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Oracle Coherence Community Edition
/*
* Copyright (c) 2000, 2020, Oracle and/or its affiliates.
*
* Licensed under the Universal Permissive License v 1.0 as shown at
* http://oss.oracle.com/licenses/upl.
*/
package com.tangosol.util.extractor;
import com.tangosol.internal.util.invoke.Lambdas;
import com.tangosol.io.ExternalizableLite;
import com.tangosol.io.pof.PofReader;
import com.tangosol.io.pof.PofWriter;
import com.tangosol.io.pof.PortableObject;
import com.tangosol.util.Base;
import com.tangosol.util.ClassHelper;
import com.tangosol.util.ValueExtractor;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import javax.json.bind.annotation.JsonbProperty;
/**
* The KeyExtractor is a special purpose ValueExtractor implementation that
* serves as an indicator that a query should be run against the key objects
* rather than the values. The major difference between the KeyExtractor and a
* standard {@link ReflectionExtractor} is that when used in various
* {@link com.tangosol.util.filter.EntryFilter} implementations it forces
* the evaluation of entry keys rather than entry values.
*
* For example, consider a key object that consists of two properties:
* "FirstName" and "LastName". To retrieve all keys that have a value of the
* "LastName" property equal to "Smith", the following query could be used:
*
* ValueExtractor extractor = new KeyExtractor("getLastName");
* Set setKeys = cache.keySet(new EqualsFilter(extractor, "Smith"));
*
*
* As of Coherence 3.5, the same effect can be achieved for subclasses of the
* AbstractExtractor, for example:
*
* ValueExtractor extractor = new ReflectionExtractor("getLastName", null,
* AbstractExtractor.KEY);
* Set setKeys = cache.keySet(new EqualsFilter(extractor, "Smith"));
*
*
* Note: This class does not function with
* {@link com.tangosol.util.extractor.PofExtractor} and the mechanism
* described above is recommended.
*
* @author gg 2006.06.12
* @since Coherence 3.2
*/
public class KeyExtractor
extends AbstractExtractor
implements ExternalizableLite, PortableObject
{
// ----- constructors ---------------------------------------------------
/**
* Default constructor (necessary for the ExternalizableLite
* and PortableObject interfaces).
*/
public KeyExtractor()
{
// this forces the m_nTarget to be initialized as KEY
this((ValueExtractor) null);
}
/**
* Construct a KeyExtractor based on a specified ValueExtractor.
*
* @param extractor the underlying ValueExtractor
*/
public KeyExtractor(ValueExtractor extractor)
{
m_nTarget = KEY;
m_extractor = extractor == null
? IdentityExtractor.INSTANCE
: Lambdas.ensureRemotable(extractor);
}
/**
* Construct a KeyExtractor for a specified method name.
*
* @param sMethod a method name to construct an underlying
* {@link ReflectionExtractor} for;
* this parameter can also be a dot-delimited sequence
* of method names which would result in a KeyExtractor
* based on the {@link ChainedExtractor} that is based on
* an array of corresponding ReflectionExtractor objects
*/
public KeyExtractor(String sMethod)
{
azzert(sMethod != null, "Method name is missing");
m_nTarget = KEY;
m_extractor = sMethod.indexOf('.') < 0 ? (ValueExtractor)
new ReflectionExtractor(sMethod) :
new ChainedExtractor(sMethod);
}
// ----- ValueExtractor interface ---------------------------------------
/**
* {@inheritDoc}
*/
public E extract(T oTarget)
{
return m_extractor.extract(oTarget);
}
// ----- CanonicallyNamed interface -------------------------------------
@Override
public String getCanonicalName()
{
if (m_sNameCanon == null)
{
// optimization in AbstractExtractor#equals(Object) requires
// AbstractExtractor.m_sNameCanon to be set.
m_sNameCanon = m_extractor.getCanonicalName();
}
return m_sNameCanon;
}
// ----- accessors ------------------------------------------------------
/**
* Obtain the underlying ValueExtractor.
*
* @return the ValueExtractor
*/
public ValueExtractor getExtractor()
{
return m_extractor;
}
// ----- helper methods -------------------------------------------------
/**
* Factory method for key extractor.
*
* @param the type of the value to extract from
* @param the type of value that will be extracted
* @param extractor an extractor to convert to key extractor
*
* @return key extractor based on the specified extractor
*/
public static ValueExtractor of(ValueExtractor extractor)
{
return extractor instanceof KeyExtractor ? extractor : new KeyExtractor<>(extractor);
}
// ----- Object methods -------------------------------------------------
@Override
public boolean equals(Object o)
{
// the super.equals() uses the canonical name comparison (if applies);
// if that succeeds, no other checks are to be made.
if (super.equals(o))
{
return true;
}
else if (isCanonicallyEquatable(o))
{
return false;
}
if (o instanceof KeyExtractor &&
m_extractor instanceof AbstractExtractor)
{
KeyExtractor that = (KeyExtractor) o;
return Base.equals(this.m_extractor, that.m_extractor);
}
return false;
}
/**
* Compute hashCode from underlying {@link ValueExtractor ValueExtractor}.
*
* @return an integer hash value for this KeyExtractor object
*/
@Override
public int hashCode()
{
return m_extractor.hashCode();
}
/**
* Return a human-readable description for this KeyExtractor.
*
* @return a String description of the KeyExtractor
*/
@Override
public String toString()
{
return ClassHelper.getSimpleName(getClass()) +
"(extractor=" + m_extractor + ')';
}
// ----- ExternalizableLite interface -----------------------------------
/**
* {@inheritDoc}
*/
public void readExternal(DataInput in)
throws IOException
{
m_extractor = readObject(in);
}
/**
* {@inheritDoc}
*/
public void writeExternal(DataOutput out)
throws IOException
{
writeObject(out, m_extractor);
}
// ----- PortableObject interface ---------------------------------------
/**
* {@inheritDoc}
*/
public void readExternal(PofReader in)
throws IOException
{
m_extractor = in.readObject(0);
}
/**
* {@inheritDoc}
*/
public void writeExternal(PofWriter out)
throws IOException
{
out.writeObject(0, m_extractor);
}
// ----- data fields ----------------------------------------------------
/**
* The underlying ValueExtractor.
*/
@JsonbProperty("extractor")
protected ValueExtractor m_extractor;
}