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com.facebook.presto.jdbc.internal.jackson.databind.MappingIterator Maven / Gradle / Ivy
package com.facebook.presto.jdbc.internal.jackson.databind;
import java.io.Closeable;
import java.io.IOException;
import java.util.*;
import com.facebook.presto.jdbc.internal.jackson.core.*;
/**
* Iterator exposed by {@link ObjectMapper} when binding sequence of
* objects. Extension is done to allow more convenient exposing of
* {@link IOException} (which basic {@link Iterator} does not expose)
*/
public class MappingIterator implements Iterator, Closeable
{
protected final static MappingIterator EMPTY_ITERATOR =
new MappingIterator(null, null, null, null, false, null);
/*
/**********************************************************
/* State constants
/**********************************************************
*/
/**
* State in which iterator is closed
*/
protected final static int STATE_CLOSED = 0;
/**
* State in which value read failed
*/
protected final static int STATE_NEED_RESYNC = 1;
/**
* State in which no recovery is needed, but "hasNextValue()" needs
* to be called first
*/
protected final static int STATE_MAY_HAVE_VALUE = 2;
/**
* State in which "hasNextValue()" has been succesfully called
* and deserializer can be called to fetch value
*/
protected final static int STATE_HAS_VALUE = 3;
/*
/**********************************************************
/* Configuration
/**********************************************************
*/
/**
* Type to bind individual elements to.
*/
protected final JavaType _type;
/**
* Context for deserialization, needed to pass through to deserializer
*/
protected final DeserializationContext _context;
/**
* Deserializer for individual element values.
*/
protected final JsonDeserializer _deserializer;
/**
* Underlying parser used for reading content to bind. Initialized
* as not null but set as null when
* iterator is closed, to denote closing.
*/
protected final JsonParser _parser;
/**
* Context to resynchronize to, in case an exception is encountered
* but caller wants to try to read more elements.
*/
protected final JsonStreamContext _seqContext;
/**
* If not null, "value to update" instead of creating a new instance
* for each call.
*/
protected final T _updatedValue;
/**
* Flag that indicates whether input {@link JsonParser} should be closed
* when we are done or not; generally only called when caller did not
* pass JsonParser.
*/
protected final boolean _closeParser;
/*
/**********************************************************
/* Parsing state
/**********************************************************
*/
/**
* State of the iterator
*/
protected int _state;
/*
/**********************************************************
/* Construction
/**********************************************************
*/
/**
* @param managedParser Whether we "own" the {@link JsonParser} passed or not:
* if true, it was created by {@link ObjectReader} and code here needs to
* close it; if false, it was passed by calling code and should not be
* closed by iterator.
*/
@SuppressWarnings("unchecked")
protected MappingIterator(JavaType type, JsonParser p, DeserializationContext ctxt,
JsonDeserializer deser,
boolean managedParser, Object valueToUpdate)
{
_type = type;
_parser = p;
_context = ctxt;
_deserializer = (JsonDeserializer) deser;
_closeParser = managedParser;
if (valueToUpdate == null) {
_updatedValue = null;
} else {
_updatedValue = (T) valueToUpdate;
}
/* Ok: one more thing; we may have to skip START_ARRAY, assuming
* "wrapped" sequence; but this is ONLY done for 'managed' parsers
* and never if JsonParser was directly passed by caller (if it
* was, caller must have either positioned it over first token of
* the first element, or cleared the START_ARRAY token explicitly).
* Note, however, that we do not try to guess whether this could be
* an unwrapped sequence of arrays/Lists: we just assume it is wrapped;
* and if not, caller needs to hand us JsonParser instead, pointing to
* the first token of the first element.
*/
if (p == null) { // can this occur?
_seqContext = null;
_state = STATE_CLOSED;
} else {
JsonStreamContext sctxt = p.getParsingContext();
if (managedParser && p.isExpectedStartArrayToken()) {
// If pointing to START_ARRAY, context should be that ARRAY
p.clearCurrentToken();
} else {
// regardless, recovery context should be whatever context we have now,
// with sole exception of pointing to a start marker, in which case it's
// the parent
JsonToken t = p.getCurrentToken();
if ((t == JsonToken.START_OBJECT) || (t == JsonToken.START_ARRAY)) {
sctxt = sctxt.getParent();
}
}
_seqContext = sctxt;
_state = STATE_MAY_HAVE_VALUE;
}
}
/**
* Method for getting an "empty" iterator instance: one that never
* has more values; may be freely shared.
