package com.cedarsoft.serialization.stax;
import com.cedarsoft.Version;
import com.cedarsoft.VersionException;
import com.cedarsoft.VersionMismatchException;
import com.cedarsoft.VersionRange;
import com.cedarsoft.serialization.AbstractXmlSerializer;
import org.jetbrains.annotations.NonNls;
import org.jetbrains.annotations.NotNull;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import java.io.IOException;
import java.io.InputStream;
/**
* Abstract base class for stax based serializers.
* <p/>
* ATTENTION:
* Serializers based on stax must consume all events for their tag (including END_ELEMENT).<br/>
* This is especially true for {@link com.cedarsoft.serialization.PluggableSerializer}s.
*
* @param <T> the type
* @param <S> the object to serialize to
*/
public abstract class AbstractStaxBasedSerializer<T, S> extends AbstractXmlSerializer<T, S, XMLStreamReader, XMLStreamException> {
/**
* Creates a new serializer
*
* @param defaultElementName the name for the root element, if this serializers is not used as delegate. For delegating serializers that value is not used.
* @param nameSpaceUriBase the name space uri base
* @param formatVersionRange the supported format version range. The upper bound represents the format that is written. All Versions within the range can be read.
*/
protected AbstractStaxBasedSerializer( @NotNull @NonNls String defaultElementName, @NonNls @NotNull String nameSpaceUriBase, @NotNull VersionRange formatVersionRange ) {
super( defaultElementName, nameSpaceUriBase, formatVersionRange );
}
@Override
@NotNull
public T deserialize( @NotNull InputStream in ) throws IOException, VersionException {
try {
XMLStreamReader reader = StaxSupport.getXmlInputFactory().createXMLStreamReader( in );
int result = reader.nextTag();
if ( result != XMLStreamReader.START_ELEMENT ) {
throw new IllegalStateException( "Expected START_ELEMENT but was <" + result + ">" );
}
//Now get the namespace and verify the version
String namespaceURI = reader.getNamespaceURI();
if ( namespaceURI == null ) {
throw new VersionException( "Version information is missing for <" + reader.getName().getLocalPart() + ">" );
}
//Parse and verify the version
Version version = parseVersionFromNamespaceUri( namespaceURI );
if ( !getFormatVersionRange().contains( version ) ) {
throw new VersionMismatchException( getFormatVersion(), version );
}
//Verify the name space
verifyNamespaceUri( namespaceURI );
T deserialized = deserialize( reader, version );
if ( !reader.isEndElement() ) {
throw new IllegalStateException( "Not consumed everything in <" + getClass().getName() + ">" );
}
if ( reader.next() != XMLStreamReader.END_DOCUMENT ) {
throw new IllegalStateException( "Not consumed everything in <" + getClass().getName() + ">" );
}
return deserialized;
} catch ( XMLStreamException e ) {
throw new IOException( "Could not parse stream due to " + e.getMessage(), e );
}
}
private void verifyNamespaceUri( @NotNull @NonNls String namespaceURI ) {
String expectedBase = getNameSpaceUriBase();
if ( !namespaceURI.startsWith( expectedBase ) ) {
throw new IllegalArgumentException( "Invalid namespace. Was <" + namespaceURI + "> but expected <" + expectedBase + "/$VERSION>" );
}
}
/**
* Ensures that the current tag equals the given tag name
*
* @param streamReader the stream reader
* @param tagName the tag name
*/
protected void ensureTag( @NotNull XMLStreamReader streamReader, @NotNull @NonNls String tagName ) {
String current = streamReader.getName().getLocalPart();
if ( !current.equals( tagName ) ) {
throw new IllegalStateException( "Invalid tag. Was <" + current + "> but expected <" + tagName + ">" );
}
}
/**
* Returns the text and closes the tag
*
* @param reader the reader
* @return the text
*
* @throws XMLStreamException
*/
@NotNull
protected String getText( @NotNull XMLStreamReader reader ) throws XMLStreamException {
StringBuilder content = new StringBuilder();
int result;
while ( ( result = reader.next() ) != XMLStreamReader.END_ELEMENT ) {
if ( result != XMLStreamReader.CHARACTERS ) {
throw new IllegalStateException( "Invalid state: " + result );
}
content.append( reader.getText() );
}
return content.toString();
}
/**
* Returns the child text
*
* @param reader the reader
* @param tagName the tag name
* @return the text of the child with the given tag name
*
* @throws XMLStreamException
*/
@NotNull
protected String getChildText( @NotNull XMLStreamReader reader, @NotNull @NonNls String tagName ) throws XMLStreamException {
reader.nextTag();
ensureTag( reader, tagName );
return getText( reader );
}
/**
* Closes the current tag
*
* @param reader the reader
* @throws XMLStreamException
*/
protected void closeTag( @NotNull XMLStreamReader reader ) throws XMLStreamException {
int result = reader.nextTag();
if ( result != XMLStreamReader.END_ELEMENT ) {
throw new IllegalStateException( "Invalid result. Expected <END_ELEMENT> but was <" + StaxSupport.getEventName( result ) + ">" );
}
}
/**
* Opens the next tag
*
* @param reader the reader
* @param tagName the tag name
* @throws XMLStreamException
*/
protected void nextTag( @NotNull XMLStreamReader reader, @NotNull @NonNls String tagName ) throws XMLStreamException {
int result = reader.nextTag();
if ( result != XMLStreamReader.START_ELEMENT ) {
throw new IllegalStateException( "Invalid result. Expected <START_ELEMENT> but was <" + StaxSupport.getEventName( result ) + ">" );
}
ensureTag( reader, tagName );
}
/**
* Attention! The current element will be closed!
*
* @param streamReader the stream reader
* @param callback the callback
* @throws XMLStreamException
* @throws IOException
*/
protected void visitChildren( @NotNull XMLStreamReader streamReader, @NotNull CB callback ) throws XMLStreamException, IOException {
while ( streamReader.nextTag() != XMLStreamReader.END_ELEMENT ) {
String tagName = streamReader.getName().getLocalPart();
callback.tagEntered( streamReader, tagName );
}
}
/**
* Callback interface used when visiting the children ({@link com.cedarsoft.serialization.stax.AbstractStaxBasedSerializer#visitChildren(XMLStreamReader, com.cedarsoft.serialization.stax.AbstractStaxBasedSerializer.CB)})
*/
public interface CB {
/**
* Is called for each child.
* ATTENTION: This method *must* close the tag
*
* @param deserializeFrom the reader
* @param tagName the tag name
* @throws XMLStreamException
* @throws IOException
*/
void tagEntered( @NotNull XMLStreamReader deserializeFrom, @NotNull @NonNls String tagName ) throws XMLStreamException, IOException;
}
}