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/*
* Copyright DataStax, Inc.
*
* Licensed 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 com.datastax.driver.extras.codecs;
import com.datastax.driver.core.ProtocolVersion;
import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.core.exceptions.InvalidTypeException;
import com.google.common.reflect.TypeToken;
import java.nio.ByteBuffer;
/**
* An abstract {@link TypeCodec} that stores JAVA objects as serialized strings. This can serve as a
* base for codecs dealing with XML or JSON formats.
*
* This codec can be seen as a convenience base class to help implementing Java-to-XML or
* Java-to-JSON mappings, but it comes with a performance penalty: each Java object is serialized in
* two steps: first to a String, and then to a {@link ByteBuffer}, which means that each
* serialization actually incurs in two potentially expensive operations being carried.
*
*
If you are using an XML or JSON library that supports writing Java objects directly to {@link
* ByteBuffer}s, consider writing your own codec instead of using this one.
*
* @param The Java type this codec serializes from and deserializes to.
*/
public abstract class ParsingCodec extends TypeCodec {
private final TypeCodec innerCodec;
public ParsingCodec(Class javaType) {
this(TypeToken.of(javaType));
}
public ParsingCodec(TypeToken javaType) {
this(TypeCodec.varchar(), javaType);
}
public ParsingCodec(TypeCodec innerCodec, Class javaType) {
this(innerCodec, TypeToken.of(javaType));
}
public ParsingCodec(TypeCodec innerCodec, TypeToken javaType) {
super(innerCodec.getCqlType(), javaType);
this.innerCodec = innerCodec;
}
@Override
public ByteBuffer serialize(T value, ProtocolVersion protocolVersion)
throws InvalidTypeException {
return value == null ? null : innerCodec.serialize(toString(value), protocolVersion);
}
@Override
public T deserialize(ByteBuffer bytes, ProtocolVersion protocolVersion)
throws InvalidTypeException {
String value = innerCodec.deserialize(bytes, protocolVersion);
return value == null ? null : fromString(value);
}
@Override
public String format(T value) throws InvalidTypeException {
return value == null ? null : innerCodec.format(toString(value));
}
@Override
public T parse(String value) throws InvalidTypeException {
return value == null || value.isEmpty() || value.equalsIgnoreCase("NULL")
? null
: fromString(innerCodec.parse(value));
}
/**
* Return the String representation of the given object; no special CQL quoting should be applied
* here. Null values should be accepted; in most cases, implementors should return null for null
* inputs.
*
* @param value the value to convert into a string
* @return the String representation of the given object
*/
protected abstract String toString(T value);
/**
* Parse the given string into an object; no special CQL unquoting should be applied here. Null
* values should be accepted; in most cases, implementors should return null for null inputs.
*
* @param value the string to parse
* @return the parsed object.
*/
protected abstract T fromString(String value);
}