SerialBinding.java

package com.sleepycat.bind.serial;
import java.io.IOException;
import com.sleepycat.bind.EntryBinding;
import com.sleepycat.je.DatabaseEntry;
import com.sleepycat.util.FastInputStream;
import com.sleepycat.util.FastOutputStream;
import com.sleepycat.util.RuntimeExceptionWrapper;
import de.ovgu.cide.jakutil.*;
/** 
 * A concrete <code>EntryBinding</code> that treats a key or data entry as a
 * serialized object.
 * <p>
 * This binding stores objects in serialized object format. The deserialized
 * objects are returned by the binding, and their <code>Class</code> must
 * implement the <code>Serializable</code> interface.
 * </p>
 * <p>
 * For key bindings, a tuple binding is usually a better choice than a serial
 * binding. A tuple binding gives a reasonable sort order, and works with
 * comparators in all cases -- see below.
 * </p>
 * <p>
 * <em>WARNING:</em> SerialBinding should not be used with Berkeley DB Java
 * Edition for key bindings, when a custom comparator is used. In JE,
 * comparators are instantiated and called internally at times when databases
 * are not accessible. Because serial bindings depend on the class catalog
 * database, a serial binding cannot be used during these times. An attempt to
 * use a serial binding with a custom comparator will result in a
 * NullPointerException during environment open or close.
 * </p>
 * @author Mark Hayes
 */
public class SerialBinding extends SerialBase implements EntryBinding {
  private ClassCatalog classCatalog;
  private Class baseClass;
  /** 
 * Creates a serial binding.
 * @param classCatalogis the catalog to hold shared class information and for a
 * database should be a {@link StoredClassCatalog}.
 * @param baseClassis the base class for serialized objects stored using this
 * binding -- all objects using this binding must be an instance
 * of this class.
 */
  public SerialBinding(  ClassCatalog classCatalog,  Class baseClass){
    if (classCatalog == null) {
      throw new NullPointerException("classCatalog must be non-null");
    }
    this.classCatalog=classCatalog;
    this.baseClass=baseClass;
  }
  /** 
 * Returns the base class for this binding.
 * @return the base class for this binding.
 */
  public final Class getBaseClass(){
    return baseClass;
  }
  /** 
 * Returns the class loader to be used during deserialization, or null if a
 * default class loader should be used. The default implementation of this
 * method returns null.
 * <p>
 * This method may be overriden to return a dynamically determined class
 * loader. For example,
 * <code>Thread.currentThread().getContextClassLoader()</code> could be
 * called to use the context class loader for the curren thread. Or
 * <code>getBaseClass().getClassLoader()</code> could be called to use the
 * class loader for the base class, assuming that a base class has been
 * specified.
 * </p>
 * <p>
 * If this method returns null, a default class loader will be used as
 * determined by the <code>java.io.ObjectInputStream.resolveClass</code>
 * method.
 * </p>
 */
  public ClassLoader getClassLoader(){
    return null;
  }
  /** 
 * Deserialize an object from an entry buffer. May only be called for data
 * that was serialized using {@link #objectToEntry}, since the fixed
 * serialization header is assumed to not be included in the input data.{@link SerialInput} is used to deserialize the object.
 * @param entryis the input serialized entry.
 * @return the output deserialized object.
 */
  public Object entryToObject(  DatabaseEntry entry){
    int length=entry.getSize();
    byte[] hdr=SerialOutput.getStreamHeader();
    byte[] bufWithHeader=new byte[length + hdr.length];
    System.arraycopy(hdr,0,bufWithHeader,0,hdr.length);
    System.arraycopy(entry.getData(),entry.getOffset(),bufWithHeader,hdr.length,length);
    try {
      SerialInput jin=new SerialInput(new FastInputStream(bufWithHeader,0,bufWithHeader.length),classCatalog,getClassLoader());
      return jin.readObject();
    }
 catch (    IOException e) {
      throw new RuntimeExceptionWrapper(e);
    }
catch (    ClassNotFoundException e) {
      throw new RuntimeExceptionWrapper(e);
    }
  }
  /** 
 * Serialize an object into an entry buffer. The fixed serialization header
 * is not included in the output data to save space, and therefore to
 * deserialize the data the complementary {@link #entryToObject} method must
 * be used. {@link SerialOutput} is used to serialize the object.
 * <p>
 * Note that this method sets the DatabaseEntry offset property to a
 * non-zero value and the size property to a value less than the length of
 * the byte array.
 * </p>
 * @param objectis the input deserialized object.
 * @param entryis the output serialized entry.
 * @throws IllegalArgumentExceptionif the object is not an instance of the base class for this
 * binding.
 */
  public void objectToEntry(  Object object,  DatabaseEntry entry){
    if (baseClass != null && !baseClass.isInstance(object)) {
      throw new IllegalArgumentException("Data object class (" + object.getClass() + ") not an instance of binding's base class ("+ baseClass+ ')');
    }
    FastOutputStream fo=getSerialOutput(object);
    try {
      SerialOutput jos=new SerialOutput(fo,classCatalog);
      jos.writeObject(object);
    }
 catch (    IOException e) {
      throw new RuntimeExceptionWrapper(e);
    }
    byte[] hdr=SerialOutput.getStreamHeader();
    entry.setData(fo.getBufferBytes(),hdr.length,fo.getBufferLength() - hdr.length);
  }
}