spring StaxUtils 源码

spring StaxUtils 代码

文件路径：/spring-core/src/main/java/org/springframework/util/xml/StaxUtils.java

/*
 * Copyright 2002-2022 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.util.xml;

import java.util.List;
import java.util.function.Supplier;

import javax.xml.stream.XMLEventFactory;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLResolver;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.XMLStreamWriter;
import javax.xml.stream.events.XMLEvent;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.stax.StAXResult;
import javax.xml.transform.stax.StAXSource;

import org.xml.sax.ContentHandler;
import org.xml.sax.XMLReader;

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

/**
 * Convenience methods for working with the StAX API. Partly historic due to JAXP 1.3
 * compatibility; as of Spring 4.0, relying on JAXP 1.4 as included in JDK 1.6 and higher.
 *
 * <p>In particular, methods for using StAX ({@code javax.xml.stream}) in combination with
 * the TrAX API ({@code javax.xml.transform}), and converting StAX readers/writers into SAX
 * readers/handlers and vice-versa.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 3.0
 */
public abstract class StaxUtils {

	private static final XMLResolver NO_OP_XML_RESOLVER =
			(publicID, systemID, base, ns) -> StreamUtils.emptyInput();


	/**
	 * Create an {@link XMLInputFactory} with Spring's defensive setup,
	 * i.e. no support for the resolution of DTDs and external entities.
	 * @return a new defensively initialized input factory instance to use
	 * @since 5.0
	 */
	public static XMLInputFactory createDefensiveInputFactory() {
		return createDefensiveInputFactory(XMLInputFactory::newInstance);
	}

	/**
	 * Variant of {@link #createDefensiveInputFactory()} with a custom instance.
	 * @param instanceSupplier supplier for the input factory instance
	 * @return a new defensively initialized input factory instance to use
	 * @since 5.0.12
	 */
	public static <T extends XMLInputFactory> T createDefensiveInputFactory(Supplier<T> instanceSupplier) {
		T inputFactory = instanceSupplier.get();
		inputFactory.setProperty(XMLInputFactory.SUPPORT_DTD, false);
		inputFactory.setProperty(XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES, false);
		inputFactory.setXMLResolver(NO_OP_XML_RESOLVER);
		return inputFactory;
	}

	/**
	 * Create a JAXP 1.4 {@link StAXSource} for the given {@link XMLStreamReader}.
	 * @param streamReader the StAX stream reader
	 * @return a source wrapping the {@code streamReader}
	 */
	public static Source createStaxSource(XMLStreamReader streamReader) {
		return new StAXSource(streamReader);
	}

	/**
	 * Create a JAXP 1.4 {@link StAXSource} for the given {@link XMLEventReader}.
	 * @param eventReader the StAX event reader
	 * @return a source wrapping the {@code eventReader}
	 */
	public static Source createStaxSource(XMLEventReader eventReader) throws XMLStreamException {
		return new StAXSource(eventReader);
	}

	/**
	 * Create a custom, non-JAXP 1.4 StAX {@link Source} for the given {@link XMLStreamReader}.
	 * @param streamReader the StAX stream reader
	 * @return a source wrapping the {@code streamReader}
	 */
	public static Source createCustomStaxSource(XMLStreamReader streamReader) {
		return new StaxSource(streamReader);
	}

	/**
	 * Create a custom, non-JAXP 1.4 StAX {@link Source} for the given {@link XMLEventReader}.
	 * @param eventReader the StAX event reader
	 * @return a source wrapping the {@code eventReader}
	 */
	public static Source createCustomStaxSource(XMLEventReader eventReader) {
		return new StaxSource(eventReader);
	}

	/**
	 * Indicate whether the given {@link Source} is a JAXP 1.4 StAX Source or
	 * custom StAX Source.
	 * @return {@code true} if {@code source} is a JAXP 1.4 {@link StAXSource} or
	 * custom StAX Source; {@code false} otherwise
	 */
	public static boolean isStaxSource(Source source) {
		return (source instanceof StAXSource || source instanceof StaxSource);
	}

