com.xiongyingqi.util.xml.XmlValidationModeDetector Maven / Gradle / Ivy

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/*
 * Copyright 2002-2007 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 com.xiongyingqi.util.xml;

import com.xiongyingqi.util.StringUtils;

import java.io.*;

/**
 * Detects whether an XML stream is using DTD- or XSD-based validation.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 */
public class XmlValidationModeDetector {

    /**
     * Indicates that the validation should be disabled.
     */
    public static final int VALIDATION_NONE = 0;

    /**
     * Indicates that the validation mode should be auto-guessed, since we cannot find
     * a clear indication (probably choked on some special characters, or the like).
     */
    public static final int VALIDATION_AUTO = 1;

    /**
     * Indicates that DTD validation should be used (we found a "DOCTYPE" declaration).
     */
    public static final int VALIDATION_DTD = 2;

    /**
     * Indicates that XSD validation should be used (found no "DOCTYPE" declaration).
     */
    public static final int VALIDATION_XSD = 3;


    /**
     * The token in a XML document that declares the DTD to use for validation
     * and thus that DTD validation is being used.
     */
    private static final String DOCTYPE = "DOCTYPE";

    /**
     * The token that indicates the start of an XML comment.
     */
    private static final String START_COMMENT = "";


    /**
     * Indicates whether or not the current parse position is inside an XML comment.
     */
    private boolean inComment;


    /**
     * Detect the validation mode for the XML document in the supplied {@link java.io.InputStream}.
     * Note that the supplied {@link java.io.InputStream} is closed by this method before returning.
     *
     * @param inputStream the InputStream to parse
     * @throws java.io.IOException in case of I/O failure
     * @see #VALIDATION_DTD
     * @see #VALIDATION_XSD
     */
    public int detectValidationMode(InputStream inputStream) throws IOException {
        // Peek into the file to look for DOCTYPE.
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        try {
            boolean isDtdValidated = false;
            String content;
            while ((content = reader.readLine()) != null) {
                content = consumeCommentTokens(content);
                if (this.inComment || !StringUtils.hasText(content)) {
                    continue;
                }
                if (hasDoctype(content)) {
                    isDtdValidated = true;
                    break;
                }
                if (hasOpeningTag(content)) {
                    // End of meaningful data...
                    break;
                }
            }
            return (isDtdValidated ? VALIDATION_DTD : VALIDATION_XSD);
        } catch (CharConversionException ex) {
            // Choked on some character encoding...
            // Leave the decision up to the caller.
            return VALIDATION_AUTO;
        } finally {
            reader.close();
        }
    }


    /**
     * Does the content contain the the DTD DOCTYPE declaration?
     */
    private boolean hasDoctype(String content) {
        return (content.indexOf(DOCTYPE) > -1);
    }

    /**
     * Does the supplied content contain an XML opening tag. If the parse state is currently
     * in an XML comment then this method always returns false. It is expected that all comment
     * tokens will have consumed for the supplied content before passing the remainder to this method.
     */
    private boolean hasOpeningTag(String content) {
        if (this.inComment) {
            return false;
        }
        int openTagIndex = content.indexOf('<');
        return (openTagIndex > -1 && content.length() > openTagIndex && Character.isLetter(content.charAt(openTagIndex + 1)));
    }

    /**
     * Consumes all the leading comment data in the given String and returns the remaining content, which
     * may be empty since the supplied content might be all comment data. For our purposes it is only important
     * to strip leading comment content on a line since the first piece of non comment content will be either
     * the DOCTYPE declaration or the root element of the document.
     */
    private String consumeCommentTokens(String line) {
        if (line.indexOf(START_COMMENT) == -1 && line.indexOf(END_COMMENT) == -1) {
            return line;
        }
        while ((line = consume(line)) != null) {
            if (!this.inComment && !line.trim().startsWith(START_COMMENT)) {
                return line;
            }
        }
        return line;
    }

    /**
     * Consume the next comment token, update the "inComment" flag
     * and return the remaining content.
     */
    private String consume(String line) {
        int index = (this.inComment ? endComment(line) : startComment(line));
        return (index == -1 ? null : line.substring(index));
    }

    /**
     * Try to consume the {@link #START_COMMENT} token.
     *
     * @see #commentToken(String, String, boolean)
     */
    private int startComment(String line) {
        return commentToken(line, START_COMMENT, true);
    }

    private int endComment(String line) {
        return commentToken(line, END_COMMENT, false);
    }

    /**
     * Try to consume the supplied token against the supplied content and update the
     * in comment parse state to the supplied value. Returns the index into the content
     * which is after the token or -1 if the token is not found.
     */
    private int commentToken(String line, String token, boolean inCommentIfPresent) {
        int index = line.indexOf(token);
        if (index > -1) {
            this.inComment = inCommentIfPresent;
        }
        return (index == -1 ? index : index + token.length());
    }

}