add pattern

role-object/README.md

@@ -20,14 +20,10 @@ individual objects, different contexts are kept separate and system configuratio
 
 ## Applicability
 Use the Role Object pattern, if:
-- you want to handle a key abstraction in different contexts and you do not want to put the resulting contextspecific interfaces into the same class interface.
-Words: 4895 Page 3 of 11
-- you want to handle the available roles dynamically so that they can be attached and removed on demand, that is
-at runtime, rather than fixing them statically at compile-time.
-- you want to treat the extensions transparently and need to preserve the logical object identity of the resulting
-object conglomerate.
-- you want to keep role/client pairs independent from each other so that changes to a role do not affect clients
-that are not interested in that role.
+- you want to handle a key abstraction in different contexts and you do not want to put the resulting context specific interfaces into the same class interface.
+- you want to handle the available roles dynamically so that they can be attached and removed on demand, that is at runtime, rather than fixing them statically at compile-time.
+- you want to treat the extensions transparently and need to preserve the logical object identity of the resultingobject conglomerate.
+- you want to keep role/client pairs independent from each other so that changes to a role do not affect clients that are not interested in that role.
 
 ## Credits
 - [Hillside - Role object pattern](https://hillside.net/plop/plop97/Proceedings/riehle.pdf)

role-object/pom.xml

@@ -33,6 +33,12 @@
   </parent>
 
   <artifactId>role-object</artifactId>
-  <dependencies/>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 
 </project>

role-object/src/main/java/com/iluwatar/roleobject/ApplicationRoleObject.java

@@ -22,6 +22,11 @@
  */
 package com.iluwatar.roleobject;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import static com.iluwatar.roleobject.Role.*;
+
 /**
  * The Role Object pattern suggests to model context-specific views
  * of an object as separate role objects which are
@@ -34,12 +39,12 @@
  * investor, respectively. Both roles could as well be played by a single Customer object.
  * The common superclass for customer-specific roles is provided by CustomerRole,
  * which also supports the Customer interface.
+ * <p>
  * The CustomerRole class is abstract and not meant to be instantiated.
  * Concrete subclasses of CustomerRole, for example Borrower or Investor,
  * define and implement the interface for specific roles. It is only
  * these subclasses which are instantiated at runtime.
- * The Borrower class defines the context-specific view of
- * Customer objects as needed by the loan department.
+ * The Borrower class defines the context-specific view of Customer objects as needed by the loan department.
  * It defines additional operations to manage the customer’s
  * credits and securities. Similarly, the Investor class adds operations specific
  * to the investment department’s view of customers.
@@ -48,13 +53,40 @@
  * Customer instance through its Customer interface. The loan application may want to check whether the Customer
  * object plays the role of Borrower.
  * To this end it calls hasRole() with a suitable role specification. For the purpose of
- * our example, let’s assume we can name roles with a simple string.
- * If the Customer object can play the role named
- * “Borrower,” the loan application will ask it to return a reference to the corresponding object.
+ * our example, let’s assume we can name roles with enum.
+ * If the Customer object can play the role named “Borrower,” the loan application will ask it to return a reference to the corresponding object.
  * The loan application may now use this reference to call Borrower-specific operations.
- *
  */
 public class ApplicationRoleObject {
+
+    private static final Logger logger = LoggerFactory.getLogger(Role.class);
+
     public static void main(String[] args) {
+        Customer customer = Customer.newCustomer(Borrower, Investor);
+
+        logger.info(" the new customer created : {}", customer);
+
+        boolean hasBorrowerRole = customer.hasRole(Borrower);
+        logger.info(" customer has a borrowed role - {}", hasBorrowerRole);
+        boolean hasInvestorRole = customer.hasRole(Investor);
+        logger.info(" customer has an investor role - {}", hasInvestorRole);
+
+        customer.getRole(Investor, InvestorRole.class)
+                .ifPresent(inv -> {
+                    inv.setAmountToInvest(1000);
+                    inv.setName("Billy");
+                });
+        customer.getRole(Borrower, BorrowerRole.class)
+                .ifPresent(inv -> inv.setName("Johny"));
+
+        customer.getRole(Investor, InvestorRole.class)
+                .map(InvestorRole::invest)
+                .ifPresent(logger::info);
+
+        customer.getRole(Borrower, BorrowerRole.class)
+                .map(BorrowerRole::borrow)
+                .ifPresent(logger::info);
     }
+
+
 }

role-object/src/main/java/com/iluwatar/roleobject/BorrowerRole.java

@@ -1,4 +1,19 @@
 package com.iluwatar.roleobject;
 
 public class BorrowerRole extends CustomerRole{
+    private String name;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String borrow(){
+        return String.join(" ",
+                "A borrower",name,"wants to get some money.");
+    }
+
 }

role-object/src/main/java/com/iluwatar/roleobject/Customer.java

@@ -2,11 +2,56 @@
 
 import java.util.Optional;
 
+/**
+ * The main abstraction to work with Customer.
+ */
 public abstract class Customer {
 
