Added first draft of Visitor pattern. Needs cleaning up.

Author: gazbert

README.md

@@ -23,6 +23,7 @@ Any comments/bugs/better ways of doing things, send 'em my way.
 1. Observer
 1. Command
 1. Template Method
+1. Visitor
 
 ### Creational Patterns
 
@@ -36,9 +37,4 @@ Any comments/bugs/better ways of doing things, send 'em my way.
 
 1. Adapter
 1. Decorator
-1. Facade
-
-##### Patterns coming soon...
-
-1. Proxy
-1. Interpreter
+1. Facade

src/main/java/com/gazbert/patterns/behavioural/visitor/AbstractTrade.java

@@ -0,0 +1,89 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+import java.math.BigDecimal;
+
+/**
+ * A domain class that represents a Trade in our class hierarchy/object graph.
+ *
+ * It is a Concrete Element and holds the Object Structure: it holds references to ALL objects that can be visited -
+ * this allows us to iterate through and 'visit' them in the accept method.
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+public abstract class AbstractTrade implements Trade { // Trade interface modified to extend Visitable
+
+    private String currency;
+    private BigDecimal price;
+
+    private BuyOrder buyOrder;
+    private SellOrder sellOrder;
+    private TransactionFee fee;
+
+
+    public AbstractTrade(String currency, BigDecimal amount) {
+
+        this.currency = currency;
+        this.price = amount;
+
+        // do all existing functionality...
+        buyOrder = new BuyOrder();
+        sellOrder = new SellOrder();
+        fee = new TransactionFee();
+    }
+
+    public BigDecimal getPrice() {
+        return price;
+    }
+
+    public String getCurrency() {
+        return currency;
+    }
+
+    public TransactionFee getFee() {
+        return fee;
+    }
+
+    /*
+     * The new Visitor method. We iterate through the object graph/hierarchy to 'visit' them.
+     */
+    @Override
+    public void accept(TradeVisitor visitor) {
+
+        // visit each component first - this just sets the Visitor on each of Elements in our Trade object graph
+        // - nothing happens yet...
+        buyOrder.accept(visitor);
+        sellOrder.accept(visitor);
+
+        // then we visit the receiver - the double dispatch (callback on invoker) - this triggers the Visitor logic
+        // on all of our Elements in the Trade object graph.
+        visitor.visit(this);
+    }
+
+    public String toString() {
+        return getClass().getName() + " : Price= " + this.getPrice();
+    }
+}

src/main/java/com/gazbert/patterns/behavioural/visitor/AbstractTradePart.java

@@ -0,0 +1,58 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+import java.math.BigDecimal;
+
+/**
+ * The base domain class that makes up part of a Trade in our class hierarchy/object graph.
+ *
+ * Does not form part of Visitor pattern per se.
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+public abstract class AbstractTradePart {
+
+    private BigDecimal price;
+    private String currency;
+    // etc... etc..
+
+
+    public String getCurrency() {
+        return currency;
+    }
+
+    public void setCurrency(String currency) {
+        this.currency = currency;
+    }
+
+    public BigDecimal getPrice() {
+        return price;
+    }
+
+    public void setPrice(BigDecimal price) {
+        this.price = price;
+    }
+}

src/main/java/com/gazbert/patterns/behavioural/visitor/BuyOrder.java

@@ -0,0 +1,43 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+/**
+ * A domain class that makes up part of a Trade in our class hierarchy/object graph.
+ *
+ * It is a Concrete Element.
+ *
+ * It has been modified to implement the Visitable (Element).
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+// public class BuyOrder extends AbstractTradePart { // here previously
+public class BuyOrder extends AbstractTradePart implements Visitable {
+
+    @Override
+    public void accept(TradeVisitor visitor) {
+        visitor.visit(this); // makes callback to the Visitor
+    }
+}

src/main/java/com/gazbert/patterns/behavioural/visitor/FuturesTrade.java

@@ -0,0 +1,39 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+import java.math.BigDecimal;
+
+/**
+ * A Futures trade domain object.
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+public class FuturesTrade extends AbstractTrade {
+
+    public FuturesTrade(String currency, BigDecimal amount) {
+        super(currency, amount);
+    }
+}

src/main/java/com/gazbert/patterns/behavioural/visitor/SellOrder.java

@@ -0,0 +1,43 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+/**
+ * A domain class that makes up part of a Trade in our class hierarchy/object graph.
+ *
+ * It is a Concrete Element.
+ *
+ * It has been modified to implement the Visitable (Element).
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+// public class SellOrder extends AbstractTradePart { // here previously
+public class SellOrder extends AbstractTradePart implements Visitable {
+
+    @Override
+    public void accept(TradeVisitor visitor) {
+        visitor.visit(this); // makes callback to the Visitor
+    }
+}

src/main/java/com/gazbert/patterns/behavioural/visitor/SpotTrade.java

@@ -0,0 +1,39 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+import java.math.BigDecimal;
+
+/**
+ * A Spot trade domain object.
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+public class SpotTrade extends AbstractTrade {
+
+    public SpotTrade(String currency, BigDecimal amount) {
+        super(currency, amount);
+    }
+}

src/main/java/com/gazbert/patterns/behavioural/visitor/Trade.java

@@ -0,0 +1,45 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Gareth Jon Lynch
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.gazbert.patterns.behavioural.visitor;
+
+import java.math.BigDecimal;
+
+/**
+ * A domain class that makes up part of a Trade in our class hierarchy/object graph.
+ *
+ * It has been modified to implement the Visitable (Element).
+ *
+ * @author gazbert
+ * @since 2016/02/27
+ */
+// public interface Trade { // here previously
+public interface Trade extends Visitable { // we impl Visitor pattern - we now extend Visitable
+
+    // existing methods
+    BigDecimal getPrice();
+    String getCurrency();
+
+    // new method to accept our Visitor
+    void accept(TradeVisitor visitor);
+}