/**
    * 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.hadoop.hbase.security.access;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  import java.lang.reflect.Array;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.NavigableSet;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configurable;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.conf.Configured;
  import org.apache.hadoop.hbase.ClusterStatus;
  import org.apache.hadoop.hbase.HColumnDescriptor;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.client.Action;
  import org.apache.hadoop.hbase.client.Append;
  import org.apache.hadoop.hbase.client.Delete;
  import org.apache.hadoop.hbase.client.Get;
  import org.apache.hadoop.hbase.client.Increment;
  import org.apache.hadoop.hbase.client.MultiAction;
  import org.apache.hadoop.hbase.client.MultiResponse;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.Row;
  import org.apache.hadoop.hbase.client.RowMutations;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.filter.BinaryComparator;
  import org.apache.hadoop.hbase.filter.BitComparator;
  import org.apache.hadoop.hbase.filter.ByteArrayComparable;
  import org.apache.hadoop.hbase.filter.ColumnCountGetFilter;
  import org.apache.hadoop.hbase.filter.ColumnPrefixFilter;
  import org.apache.hadoop.hbase.filter.ColumnRangeFilter;
  import org.apache.hadoop.hbase.filter.CompareFilter;
  import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
  import org.apache.hadoop.hbase.filter.DependentColumnFilter;
  import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
  import org.apache.hadoop.hbase.filter.InclusiveStopFilter;
  import org.apache.hadoop.hbase.filter.KeyOnlyFilter;
  import org.apache.hadoop.hbase.filter.PageFilter;
  import org.apache.hadoop.hbase.filter.PrefixFilter;
  import org.apache.hadoop.hbase.filter.QualifierFilter;
  import org.apache.hadoop.hbase.filter.RandomRowFilter;
  import org.apache.hadoop.hbase.filter.RowFilter;
  import org.apache.hadoop.hbase.filter.SingleColumnValueExcludeFilter;
  import org.apache.hadoop.hbase.filter.SingleColumnValueFilter;
  import org.apache.hadoop.hbase.filter.SkipFilter;
  import org.apache.hadoop.hbase.filter.ValueFilter;
  import org.apache.hadoop.hbase.filter.WhileMatchFilter;
  import org.apache.hadoop.hbase.io.DataOutputOutputStream;
  import org.apache.hadoop.hbase.io.WritableWithSize;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos;
  import org.apache.hadoop.hbase.regionserver.RegionOpeningState;
  import org.apache.hadoop.hbase.regionserver.wal.HLogKey;
  import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
  import org.apache.hadoop.hbase.wal.WAL.Entry;
  import org.apache.hadoop.hbase.wal.WALKey;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.ProtoUtil;
  import org.apache.hadoop.io.MapWritable;
  import org.apache.hadoop.io.Text;
  import org.apache.hadoop.io.Writable;
  import org.apache.hadoop.io.WritableFactories;
 import org.apache.hadoop.io.WritableUtils;
 
 import com.google.protobuf.Message;
 import com.google.protobuf.RpcController;
 
 /**
  * <p>This is a customized version of the polymorphic hadoop
  * {@link ObjectWritable}.  It removes UTF8 (HADOOP-414).
  * Using {@link Text} intead of UTF-8 saves ~2% CPU between reading and writing
  * objects running a short sequentialWrite Performance Evaluation test just in
  * ObjectWritable alone; more when we're doing randomRead-ing.  Other
  * optimizations include our passing codes for classes instead of the
  * actual class names themselves.  This makes it so this class needs amendment
  * if non-Writable classes are introduced -- if passed a Writable for which we
  * have no code, we just do the old-school passing of the class name, etc. --
  * but passing codes the  savings are large particularly when cell
  * data is small (If < a couple of kilobytes, the encoding/decoding of class
  * name and reflection to instantiate class was costing in excess of the cell
  * handling).
  * @deprecated This class is needed migrating TablePermissions written with
  * Writables.  It is needed to read old permissions written pre-0.96.  This
  * class is to be removed after HBase 0.96 ships since then all permissions
  * will have been migrated and written with protobufs.
  */
 @Deprecated
 @InterfaceAudience.Private
 class HbaseObjectWritableFor96Migration implements Writable, WritableWithSize, Configurable {
   protected final static Log LOG = LogFactory.getLog(HbaseObjectWritableFor96Migration.class);
 
