transform/stream/StreamSource.java

/*
 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package javax.xml.transform.stream;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import javax.xml.transform.Result;

import javax.xml.transform.Source;

/**
 * <p>Acts as an holder for a transformation Source in the form
 * of a stream of XML markup.</p>
 *
 * <p><em>Note:</em> Due to their internal use of either a {@link Reader} or {@link InputStream} instance,
 * <code>StreamSource</code> instances may only be used once.</p>
 *
 * @author Jeff Suttor
 * @since 1.4
 */
public class StreamSource implements Source {

    /** If {@link javax.xml.transform.TransformerFactory#getFeature}
     * returns true when passed this value as an argument,
     * the Transformer supports Source input of this type.
     */
    public static final String FEATURE =
        "http://javax.xml.transform.stream.StreamSource/feature";

    /**
     * <p>Zero-argument default constructor.  If this constructor is used, and
     * no Stream source is set using
     * {@link #setInputStream(java.io.InputStream inputStream)} or
     * {@link #setReader(java.io.Reader reader)}, then the
     * <code>Transformer</code> will
     * create an empty source {@link java.io.InputStream} using
     * {@link java.io.InputStream#InputStream() new InputStream()}.</p>
     *
     * @see javax.xml.transform.Transformer#transform(Source xmlSource, Result outputTarget)
     */
    public StreamSource() { }

    /**
     * Construct a StreamSource from a byte stream.  Normally,
     * a stream should be used rather than a reader, so
     * the XML parser can resolve character encoding specified
     * by the XML declaration.
     *
     * <p>If this constructor is used to process a stylesheet, normally
     * setSystemId should also be called, so that relative URI references
     * can be resolved.</p>
     *
     * @param inputStream A valid InputStream reference to an XML stream.
     */
    public StreamSource(InputStream inputStream) {
        setInputStream(inputStream);
    }

    /**
     * Construct a StreamSource from a byte stream.  Normally,
     * a stream should be used rather than a reader, so that
     * the XML parser can resolve character encoding specified
     * by the XML declaration.
     *
     * <p>This constructor allows the systemID to be set in addition
     * to the input stream, which allows relative URIs
     * to be processed.</p>
     *
     * @param inputStream A valid InputStream reference to an XML stream.
     * @param systemId Must be a String that conforms to the URI syntax.
     */
    public StreamSource(InputStream inputStream, String systemId) {
        setInputStream(inputStream);
        setSystemId(systemId);
    }

    /**
     * Construct a StreamSource from a character reader.  Normally,
     * a stream should be used rather than a reader, so that
     * the XML parser can resolve character encoding specified
     * by the XML declaration.  However, in many cases the encoding
     * of the input stream is already resolved, as in the case of
     * reading XML from a StringReader.
     *
     * @param reader A valid Reader reference to an XML character stream.
     */
    public StreamSource(Reader reader) {
        setReader(reader);
    }

    /**
     * Construct a StreamSource from a character reader.  Normally,
     * a stream should be used rather than a reader, so that
     * the XML parser may resolve character encoding specified
     * by the XML declaration.  However, in many cases the encoding
     * of the input stream is already resolved, as in the case of
     * reading XML from a StringReader.
     *
     * @param reader A valid Reader reference to an XML character stream.
     * @param systemId Must be a String that conforms to the URI syntax.
     */
    public StreamSource(Reader reader, String systemId) {
        setReader(reader);
        setSystemId(systemId);
    }

    /**
     * Construct a StreamSource from a URL.
     *
     * @param systemId Must be a String that conforms to the URI syntax.
     */
    public StreamSource(String systemId) {
        this.systemId = systemId;
    }

    /**
     * Construct a StreamSource from a File.
     *
     * @param f Must a non-null File reference.
     */
    public StreamSource(File f) {
        //convert file to appropriate URI, f.toURI().toASCIIString()
        //converts the URI to string as per rule specified in
        //RFC 2396,
        setSystemId(f.toURI().toASCIIString());
    }

    /**
     * Set the byte stream to be used as input.  Normally,
     * a stream should be used rather than a reader, so that
     * the XML parser can resolve character encoding specified
     * by the XML declaration.
     *
     * <p>If this Source object is used to process a stylesheet, normally
     * setSystemId should also be called, so that relative URL references
     * can be resolved.</p>
     *
     * @param inputStream A valid InputStream reference to an XML stream.
     */
    public void setInputStream(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    /**
     * Get the byte stream that was set with setByteStream.
     *
     * @return The byte stream that was set with setByteStream, or null
     * if setByteStream or the ByteStream constructor was not called.
     */
    public InputStream getInputStream() {
        return inputStream;
    }

