d1767bbb51
* init repo for role object * add to init * add to init * add first impl * add pattern * add license * add changes
94 lines
4.6 KiB
Java
94 lines
4.6 KiB
Java
/*
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* The MIT License
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* Copyright © 2014-2019 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.roleobject;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import static com.iluwatar.roleobject.Role.*;
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/**
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* The Role Object pattern suggests to model context-specific views
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* of an object as separate role objects which are
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* dynamically attached to and removed from the core object.
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* We call the resulting composite object structure,
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* consisting of the core and its role objects, a subject.
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* A subject often plays several roles and the same role is likely to
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* be played by different subjects.
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* As an example consider two different customers playing the role of borrower and
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* investor, respectively. Both roles could as well be played by a single {@link Customer} object.
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* The common superclass for customer-specific roles is provided by {@link CustomerRole},
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* which also supports the {@link Customer} interface.
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* <p>
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* The {@link CustomerRole} class is abstract and not meant to be instantiated.
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* Concrete subclasses of {@link CustomerRole}, for example {@link BorrowerRole} or {@link InvestorRole},
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* define and implement the interface for specific roles. It is only
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* these subclasses which are instantiated at runtime.
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* The {@link BorrowerRole} class defines the context-specific view of {@link Customer} objects as needed by the loan department.
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* It defines additional operations to manage the customer’s
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* credits and securities. Similarly, the {@link InvestorRole} class adds operations specific
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* to the investment department’s view of customers.
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* A client like the loan application may either work with objects of the {@link CustomerRole} class, using the interface class
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* {@link Customer}, or with objects of concrete {@link CustomerRole} subclasses. Suppose the loan application knows a particular
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* {@link Customer} instance through its {@link Customer} interface. The loan application may want to check whether the {@link Customer}
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* object plays the role of Borrower.
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* To this end it calls {@link Customer#hasRole(Role)} with a suitable role specification. For the purpose of
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* our example, let’s assume we can name roles with enum.
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* If the {@link Customer} object can play the role named “Borrower,” the loan application will ask it
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* to return a reference to the corresponding object.
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* The loan application may now use this reference to call Borrower-specific operations.
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*/
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public class ApplicationRoleObject {
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private static final Logger logger = LoggerFactory.getLogger(Role.class);
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public static void main(String[] args) {
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Customer customer = Customer.newCustomer(Borrower, Investor);
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logger.info(" the new customer created : {}", customer);
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boolean hasBorrowerRole = customer.hasRole(Borrower);
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logger.info(" customer has a borrowed role - {}", hasBorrowerRole);
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boolean hasInvestorRole = customer.hasRole(Investor);
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logger.info(" customer has an investor role - {}", hasInvestorRole);
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customer.getRole(Investor, InvestorRole.class)
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.ifPresent(inv -> {
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inv.setAmountToInvest(1000);
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inv.setName("Billy");
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});
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customer.getRole(Borrower, BorrowerRole.class)
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.ifPresent(inv -> inv.setName("Johny"));
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customer.getRole(Investor, InvestorRole.class)
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.map(InvestorRole::invest)
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.ifPresent(logger::info);
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customer.getRole(Borrower, BorrowerRole.class)
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.map(BorrowerRole::borrow)
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.ifPresent(logger::info);
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}
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}
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