Fix #140: add explicit null handling for Cache deserializer

Author: cowtowncoder

guava/src/main/java/com/fasterxml/jackson/datatype/guava/deser/cache/GuavaCacheDeserializer.java

@@ -1,7 +1,12 @@
 package com.fasterxml.jackson.datatype.guava.deser.cache;
 
+import java.io.IOException;
+
+import com.google.common.cache.Cache;
+
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.JsonToken;
+
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
 import com.fasterxml.jackson.databind.deser.NullValueProvider;
@@ -10,9 +15,7 @@
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
 import com.fasterxml.jackson.databind.type.LogicalType;
 import com.fasterxml.jackson.databind.type.MapLikeType;
-import com.google.common.cache.Cache;
-
-import java.io.IOException;
+import com.fasterxml.jackson.databind.util.ClassUtil;
 
 public abstract class GuavaCacheDeserializer<T extends Cache<Object, Object>> 
     extends StdDeserializer<T> implements ContextualDeserializer 
@@ -146,6 +149,11 @@ private T deserializeContents(JsonParser p, DeserializationContext ctxt)
             } else {
                 value = elementDeserializer.deserialize(p, ctxt);
             }
+            if (value == null) {
+                _tryToAddNull(p, ctxt, cache, key);
+                continue;
+            }
+
             cache.put(key, value);
         }
         return cache;
@@ -157,4 +165,26 @@ private void expect(JsonParser p, JsonToken token) throws IOException {
                 p.currentLocation());
         }
     }
+
+    /**
+     * Some/many Guava containers do not allow addition of {@code null} values,
+     * so isolate handling here.
+     *
+     * @since 2.17
+     */
+    protected void _tryToAddNull(JsonParser p, DeserializationContext ctxt,
+            T cache, Object key)
+        throws IOException
+    {
+        // Ideally we'd have better idea of where nulls are accepted, but first
+        // let's just produce something better than NPE:
+        try {
+            cache.put(key, null);
+        } catch (NullPointerException e) {
+            ctxt.handleUnexpectedToken(_valueType, JsonToken.VALUE_NULL, p,
+                    "Guava `Cache` of type %s does not accept `null` values",
+                    ClassUtil.classNameOf(cache));
+        }
+    }
+
 }

guava/src/test/java/com/fasterxml/jackson/datatype/guava/CacheDeserializationTest.java

@@ -6,6 +6,7 @@
 import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.exc.MismatchedInputException;
 import com.google.common.base.Optional;
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
@@ -176,4 +177,19 @@ public void testWithGuavaOptional() throws Exception {
         // test before and after
         assertEquals(cache.asMap().entrySet(), deserializedCache.asMap().entrySet());
     }
+
+    // [datatypes-collections#140]: handle null values
+    public void testCacheWithNulls() throws Exception {
+        Cache<String, Integer> cache;
+        try {
+            cache = MAPPER.readValue(
+                "{ \"key\": null }",
+                new TypeReference<Cache<String, Integer>>() {});
+            fail("Expected fail, deserialized as: "+cache);
+        } catch (MismatchedInputException e) {
+            verifyException(e, "Guava `Cache` of type");
+            verifyException(e, "does not accept `null` values");
+        }
+
+    }
 }

release-notes/VERSION-2.x

@@ -27,6 +27,7 @@ Active Maintainers:
  (contributed by Muhammad K)
 #138 (guava) `GuavaCollectionDeserializer` still throws NPE in some circumstances
  (contributed by Arthur C)
+#140 (guava) `Cache` deserialization fails with NPE for `null` valued entries
 
 2.16.0 (15-Nov-2023)