Implement jumpToItem in JsonItemReader

Author: jpraet

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/GsonJsonObjectReader.java

@@ -102,4 +102,11 @@ public void close() throws Exception {
 		this.jsonReader.close();
 	}
 
+	@Override
+	public void jumpToItem(int itemIndex) throws Exception {
+		for (int i = 0; i < itemIndex; i++) {
+			this.jsonReader.skipValue();
+		}
+	}
+
 }

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JacksonJsonObjectReader.java

@@ -98,4 +98,13 @@ public void close() throws Exception {
 		this.jsonParser.close();
 	}
 
+	@Override
+	public void jumpToItem(int itemIndex) throws Exception {
+		for (int i = 0; i < itemIndex; i++) {
+			if (this.jsonParser.nextToken() == JsonToken.START_OBJECT) {
+				this.jsonParser.skipChildren();
+			}
+		}
+	}
+
 }

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JsonItemReader.java

@@ -136,4 +136,9 @@ protected void doClose() throws Exception {
 		this.jsonObjectReader.close();
 	}
 
+	@Override
+	protected void jumpToItem(int itemIndex) throws Exception {
+		this.jsonObjectReader.jumpToItem(itemIndex);
+	}
+	
 }

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JsonObjectReader.java

@@ -54,4 +54,18 @@ default void close() throws Exception {
 
 	}
 
+	/**
+	 * Move to the given item index. Subclasses should override this method if there is a
+	 * more efficient way of moving to given index than re-reading the input using
+	 * {@link #read()}.
+	 * @param itemIndex index of item (0 based) to jump to.
+	 * @throws Exception Allows subclasses to throw checked exceptions for interpretation
+	 * by the framework
+	 */
+	default void jumpToItem(int itemIndex) throws Exception {
+		for (int i = 0; i < itemIndex; i++) {
+			read();
+		}
+	}
+
 }