feat: add jackson deserializer for FEEL expressions (#525)

core/pom.xml

@@ -21,6 +21,24 @@
       <scope>provided</scope>
     </dependency>
 
+    <dependency>
+      <groupId>org.camunda.feel</groupId>
+      <artifactId>feel-engine</artifactId>
+      <scope>provided</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>com.fasterxml.jackson.module</groupId>
+      <artifactId>jackson-module-scala_3</artifactId>
+      <scope>provided</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>com.fasterxml.jackson.datatype</groupId>
+      <artifactId>jackson-datatype-jsr310</artifactId>
+      <scope>provided</scope>
+    </dependency>
+
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
@@ -43,6 +61,12 @@
       <artifactId>assertj-core</artifactId>
       <scope>test</scope>
     </dependency>
+
+    <dependency>
+      <groupId>org.skyscreamer</groupId>
+      <artifactId>jsonassert</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
 </project>

core/src/main/java/io/camunda/connector/impl/feel/AbstractFeelDeserializer.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://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 io.camunda.connector.impl.feel;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
+import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
+import java.io.IOException;
+
+public abstract class AbstractFeelDeserializer<T> extends StdDeserializer<T>
+    implements ContextualDeserializer {
+  protected FeelEngineWrapper feelEngineWrapper;
+
+  protected AbstractFeelDeserializer(FeelEngineWrapper feelEngineWrapper) {
+    super(String.class);
+    this.feelEngineWrapper = feelEngineWrapper;
+  }
+
+  @Override
+  public T deserialize(JsonParser parser, DeserializationContext context) throws IOException {
+    JsonNode node = parser.getCodec().readTree(parser);
+
+    if (node != null && node.isTextual()) {
+      String value = node.textValue();
+      if (isFeelExpression(value)) {
+        return doDeserialize(value);
+      }
+    }
+    throw new IOException(
+        "Invalid input: expected a FEEL expression, but got '" + node + "' instead.");
+  }
+
+  private boolean isFeelExpression(String value) {
+    return value.startsWith("=");
+  }
+
+  protected abstract T doDeserialize(String expression);
+}

core/src/main/java/io/camunda/connector/impl/feel/FEEL.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://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 io.camunda.connector.impl.feel;
+
+import com.fasterxml.jackson.annotation.JacksonAnnotationsInside;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** A shortcut for {@link JsonDeserialize} with {@link FeelDeserializer}. */
+@Retention(RetentionPolicy.RUNTIME)
+@JacksonAnnotationsInside
+@JsonDeserialize(using = FeelDeserializer.class)
+public @interface FEEL {}

core/src/main/java/io/camunda/connector/impl/feel/FeelConnectorFunctionProvider.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://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 io.camunda.connector.impl.feel;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.camunda.feel.context.Context;
+import org.camunda.feel.context.JavaFunction;
+import org.camunda.feel.context.JavaFunctionProvider;
+import org.camunda.feel.syntaxtree.Val;
+import org.camunda.feel.syntaxtree.ValContext;
+import org.camunda.feel.syntaxtree.ValString;
+import scala.collection.immutable.Map;
+import scala.collection.immutable.Map$;
+
+/** Provider of Connector-related FEEL functions like 'bpmnError'. */
+public class FeelConnectorFunctionProvider extends JavaFunctionProvider {
+
+  private static final String BPMN_ERROR_FUNCTION_NAME = "bpmnError";
+  private static final List<String> BPMN_ERROR_ARGUMENTS = List.of("code", "message");
+  private static final JavaFunction BPMN_ERROR_FUNCTION =
+      new JavaFunction(
+          BPMN_ERROR_ARGUMENTS,
+          args ->
+              new ValContext(
+                  new Context.StaticContext(
+                      new Map.Map2<>(
+                          BPMN_ERROR_ARGUMENTS.get(0),
+                          toString(args, 0),
+                          BPMN_ERROR_ARGUMENTS.get(1),
+                          toString(args, 1)),
+                      Map$.MODULE$.empty())));
+
+  private static final java.util.Map<String, JavaFunction> functions =
+      java.util.Map.of(BPMN_ERROR_FUNCTION_NAME, BPMN_ERROR_FUNCTION);
+
+  @Override
+  public Optional<JavaFunction> resolveFunction(String functionName) {
+    return Optional.ofNullable(functions.get(functionName));
+  }
+
+  @Override
+  public Collection<String> getFunctionNames() {
+    return List.of(BPMN_ERROR_FUNCTION_NAME);
+  }
+
+  private static String toString(List<Val> arguments, int index) {
+    Val value = arguments.get(index);
+    if (value instanceof ValString) {
+      return ((ValString) value).value();
+    }
+    throw new IllegalArgumentException(
+        String.format(
+            "Parameter '%s' of function '%s' must be a String",
+            BPMN_ERROR_ARGUMENTS.get(index), BPMN_ERROR_FUNCTION_NAME));
+  }
+}

core/src/main/java/io/camunda/connector/impl/feel/FeelDeserializer.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://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 io.camunda.connector.impl.feel;
+
+import com.fasterxml.jackson.databind.BeanProperty;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import java.util.Map;
+
+/**
+ * A Jackson deserializer for FEEL expressions. It can be used to deserialize a string that contains
+ * a FEEL expression, e.g. in inbound connector properties. NB: for outbound connectors, FEEL
+ * expressions in connector variables are evaluated by Zeebe, so this deserializer is not needed.
+ */
+public class FeelDeserializer extends AbstractFeelDeserializer<Object> {
+
+  private final Class<?> outputType;
+  private static final FeelEngineWrapper FEEL_ENGINE_WRAPPER = new FeelEngineWrapper();
+
+  public FeelDeserializer() { // needed for references in @JsonDeserialize
+    this(FEEL_ENGINE_WRAPPER, Object.class);
+  }
+
+  protected FeelDeserializer(FeelEngineWrapper feelEngineWrapper, Class<?> outputType) {
+    super(feelEngineWrapper);
+    this.outputType = outputType;
+  }
+
+  @Override
+  protected Object doDeserialize(String expression) {
+    return FEEL_ENGINE_WRAPPER.evaluate(expression, Map.of(), outputType);
+  }
+
+  @Override
+  public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property) {
+    return new FeelDeserializer(FEEL_ENGINE_WRAPPER, property.getType().getRawClass());
+  }
+}