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    /*
 * Copyright 2019 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.bremersee.xml.http.codec;

import static java.util.Objects.isNull;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.BiConsumer;
import javax.xml.XMLConstants;
import jakarta.xml.bind.JAXBElement;
import jakarta.xml.bind.JAXBException;
import jakarta.xml.bind.UnmarshalException;
import jakarta.xml.bind.Unmarshaller;
import jakarta.xml.bind.annotation.XmlRootElement;
import jakarta.xml.bind.annotation.XmlSchema;
import jakarta.xml.bind.annotation.XmlType;
import javax.xml.namespace.QName;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.XMLEvent;
import org.bremersee.xml.JaxbContextBuilder;
import org.reactivestreams.Publisher;
import org.springframework.core.ResolvableType;
import org.springframework.core.codec.AbstractDecoder;
import org.springframework.core.codec.CodecException;
import org.springframework.core.codec.DecodingException;
import org.springframework.core.codec.Hints;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferLimitException;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.core.log.LogFormatUtils;
import org.springframework.http.MediaType;
import org.springframework.http.codec.xml.XmlEventDecoder;
import org.springframework.lang.NonNull;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;
import org.springframework.util.xml.StaxUtils;
import reactor.core.Exceptions;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.publisher.SynchronousSink;

/**
 * Decode from a bytes stream containing XML elements to a stream of {@code Object}s (POJOs).
 *
 * 
    The decoding parts are taken from {@link org.springframework.http.codec.xml.Jaxb2XmlDecoder}.
 *
 * @author Sebastien Deleuze
 * @author Arjen Poutsma
 * @author Christian Bremer
 */
public class ReactiveJaxbDecoder extends AbstractDecoder {

  /**
   * The default value for JAXB annotations.
   *
   * @see XmlRootElement#name()
   * @see XmlRootElement#namespace()
   * @see XmlType#name()
   * @see XmlType#namespace()
   */
  private static final String JAXB_DEFAULT_ANNOTATION_VALUE = "##default";

  private static final XMLInputFactory inputFactory = StaxUtils.createDefensiveInputFactory();


  private final XmlEventDecoder xmlEventDecoder = new XmlEventDecoder();

  private final JaxbContextBuilder jaxbContextBuilder;

  private final Set> ignoreReadingClasses;

  private int maxInMemorySize = 256 * 1024;

  /**
   * Instantiates a new reactive jaxb decoder.
   *
   * @param jaxbContextBuilder the jaxb context builder
   */
  public ReactiveJaxbDecoder(JaxbContextBuilder jaxbContextBuilder) {
    this(jaxbContextBuilder, null);
  }

  /**
   * Instantiates a new Reactive jaxb decoder.
   *
   * @param jaxbContextBuilder the jaxb context builder
   * @param ignoreReadingClasses the ignore reading classes
   */
  public ReactiveJaxbDecoder(
      JaxbContextBuilder jaxbContextBuilder,
      Set> ignoreReadingClasses) {

    super(MimeTypeUtils.APPLICATION_XML, MimeTypeUtils.TEXT_XML,
        new MediaType("application", "*+xml"));
    Assert.notNull(jaxbContextBuilder, "JaxbContextBuilder must be present.");
    this.jaxbContextBuilder = jaxbContextBuilder;
    this.ignoreReadingClasses = isNull(ignoreReadingClasses) ? Set.of() : ignoreReadingClasses;
  }

  /**
   * Set the max number of bytes that can be buffered by this decoder. This is either the size of
   * the entire input when decoding as a whole, or when using async parsing with Aalto XML, it is
   * the size of one top-level XML tree. When the limit is exceeded, {@link
   * DataBufferLimitException}* is raised.
   *
   * 
    By default this is set to 256K.
   *
   * @param byteCount the max number of bytes to buffer, or -1 for unlimited
   */
  public void setMaxInMemorySize(int byteCount) {
    this.maxInMemorySize = byteCount;
    this.xmlEventDecoder.setMaxInMemorySize(byteCount);
  }

