ignore avro-specific fields if avro is in the classpath

closes gh-2402

Signed-off-by: Emanuel Trandafir <emanueltrandafir1993@gmail.com>

Author: etrandafir93

spring-cloud-contract-verifier/pom.xml

@@ -286,6 +286,12 @@
 			<version>1.12.1</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.avro</groupId>
+			<artifactId>avro</artifactId>
+			<version>1.12.1</version>
+			<scope>provided</scope>
+		</dependency>
 	</dependencies>
 	<build>
 		<plugins>

spring-cloud-contract-verifier/src/main/java/org/springframework/cloud/contract/verifier/messaging/internal/ContractVerifierObjectMapper.java

@@ -16,24 +16,27 @@
 
 package org.springframework.cloud.contract.verifier.messaging.internal;
 
+import org.springframework.util.ClassUtils;
+
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+
 import tools.jackson.databind.json.JsonMapper;
 
 /**
  * Wrapper over {@link JsonMapper} that won't try to parse String but will directly return
  * it.
- *
  * @author Marcin Grzejszczak
  */
 public class ContractVerifierObjectMapper {
 
 	private final JsonMapper objectMapper;
 
-	public ContractVerifierObjectMapper(JsonMapper objectMapper) {
-		this.objectMapper = objectMapper;
+	public ContractVerifierObjectMapper() {
+		this(new JsonMapper());
 	}
 
-	public ContractVerifierObjectMapper() {
-		this.objectMapper = new JsonMapper();
+	public ContractVerifierObjectMapper(JsonMapper mapper) {
+		this.objectMapper = usesAvro() ? ignoreAvroFields(mapper) : mapper;
 	}
 
 	public String writeValueAsString(Object payload) {
@@ -56,4 +59,23 @@ else if (payload instanceof byte[]) {
 		return this.objectMapper.writeValueAsBytes(payload);
 	}
 
+	private static boolean usesAvro() {
+		return ClassUtils.isPresent("org.apache.avro.specific.SpecificRecordBase", null);
+	}
+
+	private static JsonMapper ignoreAvroFields(JsonMapper mapper) {
+		try {
+			return mapper.rebuild().addMixIn(
+					ClassUtils.forName("org.apache.avro.specific.SpecificRecordBase",
+							null), IgnoreAvroMixin.class).build();
+		}
+		catch (ClassNotFoundException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	@JsonIgnoreProperties({ "schema", "specificData", "classSchema", "conversion" })
+	interface IgnoreAvroMixin {
+	}
+
 }