   // Here we maintain two static maps of classes to code and vice versa.
   // Add new classes+codes as wanted or figure way to auto-generate these
   // maps.
   static final Map<Integer, Class<?>> CODE_TO_CLASS =
     new HashMap<Integer, Class<?>>();
   static final Map<Class<?>, Integer> CLASS_TO_CODE =
     new HashMap<Class<?>, Integer>();
   // Special code that means 'not-encoded'; in this case we do old school
   // sending of the class name using reflection, etc.
   private static final byte NOT_ENCODED = 0;
   //Generic array means that the array type is not one of the pre-defined arrays
   //in the CLASS_TO_CODE map, but we have to still encode the array since it's
   //elements are serializable by this class.
   private static final int GENERIC_ARRAY_CODE;
   private static final int NEXT_CLASS_CODE;
   static {
     ////////////////////////////////////////////////////////////////////////////
     // WARNING: Please do not insert, remove or swap any line in this static  //
     // block.  Doing so would change or shift all the codes used to serialize //
     // objects, which makes backwards compatibility very hard for clients.    //
     // New codes should always be added at the end. Code removal is           //
     // discouraged because code is a short now.                               //
     ////////////////////////////////////////////////////////////////////////////
 
     int code = NOT_ENCODED + 1;
     // Primitive types.
     addToMap(Boolean.TYPE, code++);
     addToMap(Byte.TYPE, code++);
     addToMap(Character.TYPE, code++);
     addToMap(Short.TYPE, code++);
     addToMap(Integer.TYPE, code++);
     addToMap(Long.TYPE, code++);
     addToMap(Float.TYPE, code++);
     addToMap(Double.TYPE, code++);
     addToMap(Void.TYPE, code++);
 
     // Other java types
     addToMap(String.class, code++);
     addToMap(byte [].class, code++);
     addToMap(byte [][].class, code++);
 
     // Hadoop types
     addToMap(Text.class, code++);
     addToMap(Writable.class, code++);
     addToMap(Writable [].class, code++);
     code++; // Removed
     addToMap(NullInstance.class, code++);
 
     // Hbase types
     addToMap(HColumnDescriptor.class, code++);
     addToMap(HConstants.Modify.class, code++);
 
     // We used to have a class named HMsg but its been removed.  Rather than
     // just axe it, use following random Integer class -- we just chose any
     // class from java.lang -- instead just so codes that follow stay
     // in same relative place.
     addToMap(Integer.class, code++);
     addToMap(Integer[].class, code++);
 
     //HRegion shouldn't be pushed across the wire.
     code++; //addToMap(HRegion.class, code++);
     code++; //addToMap(HRegion[].class, code++);
 
     addToMap(HRegionInfo.class, code++);
     addToMap(HRegionInfo[].class, code++);
     code++; // Removed
     code++; // Removed
     addToMap(HTableDescriptor.class, code++);
     addToMap(MapWritable.class, code++);
 
     //
     // HBASE-880
     //
     addToMap(ClusterStatus.class, code++);
     addToMap(Delete.class, code++);
     addToMap(Get.class, code++);
     addToMap(KeyValue.class, code++);
     addToMap(KeyValue[].class, code++);
     addToMap(Put.class, code++);
     addToMap(Put[].class, code++);
     addToMap(Result.class, code++);
     addToMap(Result[].class, code++);
     addToMap(Scan.class, code++);
 
     addToMap(WhileMatchFilter.class, code++);
     addToMap(PrefixFilter.class, code++);
     addToMap(PageFilter.class, code++);
     addToMap(InclusiveStopFilter.class, code++);
     addToMap(ColumnCountGetFilter.class, code++);
     addToMap(SingleColumnValueFilter.class, code++);
     addToMap(SingleColumnValueExcludeFilter.class, code++);
     addToMap(BinaryComparator.class, code++);
     addToMap(BitComparator.class, code++);
     addToMap(CompareFilter.class, code++);
     addToMap(RowFilter.class, code++);
     addToMap(ValueFilter.class, code++);
     addToMap(QualifierFilter.class, code++);
     addToMap(SkipFilter.class, code++);
     addToMap(ByteArrayComparable.class, code++);
     addToMap(FirstKeyOnlyFilter.class, code++);
     addToMap(DependentColumnFilter.class, code++);
 
     addToMap(Delete [].class, code++);
 
     addToMap(Entry.class, code++);
     addToMap(Entry[].class, code++);
     addToMap(HLogKey.class, code++);
 
     addToMap(List.class, code++);
 
     addToMap(NavigableSet.class, code++);
     addToMap(ColumnPrefixFilter.class, code++);
 