  /**
   * Return the {@link #setMaxInMemorySize configured} byte count limit.
   *
   * @return the max in memory size
   */
  public int getMaxInMemorySize() {
    return this.maxInMemorySize;
  }


  @Override
  public boolean canDecode(
      @NonNull ResolvableType elementType,
      @Nullable MimeType mimeType) {

    if (super.canDecode(elementType, mimeType)) {
      final Class outputClass = elementType.getRawClass();
      return !ignoreReadingClasses.contains(outputClass)
          && jaxbContextBuilder.canUnmarshal(outputClass);
    } else {
      return false;
    }
  }

  @NonNull
  @Override
  public Flux decode(
      @NonNull Publisher inputStream,
      ResolvableType elementType,
      @Nullable MimeType mimeType,
      @Nullable Map hints) {

    Flux xmlEventFlux = this.xmlEventDecoder.decode(
        inputStream, ResolvableType.forClass(XMLEvent.class), mimeType, hints);

    Class outputClass = elementType.toClass();
    QName typeName = toQName(outputClass);
    Flux> splitEvents = split(xmlEventFlux, typeName);

    return splitEvents.map(events -> {
      Object value = unmarshal(events, outputClass);
      LogFormatUtils.traceDebug(logger, traceOn -> {
        String formatted = LogFormatUtils.formatValue(value, !traceOn);
        return Hints.getLogPrefix(hints) + "Decoded [" + formatted + "]";
      });
      return value;
    });
  }

  @NonNull
  @Override
  @SuppressWarnings({"rawtypes", "unchecked", "cast"})
  // XMLEventReader is Iterator on JDK 9
  public Object decode(
      DataBuffer dataBuffer,
      ResolvableType targetType,
      @Nullable MimeType mimeType,
      @Nullable Map hints) throws DecodingException {

    try {
      Iterator eventReader = inputFactory.createXMLEventReader(dataBuffer.asInputStream());
      List events = new ArrayList<>();
      eventReader.forEachRemaining(event -> events.add((XMLEvent) event));
      return unmarshal(events, targetType.toClass());
    } catch (XMLStreamException ex) {
      throw Exceptions.propagate(ex);
    } finally {
      DataBufferUtils.release(dataBuffer);
    }
  }

  @NonNull
  @Override
  public Mono decodeToMono(
      @NonNull Publisher input,
      @NonNull ResolvableType elementType,
      @Nullable MimeType mimeType,
      @Nullable Map hints) {

    //noinspection NullableInLambdaInTransform
    return DataBufferUtils.join(input, this.maxInMemorySize)
        .map(dataBuffer -> decode(dataBuffer, elementType, mimeType, hints));
  }

  private Object unmarshal(List events, Class outputClass) {
    try {
      Unmarshaller unmarshaller = jaxbContextBuilder.buildUnmarshaller(outputClass);
      XMLEventReader eventReader = StaxUtils.createXMLEventReader(events);
      if (outputClass.isAnnotationPresent(XmlRootElement.class)) {
        return unmarshaller.unmarshal(eventReader);
      } else {
        JAXBElement jaxbElement = unmarshaller.unmarshal(eventReader, outputClass);
        return jaxbElement.getValue();
      }
    } catch (UnmarshalException ex) {
      throw new DecodingException("Could not unmarshal XML to " + outputClass, ex);
    } catch (JAXBException ex) {
      throw new CodecException("Invalid JAXB configuration", ex);
    }
  }

