com.fasterxml.jackson.databind.deser.DataFormatReaders Maven / Gradle / Ivy
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package com.fasterxml.jackson.databind.deser;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Collection;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.core.format.*;
import com.fasterxml.jackson.core.io.MergedStream;
import com.fasterxml.jackson.databind.*;
/**
* Alternative to {@link DataFormatDetector} that needs to be used when
* using data-binding.
*
* @since 2.1
*/
public class DataFormatReaders
{
/**
* By default we will look ahead at most 64 bytes; in most cases,
* much less (4 bytes or so) is needed, but we will allow bit more
* leniency to support data formats that need more complex heuristics.
*/
public final static int DEFAULT_MAX_INPUT_LOOKAHEAD = 64;
/**
* Ordered list of readers which both represent data formats to
* detect (in precedence order, starting with highest) and contain
* factories used for actual detection.
*/
protected final ObjectReader[] _readers;
/**
* Strength of match we consider to be good enough to be used
* without checking any other formats.
* Default value is {@link MatchStrength#SOLID_MATCH},
*/
protected final MatchStrength _optimalMatch;
/**
* Strength of minimal match we accept as the answer, unless
* better matches are found.
* Default value is {@link MatchStrength#WEAK_MATCH},
*/
protected final MatchStrength _minimalMatch;
/**
* Maximum number of leading bytes of the input that we can read
* to determine data format.
*
* Default value is {@link #DEFAULT_MAX_INPUT_LOOKAHEAD}.
*/
protected final int _maxInputLookahead;
/*
/**********************************************************
/* Construction
/**********************************************************
*/
public DataFormatReaders(ObjectReader... detectors) {
this(detectors, MatchStrength.SOLID_MATCH, MatchStrength.WEAK_MATCH,
DEFAULT_MAX_INPUT_LOOKAHEAD);
}
public DataFormatReaders(Collection detectors) {
this(detectors.toArray(new ObjectReader[detectors.size()]));
}
private DataFormatReaders(ObjectReader[] detectors,
MatchStrength optMatch, MatchStrength minMatch,
int maxInputLookahead)
{
_readers = detectors;
_optimalMatch = optMatch;
_minimalMatch = minMatch;
_maxInputLookahead = maxInputLookahead;
}
/*
/**********************************************************
/* Fluent factories for changing match settings
/**********************************************************
*/
public DataFormatReaders withOptimalMatch(MatchStrength optMatch) {
if (optMatch == _optimalMatch) {
return this;
}
return new DataFormatReaders(_readers, optMatch, _minimalMatch, _maxInputLookahead);
}
public DataFormatReaders withMinimalMatch(MatchStrength minMatch) {
if (minMatch == _minimalMatch) {
return this;
}
return new DataFormatReaders(_readers, _optimalMatch, minMatch, _maxInputLookahead);
}
public DataFormatReaders with(ObjectReader[] readers) {
return new DataFormatReaders(readers, _optimalMatch, _minimalMatch, _maxInputLookahead);
}
public DataFormatReaders withMaxInputLookahead(int lookaheadBytes)
{
if (lookaheadBytes == _maxInputLookahead) {
return this;
}
return new DataFormatReaders(_readers, _optimalMatch, _minimalMatch, lookaheadBytes);
}
/*
/**********************************************************
/* Fluent factories for changing underlying readers
/**********************************************************
*/
public DataFormatReaders with(DeserializationConfig config)
{
final int len = _readers.length;
ObjectReader[] r = new ObjectReader[len];
for (int i = 0; i < len; ++i) {
r[i] = _readers[i].with(config);
}
return new DataFormatReaders(r, _optimalMatch, _minimalMatch, _maxInputLookahead);
}
public DataFormatReaders withType(JavaType type)
{
final int len = _readers.length;
ObjectReader[] r = new ObjectReader[len];
for (int i = 0; i < len; ++i) {
r[i] = _readers[i].forType(type);
}
return new DataFormatReaders(r, _optimalMatch, _minimalMatch, _maxInputLookahead);
}
/*
/**********************************************************
/* Public API
/**********************************************************
*/
/**
* Method to call to find format that content (accessible via given
* {@link InputStream}) given has, as per configuration of this detector
* instance.
*
* @return Matcher object which contains result; never null, even in cases
* where no match (with specified minimal match strength) is found.
*/
public Match findFormat(InputStream in) throws IOException
{
return _findFormat(new AccessorForReader(in, new byte[_maxInputLookahead]));
}
/**
* Method to call to find format that given content (full document)
* has, as per configuration of this detector instance.
*
* @return Matcher object which contains result; never null, even in cases
* where no match (with specified minimal match strength) is found.
*/
public Match findFormat(byte[] fullInputData) throws IOException
{
return _findFormat(new AccessorForReader(fullInputData));
}
/**
* Method to call to find format that given content (full document)
* has, as per configuration of this detector instance.
*
* @return Matcher object which contains result; never null, even in cases
* where no match (with specified minimal match strength) is found.