     // Multi
     addToMap(Row.class, code++);
     addToMap(Action.class, code++);
     addToMap(MultiAction.class, code++);
     addToMap(MultiResponse.class, code++);
 
     // coprocessor execution
     // Exec no longer exists --> addToMap(Exec.class, code++);
     code++;
     addToMap(Increment.class, code++);
 
     addToMap(KeyOnlyFilter.class, code++);
 
     // serializable
     addToMap(Serializable.class, code++);
 
     addToMap(RandomRowFilter.class, code++);
 
     addToMap(CompareOp.class, code++);
 
     addToMap(ColumnRangeFilter.class, code++);
 
     // HServerLoad no longer exists; increase code so other classes stay the same.
     code++;
     //addToMap(HServerLoad.class, code++);
 
     addToMap(RegionOpeningState.class, code++);
 
     addToMap(HTableDescriptor[].class, code++);
 
     addToMap(Append.class, code++);
 
     addToMap(RowMutations.class, code++);
 
     addToMap(Message.class, code++);
 
     //java.lang.reflect.Array is a placeholder for arrays not defined above
     GENERIC_ARRAY_CODE = code++;
     addToMap(Array.class, GENERIC_ARRAY_CODE);
 
     addToMap(RpcController.class, code++);
 
     // make sure that this is the last statement in this static block
     NEXT_CLASS_CODE = code;
   }
 
   private Class<?> declaredClass;
   private Object instance;
   private Configuration conf;
 
   /** default constructor for writable */
   HbaseObjectWritableFor96Migration() {
     super();
   }
 
   /**
    * @param instance
    */
   HbaseObjectWritableFor96Migration(Object instance) {
     set(instance);
   }
 
   /**
    * @param declaredClass
    * @param instance
    */
   HbaseObjectWritableFor96Migration(Class<?> declaredClass, Object instance) {
     this.declaredClass = declaredClass;
     this.instance = instance;
   }
 
   /** @return the instance, or null if none. */
   Object get() { return instance; }
 
   /** @return the class this is meant to be. */
   Class<?> getDeclaredClass() { return declaredClass; }
 
   /**
    * Reset the instance.
    * @param instance
    */
   void set(Object instance) {
     this.declaredClass = instance.getClass();
     this.instance = instance;
   }
 
   /**
    * @see java.lang.Object#toString()
    */
   @Override
   public String toString() {
     return "OW[class=" + declaredClass + ",value=" + instance + "]";
   }
 
 
   public void readFields(DataInput in) throws IOException {
     readObject(in, this, this.conf);
   }
 
   public void write(DataOutput out) throws IOException {
     writeObject(out, instance, declaredClass, conf);
   }
 
   public long getWritableSize() {
     return getWritableSize(instance, declaredClass, conf);
   }
 
   private static class NullInstance extends Configured implements Writable {
     Class<?> declaredClass;
     /** default constructor for writable */
     @SuppressWarnings("unused")
     public NullInstance() { super(null); }
 
     /**
      * @param declaredClass
      * @param conf
      */
     public NullInstance(Class<?> declaredClass, Configuration conf) {
       super(conf);
       this.declaredClass = declaredClass;
     }
 
     public void readFields(DataInput in) throws IOException {
       this.declaredClass = CODE_TO_CLASS.get(WritableUtils.readVInt(in));
     }
 
     public void write(DataOutput out) throws IOException {
       writeClassCode(out, this.declaredClass);
     }
   }
 
   static Integer getClassCode(final Class<?> c)
   throws IOException {
     Integer code = CLASS_TO_CODE.get(c);
     if (code == null ) {
       if (List.class.isAssignableFrom(c)) {
         code = CLASS_TO_CODE.get(List.class);
       } else if (Writable.class.isAssignableFrom(c)) {
         code = CLASS_TO_CODE.get(Writable.class);
       } else if (c.isArray()) {
         code = CLASS_TO_CODE.get(Array.class);
       } else if (Message.class.isAssignableFrom(c)) {
         code = CLASS_TO_CODE.get(Message.class);
       } else if (Serializable.class.isAssignableFrom(c)){
         code = CLASS_TO_CODE.get(Serializable.class);
       } else if (Scan.class.isAssignableFrom(c)) {
         code = CLASS_TO_CODE.get(Scan.class);
       }
     }
     return code;
   }
 
