lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.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
 *
 *     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.specific;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Map;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.LinkedHashMap;
import java.nio.ByteBuffer;
import java.lang.reflect.Constructor;
import java.lang.reflect.ParameterizedType;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import org.apache.avro.Schema;
import org.apache.avro.Protocol;
import org.apache.avro.AvroRuntimeException;
import org.apache.avro.AvroTypeException;
import org.apache.avro.Schema.Type;
import org.apache.avro.util.ClassUtils;
import org.apache.avro.generic.GenericData;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.io.BinaryEncoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.BinaryDecoder;

/** Utilities for generated Java classes and interfaces. */
public class SpecificData extends GenericData {

  private static final SpecificData INSTANCE = new SpecificData();

  private static final Class<?>[] NO_ARG = new Class[]{};
  private static final Class<?>[] SCHEMA_ARG = new Class[]{Schema.class};
  private static final Map<Class,Constructor> CTOR_CACHE =
    new ConcurrentHashMap<Class,Constructor>();

  public static final String CLASS_PROP = "java-class";
  public static final String KEY_CLASS_PROP = "java-key-class";
  public static final String ELEMENT_PROP = "java-element-class";

  /** List of Java reserved words from
   * http://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.9
   * combined with the boolean and null literals.
   * combined with the classnames used internally in the generated avro code.
   */
  public static final Set<String> RESERVED_WORDS = new HashSet<String>
    (Arrays.asList(new String[] {
        "abstract", "assert", "boolean", "break", "byte", "case", "catch",
        "char", "class", "const", "continue", "default", "do", "double",
        "else", "enum", "extends", "false", "final", "finally", "float",
        "for", "goto", "if", "implements", "import", "instanceof", "int",
        "interface", "long", "native", "new", "null", "package", "private",
        "protected", "public", "return", "short", "static", "strictfp",
        "super", "switch", "synchronized", "this", "throw", "throws",
        "transient", "true", "try", "void", "volatile", "while",
        /* classnames use internally by the avro code generator */
        "Builder"
      }));

  /** Read/write some common builtin classes as strings.  Representing these as
   * strings isn't always best, as they aren't always ordered ideally, but at
   * least they're stored.  Also note that, for compatibility, only classes
   * that wouldn't be otherwise correctly readable or writable should be added
   * here, e.g., those without a no-arg constructor or those whose fields are
   * all transient. */
  protected Set<Class> stringableClasses = new HashSet<Class>();
  {
    stringableClasses.add(java.math.BigDecimal.class);
    stringableClasses.add(java.math.BigInteger.class);
    stringableClasses.add(java.net.URI.class);
    stringableClasses.add(java.net.URL.class);
    stringableClasses.add(java.io.File.class);
  }

  /** For subclasses.  Applications normally use {@link SpecificData#get()}. */
  public SpecificData() {}

  /** Construct with a specific classloader. */
  public SpecificData(ClassLoader classLoader) {
    super(classLoader);
  }

  @Override
  public DatumReader createDatumReader(Schema schema) {
    return new SpecificDatumReader(schema, schema, this);
  }

  @Override
  public DatumReader createDatumReader(Schema writer, Schema reader) {
    return new SpecificDatumReader(writer, reader, this);
  }

  @Override
  public DatumWriter createDatumWriter(Schema schema) {
    return new SpecificDatumWriter(schema, this);
  }

  /** Return the singleton instance. */
  public static SpecificData get() { return INSTANCE; }

  @Override
  protected boolean isEnum(Object datum) {
    return datum instanceof Enum || super.isEnum(datum);
  }

  @Override
  public Object createEnum(String symbol, Schema schema) {
    Class c = getClass(schema);
    if (c == null) return super.createEnum(symbol, schema); // punt to generic
    if (RESERVED_WORDS.contains(symbol))
      symbol += "$";
    return Enum.valueOf(c, symbol);
  }

  @Override
  protected Schema getEnumSchema(Object datum) {
    return (datum instanceof Enum)
      ? getSchema(datum.getClass())
      : super.getEnumSchema(datum);
  }

  private Map<String,Class> classCache = new ConcurrentHashMap<String,Class>();

  private static final Class NO_CLASS = new Object(){}.getClass();
  private static final Schema NULL_SCHEMA = Schema.create(Schema.Type.NULL);

