Java tutorial
/* * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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; }