GH-10058: Add SpEL JSON accessors and converter with Jackson 3

spring-integration-core/src/main/java/org/springframework/integration/json/JacksonIndexAccessor.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2025-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.json;
+
+import org.jspecify.annotations.Nullable;
+import tools.jackson.databind.node.ArrayNode;
+
+import org.springframework.expression.AccessException;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.IndexAccessor;
+import org.springframework.expression.TypedValue;
+
+/**
+ * A SpEL {@link IndexAccessor} that knows how to read indexes from JSON arrays, using
+ * Jackson's {@link ArrayNode} API.
+ *
+ * <p>Supports indexes supplied as an integer literal &mdash; for example, {@code myJsonArray[1]}.
+ * Also supports negative indexes &mdash; for example, {@code myJsonArray[-1]} which equates
+ * to {@code myJsonArray[myJsonArray.length - 1]}. Furthermore, {@code null} is returned for
+ * any index that is out of bounds (see {@link ArrayNode#get(int)} for details).
+ *
+ * @author Jooyoung Pyoung
+ *
+ * @since 7.0
+ * @see JacksonPropertyAccessor
+ */
+public class JacksonIndexAccessor implements IndexAccessor {
+
+	private static final Class<?>[] SUPPORTED_CLASSES = { ArrayNode.class };
+
+	@Override
+	public Class<?>[] getSpecificTargetClasses() {
+		return SUPPORTED_CLASSES;
+	}
+
+	@Override
+	public boolean canRead(EvaluationContext context, Object target, Object index) {
+		return (target instanceof ArrayNode && index instanceof Integer);
+	}
+
+	@Override
+	public TypedValue read(EvaluationContext context, Object target, Object index) throws AccessException {
+		ArrayNode arrayNode = (ArrayNode) target;
+		Integer intIndex = (Integer) index;
+		if (intIndex < 0) {
+			// negative index: get from the end of array, for compatibility with JacksonPropertyAccessor.ArrayNodeAsList.
+			intIndex = arrayNode.size() + intIndex;
+		}
+		return JacksonPropertyAccessor.typedValue(arrayNode.get(intIndex));
+	}
+
+	@Override
+	public boolean canWrite(EvaluationContext context, Object target, Object index) {
+		return false;
+	}
+
+	@Override
+	public void write(EvaluationContext context, Object target, Object index, @Nullable Object newValue) {
+		throw new UnsupportedOperationException("Write is not supported");
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/json/JacksonPropertyAccessor.java

@@ -0,0 +1,314 @@
+/*
+ * Copyright 2025-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.json;
+
+import java.util.AbstractList;
+import java.util.Iterator;
+
+import org.jspecify.annotations.Nullable;
+import tools.jackson.core.JacksonException;
+import tools.jackson.databind.JsonNode;
+import tools.jackson.databind.ObjectMapper;
+import tools.jackson.databind.json.JsonMapper;
+import tools.jackson.databind.node.ArrayNode;
+import tools.jackson.databind.node.NullNode;
+
+import org.springframework.expression.AccessException;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.PropertyAccessor;
+import org.springframework.expression.TypedValue;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * A SpEL {@link PropertyAccessor} that knows how to read properties from JSON objects.
+ * <p>Uses Jackson {@link JsonNode} API for nested properties access.
+ *
+ * @author Jooyoung Pyoung
+ *
+ * @since 7.0
+ * @see JacksonIndexAccessor
+ */
+public class JacksonPropertyAccessor implements PropertyAccessor {
+
+	/**
+	 * The kind of types this can work with.
+	 */
+	private static final Class<?>[] SUPPORTED_CLASSES =
+			{
+					String.class,
+					JsonNodeWrapper.class,
+					JsonNode.class
+			};
+
+	private ObjectMapper objectMapper = JsonMapper.builder()
+			.findAndAddModules(JacksonPropertyAccessor.class.getClassLoader())
+			.build();
+
+	public void setObjectMapper(ObjectMapper objectMapper) {
+		Assert.notNull(objectMapper, "'objectMapper' cannot be null");
+		this.objectMapper = objectMapper;
+	}
+
+	@Override
+	public Class<?>[] getSpecificTargetClasses() {
+		return SUPPORTED_CLASSES;
+	}
+
+	@Override
+	public boolean canRead(EvaluationContext context, Object target, String name) throws AccessException {
+		JsonNode node;
+		try {
+			node = asJson(target);
+		}
+		catch (AccessException e) {
+			// Cannot parse - treat as not a JSON
+			return false;
+		}
+		if (node instanceof ArrayNode) {
+			return maybeIndex(name) != null;
+		}
+		return true;
+	}
+
+	private JsonNode asJson(Object target) throws AccessException {
+		if (target instanceof JsonNode jsonNode) {
+			return jsonNode;
+		}
+		else if (target instanceof JsonNodeWrapper<?> jsonNodeWrapper) {
+			return jsonNodeWrapper.getRealNode();
+		}
+		else if (target instanceof String content) {
+			try {
+				return this.objectMapper.readTree(content);
+			}
+			catch (JacksonException e) {
+				throw new AccessException("Exception while trying to deserialize String", e);
+			}
+		}
+		else {
+			throw new IllegalStateException("Can't happen. Check SUPPORTED_CLASSES");
+		}
+	}
+
+	/**
+	 * Return an integer if the String property name can be parsed as an int, or null otherwise.