    /**
     * Set the input to be a character reader.  Normally,
     * a stream should be used rather than a reader, so that
     * the XML parser can resolve character encoding specified
     * by the XML declaration.  However, in many cases the encoding
     * of the input stream is already resolved, as in the case of
     * reading XML from a StringReader.
     *
     * @param reader A valid Reader reference to an XML CharacterStream.
     */
    public void setReader(Reader reader) {
        this.reader = reader;
    }

    /**
     * Get the character stream that was set with setReader.
     *
     * @return The character stream that was set with setReader, or null
     * if setReader or the Reader constructor was not called.
     */
    public Reader getReader() {
        return reader;
    }

    /**
     * Set the public identifier for this Source.
     *
     * <p>The public identifier is always optional: if the application
     * writer includes one, it will be provided as part of the
     * location information.</p>
     *
     * @param publicId The public identifier as a string.
     */
    public void setPublicId(String publicId) {
        this.publicId = publicId;
    }

    /**
     * Get the public identifier that was set with setPublicId.
     *
     * @return The public identifier that was set with setPublicId, or null
     * if setPublicId was not called.
     */
    public String getPublicId() {
        return publicId;
    }

    /**
     * Set the system identifier for this Source.
     *
     * <p>The system identifier is optional if there is a byte stream
     * or a character stream, but it is still useful to provide one,
     * since the application can use it to resolve relative URIs
     * and can include it in error messages and warnings (the parser
     * will attempt to open a connection to the URI only if
     * there is no byte stream or character stream specified).</p>
     *
     * @param systemId The system identifier as a URL string.
     */
    @Override
    public void setSystemId(String systemId) {
        this.systemId = systemId;
    }

    /**
     * Get the system identifier that was set with setSystemId.
     *
     * @return The system identifier that was set with setSystemId, or null
     * if setSystemId was not called.
     */
    @Override
    public String getSystemId() {
        return systemId;
    }

    /**
     * Set the system ID from a File reference.
     *
     * @param f Must a non-null File reference.
     */
    public void setSystemId(File f) {
        //convert file to appropriate URI, f.toURI().toASCIIString()
        //converts the URI to string as per rule specified in
        //RFC 2396,
        this.systemId = f.toURI().toASCIIString();
    }

    /**
     * Indicates whether the {@code StreamSource} object is empty. Empty is
     * defined as follows:
     * <ul>
     * <li>All of the input sources, including the public identifier, system
     * identifier, byte stream, and character stream, are {@code null}.
     * </li>
     * <li>The public identifier and system identifier are {@code null}, and
     * byte and character stream are either {@code null} or contain no byte or
     * character.
     * <p>
     * Note that this method will reset the byte stream if it is provided, or
     * the character stream if the byte stream is not provided.
     * </li>
     * </ul>
     * <p>
     * In case of error while checking the byte or character stream, the method
     * will return false to allow the XML processor to handle the error.
     *
     * @return true if the {@code StreamSource} object is empty, false otherwise
     */
    @Override
    public boolean isEmpty() {
        return (publicId == null && systemId == null && isStreamEmpty());
    }

    private boolean isStreamEmpty() {
        boolean empty = true;
        try {
            if (inputStream != null) {
                inputStream.reset();
                int bytesRead = inputStream.available();
                if (bytesRead > 0) {
                    return false;
                }
            }

            if (reader != null) {
                reader.reset();
                int c = reader.read();
                reader.reset();
                if (c != -1) {
                    return false;
                }
            }
        } catch (IOException ex) {
            //in case of error, return false
            return false;
        }

        return empty;
    }

    //////////////////////////////////////////////////////////////////////
    // Internal state.
    //////////////////////////////////////////////////////////////////////

    /**
     * The public identifier for this input source, or null.
     */
    private String publicId;

    /**
     * The system identifier as a URL string, or null.
     */
    private String systemId;

    /**
     * The byte stream for this Source, or null.
     */
    private InputStream inputStream;

    /**
     * The character stream for this Source, or null.
     */
    private Reader reader;
}