Fix #4248: add special handling for null "cause" for Throwable deserialization

release-notes/VERSION-2.x

@@ -19,6 +19,7 @@ Project: jackson-databind
 #4214: `EnumSet` deserialization does not work when we activate
   default typing in `ObjectMapper`
  (reported by @dvhvsekhar)
+#4248: `ThrowableDeserializer` does not handle `null` well for `cause`
 
 2.16.1 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/deser/std/ThrowableDeserializer.java

@@ -1,6 +1,7 @@
 package com.fasterxml.jackson.databind.deser.std;
 
 import java.io.IOException;
+import java.util.Arrays;
 
 import com.fasterxml.jackson.core.*;
 
@@ -97,18 +98,22 @@ public Object deserializeFromObject(JsonParser p, DeserializationContext ctxt) t
             return ctxt.handleMissingInstantiator(handledType(), getValueInstantiator(), p,
                     "Throwable needs a default constructor, a single-String-arg constructor; or explicit @JsonCreator");
         }
-
         Throwable throwable = null;
         Object[] pending = null;
         Throwable[] suppressed = null;
         int pendingIx = 0;
-
         for (; !p.hasToken(JsonToken.END_OBJECT); p.nextToken()) {
             String propName = p.currentName();
             SettableBeanProperty prop = _beanProperties.find(propName);
             p.nextToken(); // to point to field value
 
             if (prop != null) { // normal case
+                // 07-Dec-2023, tatu: [databind#4248] Interesting that "cause"
+                //    with `null` blows up. So, avoid.
+                if ("cause".equals(prop.getName())
+                        && p.hasToken(JsonToken.VALUE_NULL)) {
+                    continue;
+                }
                 if (throwable != null) {
                     prop.deserializeAndSet(p, ctxt, throwable);
                     continue;
@@ -117,6 +122,13 @@ public Object deserializeFromObject(JsonParser p, DeserializationContext ctxt) t
                 if (pending == null) {
                     int len = _beanProperties.size();
                     pending = new Object[len + len];
+                } else if (pendingIx == pending.length) {
+                    // NOTE: only occurs with duplicate properties, possible
+                    // with some formats (most notably XML; but possibly with
+                    // JSON if duplicate detection not enabled). Most likely
+                    // only occurs with malicious content so use linear buffer
+                    // resize (no need to optimize performance)
+                    pending = Arrays.copyOf(pending, pendingIx + 16);
                 }
                 pending[pendingIx++] = prop;
                 pending[pendingIx++] = prop.deserialize(p, ctxt);
@@ -142,7 +154,13 @@ public Object deserializeFromObject(JsonParser p, DeserializationContext ctxt) t
                 continue;
             }
             if (PROP_NAME_SUPPRESSED.equalsIgnoreCase(propName)) { // or "suppressed"?
-                suppressed = ctxt.readValue(p, Throwable[].class);
+                // 07-Dec-2023, tatu: Not sure how/why, but JSON Null is otherwise
+                //    not handled with such call so...
+                if (p.hasToken(JsonToken.VALUE_NULL)) {
+                    suppressed = null;
+                } else {
+                    suppressed = ctxt.readValue(p, Throwable[].class);
+                }
                 continue;
             }
             if (PROP_NAME_LOCALIZED_MESSAGE.equalsIgnoreCase(propName)) {

src/main/java/com/fasterxml/jackson/databind/util/ClassUtil.java

@@ -693,8 +693,19 @@ public static String getTypeDescription(JavaType fullType)
         if (fullType == null) {
             return "[null]";
         }
+        // 07-Dec-2023, tatu: Instead of cryptic notation for array types
+        //    (JLS-specified for JDK deserialization), let's use trailing "[]"s
+        //    to indicate dimensions instead
+        int arrays = 0;
+        while (fullType.isArrayType()) {
+            ++arrays;
+            fullType = fullType.getContentType();
+        }
         StringBuilder sb = new StringBuilder(80).append('`');
         sb.append(fullType.toCanonical());
+        while (arrays-- > 0) {
+            sb.append("[]");
+        }
         return sb.append('`').toString();
     }
 

src/test/java/com/fasterxml/jackson/databind/exc/ExceptionDeserializationTest.java

@@ -56,7 +56,7 @@ static class MyNoArgException extends Exception
 
     private final ObjectMapper MAPPER = new ObjectMapper();
 