	/**
	 * Return the {@link XMLStreamReader} for the given StAX Source.
	 * @param source a JAXP 1.4 {@link StAXSource}
	 * @return the {@link XMLStreamReader}
	 * @throws IllegalArgumentException if {@code source} isn't a JAXP 1.4 {@link StAXSource}
	 * or custom StAX Source
	 */
	@Nullable
	public static XMLStreamReader getXMLStreamReader(Source source) {
		if (source instanceof StAXSource stAXSource) {
			return stAXSource.getXMLStreamReader();
		}
		else if (source instanceof StaxSource staxSource) {
			return staxSource.getXMLStreamReader();
		}
		else {
			throw new IllegalArgumentException("Source '" + source + "' is neither StaxSource nor StAXSource");
		}
	}

	/**
	 * Return the {@link XMLEventReader} for the given StAX Source.
	 * @param source a JAXP 1.4 {@link StAXSource}
	 * @return the {@link XMLEventReader}
	 * @throws IllegalArgumentException if {@code source} isn't a JAXP 1.4 {@link StAXSource}
	 * or custom StAX Source
	 */
	@Nullable
	public static XMLEventReader getXMLEventReader(Source source) {
		if (source instanceof StAXSource stAXSource) {
			return stAXSource.getXMLEventReader();
		}
		else if (source instanceof StaxSource staxSource) {
			return staxSource.getXMLEventReader();
		}
		else {
			throw new IllegalArgumentException("Source '" + source + "' is neither StaxSource nor StAXSource");
		}
	}

	/**
	 * Create a JAXP 1.4 {@link StAXResult} for the given {@link XMLStreamWriter}.
	 * @param streamWriter the StAX stream writer
	 * @return a result wrapping the {@code streamWriter}
	 */
	public static Result createStaxResult(XMLStreamWriter streamWriter) {
		return new StAXResult(streamWriter);
	}

	/**
	 * Create a JAXP 1.4 {@link StAXResult} for the given {@link XMLEventWriter}.
	 * @param eventWriter the StAX event writer
	 * @return a result wrapping {@code streamReader}
	 */
	public static Result createStaxResult(XMLEventWriter eventWriter) {
		return new StAXResult(eventWriter);
	}

	/**
	 * Create a custom, non-JAXP 1.4 StAX {@link Result} for the given {@link XMLStreamWriter}.
	 * @param streamWriter the StAX stream writer
	 * @return a source wrapping the {@code streamWriter}
	 */
	public static Result createCustomStaxResult(XMLStreamWriter streamWriter) {
		return new StaxResult(streamWriter);
	}

	/**
	 * Create a custom, non-JAXP 1.4 StAX {@link Result} for the given {@link XMLEventWriter}.
	 * @param eventWriter the StAX event writer
	 * @return a source wrapping the {@code eventWriter}
	 */
	public static Result createCustomStaxResult(XMLEventWriter eventWriter) {
		return new StaxResult(eventWriter);
	}

	/**
	 * Indicate whether the given {@link Result} is a JAXP 1.4 StAX Result or
	 * custom StAX Result.
	 * @return {@code true} if {@code result} is a JAXP 1.4 {@link StAXResult} or
	 * custom StAX Result; {@code false} otherwise
	 */
	public static boolean isStaxResult(Result result) {
		return (result instanceof StAXResult || result instanceof StaxResult);
	}

	/**
	 * Return the {@link XMLStreamWriter} for the given StAX Result.
	 * @param result a JAXP 1.4 {@link StAXResult}
	 * @return the {@link XMLStreamReader}
	 * @throws IllegalArgumentException if {@code source} isn't a JAXP 1.4 {@link StAXResult}
	 * or custom StAX Result
	 */
	@Nullable
	public static XMLStreamWriter getXMLStreamWriter(Result result) {
		if (result instanceof StAXResult stAXResult) {
			return stAXResult.getXMLStreamWriter();
		}
		else if (result instanceof StaxResult staxResult) {
			return staxResult.getXMLStreamWriter();
		}
		else {
			throw new IllegalArgumentException("Result '" + result + "' is neither StaxResult nor StAXResult");
		}
	}

