#355 document, abstract base, traits and example domain

abstract-document/src/main/java/com/iluwatar/abstractdocument/AbstractDocument.java

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+package com.iluwatar.abstractdocument;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+public abstract class AbstractDocument implements Document {
+
+	private final Map<String, Object> properties;
+
+	protected AbstractDocument(Map<String, Object> properties) {
+		Objects.requireNonNull(properties, "properties map is required");
+		this.properties = properties;
+	}
+
+	@Override
+	public Void put(String key, Object value) {
+		properties.put(key, value);
+		return null;
+	}
+
+	@Override
+	public Object get(String key) {
+		return properties.get(key);
+	}
+
+	@Override
+	public <T> Stream<T> children(String key, Function<Map<String, Object>, T> constructor) {
+		return Stream.of(get(key))
+				.filter(el -> el != null)
+				.map(el -> (List<Map<String, Object>>) el)
+				.findFirst().get().stream()
+				.map(constructor);
+	}
+
+}

abstract-document/src/main/java/com/iluwatar/abstractdocument/Document.java

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+package com.iluwatar.abstractdocument;
+
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+public interface Document {
+
+	/**
+	 * Puts the value related to the key
+	 * 
+	 * @param key
+	 * @param value
+	 * @return Void
+	 */
+	Void put(String key, Object value);
+
+	/**
+	 * Gets the value for the key
+	 * 
+	 * @param key
+	 * @return value or null
+	 */
+	Object get(String key);
+
+	/**
+	 * Gets the stream of child documents
+	 * 
+	 * @param key
+	 * @param constructor
+	 * @return child documents
+	 */
+	<T> Stream<T> children(String key, Function<Map<String, Object>, T> constructor);
+}

abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Car.java

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+package com.iluwatar.abstractdocument.domain;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import com.iluwatar.abstractdocument.AbstractDocument;
+
+public class Car extends AbstractDocument implements HasModel, HasPrice, HasParts {
+
+	protected Car() {
+		super(new HashMap<String, Object>());
+	}
+	
+	protected Car(Map<String,Object> properties) {
+		super(properties);
+	}
+
+}

abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasModel.java

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+package com.iluwatar.abstractdocument.domain;
+
+import java.util.Optional;
+
+import com.iluwatar.abstractdocument.Document;
+
+public interface HasModel extends Document {
+	
+	default Optional<String> getModel() {
+		return Optional.ofNullable((String) get("model"));
+	}
+
+}

abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasParts.java

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+package com.iluwatar.abstractdocument.domain;
+
+import java.util.stream.Stream;
+
+import com.iluwatar.abstractdocument.Document;
+
+public interface HasParts extends Document {
+	
+	default Stream<Part> getParts() {
+		return children("parts", Part::new);
+	}
+
+}

abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasPrice.java

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+package com.iluwatar.abstractdocument.domain;
+
+import java.util.Optional;
+
+import com.iluwatar.abstractdocument.Document;
+
+public interface HasPrice extends Document {
+	
+	default Optional<Number> getPartner() {
+		return Optional.ofNullable((Number) get("price"));
+	}
+
+}

abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Part.java

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+package com.iluwatar.abstractdocument.domain;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import com.iluwatar.abstractdocument.AbstractDocument;
+
+public class Part extends AbstractDocument implements HasModel, HasPrice {
+
+	protected Part() {
+		super(new HashMap<String, Object>());
+	}
+	
+	protected Part(Map<String, Object> properties) {
+		super(properties);
+	}
+
+}