   /**
    * @return the next object code in the list.  Used in testing to verify that additional fields are not added 
    */
   static int getNextClassCode(){
     return NEXT_CLASS_CODE;
   }
 
   /**
    * Write out the code for passed Class.
    * @param out
    * @param c
    * @throws IOException
    */
   static void writeClassCode(final DataOutput out, final Class<?> c)
       throws IOException {
     Integer code = getClassCode(c);
 
     if (code == null) {
       LOG.error("Unsupported type " + c);
       StackTraceElement[] els = new Exception().getStackTrace();
       for(StackTraceElement elem : els) {
         LOG.error(elem.getMethodName());
       }
       throw new UnsupportedOperationException("No code for unexpected " + c);
     }
     WritableUtils.writeVInt(out, code);
   }
 
   static long getWritableSize(Object instance, Class declaredClass,
                                      Configuration conf) {
     return 0L; // no hint is the default.
   }
   /**
    * Write a {@link Writable}, {@link String}, primitive type, or an array of
    * the preceding.
    * @param out
    * @param instance
    * @param declaredClass
    * @param conf
    * @throws IOException
    */
   @SuppressWarnings("unchecked")
   static void writeObject(DataOutput out, Object instance,
                                  Class declaredClass,
                                  Configuration conf)
   throws IOException {
 
     Object instanceObj = instance;
     Class declClass = declaredClass;
 
     if (instanceObj == null) {                       // null
       instanceObj = new NullInstance(declClass, conf);
       declClass = Writable.class;
     }
     writeClassCode(out, declClass);
     if (declClass.isArray()) {                // array
       // If bytearray, just dump it out -- avoid the recursion and
       // byte-at-a-time we were previously doing.
       if (declClass.equals(byte [].class)) {
         Bytes.writeByteArray(out, (byte [])instanceObj);
       } else {
         //if it is a Generic array, write the element's type
         if (getClassCode(declaredClass) == GENERIC_ARRAY_CODE) {
           Class<?> componentType = declaredClass.getComponentType();
           writeClass(out, componentType);
         }
 
