- Spring 5 Design Patterns
- Dinesh Rajput
- 401字
- 2021-07-08 09:59:39
Implementing the Decorator pattern
Let's look at the following code to demonstrate the Decorator design pattern.
Create a component class:
Following is the Account.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public interface Account { String getTotalBenefits(); }
Create concrete components classes:
Following is the SavingAccount.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public class SavingAccount implements Account { @Override public String getTotalBenefits() { return "This account has 4% interest rate with per day
$5000 withdrawal limit"; } }
Let's create another concrete class for Account component:
Following is the CurrentAccount.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public class CurrentAccount implements Account { @Override public String getTotalBenefits() { return "There is no withdrawal limit for current account"; } }
Let's create a Decorator class for Account component. This decorator class apply other run time behavior to the Account component classes.
Following is the AccountDecorator.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public abstract class AccountDecorator implements Account { abstract String applyOtherBenefits(); }
Let's create a ConcreteDecorator class to implement the AccountDecorator class. Following class SeniorCitizen is extended AccountDecorator class to access other run time behavior such as applyOtherBenefits().
Following is the SeniorCitizen.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public class SeniorCitizen extends AccountDecorator { Account account; public SeniorCitizen(Account account) { super(); this.account = account; } public String getTotalBenefits() { return account.getTotalBenefits() + " other benefits are
"+applyOtherBenefits(); } String applyOtherBenefits() { return " an medical insurance of up to $1,000 for Senior
Citizen"; } }
Let's create another ConcreteDecorator class to implement the AccountDecorator class. Following class Privilege is extended AccountDecorator class to access other run time behavior such as applyOtherBenefits().
Following is the Privilege.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public class Privilege extends AccountDecorator { Account account; public Privilege(Account account) { this.account = account; } public String getTotalBenefits() { return account.getTotalBenefits() + " other benefits are
"+applyOtherBenefits(); } String applyOtherBenefits() { return " an accident insurance of up to $1,600 and
an overdraft facility of $84"; } }
Let's now write some test code to see how the Decorator pattern works at runtime:
Following is the DecoratorPatternMain.java file:
package com.packt.patterninspring.chapter3.decorator.pattern; public class DecoratorPatternMain { public static void main(String[] args) { /*Saving account with no decoration*/ Account basicSavingAccount = new SavingAccount(); System.out.println(basicSavingAccount.getTotalBenefits()); /*Saving account with senior citizen benefits decoration*/ Account seniorCitizenSavingAccount = new SavingAccount(); seniorCitizenSavingAccount = new
SeniorCitizen(seniorCitizenSavingAccount); System.out.println
(seniorCitizenSavingAccount.getTotalBenefits()); /*Saving account with privilege decoration*/ Account privilegeCitizenSavingAccount = new SavingAccount(); privilegeCitizenSavingAccount = new
Privilege(privilegeCitizenSavingAccount); System.out.println
(privilegeCitizenSavingAccount.getTotalBenefits()); } }
Let's run this demo class and see the following output at the console:

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