/*
* Copyright 2007 Kasper B. Graversen
*
* 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 org.supercsv.cellprocessor;
import org.supercsv.cellprocessor.ift.BoolCellProcessor;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.cellprocessor.ift.DateCellProcessor;
import org.supercsv.cellprocessor.ift.DoubleCellProcessor;
import org.supercsv.cellprocessor.ift.LongCellProcessor;
import org.supercsv.cellprocessor.ift.StringCellProcessor;
import org.supercsv.exception.SuperCsvCellProcessorException;
import org.supercsv.util.CsvContext;
/**
* Abstract super class containing shared behaviour of all cell processors. Processors are linked together in a linked
* list. The end element of this list should always be an instance of <tt>NullObjectPattern</tt>.
*
* @author Kasper B. Graversen
* @author James Bassett
*/
public abstract class CellProcessorAdaptor implements CellProcessor {
/** the next processor in the chain */
protected final CellProcessor next;
/**
* Constructor used by CellProcessors to indicate that they are the last processor in the chain.
*/
protected CellProcessorAdaptor() {
super();
this.next = NullObjectPattern.INSTANCE;
}
/**
* Constructor used by CellProcessors that require <tt>CellProcessor</tt> chaining (further processing is required).
*
* @param next
* the next <tt>CellProcessor</tt> in the chain
* @throws NullPointerException
* if next is null
*/
protected CellProcessorAdaptor(final CellProcessor next) {
super();
if( next == null ) {
throw new NullPointerException("next CellProcessor should not be null");
}
this.next = next;
}
/**
* Checks that the input value is not <tt>null</tt>, throwing a <tt>NullInputException</tt> if it is. This method
* should be called by all processors that need to ensure the input is not <tt>null</tt>.
*
* @param value
* the input value
* @param context
* the CSV context
* @throws SuperCsvCellProcessorException
* if value is null
* @since 2.0.0
*/
protected final void validateInputNotNull(final Object value, final CsvContext context) {
if( value == null ) {
throw new SuperCsvCellProcessorException(
"this processor does not accept null input - if the column is optional then chain an Optional() processor before this one",
context, this);
}
}
/**
* Returns the CellProccessor's fully qualified class name.
*/
@Override
public String toString() {
return getClass().getName();
}
/**
* This is an implementation-specific processor and should only be used by the <tt>CellProcessorAdaptor</tt> class.
* It is the implementation of the null object pattern (it does nothing - just returns the value!) and should always
* be the last <tt>CellProcessor</tt> in the chain. It is implemented as a reusable singleton to avoid unnecessary
* object creation.
*
* @author Kasper B. Graversen
* @author James Bassett
*/
private static final class NullObjectPattern implements BoolCellProcessor, DateCellProcessor, DoubleCellProcessor,
LongCellProcessor, StringCellProcessor {
private static final NullObjectPattern INSTANCE = new NullObjectPattern();
/*
* This processor must not be instantiated outside of CellProcessorAdaptor.
*/
private NullObjectPattern() {
super();
}
/**
* {@inheritDoc}
*/
public Object execute(final Object value, final CsvContext context) {
return value;
}
}
}
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