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Spring Framework example source code file (HtmlCharacterEntityDecoder.java)

This example Spring Framework source code file (HtmlCharacterEntityDecoder.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

htmlcharacterentitydecoder, htmlcharacterentitydecoder, htmlcharacterentityreferences, max_reference_size, max_reference_size, numberformatexception, numberformatexception, string, string, stringbuffer, x

The Spring Framework HtmlCharacterEntityDecoder.java source code

/*
 * Copyright 2002-2005 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
 *
 *      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.springframework.web.util;

/**
 * Helper for decoding HTML Strings by replacing character
 * entity references with the referred character.
 *
 * @author Juergen Hoeller
 * @author Martin Kersten
 * @since 1.2.1
 */
class HtmlCharacterEntityDecoder {

	private static final int MAX_REFERENCE_SIZE = 10;


	private final HtmlCharacterEntityReferences characterEntityReferences;

	private final String originalMessage;

	private final StringBuffer decodedMessage;

	private int currentPosition = 0;

	private int nextPotentialReferencePosition = -1;

	private int nextSemicolonPosition = -2;


	public HtmlCharacterEntityDecoder(HtmlCharacterEntityReferences characterEntityReferences, String original) {
		this.characterEntityReferences = characterEntityReferences;
		this.originalMessage = original;
		this.decodedMessage = new StringBuffer(originalMessage.length());
	}

	public String decode() {
		while (currentPosition < originalMessage.length()) {
			findNextPotentialReference(currentPosition);
			copyCharactersTillPotentialReference();
			processPossibleReference();
		}
		return decodedMessage.toString();
	}

	private void findNextPotentialReference(int startPosition) {
		nextPotentialReferencePosition = Math.max(startPosition, nextSemicolonPosition - MAX_REFERENCE_SIZE);

		do {
			nextPotentialReferencePosition =
					originalMessage.indexOf('&', nextPotentialReferencePosition);

			if (nextSemicolonPosition != -1 &&
					nextSemicolonPosition < nextPotentialReferencePosition)
				nextSemicolonPosition = originalMessage.indexOf(';', nextPotentialReferencePosition + 1);

			boolean isPotentialReference =
					nextPotentialReferencePosition != -1
					&& nextSemicolonPosition != -1
					&& nextPotentialReferencePosition - nextSemicolonPosition < MAX_REFERENCE_SIZE;

			if (isPotentialReference) {
				break;
			}
			if (nextPotentialReferencePosition == -1) {
				break;
			}
			if (nextSemicolonPosition == -1) {
				nextPotentialReferencePosition = -1;
				break;
			}

			nextPotentialReferencePosition = nextPotentialReferencePosition + 1;
		}
		while (nextPotentialReferencePosition != -1);
	}


	private void copyCharactersTillPotentialReference() {
		if (nextPotentialReferencePosition != currentPosition) {
			int skipUntilIndex = nextPotentialReferencePosition != -1 ?
					nextPotentialReferencePosition : originalMessage.length();
			if (skipUntilIndex - currentPosition > 3) {
				decodedMessage.append(originalMessage.substring(currentPosition, skipUntilIndex));
				currentPosition = skipUntilIndex;
			}
			else {
				while (currentPosition < skipUntilIndex)
					decodedMessage.append(originalMessage.charAt(currentPosition++));
			}
		}
	}

	private void processPossibleReference() {
		if (nextPotentialReferencePosition != -1) {
			boolean isNumberedReference = originalMessage.charAt(currentPosition + 1) == '#';
			boolean wasProcessable = isNumberedReference ? processNumberedReference() : processNamedReference();
			if (wasProcessable) {
				currentPosition = nextSemicolonPosition + 1;
			}
			else {
				char currentChar = originalMessage.charAt(currentPosition);
				decodedMessage.append(currentChar);
				currentPosition++;
			}
		}
	}

	private boolean processNumberedReference() {
		boolean isHexNumberedReference =
				originalMessage.charAt(nextPotentialReferencePosition + 2) == 'x' ||
				originalMessage.charAt(nextPotentialReferencePosition + 2) == 'X';
		try {
			int value = (!isHexNumberedReference) ?
					Integer.parseInt(getReferenceSubstring(2)) :
					Integer.parseInt(getReferenceSubstring(3), 16);
			decodedMessage.append((char) value);
			return true;
		}
		catch (NumberFormatException ex) {
			return false;
		}
	}

	private boolean processNamedReference() {
		String referenceName = getReferenceSubstring(1);
		char mappedCharacter = characterEntityReferences.convertToCharacter(referenceName);
		if (mappedCharacter != HtmlCharacterEntityReferences.CHAR_NULL) {
			decodedMessage.append(mappedCharacter);
			return true;
		}
		return false;
	}

	private String getReferenceSubstring(int referenceOffset) {
		return originalMessage.substring(nextPotentialReferencePosition + referenceOffset, nextSemicolonPosition);
	}

}

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