Prevention of StackOverflowError exception when base class is explicitly in @JsonSubTypes or @union annotations.

Author: MichalFoksa

avro/src/main/java/com/fasterxml/jackson/dataformat/avro/schema/RecordVisitor.java

@@ -85,17 +85,26 @@ public RecordVisitor(SerializerProvider p, JavaType type, VisitorFormatWrapperIm
 
             List<NamedType> subTypes = getProvider().getAnnotationIntrospector().findSubtypes(bean.getClassInfo());
             if (subTypes != null && !subTypes.isEmpty()) {
+                // alreadySeenClasses prevents subType processing in endless loop
+                Set<Class<?>> alreadySeenClasses = new HashSet<>();
+                alreadySeenClasses.add(_type.getRawClass());
+
                 // At this point calculating hashCode for _typeSchema fails with NPE because RecordSchema.fields is NULL
                 // see org.apache.avro.Schema.RecordSchema#computeHash.
                 // Therefore, unionSchemas must not be HashSet (or any other type using hashCode() for equality check).
+                // Set ensures that each subType schema is once in resulting union.
                 // IdentityHashMap is used because it is using reference-equality.
                 Set<Schema> unionSchemas = Collections.newSetFromMap(new IdentityHashMap<>());
                 // Initialize with this schema
                 if (_type.isConcrete()) {
                     unionSchemas.add(_typeSchema);
                 }
+
                 try {
                     for (NamedType subType : subTypes) {
+                        if (!alreadySeenClasses.add(subType.getType())) {
+                            continue;
+                        }
                         JsonSerializer<?> ser = getProvider().findValueSerializer(subType.getType());
                         VisitorFormatWrapperImpl visitor = _visitorWrapper.createChildWrapper();
                         ser.acceptJsonFormatVisitor(visitor, getProvider().getTypeFactory().constructType(subType.getType()));

avro/src/test/java/com/fasterxml/jackson/dataformat/avro/schema/PolymorphicTypeAnnotationsTest.java

@@ -5,6 +5,7 @@
 import com.fasterxml.jackson.dataformat.avro.AvroMapper;
 import com.fasterxml.jackson.dataformat.avro.annotation.AvroNamespace;
 import org.apache.avro.Schema;
+import org.apache.avro.reflect.Union;
 import org.junit.jupiter.api.Test;
 
 import java.io.IOException;
@@ -195,4 +196,101 @@ public void class_is_referenced_twice_in_hierarchy_test() throws JsonMappingExce
         assertThat(actualSchema.getTypes()).containsExactlyInAnyOrder(heliumSchema, oxygenSchema);
     }
 
+    @JsonSubTypes({
+            // Base class being explicitly in @JsonSubTypes led to StackOverflowError exception.
+            @JsonSubTypes.Type(value = Image.class),
+            @JsonSubTypes.Type(value = Jpeg.class),
+            @JsonSubTypes.Type(value = Png.class),
+    })
+    @AvroNamespace(TEST_NAMESPACE) // @AvroNamespace makes it easier to create schema string representation
+    private static class Image {
+    }
+
+    private static final String IMAGE_ITSELF_SCHEMA_STR = "{\"type\":\"record\",\"name\":\"Image\",\"namespace\":\"test\",\"fields\":[]}";
+
+    private static class Jpeg extends Image {
+    }
+
+    private static class Png extends Image {
+    }
+
+    @Test
+    public void base_class_explicitly_in_JsonSubTypes_annotation_test() throws IOException {
+        // GIVEN
+        final Schema imageItselfSchema = MAPPER.schemaFrom(IMAGE_ITSELF_SCHEMA_STR).getAvroSchema();
+        final Schema jpegSchema = MAPPER.schemaFor(Jpeg.class).getAvroSchema();
+        final Schema pngSchema = MAPPER.schemaFor(Png.class).getAvroSchema();
+
+        // WHEN
+        Schema actualSchema = MAPPER.schemaFor(Image.class).getAvroSchema();
+
+        System.out.println("Image schema:\n" + actualSchema.toString(true));
+
+        // THEN
+        assertThat(actualSchema.getType()).isEqualTo(Schema.Type.UNION);
+        assertThat(actualSchema.getTypes()).containsExactlyInAnyOrder(imageItselfSchema, jpegSchema, pngSchema);
+    }
+    
+    @Union({
+            // Base class being explicitly in @Union led to StackOverflowError exception.
+            Sport.class,
+            Football.class, Basketball.class})
+    @AvroNamespace(TEST_NAMESPACE) // @AvroNamespace makes it easier to create schema string representation
+    private static class Sport {
+    }
+
+    private static final String SPORT_ITSELF_SCHEMA_STR = "{\"type\":\"record\",\"name\":\"Sport\",\"namespace\":\"test\",\"fields\":[]}";
+
+    private static class Football extends Sport {
+    }
+
+    private static class Basketball extends Sport {
+    }
+
+    @Test
+    public void base_class_explicitly_in_Union_annotation_test() throws IOException {
+        // GIVEN
+        final Schema sportItselfSchema = MAPPER.schemaFrom(SPORT_ITSELF_SCHEMA_STR).getAvroSchema();
+        final Schema footballSchema = MAPPER.schemaFor(Football.class).getAvroSchema();
+        final Schema basketballSchema = MAPPER.schemaFor(Basketball.class).getAvroSchema();
+
+        // WHEN
+        Schema actualSchema = MAPPER.schemaFor(Sport.class).getAvroSchema();
+
+        System.out.println("Sport schema:\n" + actualSchema.toString(true));
+
+        // THEN
+        assertThat(actualSchema.getType()).isEqualTo(Schema.Type.UNION);
+        assertThat(actualSchema.getTypes()).containsExactlyInAnyOrder(sportItselfSchema, footballSchema, basketballSchema);
+    }
+
+    @Union({
+            // Interface being explicitly in @Union led to StackOverflowError exception.
+            DocumentInterface.class,
+            Word.class, Excel.class})
+    private interface DocumentInterface {
+    }
+
+    private static class Word implements DocumentInterface {
+    }
+
+    private static class Excel implements DocumentInterface {
+    }
+
+    @Test
+    public void interface_explicitly_in_Union_annotation_test() throws IOException {
+        // GIVEN
+        final Schema wordSchema = MAPPER.schemaFor(Word.class).getAvroSchema();
+        final Schema excelSchema = MAPPER.schemaFor(Excel.class).getAvroSchema();
+
+        // WHEN
+        Schema actualSchema = MAPPER.schemaFor(DocumentInterface.class).getAvroSchema();
+
+        System.out.println("Document schema:\n" + actualSchema.toString(true));
+
+        // THEN
+        assertThat(actualSchema.getType()).isEqualTo(Schema.Type.UNION);
+        assertThat(actualSchema.getTypes()).containsExactlyInAnyOrder(wordSchema, excelSchema);
+    }
+
 }