         int length = Array.getLength(instanceObj);
         out.writeInt(length);
         for (int i = 0; i < length; i++) {
           Object item = Array.get(instanceObj, i);
           writeObject(out, item,
                     item.getClass(), conf);
         }
       }
     } else if (List.class.isAssignableFrom(declClass)) {
       List list = (List)instanceObj;
       int length = list.size();
       out.writeInt(length);
       for (int i = 0; i < length; i++) {
         Object elem = list.get(i);
         writeObject(out, elem,
                   elem == null ? Writable.class : elem.getClass(), conf);
       }
     } else if (declClass == String.class) {   // String
       Text.writeString(out, (String)instanceObj);
     } else if (declClass.isPrimitive()) {     // primitive type
       if (declClass == Boolean.TYPE) {        // boolean
         out.writeBoolean(((Boolean)instanceObj).booleanValue());
       } else if (declClass == Character.TYPE) { // char
         out.writeChar(((Character)instanceObj).charValue());
       } else if (declClass == Byte.TYPE) {    // byte
         out.writeByte(((Byte)instanceObj).byteValue());
       } else if (declClass == Short.TYPE) {   // short
         out.writeShort(((Short)instanceObj).shortValue());
       } else if (declClass == Integer.TYPE) { // int
         out.writeInt(((Integer)instanceObj).intValue());
       } else if (declClass == Long.TYPE) {    // long
         out.writeLong(((Long)instanceObj).longValue());
       } else if (declClass == Float.TYPE) {   // float
         out.writeFloat(((Float)instanceObj).floatValue());
       } else if (declClass == Double.TYPE) {  // double
         out.writeDouble(((Double)instanceObj).doubleValue());
       } else if (declClass == Void.TYPE) {    // void
       } else {
         throw new IllegalArgumentException("Not a primitive: "+declClass);
       }
     } else if (declClass.isEnum()) {         // enum
       Text.writeString(out, ((Enum)instanceObj).name());
     } else if (Message.class.isAssignableFrom(declaredClass)) {
       Text.writeString(out, instanceObj.getClass().getName());
       ((Message)instance).writeDelimitedTo(
           DataOutputOutputStream.constructOutputStream(out));
     } else if (Writable.class.isAssignableFrom(declClass)) { // Writable
       Class <?> c = instanceObj.getClass();
       Integer code = CLASS_TO_CODE.get(c);
       if (code == null) {
         out.writeByte(NOT_ENCODED);
         Text.writeString(out, c.getName());
       } else {
         writeClassCode(out, c);
       }
       ((Writable)instanceObj).write(out);
     } else if (Serializable.class.isAssignableFrom(declClass)) {
       Class <?> c = instanceObj.getClass();
       Integer code = CLASS_TO_CODE.get(c);
       if (code == null) {
         out.writeByte(NOT_ENCODED);
         Text.writeString(out, c.getName());
       } else {
         writeClassCode(out, c);
       }
       ByteArrayOutputStream bos = null;
       ObjectOutputStream oos = null;
       try{
         bos = new ByteArrayOutputStream();
         oos = new ObjectOutputStream(bos);
         oos.writeObject(instanceObj);
         byte[] value = bos.toByteArray();
         out.writeInt(value.length);
         out.write(value);
       } finally {
         if(bos!=null) bos.close();
         if(oos!=null) oos.close();
       }
     } else if (Scan.class.isAssignableFrom(declClass)) {
       Scan scan = (Scan)instanceObj;
       byte [] scanBytes = ProtobufUtil.toScan(scan).toByteArray();
       out.writeInt(scanBytes.length);
       out.write(scanBytes);
     } else if (Entry.class.isAssignableFrom(declClass)) {
       // Entry is no longer Writable, maintain compatible serialization.
       // Writables write their exact runtime class
       Class <?> c = instanceObj.getClass();
       Integer code = CLASS_TO_CODE.get(c);
       if (code == null) {
         out.writeByte(NOT_ENCODED);
         Text.writeString(out, c.getName());
       } else {
         writeClassCode(out, c);
       }
       final Entry entry = (Entry)instanceObj;
       // We only support legacy HLogKey
       WALKey key = entry.getKey();
       if (!(key instanceof HLogKey)) {
         throw new IOException("Can't write Entry '" + instanceObj + "' due to key class '" +
             key.getClass() + "'");
       }
       ((HLogKey)key).write(out);
       entry.getEdit().write(out);
     } else {
       throw new IOException("Can't write: "+instanceObj+" as "+declClass);
     }
   }
 
   /** Writes the encoded class code as defined in CLASS_TO_CODE, or
    * the whole class name if not defined in the mapping.
    */
   static void writeClass(DataOutput out, Class<?> c) throws IOException {
     Integer code = CLASS_TO_CODE.get(c);
     if (code == null) {
       WritableUtils.writeVInt(out, NOT_ENCODED);
       Text.writeString(out, c.getName());
     } else {
       WritableUtils.writeVInt(out, code);
     }
   }
 
   /** Reads and returns the class as written by {@link #writeClass(DataOutput, Class)} */
   static Class<?> readClass(Configuration conf, DataInput in) throws IOException {
     Class<?> instanceClass = null;
     int b = (byte)WritableUtils.readVInt(in);
     if (b == NOT_ENCODED) {
       String className = Text.readString(in);
       try {
         instanceClass = getClassByName(conf, className);
       } catch (ClassNotFoundException e) {
         LOG.error("Can't find class " + className, e);
         throw new IOException("Can't find class " + className, e);
       }
     } else {
       instanceClass = CODE_TO_CLASS.get(b);
     }
     return instanceClass;
   }
 
   /**
    * Read a {@link Writable}, {@link String}, primitive type, or an array of
    * the preceding.
    * @param in
    * @param conf
    * @return the object
    * @throws IOException
    */
   static Object readObject(DataInput in, Configuration conf)
     throws IOException {
     return readObject(in, null, conf);
   }
 
