我在维基百科上读到了关于抽象工厂模式的内容。但我不太明白使用这种模式真正的好处。你能否给出一个例子,说明在某些情况下很难避免使用抽象工厂模式。考虑以下Java代码:
public abstract class FinancialToolsFactory {
public abstract TaxProcessor createTaxProcessor();
public abstract ShipFeeProcessor createShipFeeProcessor();
}
public abstract class ShipFeeProcessor {
abstract void calculateShipFee(Order order);
}
public abstract class TaxProcessor {
abstract void calculateTaxes(Order order);
}
// Factories
public class CanadaFinancialToolsFactory extends FinancialToolsFactory {
public TaxProcessor createTaxProcessor() {
return new CanadaTaxProcessor();
}
public ShipFeeProcessor createShipFeeProcessor() {
return new CanadaShipFeeProcessor();
}
}
public class EuropeFinancialToolsFactory extends FinancialToolsFactory {
public TaxProcessor createTaxProcessor() {
return new EuropeTaxProcessor();
}
public ShipFeeProcessor createShipFeeProcessor() {
return new EuropeShipFeeProcessor();
}
}
// Products
public class EuropeShipFeeProcessor extends ShipFeeProcessor {
public void calculateShipFee(Order order) {
// insert here Europe specific ship fee calculation
}
}
public class CanadaShipFeeProcessor extends ShipFeeProcessor {
public void calculateShipFee(Order order) {
// insert here Canada specific ship fee calculation
}
}
public class EuropeTaxProcessor extends TaxProcessor {
public void calculateTaxes(Order order) {
// insert here Europe specific tax calculation
}
}
public class CanadaTaxProcessor extends TaxProcessor {
public void calculateTaxes(Order order) {
// insert here Canada specific tax calculation
}
}
如果我们在代码中只需要创建1-2次对象,那么可以使用new运算符。那么为什么我们需要抽象工厂?