Add abstraction for a CoffeeNet view model

Multiple parts of CoffeeNet contribute UI/UX components to the final
application. This abstraction allows to write these in a
technology-agnostic way.

coffeenet-platform-domain/pom.xml

@@ -22,6 +22,12 @@
     </description>
 
     <dependencies>
+        <!-- Runtime dependencies -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-annotations</artifactId>
+        </dependency>
+
         <!-- Test -->
         <dependency>
             <groupId>org.springframework.boot</groupId>

coffeenet-platform-domain/src/main/java/rocks/coffeenet/platform/domain/web/CoffeeNetModel.java

@@ -0,0 +1,109 @@
+package rocks.coffeenet.platform.domain.web;
+
+import com.fasterxml.jackson.annotation.JsonAnyGetter;
+
+import java.util.AbstractMap;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+
+
+/**
+ * This view model makes common attributes available to the view layer in web applications. It is made available under
+ * the name {@link CoffeeNetModel#MODEL_NAME}.
+ *
+ * <p>Each attribute element can be singular or a hierarchical object like a POJO or nested Map.</p>
+ *
+ * @author  Florian 'punycode' Krupicka - [email protected]
+ */
+public class CoffeeNetModel extends AbstractMap<String, Object> {
+
+    public static final String MODEL_NAME = "coffeenet";
+
+    private final Map<String, Object> attributes;
+
+    private CoffeeNetModel(Builder builder) {
+
+        this.attributes = Collections.unmodifiableMap(builder.content);
+    }
+
+    @Override
+    public Set<Entry<String, Object>> entrySet() {
+
+        return attributes.entrySet();
+    }
+
+
+    @JsonAnyGetter
+    Map<String, Object> getAttributes() {
+
+        return attributes;
+    }
+
+
+    @Override
+    public boolean equals(Object o) {
+
+        if (this == o) {
+            return true;
+        }
+
+        if (o == null || getClass() != o.getClass() || !super.equals(o)) {
+            return false;
+        }
+
+        return Objects.equals(attributes, ((CoffeeNetModel) o).attributes);
+    }
+
+
+    @Override
+    public int hashCode() {
+
+        return Objects.hash(super.hashCode(), attributes);
+    }
+
+    /**
+     * Builder for creating immutable {@link CoffeeNetModel} instances.
+     */
+    public static class Builder {
+
+        private final Map<String, Object> content;
+
+        public Builder() {
+
+            this.content = new LinkedHashMap<>();
+        }
+
+        /**
+         * Contribute a view model property using given {@code key} and {@code value}.
+         */
+        public Builder withDetail(String key, Object value) {
+
+            this.content.put(key, value);
+
+            return this;
+        }
+
+
+        /**
+         * Contribute multiple view model properties given the contents of {@code details}.
+         */
+        public Builder withDetails(Map<String, Object> details) {
+
+            this.content.putAll(details);
+
+            return this;
+        }
+
+
+        /**
+         * Create a new {@link CoffeeNetModel} instance based on the state of this builder.
+         */
+        public CoffeeNetModel build() {
+
+            return new CoffeeNetModel(this);
+        }
+    }
+}

coffeenet-platform-domain/src/main/java/rocks/coffeenet/platform/domain/web/CoffeeNetModelContributor.java

@@ -0,0 +1,17 @@
+package rocks.coffeenet.platform.domain.web;
+
+/**
+ * Contributes additional properties to the global COLA view model.
+ *
+ * @author  Florian 'punycode' Krupicka - [email protected]
+ */
+@FunctionalInterface
+public interface CoffeeNetModelContributor {
+
+    /**
+     * Contribute parameters.
+     *
+     * @param  builder
+     */
+    void contribute(CoffeeNetModel.Builder builder);
+}

coffeenet-platform-domain/src/test/java/rocks/coffeenet/platform/domain/web/CoffeeNetModelContributorTests.java

@@ -0,0 +1,86 @@
+package rocks.coffeenet.platform.domain.web;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
+
+
+/**
+ * @author  Florian 'punycode' Krupicka - [email protected]
+ */
+class CoffeeNetModelContributorTests {
+
+    private CoffeeNetModel.Builder builder;
+
+    @BeforeEach
+    void setup() {
+
+        builder = new CoffeeNetModel.Builder();
+    }
+
+
+    @Test
+    @DisplayName("should add singular detail from contributer")
+    void singularDetail() {
+
+        CoffeeNetModelContributor c = (b) -> b.withDetail("single", "value");
+
+        c.contribute(builder);
+
+        CoffeeNetModel model = builder.build();
+        assertThat(model).containsExactly(entry("single", "value"));
+    }
+
+
+    @Test
+    @DisplayName("should add complex detail from contributer")
+    void complexDetail() {
+
+        Map<String, Object> complex = Collections.singletonMap("key", "value");
+        CoffeeNetModelContributor c = (b) -> b.withDetail("complex", complex);
+
+        c.contribute(builder);
+
+        CoffeeNetModel model = builder.build();
+        assertThat(model).contains(entry("complex", complex));
+    }
+
+
+    @Test
+    @DisplayName("should add details from multiple contributers")
+    void multipleContributors() {
+
+        CoffeeNetModelContributor c1 = (b) -> b.withDetail("key1", "value1");
+        CoffeeNetModelContributor c2 = (b) -> b.withDetail("key2", "value2");
+
+        c1.contribute(builder);
+        c2.contribute(builder);
+
+        CoffeeNetModel model = builder.build();
+        assertThat(model).contains(entry("key2", "value2"), entry("key1", "value1"));
+    }
+
+
+    @Test
+    @DisplayName("should add multiple details from contributer")
+    void multipleDetails() {
+
+        HashMap<String, Object> map = new HashMap<>();
+        map.put("key1", "value1");
+        map.put("key2", "value2");
+
+        CoffeeNetModelContributor c = (b) -> b.withDetails(map);
+
+        c.contribute(builder);
+
+        CoffeeNetModel model = builder.build();
+        assertThat(model).containsExactly(entry("key1", "value1"), entry("key2", "value2"));
+    }
+}