	/**
	 * Return the {@link XMLEventWriter} for the given StAX Result.
	 * @param result a JAXP 1.4 {@link StAXResult}
	 * @return the {@link XMLStreamReader}
	 * @throws IllegalArgumentException if {@code source} isn't a JAXP 1.4 {@link StAXResult}
	 * or custom StAX Result
	 */
	@Nullable
	public static XMLEventWriter getXMLEventWriter(Result result) {
		if (result instanceof StAXResult stAXResult) {
			return stAXResult.getXMLEventWriter();
		}
		else if (result instanceof StaxResult staxResult) {
			return staxResult.getXMLEventWriter();
		}
		else {
			throw new IllegalArgumentException("Result '" + result + "' is neither StaxResult nor StAXResult");
		}
	}

	/**
	 * Create a {@link XMLEventReader} from the given list of {@link XMLEvent}.
	 * @param events the list of {@link XMLEvent XMLEvents}.
	 * @return an {@code XMLEventReader} that reads from the given events
	 * @since 5.0
	 */
	public static XMLEventReader createXMLEventReader(List<XMLEvent> events) {
		return new ListBasedXMLEventReader(events);
	}

	/**
	 * Create a SAX {@link ContentHandler} that writes to the given StAX {@link XMLStreamWriter}.
	 * @param streamWriter the StAX stream writer
	 * @return a content handler writing to the {@code streamWriter}
	 */
	public static ContentHandler createContentHandler(XMLStreamWriter streamWriter) {
		return new StaxStreamHandler(streamWriter);
	}

	/**
	 * Create a SAX {@link ContentHandler} that writes events to the given StAX {@link XMLEventWriter}.
	 * @param eventWriter the StAX event writer
	 * @return a content handler writing to the {@code eventWriter}
	 */
	public static ContentHandler createContentHandler(XMLEventWriter eventWriter) {
		return new StaxEventHandler(eventWriter);
	}

	/**
	 * Create a SAX {@link XMLReader} that reads from the given StAX {@link XMLStreamReader}.
	 * @param streamReader the StAX stream reader
	 * @return a XMLReader reading from the {@code streamWriter}
	 */
	public static XMLReader createXMLReader(XMLStreamReader streamReader) {
		return new StaxStreamXMLReader(streamReader);
	}

	/**
	 * Create a SAX {@link XMLReader} that reads from the given StAX {@link XMLEventReader}.
	 * @param eventReader the StAX event reader
	 * @return a XMLReader reading from the {@code eventWriter}
	 */
	public static XMLReader createXMLReader(XMLEventReader eventReader) {
		return new StaxEventXMLReader(eventReader);
	}

	/**
	 * Return a {@link XMLStreamReader} that reads from a {@link XMLEventReader}.
	 * Useful because the StAX {@code XMLInputFactory} allows one to create an
	 * event reader from a stream reader, but not vice-versa.
	 * @return a stream reader that reads from an event reader
	 */
	public static XMLStreamReader createEventStreamReader(XMLEventReader eventReader) throws XMLStreamException {
		return new XMLEventStreamReader(eventReader);
	}

	/**
	 * Return a {@link XMLStreamWriter} that writes to a {@link XMLEventWriter}.
	 * @return a stream writer that writes to an event writer
	 * @since 3.2
	 */
	public static XMLStreamWriter createEventStreamWriter(XMLEventWriter eventWriter) {
		return new XMLEventStreamWriter(eventWriter, XMLEventFactory.newFactory());
	}

	/**
	 * Return a {@link XMLStreamWriter} that writes to a {@link XMLEventWriter}.
	 * @return a stream writer that writes to an event writer
	 * @since 3.0.5
	 */
	public static XMLStreamWriter createEventStreamWriter(XMLEventWriter eventWriter, XMLEventFactory eventFactory) {
		return new XMLEventStreamWriter(eventWriter, eventFactory);
	}

}

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