   /**
    * Read a {@link Writable}, {@link String}, primitive type, or an array of
    * the preceding.
    * @param in
    * @param objectWritable
    * @param conf
    * @return the object
    * @throws IOException
    */
   @SuppressWarnings("unchecked")
   static Object readObject(DataInput in,
       HbaseObjectWritableFor96Migration objectWritable, Configuration conf)
   throws IOException {
     Class<?> declaredClass = CODE_TO_CLASS.get(WritableUtils.readVInt(in));
     Object instance;
     if (declaredClass.isPrimitive()) {            // primitive types
       if (declaredClass == Boolean.TYPE) {             // boolean
         instance = Boolean.valueOf(in.readBoolean());
       } else if (declaredClass == Character.TYPE) {    // char
         instance = Character.valueOf(in.readChar());
       } else if (declaredClass == Byte.TYPE) {         // byte
         instance = Byte.valueOf(in.readByte());
       } else if (declaredClass == Short.TYPE) {        // short
         instance = Short.valueOf(in.readShort());
       } else if (declaredClass == Integer.TYPE) {      // int
         instance = Integer.valueOf(in.readInt());
       } else if (declaredClass == Long.TYPE) {         // long
         instance = Long.valueOf(in.readLong());
       } else if (declaredClass == Float.TYPE) {        // float
         instance = Float.valueOf(in.readFloat());
       } else if (declaredClass == Double.TYPE) {       // double
         instance = Double.valueOf(in.readDouble());
       } else if (declaredClass == Void.TYPE) {         // void
         instance = null;
       } else {
         throw new IllegalArgumentException("Not a primitive: "+declaredClass);
       }
     } else if (declaredClass.isArray()) {              // array
       if (declaredClass.equals(byte [].class)) {
         instance = Bytes.readByteArray(in);
       } else {
         int length = in.readInt();
         instance = Array.newInstance(declaredClass.getComponentType(), length);
         for (int i = 0; i < length; i++) {
           Array.set(instance, i, readObject(in, conf));
         }
       }
     } else if (declaredClass.equals(Array.class)) { //an array not declared in CLASS_TO_CODE
       Class<?> componentType = readClass(conf, in);
       int length = in.readInt();
       instance = Array.newInstance(componentType, length);
       for (int i = 0; i < length; i++) {
         Array.set(instance, i, readObject(in, conf));
       }
     } else if (List.class.isAssignableFrom(declaredClass)) {            // List
       int length = in.readInt();
       instance = new ArrayList(length);
       for (int i = 0; i < length; i++) {
         ((ArrayList)instance).add(readObject(in, conf));
       }
     } else if (declaredClass == String.class) {        // String
       instance = Text.readString(in);
     } else if (declaredClass.isEnum()) {         // enum
       instance = Enum.valueOf((Class<? extends Enum>) declaredClass,
         Text.readString(in));
     } else if (declaredClass == Message.class) {
       String className = Text.readString(in);
       try {
         declaredClass = getClassByName(conf, className);
         instance = tryInstantiateProtobuf(declaredClass, in);
       } catch (ClassNotFoundException e) {
         LOG.error("Can't find class " + className, e);
         throw new IOException("Can't find class " + className, e);
       }
     } else if (Scan.class.isAssignableFrom(declaredClass)) {
       int length = in.readInt();
       byte [] scanBytes = new byte[length];
       in.readFully(scanBytes);
       ClientProtos.Scan.Builder scanProto = ClientProtos.Scan.newBuilder();
       ProtobufUtil.mergeFrom(scanProto, scanBytes);
       instance = ProtobufUtil.toScan(scanProto.build());
     } else {                                      // Writable or Serializable
       Class instanceClass = null;
       int b = (byte)WritableUtils.readVInt(in);
       if (b == NOT_ENCODED) {
         String className = Text.readString(in);
         if ("org.apache.hadoop.hbase.regionserver.wal.HLog$Entry".equals(className)) {
           className = Entry.class.getName();
         }
         try {
           instanceClass = getClassByName(conf, className);
         } catch (ClassNotFoundException e) {
           LOG.error("Can't find class " + className, e);
           throw new IOException("Can't find class " + className, e);
         }
       } else {
         instanceClass = CODE_TO_CLASS.get(b);
       }
       if(Writable.class.isAssignableFrom(instanceClass)){
         Writable writable = WritableFactories.newInstance(instanceClass, conf);
         try {
           writable.readFields(in);
         } catch (Exception e) {
           LOG.error("Error in readFields", e);
           throw new IOException("Error in readFields" , e);
         }
         instance = writable;
         if (instanceClass == NullInstance.class) {  // null
           declaredClass = ((NullInstance)instance).declaredClass;
           instance = null;
         }
       } else if (Entry.class.isAssignableFrom(instanceClass)) {
         // Entry stopped being Writable; maintain serialization support.
         final HLogKey key = new HLogKey();
         final WALEdit edit = new WALEdit();
         key.readFields(in);
         edit.readFields(in);
         instance = new Entry(key, edit);
       } else {
         int length = in.readInt();
         byte[] objectBytes = new byte[length];
         in.readFully(objectBytes);
         ByteArrayInputStream bis = null;
         ObjectInputStream ois = null;
         try {
           bis = new ByteArrayInputStream(objectBytes);
           ois = new ObjectInputStream(bis);
           instance = ois.readObject();
         } catch (ClassNotFoundException e) {
           LOG.error("Class not found when attempting to deserialize object", e);
           throw new IOException("Class not found when attempting to " +
               "deserialize object", e);
         } finally {
           if(bis!=null) bis.close();
           if(ois!=null) ois.close();
         }
       }
     }
     if (objectWritable != null) {                 // store values
       objectWritable.declaredClass = declaredClass;
       objectWritable.instance = instance;
     }
     return instance;
   }
 
