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/*******************************************************************************
* Copyright 2014 uniVocity Software Pty Ltd
*
* 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.univocity.parsers.conversions;
import java.util.*;
import com.univocity.parsers.common.*;
/**
* Converts Strings to null and vice versa
*
* This class supports multiple representations of null values. For example, you can define conversions from different Strings such as "N/A, ?, -" to null.
*
*
The reverse conversion from a null to String (in {@link NullStringConversion#revert(Object)} will return the first String provided in this class constructor if the object is null.
*
Using the previous example, a call to {@link NullStringConversion#revert(Object)} will produce "N/A".
*
* @author uniVocity Software Pty Ltd - [email protected]
*
*/
public class NullStringConversion implements Conversion {
private Set nullStrings = new HashSet();
private String defaultNullString;
/**
* Creates conversions from Strings to null.
* The list of Strings that identify nulls are mandatory.
* @param nullRepresentations Strings that identify a true value. The first element will be returned when executing {@link NullStringConversion#revert(Object)}
*/
public NullStringConversion(String... nullRepresentations) {
ArgumentUtils.noNulls("Null representation strings", nullRepresentations);
for (String nullRepresentation : nullRepresentations) {
nullStrings.add(nullRepresentation);
}
this.defaultNullString = nullRepresentations[0];
}
/**
* Converts an Object to null. The string representation of the object will be used to match the string elements provided in the constructor.
* @param input an Object to be converted to null.
* @return null if the string representation of the object matches any one of the Strings provided in the constructor of this class. Otherwise, the original object will be returned.
*/
@Override
public Object execute(Object input) {
if (input == null) {
return null;
}
if (nullStrings.contains(String.valueOf(input))) {
return null;
}
return input;
}
/**
* Converts a null input to a String representation. The String returned will be the first element provided in the constructor of this class.
* @param input an Object that, if null, will be transformed to a String.
* @return If the input is null, the string representation for null objects. Otherwise, the original object will be returned.
*/
@Override
public Object revert(Object input) {
if (input == null) {
return defaultNullString;
} else {
return input;
}
}
}