/*
* Copyright 2013 Nicolas Morel
*
* 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 com.github.nmorel.gwtjackson.client;
import com.github.nmorel.gwtjackson.client.exception.JsonDeserializationException;
import com.github.nmorel.gwtjackson.client.stream.JsonReader;
import com.github.nmorel.gwtjackson.client.stream.JsonToken;
/**
* Base class for all the deserializer. It handles null values and exceptions. The rest is delegated to implementations.
*
* @author Nicolas Morel
*/
public abstract class JsonDeserializer<T> {
/**
* Deserializes a JSON input into an object.
*
* @param reader {@link JsonReader} used to read the JSON input
* @param ctx Context for the full deserialization process
*
* @return the deserialized object
* @throws JsonDeserializationException if an error occurs during the deserialization
*/
public T deserialize( JsonReader reader, JsonDeserializationContext ctx ) throws JsonDeserializationException {
return deserialize( reader, ctx, JsonDeserializerParameters.DEFAULT );
}
/**
* Deserializes a JSON input into an object.
*
* @param reader {@link JsonReader} used to read the JSON input
* @param ctx Context for the full deserialization process
* @param params Parameters for this deserialization
*
* @return the deserialized object
* @throws JsonDeserializationException if an error occurs during the deserialization
*/
public T deserialize( JsonReader reader, JsonDeserializationContext ctx, JsonDeserializerParameters params ) throws
JsonDeserializationException {
if ( JsonToken.NULL.equals( reader.peek() ) ) {
return deserializeNullValue( reader, ctx, params );
}
return doDeserialize( reader, ctx, params );
}
/**
* Deserialize the null value. This method allows children to override the default behaviour.
*
* @param reader {@link JsonReader} used to read the JSON input
* @param ctx Context for the full deserialization process
* @param params Parameters for this deserialization
*
* @return the deserialized object
*/
protected T deserializeNullValue( JsonReader reader, JsonDeserializationContext ctx, JsonDeserializerParameters params ) {
reader.skipValue();
return null;
}
/**
* Deserializes a non-null JSON input into an object.
*
* @param reader {@link JsonReader} used to read the JSON input
* @param ctx Context for the full deserialization process
* @param params Parameters for this deserialization
*
* @return the deserialized object
*/
protected abstract T doDeserialize( JsonReader reader, JsonDeserializationContext ctx, JsonDeserializerParameters params );
/**
* Set the back reference.
*
* @param referenceName name of the reference
* @param reference reference to set
* @param value value to set the reference to.
* @param ctx Context for the full deserialization process
*
* @see com.fasterxml.jackson.annotation.JsonBackReference
*/
public void setBackReference( String referenceName, Object reference, T value, JsonDeserializationContext ctx ) {
throw new JsonDeserializationException( "Cannot set a back reference to the type managed by this deserializer" );
}
}