  /**
   * Returns the qualified name for the given class, according to the mapping rules in the JAXB
   * specification.
   *
   * @param outputClass the output class
   * @return the q name
   */
  QName toQName(Class outputClass) {
    String localPart;
    String namespaceUri;

    if (outputClass.isAnnotationPresent(XmlRootElement.class)) {
      XmlRootElement annotation = outputClass.getAnnotation(XmlRootElement.class);
      localPart = annotation.name();
      namespaceUri = annotation.namespace();
    } else if (outputClass.isAnnotationPresent(XmlType.class)) {
      XmlType annotation = outputClass.getAnnotation(XmlType.class);
      localPart = annotation.name();
      namespaceUri = annotation.namespace();
    } else {
      throw new IllegalArgumentException("Output class [" + outputClass.getName()
          + "] is neither annotated with @XmlRootElement nor @XmlType");
    }

    if (JAXB_DEFAULT_ANNOTATION_VALUE.equals(localPart)) {
      localPart = ClassUtils.getShortNameAsProperty(outputClass);
    }
    if (JAXB_DEFAULT_ANNOTATION_VALUE.equals(namespaceUri)) {
      Package outputClassPackage = outputClass.getPackage();
      if (outputClassPackage != null && outputClassPackage.isAnnotationPresent(XmlSchema.class)) {
        XmlSchema annotation = outputClassPackage.getAnnotation(XmlSchema.class);
        namespaceUri = annotation.namespace();
      } else {
        namespaceUri = XMLConstants.NULL_NS_URI;
      }
    }
    return new QName(namespaceUri, localPart);
  }

  /**
   * Split a flux of {@link XMLEvent XMLEvents} into a flux of XMLEvent lists, one list for each
   * branch of the tree that starts with the given qualified name. That is, given the XMLEvents
   * shown {@linkplain XmlEventDecoder here}, and the {@code desiredName} "{@code child}", this
   * method returns a flux of two lists, each of which containing the events of a particular branch
   * of the tree that starts with "{@code child}".
   * 
      
   * 
    1. The first list, dealing with the first branch of the tree:
   * 
        
   * 
      1. {@link javax.xml.stream.events.StartElement} {@code child}
        2. 
   * 
      2. {@link javax.xml.stream.events.Characters} {@code foo}
        3. 
   * 
      3. {@link javax.xml.stream.events.EndElement} {@code child}
        4. 
   * 
      
   * 
    2. The second list, dealing with the second branch of the tree:
   * 
        
   * 
      1. {@link javax.xml.stream.events.StartElement} {@code child}
        2. 
   * 
      2. {@link javax.xml.stream.events.Characters} {@code bar}
        3. 
   * 
      3. {@link javax.xml.stream.events.EndElement} {@code child}
        4. 
   * 
      
   * 
      3. 
   * 
    
   *
   * @param xmlEventFlux the xml event as flux
   * @param desiredName the desired name
   * @return the list of xml events as flux
   */
  Flux> split(Flux xmlEventFlux, QName desiredName) {
    return xmlEventFlux.handle(new SplitHandler(desiredName));
  }

  private static class SplitHandler implements
      BiConsumer>> {

    private final QName desiredName;

    private List events;

    private int elementDepth = 0;

    private int barrier = Integer.MAX_VALUE;

    /**
     * Instantiates a new split handler.
     *
     * @param desiredName the desired name
     */
    public SplitHandler(QName desiredName) {
      this.desiredName = desiredName;
    }

    @Override
    public void accept(XMLEvent event, SynchronousSink> sink) {
      if (event.isStartElement()) {
        if (this.barrier == Integer.MAX_VALUE) {
          QName startElementName = event.asStartElement().getName();
          if (this.desiredName.equals(startElementName)) {
            this.events = new ArrayList<>();
            this.barrier = this.elementDepth;
          }
        }
        this.elementDepth++;
      }
      if (this.elementDepth > this.barrier) {
        Assert.state(this.events != null, "No XMLEvent List");
        this.events.add(event);
      }
      if (event.isEndElement()) {
        this.elementDepth--;
        if (this.elementDepth == this.barrier) {
          this.barrier = Integer.MAX_VALUE;
          Assert.state(this.events != null, "No XMLEvent List");
          sink.next(this.events);
        }
      }
    }
  }

}
    
    
    
    

    




    
    
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