+    /**
+     * Add specific role @see {@link Role}
+     *
+     * @param role to add
+     * @return true if the operation has been successful otherwise false
+     */
     public abstract boolean addRole(Role role);
+
+    /**
+     * Check specific role @see {@link Role}
+     *
+     * @param role to check
+     * @return true if the role exists otherwise false
+     */
+
     public abstract boolean hasRole(Role role);
+
+    /**
+     * Remove specific role @see {@link Role}
+     *
+     * @param role to remove
+     * @return true if the operation has been successful otherwise false
+     */
     public abstract boolean remRole(Role role);
-    public abstract <T extends Customer> Optional<T> getRole(Role role,Class<T> expectedRole);
+
+    /**
+     * Get specific instance associated with this role @see {@link Role}
+     *
+     * @param role         to get
+     * @param expectedRole instance class expected to get
+     * @return optional with value if the instance exists and corresponds expected class
+     */
+    public abstract <T extends Customer> Optional<T> getRole(Role role, Class<T> expectedRole);
+
+
+    public static Customer newCustomer() {
+        return new CustomerCore();
+    }
+
+    public static Customer newCustomer(Role... role) {
+        Customer customer = newCustomer();
+        for (Role r : role) {
+            customer.addRole(r);
+        }
+        return customer;
+    }
 
 }

role-object/src/main/java/com/iluwatar/roleobject/CustomerCore.java

@@ -1,19 +1,30 @@
 package com.iluwatar.roleobject;
 
-import java.util.Map;
-import java.util.Objects;
-import java.util.Optional;
-
+import java.util.*;
+
+/**
+ * Core class to store different customer roles
+ *
+ * @see CustomerRole
+ * Note: not thread safe
+ */
 public class CustomerCore extends Customer {
 
     private Map<Role, CustomerRole> roles;
 
+    public CustomerCore() {
+        roles = new HashMap<>();
+    }
 
     @Override
     public boolean addRole(Role role) {
-        return role.instance()
-                .map(rI -> roles.put(role, rI))
-                .isPresent();
+        return role
+                .instance()
+                .map(inst -> {
+                    roles.put(role, inst);
+                    return true;
+                })
+                .orElse(false);
     }
 
     @Override
@@ -28,8 +39,15 @@ public boolean remRole(Role role) {
 
     @Override
     public <T extends Customer> Optional<T> getRole(Role role, Class<T> expectedRole) {
-        return Optional.ofNullable(roles.get(role))
+        return Optional
+                .ofNullable(roles.get(role))
                 .filter(expectedRole::isInstance)
                 .map(expectedRole::cast);
     }
+
+    @Override
+    public String toString() {
+        String roles = Arrays.toString(this.roles.keySet().toArray());
+        return "Customer{roles=" + roles + "}";
+    }
 }

role-object/src/main/java/com/iluwatar/roleobject/CustomerRole.java

@@ -1,25 +1,6 @@
 package com.iluwatar.roleobject;
 
-import java.util.Optional;
-
-public class CustomerRole extends Customer{
-    @Override
-    public boolean addRole(Role role) {
-        return false;
-    }
-
-    @Override
-    public boolean hasRole(Role role) {
-        return false;
-    }
-
-    @Override
-    public boolean remRole(Role role) {
-        return false;
-    }
-
-    @Override
-    public <T extends Customer> Optional<T> getRole(Role role, Class<T> expectedRole) {
-        return Optional.empty();
-    }
-}
+/**
+ * Key abstraction for segregated roles
+ */
+public abstract class CustomerRole extends CustomerCore{}

role-object/src/main/java/com/iluwatar/roleobject/InvestorRole.java

@@ -1,4 +1,27 @@
 package com.iluwatar.roleobject;
 
-public class InvestorRole extends CustomerRole{
+public class InvestorRole extends CustomerRole {
+    private String name;
+    private long amountToInvest;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public long getAmountToInvest() {
+        return amountToInvest;
+    }
+
+    public void setAmountToInvest(long amountToInvest) {
+        this.amountToInvest = amountToInvest;
+    }
+
+    public String invest() {
+        return String.join(" ",
+                "Investor", name, "has invested", String.valueOf(amountToInvest), "dollars");
+    }
 }

role-object/src/main/java/com/iluwatar/roleobject/Role.java

@@ -2,27 +2,30 @@
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import sun.rmi.runtime.Log;
 
 import java.util.Optional;
 
+/**
+ * Possible roles
+ */
 public enum Role {
     Borrower(BorrowerRole.class), Investor(InvestorRole.class);
 
-    private Class<? extends Customer> typeCst;
+    private Class<? extends CustomerRole> typeCst;
 
-    Role(Class<? extends Customer> typeCst) {
+    Role(Class<? extends CustomerRole> typeCst) {
         this.typeCst = typeCst;
     }
+
     private static final Logger logger = LoggerFactory.getLogger(Role.class);
 
     @SuppressWarnings("unchecked")
-    <T extends CustomerRole>Optional<T> instance(){
-        Class<? extends Customer> typeCst = this.typeCst;
+    public <T extends CustomerRole> Optional<T> instance() {
+        Class<? extends CustomerRole> typeCst = this.typeCst;
         try {
             return (Optional<T>) Optional.of(typeCst.newInstance());
         } catch (InstantiationException | IllegalAccessException e) {
-            logger.error("error creating an object",e);
+            logger.error("error creating an object", e);
         }
         return Optional.empty();
     }

role-object/src/test/java/com/iluwatar/roleobject/ApplicationRoleObjectTest.java

@@ -0,0 +1,13 @@
+package com.iluwatar.roleobject;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class ApplicationRoleObjectTest {
+
+    @Test
+    public void mainTest() {
+        ApplicationRoleObject.main(new String[]{});
+    }
+}

role-object/src/test/java/com/iluwatar/roleobject/BorrowerRoleTest.java

@@ -0,0 +1,18 @@
+package com.iluwatar.roleobject;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class BorrowerRoleTest {
+
+    @Test
+    public void borrowTest() {
+        BorrowerRole borrowerRole = new BorrowerRole();
+        borrowerRole.setName("test");
+        String res = "A borrower test wants to get some money.";
+
+        Assert.assertEquals(borrowerRole.borrow(),res);
+    }
+}