   /**
    * Try to instantiate a protocol buffer of the given message class
    * from the given input stream.
    *
    * @param protoClass the class of the generated protocol buffer
    * @param dataIn the input stream to read from
    * @return the instantiated Message instance
    * @throws IOException if an IO problem occurs
    */
   static Message tryInstantiateProtobuf(
       Class<?> protoClass,
       DataInput dataIn) throws IOException {
 
     try {
       if (dataIn instanceof InputStream) {
         // We can use the built-in parseDelimitedFrom and not have to re-copy
         // the data
         Method parseMethod = getStaticProtobufMethod(protoClass,
             "parseDelimitedFrom", InputStream.class);
         return (Message)parseMethod.invoke(null, (InputStream)dataIn);
       } else {
         // Have to read it into a buffer first, since protobuf doesn't deal
         // with the DataInput interface directly.
 
         // Read the size delimiter that writeDelimitedTo writes
         int size = ProtoUtil.readRawVarint32(dataIn);
         if (size < 0) {
           throw new IOException("Invalid size: " + size);
         }
 
         byte[] data = new byte[size];
         dataIn.readFully(data);
         Method parseMethod = getStaticProtobufMethod(protoClass,
             "parseFrom", byte[].class);
         return (Message)parseMethod.invoke(null, data);
       }
     } catch (InvocationTargetException e) {
 
       if (e.getCause() instanceof IOException) {
         throw (IOException)e.getCause();
       } else {
         throw new IOException(e.getCause());
       }
     } catch (IllegalAccessException iae) {
       throw new AssertionError("Could not access parse method in " +
           protoClass);
     }
   }
 
   static Method getStaticProtobufMethod(Class<?> declaredClass, String method,
       Class<?> ... args) {
 
     try {
       return declaredClass.getMethod(method, args);
     } catch (Exception e) {
       // This is a bug in Hadoop - protobufs should all have this static method
       throw new AssertionError("Protocol buffer class " + declaredClass +
           " does not have an accessible parseFrom(InputStream) method!");
     }
   }
 
   @SuppressWarnings("unchecked")
   private static Class getClassByName(Configuration conf, String className)
   throws ClassNotFoundException {
     if(conf != null) {
       return conf.getClassByName(className);
     }
     ClassLoader cl = Thread.currentThread().getContextClassLoader();
     if(cl == null) {
       cl = HbaseObjectWritableFor96Migration.class.getClassLoader();
     }
     return Class.forName(className, true, cl);
   }
 
   private static void addToMap(final Class<?> clazz, final int code) {
     CLASS_TO_CODE.put(clazz, code);
     CODE_TO_CLASS.put(code, clazz);
   }
 
   public void setConf(Configuration conf) {
     this.conf = conf;
   }
 
   public Configuration getConf() {
     return this.conf;
   }
 }