*
* @since 2.1
*/
public Match findFormat(byte[] fullInputData, int offset, int len) throws IOException
{
return _findFormat(new AccessorForReader(fullInputData, offset, len));
}
/*
/**********************************************************
/* Overrides
/**********************************************************
*/
@Override
public String toString()
{
StringBuilder sb = new StringBuilder();
sb.append('[');
final int len = _readers.length;
if (len > 0) {
sb.append(_readers[0].getFactory().getFormatName());
for (int i = 1; i < len; ++i) {
sb.append(", ");
sb.append(_readers[i].getFactory().getFormatName());
}
}
sb.append(']');
return sb.toString();
}
/*
/**********************************************************
/* Internal methods
/**********************************************************
*/
private Match _findFormat(AccessorForReader acc) throws IOException
{
ObjectReader bestMatch = null;
MatchStrength bestMatchStrength = null;
for (ObjectReader f : _readers) {
acc.reset();
MatchStrength strength = f.getFactory().hasFormat(acc);
// if not better than what we have so far (including minimal level limit), skip
if (strength == null || strength.ordinal() < _minimalMatch.ordinal()) {
continue;
}
// also, needs to better match than before
if (bestMatch != null) {
if (bestMatchStrength.ordinal() >= strength.ordinal()) {
continue;
}
}
// finally: if it's good enough match, we are done
bestMatch = f;
bestMatchStrength = strength;
if (strength.ordinal() >= _optimalMatch.ordinal()) {
break;
}
}
return acc.createMatcher(bestMatch, bestMatchStrength);
}
/*
/**********************************************************
/* Helper classes
/**********************************************************
*/
/**
* We need sub-class here as well, to be able to access efficiently.
*/
protected class AccessorForReader extends InputAccessor.Std
{
public AccessorForReader(InputStream in, byte[] buffer) {
super(in, buffer);
}
public AccessorForReader(byte[] inputDocument) {
super(inputDocument);
}
public AccessorForReader(byte[] inputDocument, int start, int len) {
super(inputDocument, start, len);
}
public Match createMatcher(ObjectReader match, MatchStrength matchStrength)
{
return new Match(_in, _buffer, _bufferedStart, (_bufferedEnd - _bufferedStart),
match, matchStrength);
}
}
/**
* Result class, similar to {@link DataFormatMatcher}
*/
public static class Match
{
protected final InputStream _originalStream;
/**
* Content read during format matching process
*/
protected final byte[] _bufferedData;
/**
* Pointer to the first byte in buffer available for reading
*/
protected final int _bufferedStart;
/**
* Number of bytes available in buffer.
*/
protected final int _bufferedLength;
/**
* Factory that produced sufficient match (if any)
*/
protected final ObjectReader _match;
/**
* Strength of match with {@link #_match}
*/
protected final MatchStrength _matchStrength;
protected Match(InputStream in, byte[] buffered,
int bufferedStart, int bufferedLength,
ObjectReader match, MatchStrength strength)
{
_originalStream = in;
_bufferedData = buffered;
_bufferedStart = bufferedStart;
_bufferedLength = bufferedLength;
_match = match;
_matchStrength = strength;
}
/*
/**********************************************************
/* Public API, simple accessors
/**********************************************************
*/
/**
* Accessor to use to see if any formats matched well enough with
* the input data.
*/
public boolean hasMatch() { return _match != null; }
/**
* Method for accessing strength of the match, if any; if no match,
* will return {@link MatchStrength#INCONCLUSIVE}.
*/
public MatchStrength getMatchStrength() {
return (_matchStrength == null) ? MatchStrength.INCONCLUSIVE : _matchStrength;
}
/**
* Accessor for {@link JsonFactory} that represents format that data matched.
*/
public ObjectReader getReader() { return _match; }
/**
* Accessor for getting brief textual name of matched format if any (null
* if none). Equivalent to:
*
* return hasMatch() ? getMatch().getFormatName() : null;
*
*/
public String getMatchedFormatName() {
return _match.getFactory().getFormatName();
}
/*
/**********************************************************
/* Public API, factory methods
/**********************************************************
*/
/**
* Convenience method for trying to construct a {@link JsonParser} for
* parsing content which is assumed to be in detected data format.
* If no match was found, returns null.
*/
public JsonParser createParserWithMatch() throws IOException
{
if (_match == null) {
return null;
}
JsonFactory jf = _match.getFactory();
if (_originalStream == null) {
return jf.createParser(_bufferedData, _bufferedStart, _bufferedLength);
}
return jf.createParser(getDataStream());
}
/**
* Method to use for accessing input for which format detection has been done.
* This must be used instead of using stream passed to detector
* unless given stream itself can do buffering.
* Stream will return all content that was read during matching process, as well
* as remaining contents of the underlying stream.
*/
public InputStream getDataStream() {
if (_originalStream == null) {
return new ByteArrayInputStream(_bufferedData, _bufferedStart, _bufferedLength);
}
return new MergedStream(null, _originalStream, _bufferedData, _bufferedStart, _bufferedLength);
}
}
}