  /** Return the class that implements a schema, or null if none exists. */
  public Class getClass(Schema schema) {
    switch (schema.getType()) {
    case FIXED:
    case RECORD:
    case ENUM:
      String name = schema.getFullName();
      if (name == null) return null;
      Class c = classCache.get(name);
      if (c == null) {
        try {
          c = ClassUtils.forName(getClassLoader(), getClassName(schema));
        } catch (ClassNotFoundException e) {
          c = NO_CLASS;
        }
        classCache.put(name, c);
      }
      return c == NO_CLASS ? null : c;
    case ARRAY:   return List.class;
    case MAP:     return Map.class;
    case UNION:
      List<Schema> types = schema.getTypes();     // elide unions with null
      if ((types.size() == 2) && types.contains(NULL_SCHEMA))
        return getWrapper(types.get(types.get(0).equals(NULL_SCHEMA) ? 1 : 0));
      return Object.class;
    case STRING:
      if (STRING_TYPE_STRING.equals(schema.getProp(STRING_PROP)))
        return String.class;
      return CharSequence.class;
    case BYTES:   return ByteBuffer.class;
    case INT:     return Integer.TYPE;
    case LONG:    return Long.TYPE;
    case FLOAT:   return Float.TYPE;
    case DOUBLE:  return Double.TYPE;
    case BOOLEAN: return Boolean.TYPE;
    case NULL:    return Void.TYPE;
    default: throw new AvroRuntimeException("Unknown type: "+schema);
    }
  }

  private Class getWrapper(Schema schema) {
    switch (schema.getType()) {
    case INT:     return Integer.class;
    case LONG:    return Long.class;
    case FLOAT:   return Float.class;
    case DOUBLE:  return Double.class;
    case BOOLEAN: return Boolean.class;
    }
    return getClass(schema);
  }

  /** Returns the Java class name indicated by a schema's name and namespace. */
  public static String getClassName(Schema schema) {
    String namespace = schema.getNamespace();
    String name = schema.getName();
    if (namespace == null || "".equals(namespace))
      return name;
    String dot = namespace.endsWith("$") ? "" : ".";
    return namespace + dot + name;
  }

  private final WeakHashMap<java.lang.reflect.Type,Schema> schemaCache =
    new WeakHashMap<java.lang.reflect.Type,Schema>();

  /** Find the schema for a Java type. */
  public Schema getSchema(java.lang.reflect.Type type) {
    Schema schema = schemaCache.get(type);
    if (schema == null) {
      schema = createSchema(type, new LinkedHashMap<String,Schema>());
      schemaCache.put(type, schema);
    }
    return schema;
  }

  /** Create the schema for a Java type. */
  @SuppressWarnings(value="unchecked")
  protected Schema createSchema(java.lang.reflect.Type type,
                                Map<String,Schema> names) {
    if (type instanceof Class
        && CharSequence.class.isAssignableFrom((Class)type))
      return Schema.create(Type.STRING);
    else if (type == ByteBuffer.class)
      return Schema.create(Type.BYTES);
    else if ((type == Integer.class) || (type == Integer.TYPE))
      return Schema.create(Type.INT);
    else if ((type == Long.class) || (type == Long.TYPE))
      return Schema.create(Type.LONG);
    else if ((type == Float.class) || (type == Float.TYPE))
      return Schema.create(Type.FLOAT);
    else if ((type == Double.class) || (type == Double.TYPE))
      return Schema.create(Type.DOUBLE);
    else if ((type == Boolean.class) || (type == Boolean.TYPE))
      return Schema.create(Type.BOOLEAN);
    else if ((type == Void.class) || (type == Void.TYPE))
      return Schema.create(Type.NULL);
    else if (type instanceof ParameterizedType) {
      ParameterizedType ptype = (ParameterizedType)type;
      Class raw = (Class)ptype.getRawType();
      java.lang.reflect.Type[] params = ptype.getActualTypeArguments();
      if (Collection.class.isAssignableFrom(raw)) { // array
        if (params.length != 1)
          throw new AvroTypeException("No array type specified.");
        return Schema.createArray(createSchema(params[0], names));
      } else if (Map.class.isAssignableFrom(raw)) {   // map
        java.lang.reflect.Type key = params[0];
        java.lang.reflect.Type value = params[1];
        if (!(key instanceof Class
              && CharSequence.class.isAssignableFrom((Class)key)))
          throw new AvroTypeException("Map key class not CharSequence: "+key);
        return Schema.createMap(createSchema(value, names));
      } else {
        return createSchema(raw, names);
      }
    } else if (type instanceof Class) {               // class
      Class c = (Class)type;
      String fullName = c.getName();
      Schema schema = names.get(fullName);
      if (schema == null)
        try {
          schema = (Schema)(c.getDeclaredField("SCHEMA$").get(null));

