AVRO-2114: Make missing value exceptions in nested structures easier …

…to read.

This closes #263

CHANGES.txt

@@ -96,6 +96,9 @@ Trunk (not yet released)
     AVRO-2080: Fix Javadoc Warnings in Generated Records
     (Bridger Howell via Niels Basjes)
 
+    AVRO-2114: Make missing value exceptions in nested structures easier to read.
+    (Niels Basjes)
+
   BUG FIXES
 
     AVRO-1741: Python3: Fix error when codec is not in the header.

lang/java/avro/src/main/java/org/apache/avro/AvroMissingFieldException.java

@@ -0,0 +1,46 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.avro;
+
+import org.apache.avro.Schema.Field;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** Avro exception in case of missing fields. */
+public class AvroMissingFieldException extends AvroRuntimeException {
+  private List<Field> chainOfFields = new ArrayList<>(8);
+  public AvroMissingFieldException(String message, Field field) {
+    super(message);
+    chainOfFields.add(field);
+  }
+
+  public void addParentField(Field field) {
+    chainOfFields.add(field);
+  }
+
+  @Override
+  public String toString() {
+    String result = "";
+    for (Field field: chainOfFields) {
+      result = " --> " + field.name() + result;
+    }
+    return "Path in schema:" + result;
+  }
+}

lang/java/avro/src/main/java/org/apache/avro/generic/GenericData.java

@@ -31,6 +31,7 @@
 import java.util.List;
 import java.util.Map;
 
+import org.apache.avro.AvroMissingFieldException;
 import org.apache.avro.AvroRuntimeException;
 import org.apache.avro.AvroTypeException;
 import org.apache.avro.Conversion;
@@ -995,8 +996,8 @@ protected int compare(Object o1, Object o2, Schema s, boolean equals) {
   public Object getDefaultValue(Field field) {
     JsonNode json = field.defaultValue();
     if (json == null)
-      throw new AvroRuntimeException("Field " + field
-                                     + " not set and has no default value");
+      throw new AvroMissingFieldException("Field " + field
+                                          + " not set and has no default value", field);
     if (json.isNull()
         && (field.schema().getType() == Type.NULL
             || (field.schema().getType() == Type.UNION