/*
 * Copyright 2002-2017 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.beans.propertyeditors;

import java.beans.PropertyEditorSupport;

import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;

Editor for a Character, to populate a property of type Character or char from a String value. 
Note that the JDK does not contain a default property editor for char! BeanWrapperImpl will register this editor by default. 
Also supports conversion from a Unicode character sequence; e.g. u0041 ('A'). 
Author:
Juergen Hoeller, Rob Harrop, Rick Evans
See Also:
Character
BeanWrapperImpl
Since:
1.2/**
 * Editor for a {@link Character}, to populate a property
 * of type {@code Character} or {@code char} from a String value.
 *
 * <p>Note that the JDK does not contain a default
 * {@link java.beans.PropertyEditor property editor} for {@code char}!
 * {@link org.springframework.beans.BeanWrapperImpl} will register this
 * editor by default.
 *
 * <p>Also supports conversion from a Unicode character sequence; e.g.
 * {@code u0041} ('A').
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rick Evans
 * @since 1.2
 * @see Character
 * @see org.springframework.beans.BeanWrapperImpl
 */
public class CharacterEditor extends PropertyEditorSupport {

	
The prefix that identifies a string as being a Unicode character sequence.
/**
	 * The prefix that identifies a string as being a Unicode character sequence.
	 */
	private static final String UNICODE_PREFIX = "\\u";

	
The length of a Unicode character sequence.
/**
	 * The length of a Unicode character sequence.
	 */
	private static final int UNICODE_LENGTH = 6;


	private final boolean allowEmpty;


	
Create a new CharacterEditor instance.
The "allowEmpty" parameter controls whether an empty String is to be allowed in parsing, i.e. be interpreted as the null value when text is being converted. If false, an IllegalArgumentException will be thrown at that time. 
Params:
allowEmpty – if empty strings are to be allowed/**
	 * Create a new CharacterEditor instance.
	 * <p>The "allowEmpty" parameter controls whether an empty String is to be
	 * allowed in parsing, i.e. be interpreted as the {@code null} value when
	 * {@link #setAsText(String) text is being converted}. If {@code false},
	 * an {@link IllegalArgumentException} will be thrown at that time.
	 * @param allowEmpty if empty strings are to be allowed
	 */
	public CharacterEditor(boolean allowEmpty) {
		this.allowEmpty = allowEmpty;
	}


	@Override
	public void setAsText(@Nullable String text) throws IllegalArgumentException {
		if (this.allowEmpty && !StringUtils.hasLength(text)) {
			// Treat empty String as null value.
			setValue(null);
		}
		else if (text == null) {
			throw new IllegalArgumentException("null String cannot be converted to char type");
		}
		else if (isUnicodeCharacterSequence(text)) {
			setAsUnicode(text);
		}
		else if (text.length() == 1) {
			setValue(text.charAt(0));
		}
		else {
			throw new IllegalArgumentException("String [" + text + "] with length " +
					text.length() + " cannot be converted to char type: neither Unicode nor single character");
		}
	}

	@Override
	public String getAsText() {
		Object value = getValue();
		return (value != null ? value.toString() : "");
	}


	private boolean isUnicodeCharacterSequence(String sequence) {
		return (sequence.startsWith(UNICODE_PREFIX) && sequence.length() == UNICODE_LENGTH);
	}

	private void setAsUnicode(String text) {
		int code = Integer.parseInt(text.substring(UNICODE_PREFIX.length()), 16);
		setValue((char) code);
	}

}