Design Patterns | Abstract Factory

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1. References
2. Example
   • The Abstract Product
   • The Concrete Product
   • The Abstract Factory
   • The Concrete Factory
   • The Factory Method (optional)
   • A simple class to test the Abstract Factory design pattern

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1. References
   • Definition: (source: http://en.wikipedia.org/wiki/Abstract_factory_pattern)
     
     The essence of the Abstract Factory Pattern is to "Provide an interface for creating families of related or dependent objects without specifying their concrete classes."
     
     
   • Class diagram: (source: http://en.wikipedia.org/wiki/Abstract_factory_pattern)
     
     
2. Example
   • The Abstract Product:
     
     
     • Product A:
       
       public interface Table { public String toSQL(); }
       
     • Product B:
       
       public interface Column { public String toSQL(); }
       
   • The Concrete Product:
     
     
     • Product A:
       
       
       • Implementation 1:
         
         public class TableOracle implements Table { public String toSQL() { return "TableOracle - toSQL"; } }
         
       • Implementation 2:
         
         public class TableDerby implements Table { public String toSQL() { return "TableDerby - toSQL"; } }
         
     • Product B:
       
       
       • Implementation 1:
         
         public class ColumnOracle implements Column { public String toSQL() { return "ColumnOracle - toSQL"; } }
         
       • Implementation 2:
         
         public class ColumnDerby implements Column { public String toSQL() { return "ColumnDerby - toSQL"; } }
         
   • The Abstract Factory:
     
     public interface Schema { public Table createTable(); public Column createColumn(); }
     
   • The Concrete Factory:
     
     
     • Implementation 1:
       
       public class SchemaOracle implements Schema { public Table createTable() { return new TableOracle(); } public Column createColumn() { return new ColumnOracle(); } }
       
     • Implementation 2:
       
       public class SchemaDerby implements Schema { public Table createTable() { return new TableDerby(); } public Column createColumn() { return new ColumnDerby(); } }
       
   • The Factory Method (optional):
     
     public class FactoryMethodSchema { public static Schema getSchema(final String type) { if ("oracle".equalsIgnoreCase(type)) { return new SchemaOracle(); } else if ("derby".equalsIgnoreCase(type)) { return new SchemaDerby(); } return null; } }
     
   • A simple class to test the Abstract Factory design pattern:
     
     public class AbstractFactoryPatternTest { public static void main(String[] args) { // .... Example 1: Oracle Schema .... // create the factory : Oracle final Schema oracleSchema = FactoryMethodSchema.getSchema("oracle"); // create instances final Table tableOracle = oracleSchema.createTable(); final Column columnOracle = oracleSchema.createColumn(); // call methods final String s_tableOracle = tableOracle.toSQL(); final String s_columnOracle = columnOracle.toSQL(); System.out.println(s_tableOracle + " / " + s_columnOracle); // .... Example 2: Derby Schema .... // create the factory : Derby final Schema derbySchema = FactoryMethodSchema.getSchema("derby"); // create instances final Table tableDerby = derbySchema.createTable(); final Column columnDerby = derbySchema.createColumn(); // call methods final String s_tableDerby = tableDerby.toSQL(); final String s_columnDerby = columnDerby.toSQL(); System.out.println(s_tableDerby + " / " + s_columnDerby); } }