-    public void testIOException() throws IOException
+    public void testIOException() throws Exception
     {
         IOException ioe = new IOException("TEST");
         String json = MAPPER.writerWithDefaultPrettyPrinter()
@@ -65,7 +65,7 @@ public void testIOException() throws IOException
         assertEquals(ioe.getMessage(), result.getMessage());
     }
 
-    public void testWithCreator() throws IOException
+    public void testWithCreator() throws Exception
     {
         final String MSG = "the message";
         String json = MAPPER.writeValueAsString(new MyException(MSG, 3));
@@ -82,7 +82,7 @@ public void testWithCreator() throws IOException
         assertTrue(result.stuff.containsKey("suppressed"));
     }
 
-    public void testWithNullMessage() throws IOException
+    public void testWithNullMessage() throws Exception
     {
         final ObjectMapper mapper = new ObjectMapper();
         mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
@@ -92,14 +92,14 @@ public void testWithNullMessage() throws IOException
         assertNull(result.getMessage());
     }
 
-    public void testNoArgsException() throws IOException
+    public void testNoArgsException() throws Exception
     {
         MyNoArgException exc = MAPPER.readValue("{}", MyNoArgException.class);
         assertNotNull(exc);
     }
 
     // try simulating JDK 7 behavior
-    public void testJDK7SuppressionProperty() throws IOException
+    public void testJDK7SuppressionProperty() throws Exception
     {
         Exception exc = MAPPER.readValue("{\"suppressed\":[]}", IOException.class);
         assertNotNull(exc);
@@ -124,7 +124,7 @@ public void testSingleValueArrayDeserialization() throws Exception
         _assertEquality(exp.getStackTrace(), cloned.getStackTrace());
     }
 
-    public void testExceptionCauseDeserialization() throws IOException
+    public void testExceptionCauseDeserialization() throws Exception
     {
         ObjectMapper mapper = new ObjectMapper();
 
@@ -139,7 +139,7 @@ public void testExceptionCauseDeserialization() throws IOException
     }
 
 
-    public void testSuppressedGenericThrowableDeserialization() throws IOException
+    public void testSuppressedGenericThrowableDeserialization() throws Exception
     {
         ObjectMapper mapper = new ObjectMapper();
 
@@ -155,7 +155,7 @@ public void testSuppressedGenericThrowableDeserialization() throws IOException
         _assertEquality(exp.getSuppressed()[0].getStackTrace(), act.getSuppressed()[0].getStackTrace());
     }
 
-    public void testSuppressedTypedExceptionDeserialization() throws IOException
+    public void testSuppressedTypedExceptionDeserialization() throws Exception
     {
         PolymorphicTypeValidator typeValidator = BasicPolymorphicTypeValidator.builder()
                 .allowIfSubTypeIsArray()
@@ -231,7 +231,7 @@ public void testSingleValueArrayDeserializationException() throws Exception {
     }
 
     // mostly to help with XML module (and perhaps CSV)
-    public void testLineNumberAsString() throws IOException
+    public void testLineNumberAsString() throws Exception
     {
         Exception exc = MAPPER.readValue(a2q(
                 "{'message':'Test',\n'stackTrace': "
@@ -241,7 +241,7 @@ public void testLineNumberAsString() throws IOException
     }
 
     // [databind#1842]
-    public void testNullAsMessage() throws IOException
+    public void testNullAsMessage() throws Exception
     {
         Exception exc = MAPPER.readValue(a2q(
                 "{'message':null, 'localizedMessage':null }"
@@ -278,4 +278,24 @@ private void _testRoundtripWith(ObjectMapper mapper) throws Exception
         assertNotNull(result.getCause());
         assertEquals(root.getMessage(), result.getCause().getMessage());
     }
+
+    // [databind#4248]
+    public void testWithDups() throws Exception
+    {
+        // NOTE: by default JSON parser does NOT fail on duplicate properties;
+        // we only use them to mimic formats like XML where duplicates can occur
+        // (or, malicious JSON...)
+        final StringBuilder sb = new StringBuilder(100);
+        sb.append("{");
+        sb.append("'suppressed': [],\n");
+        sb.append("'cause': null,\n");
+        for (int i = 0; i < 10; ++i) { // just needs to be more than max distinct props
+            sb.append("'stackTrace': [],\n");
+        }
+        sb.append("'message': 'foo',\n");
+        sb.append("'localizedMessage': 'bar'\n}");
+        IOException exc = MAPPER.readValue(a2q(sb.toString()), IOException.class);
+        assertNotNull(exc);
+        assertEquals("foo", exc.getLocalizedMessage());
+    }
 }