From 0f6038af70434a20fc4112a79c00c411ab88e519 Mon Sep 17 00:00:00 2001
From: Rossen Stoyanchev <rstoyanchev@vmware.com>
Date: Mon, 2 Nov 2020 17:25:39 +0000
Subject: [PATCH] Log can[Se]Deserialize error in Jackson codecs

Closes gh-25892
---
 .../codec/json/AbstractJackson2Decoder.java   | 17 +++++++++--
 .../codec/json/AbstractJackson2Encoder.java   | 20 +++++++++++--
 .../http/codec/json/Jackson2CodecSupport.java | 30 ++++++++++++++++++-
 3 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Decoder.java b/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Decoder.java
index a0b400ef7d0..c6f75a8ffda 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Decoder.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Decoder.java
@@ -21,6 +21,7 @@ import java.lang.annotation.Annotation;
 import java.math.BigDecimal;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
@@ -99,8 +100,20 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 	public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
 		JavaType javaType = getObjectMapper().constructType(elementType.getType());
 		// Skip String: CharSequenceDecoder + "*/*" comes after
-		return (!CharSequence.class.isAssignableFrom(elementType.toClass()) &&
-				getObjectMapper().canDeserialize(javaType) && supportsMimeType(mimeType));
+		if (CharSequence.class.isAssignableFrom(elementType.toClass()) || !supportsMimeType(mimeType)) {
+			return false;
+		}
+		if (!logger.isDebugEnabled()) {
+			return getObjectMapper().canDeserialize(javaType);
+		}
+		else {
+			AtomicReference<Throwable> causeRef = new AtomicReference<>();
+			if (getObjectMapper().canDeserialize(javaType, causeRef)) {
+				return true;
+			}
+			logWarningIfNecessary(javaType, causeRef.get());
+			return false;
+		}
 	}
 
 	@Override
diff --git a/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java b/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java
index 70d9df4c7ed..ae90df4115f 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java
@@ -23,6 +23,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
 
 import com.fasterxml.jackson.core.JsonEncoding;
 import com.fasterxml.jackson.core.JsonGenerator;
@@ -111,8 +112,23 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 				return false;
 			}
 		}
-		return (Object.class == clazz ||
-				(!String.class.isAssignableFrom(elementType.resolve(clazz)) && getObjectMapper().canSerialize(clazz)));
+		if (String.class.isAssignableFrom(elementType.resolve(clazz))) {
+			return false;
+		}
+		if (Object.class == clazz) {
+			return true;
+		}
+		if (!logger.isDebugEnabled()) {
+			return getObjectMapper().canSerialize(clazz);
+		}
+		else {
+			AtomicReference<Throwable> causeRef = new AtomicReference<>();
+			if (getObjectMapper().canSerialize(clazz, causeRef)) {
+				return true;
+			}
+			logWarningIfNecessary(clazz, causeRef.get());
+			return false;
+		}
 	}
 
 	@Override
diff --git a/spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java b/spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java
index 07390ba362e..5d68e63265f 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java
@@ -26,6 +26,7 @@ import java.util.Map;
 
 import com.fasterxml.jackson.annotation.JsonView;
 import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.commons.logging.Log;
 
@@ -108,7 +109,34 @@ public abstract class Jackson2CodecSupport {
 
 
 	protected boolean supportsMimeType(@Nullable MimeType mimeType) {
-		return (mimeType == null || this.mimeTypes.stream().anyMatch(m -> m.isCompatibleWith(mimeType)));
+		if (mimeType == null) {
+			return true;
+		}
+		for (MimeType supportedMimeType : this.mimeTypes) {
+			if (supportedMimeType.isCompatibleWith(mimeType)) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Determine whether to log the given exception coming from a
+	 * {@link ObjectMapper#canDeserialize} / {@link ObjectMapper#canSerialize} check.
+	 * @param type the class that Jackson tested for (de-)serializability
+	 * @param cause the Jackson-thrown exception to evaluate
+	 * (typically a {@link JsonMappingException})
+	 * @since 5.3.1
+	 */
+	protected void logWarningIfNecessary(Type type, @Nullable Throwable cause) {
+		if (cause == null) {
+			return;
+		}
+		if (logger.isDebugEnabled()) {
+			String msg = "Failed to evaluate Jackson " + (type instanceof JavaType ? "de" : "") +
+					"serialization for type [" + type + "]";
+			logger.debug(msg, cause);
+		}
 	}
 
 	protected JavaType getJavaType(Type type, @Nullable Class<?> contextClass) {