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/*-
* #%L
* Amazon Athena Query Federation SDK
* %%
* Copyright (C) 2019 - 2020 Amazon Web Services
* %%
* 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.
* #L%
*/
package com.amazonaws.athena.connector.lambda.serde;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import static com.amazonaws.athena.connector.lambda.serde.BaseSerializer.TYPE_FIELD;
public abstract class BaseDeserializer extends StdDeserializer implements VersionedSerDe.Deserializer
{
protected BaseDeserializer(Class clazz)
{
super(clazz);
}
@Override
public T deserialize(JsonParser jparser, DeserializationContext ctxt)
throws IOException
{
if (jparser.nextToken() != JsonToken.VALUE_NULL) {
validateObjectStart(jparser.getCurrentToken());
T result = doDeserialize(jparser, ctxt);
validateObjectEnd(jparser);
return result;
}
else {
return null;
}
}
@Override
public Object deserializeWithType(JsonParser jp, DeserializationContext ctxt, TypeDeserializer typeDeserializer)
throws IOException
{
// TODO leverage TypeDeserializer if it simplifies things
return deserialize(jp, ctxt);
}
public abstract T doDeserialize(JsonParser jparser, DeserializationContext ctxt)
throws IOException;
/**
* Helper used to extract named String fields from the json parser in a streaming fashion.
*
* @param jparser The parser to use for extraction.
* @param expectedFieldName The expected name of the next field in the stream.
* @return The string representation of the requested field.
* @throws IOException If there is an error parsing the field.
*/
protected String getNextStringField(JsonParser jparser, String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
//move to the value token
jparser.nextToken();
return jparser.getValueAsString();
}
/**
* Helper used to extract named boolean fields from the json parser in a streaming fashion.
*
* @param jparser The parser to use for extraction.
* @param expectedFieldName The expected name of the next field in the stream.
* @return The boolean representation of the requested field.
* @throws IOException If there is an error parsing the field.
*/
protected boolean getNextBoolField(final JsonParser jparser, final String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
//move to the value token
jparser.nextToken();
return jparser.getValueAsBoolean();
}
/**
* Helper used to extract named byte array fields from the json parser in a streaming fashion.
*
* @param jparser The parser to use for extraction.
* @param expectedFieldName The expected name of the next field in the stream.
* @return The byte array representation of the requested field.
* @throws IOException If there is an error parsing the field.
*/
protected byte[] getNextBinaryField(final JsonParser jparser, final String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
//move to the value token
jparser.nextToken();
return jparser.getBinaryValue();
}
/**
* Helper used to extract named integer fields from the json parser in a streaming fashion.
*
* @param jparser The parser to use for extraction.
* @param expectedFieldName The expected name of the next field in the stream.
* @return The integer representation of the requested field.
* @throws IOException If there is an error parsing the field.
*/
protected int getNextIntField(JsonParser jparser, String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
//move to the value token
jparser.nextToken();
return jparser.getValueAsInt();
}
/**
* Helper used to extract named long fields from the json parser in a streaming fashion.
*
* @param jparser The parser to use for extraction.
* @param expectedFieldName The expected name of the next field in the stream.
* @return The integer representation of the requested field.
* @throws IOException If there is an error parsing the field.
*/
protected long getNextLongField(JsonParser jparser, String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
//move to the value token
jparser.nextToken();
return jparser.getValueAsLong();
}
/**
* Helper used to help serialize a list of strings.
*
* @param jgen The json generator to use.
* @param fieldname The name to associated to the resulting json array.
* @param values The values to populate the array with.
* @throws IOException If an error occurs while writing to the generator.
*/
protected void writeStringArray(JsonGenerator jgen, String fieldname, Collection values)
throws IOException
{
jgen.writeArrayFieldStart(fieldname);
for (String nextElement : values) {
jgen.writeString(nextElement);
}
jgen.writeEndArray();
}
/**
* Helper used to read a list of strings.
*
* @param jparser The parser to read from.
* @param expectedFieldName The expected name of the field containing the string array.
* @return The contents of the array as a list.
* @throws IOException If an error occurs while reading from the parser.
*/
protected List getNextStringArray(JsonParser jparser, String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
validateArrayStart(jparser);
List result = new ArrayList<>();
while (jparser.nextToken() != JsonToken.END_ARRAY) {
result.add(jparser.getValueAsString());
}
return result;
}
/**
* Helper used to read a Map of strings to strings.
