Adding JacksonJsUtils.toArrayNode()

pom.xml

@@ -221,6 +221,7 @@
 
 		<!-- Required by 
 		  uk.ac.ebi.utils.opt.config
+		  uk.ac.ebi.utils.opt.json
 		-->
 		<dependency>
 			<groupId>com.fasterxml.jackson.dataformat</groupId>

revision-history.md

@@ -1,12 +1,13 @@
 # Revision History
 
-*This file was last revised on 2024-04-15*. **Please keep this note updated**.
+*This file was last revised on 2024-05-13*. **Please keep this note updated**.
 
 ## 14.1-SNAPSHOT
 * `ChainExecutor.andThen()` added (to be tested).
 * `StreamUtils.sampleStream()` added.
 * `uk.ac.ebi.utils.statistics.FisherExact` imported from the USeq project.
-* `CollectionUtils`, adding functions to copy collections and make them read-only.
+* `CollectionUtils`, adding functions to copy collections and making them read-only.
+* `JacksonJsUtils.toArrayNode()` added.
 
 ## 14.0.1
 * Various dependency upgrades.

src/main/java/uk/ac/ebi/utils/opt/json/JacksonJsUtils.java

@@ -0,0 +1,63 @@
+package uk.ac.ebi.utils.opt.json;
+
+import static java.util.stream.Collector.Characteristics.IDENTITY_FINISH;
+import static java.util.stream.Collector.Characteristics.UNORDERED;
+
+import java.util.function.BiConsumer;
+import java.util.stream.Collector;
+import java.util.stream.Collector.Characteristics;
+import java.util.stream.Stream;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+
+/**
+ * JSON utils based on the Jackson library.
+ *
+ * @author Marco Brandizi
+ * <dl><dt>Date:</dt><dd>13 May 2024</dd></dl>
+ *
+ */
+public class JacksonJsUtils
+{
+
+	/**
+	 * Returns a collector (i.e., for {@link Stream#collect(Collector)} and the like) that
+	 * collects the elements of type T into an {@link ArrayNode}.
+	 * 
+	 * This is a serialised collector, which requires synchronisation when elements are accumulated (ie, 
+	 * it doesn't have {@link Characteristics#CONCURRENT}.
+	 * 
+	 * At the same time, it's an {@link Characteristics#UNORDERED} and {@link Characteristics#IDENTITY_FINISH}
+	 * collector.
+	 * 
+	 * @param objectMapper the mapper where the {@link ObjectMapper#createArrayNode()} is taken.
+	 * @param accumulator method to add an element to a node. This is typically an addXXX() method
+	 * from {@link ArrayNode}.
+	 * 
+	 * TODO: tests
+	 * 
+	 */
+	public static <T> Collector<T, ArrayNode, ArrayNode> toArrayNode ( 
+		ObjectMapper objectMapper, BiConsumer<ArrayNode, T> accumulator
+	)
+	{
+		return Collector.<T, ArrayNode> of (
+			objectMapper::createArrayNode,
+			accumulator,
+			ArrayNode::addAll,
+			UNORDERED
+		);
+	}
+
+	/**
+	 * Flavour that uses {@link ArrayNode#add(JsonNode)} 
+	 */
+	public static Collector<JsonNode, ArrayNode, ArrayNode> toArrayNode ( 
+		ObjectMapper objectMapper
+	)
+	{
+		return toArrayNode ( objectMapper, ArrayNode::add );
+	}	
+}