          if (!fullName.equals(getClassName(schema)))
            // HACK: schema mismatches class. maven shade plugin? try replacing.
            schema = Schema.parse
              (schema.toString().replace(schema.getNamespace(),
                                         c.getPackage().getName()));
        } catch (NoSuchFieldException e) {
          throw new AvroRuntimeException("Not a Specific class: "+c);
        } catch (IllegalAccessException e) {
          throw new AvroRuntimeException(e);
        }
      names.put(fullName, schema);
      return schema;
    }
    throw new AvroTypeException("Unknown type: "+type);
  }

  @Override
  protected String getSchemaName(Object datum) {
    if (datum != null) {
      Class c = datum.getClass();
      if (isStringable(c))
        return Schema.Type.STRING.getName();
    }
    return super.getSchemaName(datum);
  }

  /** True iff a class should be serialized with toString(). */
  protected boolean isStringable(Class<?> c) {
    return stringableClasses.contains(c);
  }

  /** Return the protocol for a Java interface. */
  public Protocol getProtocol(Class iface) {
    try {
      Protocol p = (Protocol)(iface.getDeclaredField("PROTOCOL").get(null));
      if (!p.getNamespace().equals(iface.getPackage().getName()))
        // HACK: protocol mismatches iface. maven shade plugin? try replacing.
        p = Protocol.parse(p.toString().replace(p.getNamespace(),
                                                iface.getPackage().getName()));
      return p;
   } catch (NoSuchFieldException e) {
      throw new AvroRuntimeException("Not a Specific protocol: "+iface);
    } catch (IllegalAccessException e) {
      throw new AvroRuntimeException(e);
    }
  }

  @Override
  protected int compare(Object o1, Object o2, Schema s, boolean eq) {
    switch (s.getType()) {
    case ENUM:
      if (o1 instanceof Enum)
        return ((Enum)o1).ordinal() - ((Enum)o2).ordinal();
    default:
      return super.compare(o1, o2, s, eq);
    }
  }

  /** Create an instance of a class.  If the class implements {@link
   * SchemaConstructable}, call a constructor with a {@link
   * org.apache.avro.Schema} parameter, otherwise use a no-arg constructor. */
  @SuppressWarnings("unchecked")
  public static Object newInstance(Class c, Schema s) {
    boolean useSchema = SchemaConstructable.class.isAssignableFrom(c);
    Object result;
    try {
      Constructor meth = (Constructor)CTOR_CACHE.get(c);
      if (meth == null) {
        meth = c.getDeclaredConstructor(useSchema ? SCHEMA_ARG : NO_ARG);
        meth.setAccessible(true);
        CTOR_CACHE.put(c, meth);
      }
      result = meth.newInstance(useSchema ? new Object[]{s} : (Object[])null);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
    return result;
  }

  @Override
  public Object createFixed(Object old, Schema schema) {
    Class c = getClass(schema);
    if (c == null) return super.createFixed(old, schema); // punt to generic
    return c.isInstance(old) ? old : newInstance(c, schema);
  }

  @Override
  public Object newRecord(Object old, Schema schema) {
    Class c = getClass(schema);
    if (c == null) return super.newRecord(old, schema); // punt to generic
    return (c.isInstance(old) ? old : newInstance(c, schema));
  }

  /** Tag interface that indicates that a class has a one-argument constructor
   * that accepts a Schema.
   * @see #newInstance
   */
  public interface SchemaConstructable {}

  /** Runtime utility used by generated classes. */
  public static BinaryDecoder getDecoder(ObjectInput in) {
    return DecoderFactory.get()
      .directBinaryDecoder(new ExternalizableInput(in), null);
  }
  /** Runtime utility used by generated classes. */
  public static BinaryEncoder getEncoder(ObjectOutput out) {
    return EncoderFactory.get()
      .directBinaryEncoder(new ExternalizableOutput(out), null);
  }

}