*
* @param jparser The parser to read from.
* @param expectedFieldName The expected name of the field containing the string map.
* @return The contents of the array as a map.
* @throws IOException If an error occurs while reading from the parser.
*/
protected Map getNextStringMap(JsonParser jparser, String expectedFieldName)
throws IOException
{
assertFieldName(jparser, expectedFieldName);
validateObjectStart(jparser);
Map result = new HashMap<>();
while (jparser.nextToken() != JsonToken.END_OBJECT) {
result.put(jparser.getCurrentName(), jparser.getValueAsString());
}
return result;
}
/**
* Helper used to validate an expected field name.
*
* @param jparser The parser to read from.
* @param expectedFieldName The expected name of the next field.
* @throws IOException If an error occurs while reading from the parser.
*/
protected void assertFieldName(JsonParser jparser, String expectedFieldName)
throws IOException
{
jparser.nextToken();
if (jparser.getCurrentToken() != JsonToken.FIELD_NAME) {
throw new IllegalStateException("Expected field name token but got " + jparser.getCurrentToken());
}
String fieldNameToken = jparser.getCurrentName();
if (expectedFieldName != null && !expectedFieldName.equals(fieldNameToken)) {
throw new IllegalStateException("Unexpected field[" + fieldNameToken + "] while expecting[" + expectedFieldName + "]");
}
}
/**
* Helper used to validate that an object is starting (open brace) at the provided {@link JsonToken}.
*
* @param token The token expected to be an object start.
* @throws IOException If an error occurs while reading from the parser.
*/
protected void validateObjectStart(JsonToken token)
throws IOException
{
if (!JsonToken.START_OBJECT.equals(token)) {
throw new IllegalStateException("Expected " + JsonToken.START_OBJECT + " found " + token.asString());
}
}
/**
* Helper used to validate that an object is ending (close brace) at the next token.
*
* @param jparser The parser to read from.
* @throws IOException If an error occurs while reading from the parser.
*/
protected void validateObjectEnd(JsonParser jparser)
throws IOException
{
if (!JsonToken.END_OBJECT.equals(jparser.nextToken())) {
throw new IllegalStateException("Expected " + JsonToken.END_OBJECT + " found " + jparser.getText());
}
}
/**
* Helper used to validate that an array is starting (open bracket) at the next token.
*
* @param jparser The parser to read from.
* @throws IOException If an error occurs while reading from the parser.
*/
protected void validateArrayStart(JsonParser jparser)
throws IOException
{
if (!JsonToken.START_ARRAY.equals(jparser.nextToken())) {
throw new IllegalStateException("Expected " + JsonToken.START_ARRAY + " found " + jparser.getText());
}
}
/**
* Helper used to validate that an object is starting (open brace) at the next token.
*
* @param jparser The parser to read from.
* @throws IOException If an error occurs while reading from the parser.
*/
protected void validateObjectStart(JsonParser jparser)
throws IOException
{
if (!JsonToken.START_OBJECT.equals(jparser.nextToken())) {
throw new IllegalStateException("Expected " + JsonToken.START_OBJECT + " found " + jparser.getText());
}
}
/**
* Helper used to parse the type of the object (usually the class name).
*
* @param jparser The parser to use for extraction.
* @return The type name of the object being deserialized.
* @throws IOException If there is an error parsing the field.
*/
protected String getType(JsonParser jparser)
throws IOException
{
assertFieldName(jparser, TYPE_FIELD);
jparser.nextToken();
return jparser.getValueAsString();
}
/**
* Helper used to skip to the end of the current object. Useful for forwards compatibility.
*
* @param jparser The parser to use for extraction.
* @throws IOException If there is an error parsing.
*/
protected void ignoreRestOfObject(JsonParser jparser)
throws IOException
{
if (jparser.getCurrentToken() == JsonToken.END_OBJECT) {
return;
}
int open = 1;
/* Since proper matching of start/end markers is handled
* by nextToken(), we'll just count nesting levels here
*/
while (true) {
JsonToken t = jparser.nextToken();
if (t == null) {
throw new IllegalStateException("Expected " + JsonToken.END_OBJECT + " found " + jparser.getText());
}
if (t.isStructStart()) {
++open;
}
else if (t == JsonToken.END_OBJECT) {
if (--open == 0) {
return;
}
}
}
}
}
