int itemID, int qty) {
				ProductDescription desc = catalog.getProductDescription(itemID);
				currentSale.makeLineItem(desc, qty);
		}
}

Collection classes in code 🔗

An important tool for managing and manipulating multiple objects in object-oriented programming.
They are especially useful for representing
one-to-many
relationships.

Object-oriented languages implement this by introducing

collection objects

List (ArrayList implementing the List interface): An ordered list that can grow.
Map (HashMap implementing the Map interface): Key-based lookup.
Plain arrays.

Implementation order 🔗

Implement classes in order from lower coupling to higher coupling.

Payment or ProductDescription can be implemented first.
Next come classes that depend only on those already implemented, such as ProductCatalog or SalesLineItem.

Mapping a Design to Code | PromleeBlog