+	 */
+	private static Integer maybeIndex(String name) {
+		if (!isNumeric(name)) {
+			return null;
+		}
+		try {
+			return Integer.valueOf(name);
+		}
+		catch (NumberFormatException e) {
+			return null;
+		}
+	}
+
+	@Override
+	public TypedValue read(EvaluationContext context, @Nullable Object target, String name) throws AccessException {
+		JsonNode node = asJson(target);
+		Integer index = maybeIndex(name);
+		if (index != null && node.has(index)) {
+			return typedValue(node.get(index));
+		}
+		else {
+			return typedValue(node.get(name));
+		}
+	}
+
+	@Override
+	public boolean canWrite(EvaluationContext context, Object target, String name) {
+		return false;
+	}
+
+	@Override
+	public void write(EvaluationContext context, Object target, String name, Object newValue) {
+		throw new UnsupportedOperationException("Write is not supported");
+	}
+
+	/**
+	 * Check if the string is a numeric representation (all digits) or not.
+	 */
+	private static boolean isNumeric(String str) {
+		if (!StringUtils.hasLength(str)) {
+			return false;
+		}
+		int length = str.length();
+		for (int i = 0; i < length; i++) {
+			if (!Character.isDigit(str.charAt(i))) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	static TypedValue typedValue(JsonNode json) throws AccessException {
+		if (json == null || json instanceof NullNode) {
+			return TypedValue.NULL;
+		}
+		else if (json.isValueNode()) {
+			return new TypedValue(getValue(json));
+		}
+		return new TypedValue(wrap(json));
+	}
+
+	private static Object getValue(JsonNode json) throws AccessException {
+		if (json.isString()) {
+			return json.asString();
+		}
+		else if (json.isNumber()) {
+			return json.numberValue();
+		}
+		else if (json.isBoolean()) {
+			return json.asBoolean();
+		}
+		else if (json.isNull()) {
+			return null;
+		}
+		else if (json.isBinary()) {
+			try {
+				return json.binaryValue();
+			}
+			catch (JacksonException e) {
+				throw new AccessException(
+						"Can not get content of binary value: " + json, e);
+			}
+		}
+		throw new IllegalArgumentException("Json is not ValueNode.");
+	}
+
+	public static Object wrap(JsonNode json) throws AccessException {
+		if (json == null) {
+			return null;
+		}
+		else if (json instanceof ArrayNode arrayNode) {
+			return new ArrayNodeAsList(arrayNode);
+		}
+		else if (json.isValueNode()) {
+			return getValue(json);
+		}
+		else {
+			return new ComparableJsonNode(json);
+		}
+	}
+
+	interface JsonNodeWrapper<T> extends Comparable<T> {
+
+		JsonNode getRealNode();
+
+	}
+
+	static class ComparableJsonNode implements JsonNodeWrapper<ComparableJsonNode> {
+
+		private final JsonNode delegate;
+
+		ComparableJsonNode(JsonNode delegate) {
+			this.delegate = delegate;
+		}
+
+		@Override
+		public JsonNode getRealNode() {
+			return this.delegate;
+		}
+
+		@Override
+		public String toString() {
+			return this.delegate.toString();
+		}
+
+		@Override
+		public int compareTo(ComparableJsonNode o) {
+			return this.delegate.equals(o.delegate) ? 0 : 1;
+		}
+
+	}
+
+	/**
+	 * An {@link AbstractList} implementation around {@link ArrayNode} with {@link JsonNodeWrapper} aspect.
+	 * @since 5.0
+	 */
+	static class ArrayNodeAsList extends AbstractList<Object> implements JsonNodeWrapper<Object> {
+
+		private final ArrayNode delegate;
+
+		ArrayNodeAsList(ArrayNode node) {
+			this.delegate = node;
+		}
+
+		@Override
+		public JsonNode getRealNode() {
+			return this.delegate;
+		}
+
+		@Override
+		public String toString() {
+			return this.delegate.toString();
+		}
+
+		@Override
+		public Object get(int index) {
+			// negative index - get from the end of list
+			int i = index < 0 ? this.delegate.size() + index : index;
+			try {
+				return wrap(this.delegate.get(i));
+			}
+			catch (AccessException ex) {
+				throw new IllegalArgumentException(ex);
+			}
+		}
+
+		@Override
+		public int size() {
+			return this.delegate.size();
+		}
+
+		@Override
+		public Iterator<Object> iterator() {
+
+			return new Iterator<>() {
+
+				private final Iterator<JsonNode> it = ArrayNodeAsList.this.delegate.iterator();
+
+				@Override
+				public boolean hasNext() {
+					return this.it.hasNext();
+				}
+
+				@Override
+				public Object next() {
+					try {
+						return wrap(this.it.next());
+					}
+					catch (AccessException e) {
+						throw new IllegalArgumentException(e);
+					}
+				}
+
+			};
+		}
+
+		@Override
+		public int compareTo(Object o) {
+			Object that = (o instanceof JsonNodeWrapper<?> wrapper ? wrapper.getRealNode() : o);
+			return this.delegate.equals(that) ? 0 : 1;
+		}
+
+	}
+
+}