*
* @since 2.10 Existed earlier but {@code public} since 2.10
*/
@SuppressWarnings("unchecked")
public static MappingIterator emptyIterator() {
return (MappingIterator) EMPTY_ITERATOR;
}
/*
/**********************************************************
/* Basic iterator impl
/**********************************************************
*/
@Override
public boolean hasNext()
{
try {
return hasNextValue();
} catch (JsonMappingException e) {
return (Boolean) _handleMappingException(e);
} catch (IOException e) {
return (Boolean) _handleIOException(e);
}
}
@SuppressWarnings("unchecked")
@Override
public T next()
{
try {
return nextValue();
} catch (JsonMappingException e) {
return (T) _handleMappingException(e);
} catch (IOException e) {
return (T) _handleIOException(e);
}
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void close() throws IOException {
if (_state != STATE_CLOSED) {
_state = STATE_CLOSED;
if (_parser != null) {
_parser.close();
}
}
}
/*
/**********************************************************
/* Extended API, iteration
/**********************************************************
*/
/**
* Equivalent of {@link #next} but one that may throw checked
* exceptions from Jackson due to invalid input.
*/
public boolean hasNextValue() throws IOException
{
switch (_state) {
case STATE_CLOSED:
return false;
case STATE_NEED_RESYNC:
_resync();
// fall-through
case STATE_MAY_HAVE_VALUE:
JsonToken t = _parser.getCurrentToken();
if (t == null) { // un-initialized or cleared; find next
t = _parser.nextToken();
// If EOF, no more, or if we hit END_ARRAY (although we don't clear the token).
if (t == null || t == JsonToken.END_ARRAY) {
_state = STATE_CLOSED;
if (_closeParser && (_parser != null)) {
_parser.close();
}
return false;
}
}
_state = STATE_HAS_VALUE;
return true;
case STATE_HAS_VALUE:
// fall through
}
return true;
}
public T nextValue() throws IOException
{
switch (_state) {
case STATE_CLOSED:
return _throwNoSuchElement();
case STATE_NEED_RESYNC: // fall-through, will do re-sync
case STATE_MAY_HAVE_VALUE:
if (!hasNextValue()) {
return _throwNoSuchElement();
}
break;
case STATE_HAS_VALUE:
break;
}
int nextState = STATE_NEED_RESYNC;
try {
T value;
if (_updatedValue == null) {
value = _deserializer.deserialize(_parser, _context);
} else{
_deserializer.deserialize(_parser, _context, _updatedValue);
value = _updatedValue;
}
nextState = STATE_MAY_HAVE_VALUE;
return value;
} finally {
_state = nextState;
/* 24-Mar-2015, tatu: As per [#733], need to mark token consumed no
* matter what, to avoid infinite loop for certain failure cases.
* For 2.6 need to improve further.
*/
_parser.clearCurrentToken();
}
}
/**
* Convenience method for reading all entries accessible via
* this iterator; resulting container will be a {@link java.util.ArrayList}.
*
* @return List of entries read
*
* @since 2.2
*/
public List readAll() throws IOException {
return readAll(new ArrayList());
}
/**
* Convenience method for reading all entries accessible via
* this iterator
*
* @return List of entries read (same as passed-in argument)
*
* @since 2.2
*/
public > L readAll(L resultList) throws IOException
{
while (hasNextValue()) {
resultList.add(nextValue());
}
return resultList;
}
/**
* Convenience method for reading all entries accessible via
* this iterator
*
* @since 2.5
*/
public > C readAll(C results) throws IOException
{
while (hasNextValue()) {
results.add(nextValue());
}
return results;
}
/*
/**********************************************************
/* Extended API, accessors
/**********************************************************
*/
/**
* Accessor for getting underlying parser this iterator uses.
*
* @since 2.2
*/
public JsonParser getParser() {
return _parser;
}
/**
* Accessor for accessing {@link FormatSchema} that the underlying parser
* (as per {@link #getParser}) is using, if any; only parser of schema-aware
* formats use schemas.
*
* @since 2.2
*/
public FormatSchema getParserSchema() {
return _parser.getSchema();
}
/**
* Convenience method, functionally equivalent to:
*
* iterator.getParser().getCurrentLocation()
*
*
* @return Location of the input stream of the underlying parser
*
* @since 2.2.1
*/
public JsonLocation getCurrentLocation() {
return _parser.getCurrentLocation();
}
/*
/**********************************************************
/* Helper methods
/**********************************************************
*/
protected void _resync() throws IOException
{
final JsonParser p = _parser;
// First, a quick check to see if we might have been lucky and no re-sync needed
if (p.getParsingContext() == _seqContext) {
return;
}
while (true) {
JsonToken t = p.nextToken();
if ((t == JsonToken.END_ARRAY) || (t == JsonToken.END_OBJECT)) {
if (p.getParsingContext() == _seqContext) {
p.clearCurrentToken();
return;
}
} else if ((t == JsonToken.START_ARRAY) || (t == JsonToken.START_OBJECT)) {
p.skipChildren();
} else if (t == null) {
return;
}
}
}
protected R _throwNoSuchElement() {
throw new NoSuchElementException();
}
protected R _handleMappingException(JsonMappingException e) {
throw new RuntimeJsonMappingException(e.getMessage(), e);
}
protected R _handleIOException(IOException e) {
throw new RuntimeException(e.getMessage(), e);
}
}
