lang/java/avro/src/main/java/org/apache/avro/path/TracingClassCastException.java

/*
 * 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
 *
 *     https://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.path;

import org.apache.avro.Schema;
import org.apache.avro.util.SchemaUtil;

import java.util.ArrayList;
import java.util.List;

/**
 * a {@link ClassCastException} with extra fields used to trace back the path to
 * a bad value through an object graph
 */
public class TracingClassCastException extends ClassCastException implements PathTracingException<ClassCastException> {
  private final ClassCastException cause;
  private final Object datum;
  private final Schema expected;
  private final boolean customCoderUsed;
  private final List<PathElement> reversePath;

  public TracingClassCastException(ClassCastException cause, Object datum, Schema expected, boolean customCoderUsed) {
    this.cause = cause;
    this.datum = datum;
    this.expected = expected;
    this.customCoderUsed = customCoderUsed;
    this.reversePath = new ArrayList<>(3); // assume short
  }

  @Override
  public void tracePath(PathElement step) {
    reversePath.add(step);
  }

  @Override
  public synchronized ClassCastException getCause() {
    return cause;
  }

  /**
   * @return a hopefully helpful error message
   */
  @Override
  public ClassCastException summarize(Schema root) {
    StringBuilder sb = new StringBuilder();
    sb.append("value ").append(SchemaUtil.describe(datum));
    sb.append(" cannot be cast to expected type ").append(SchemaUtil.describe(expected));
    if (reversePath == null || reversePath.isEmpty()) {
      // very simple "shallow" NPE, no nesting at all, or custom coders used means we
      // have no data
      if (customCoderUsed) {
        sb.append(". No further details available as custom coders were used");
      }
    } else {
      sb.append(" at ");
      if (root != null) {
        sb.append(SchemaUtil.describe(root));
      }
      for (int i = reversePath.size() - 1; i >= 0; i--) {
        PathElement step = reversePath.get(i);
        sb.append(step.toString());
      }
    }
    ClassCastException summary = new ClassCastException(sb.toString());
    summary.initCause(cause);
    return summary;
  }
}