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gwt-jackson is a GWT JSON serializer/deserializer mechanism based on Jackson annotations
There is a newer version: 0.15.4
package com.github.nmorel.gwtjackson.client;

import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.fasterxml.jackson.annotation.ObjectIdGenerator.IdKey;
import com.github.nmorel.gwtjackson.client.exception.JsonDeserializationException;
import com.github.nmorel.gwtjackson.client.stream.JsonReader;
import com.github.nmorel.gwtjackson.client.stream.StringReader;
import com.google.gwt.logging.client.LogConfiguration;

/**
 * Context for the deserialization process.
 *
 * @author Nicolas Morel
 */
public class JsonDeserializationContext extends JsonMappingContext {

    public static class Builder {

        private boolean failOnUnknownProperties = true;

        /**
         * Determines whether encountering of unknown
         * properties (ones that do not map to a property, and there is
         * no "any setter" or handler that can handle it)
         * should result in a failure (by throwing a
         * {@link JsonDeserializationException}) or not.
         * This setting only takes effect after all other handling
         * methods for unknown properties have been tried, and
         * property remains unhandled.
         * 
         * Feature is enabled by default (meaning that a
         * {@link JsonDeserializationException} will be thrown if an unknown property
         * is encountered).
         */
        public Builder failOnUnknownProperties( boolean failOnUnknownProperties ) {
            this.failOnUnknownProperties = failOnUnknownProperties;
            return this;
        }

        public JsonDeserializationContext build() {
            return new JsonDeserializationContext( failOnUnknownProperties );
        }
    }

    private static final Logger logger = Logger.getLogger( "JsonDeserialization" );

    private Map idToObject;

    /*
     * Deserialization options
     */
    private final boolean failOnUnknownProperties;

    private JsonDeserializationContext( boolean failOnUnknownProperties ) {
        this.failOnUnknownProperties = failOnUnknownProperties;
    }

    @Override
    public Logger getLogger() {
        return logger;
    }

    public boolean isFailOnUnknownProperties() {
        return failOnUnknownProperties;
    }

    public JsonReader newJsonReader( String input ) {
        return new JsonReader( new StringReader( input ) );
    }

    /**
     * Trace an error with current reader state and returns a corresponding exception.
     *
     * @param message error message
     *
     * @return a {@link JsonDeserializationException} with the given message
     */
    public JsonDeserializationException traceError( String message ) {
        getLogger().log( Level.SEVERE, message );
        return new JsonDeserializationException( message );
    }

    /**
     * Trace an error with current reader state and returns a corresponding exception.
     *
     * @param message error message
     * @param reader current reader
     *
     * @return a {@link JsonDeserializationException} with the given message
     */
    public JsonDeserializationException traceError( String message, JsonReader reader ) {
        JsonDeserializationException exception = traceError( message );
        traceReaderInfo( reader );
        return exception;
    }

    /**
     * Trace an error and returns a corresponding exception.
     *
     * @param cause cause of the error
     *
     * @return a {@link JsonDeserializationException} with the given cause
     */
    public JsonDeserializationException traceError( Exception cause ) {
        getLogger().log( Level.SEVERE, "Error during deserialization", cause );
        return new JsonDeserializationException( cause );
    }

    /**
     * Trace an error with current reader state and returns a corresponding exception.
     *
     * @param cause cause of the error
     * @param reader current reader
     *
     * @return a {@link JsonDeserializationException} with the given cause
     */
    public JsonDeserializationException traceError( Exception cause, JsonReader reader ) {
        JsonDeserializationException exception = traceError( cause );
        traceReaderInfo( reader );
        return exception;
    }

    /**
     * Trace the current reader state
     */
    private void traceReaderInfo( JsonReader reader ) {
        if ( LogConfiguration.loggingIsEnabled( Level.INFO ) ) {
            getLogger().log( Level.INFO, "Error at line " + reader.getLineNumber() + " and column " + reader
                .getColumnNumber() + " of input <" + reader.getInput() + ">" );
        }
    }

    public void addObjectId( IdKey id, Object instance ) {
        if ( null == idToObject ) {
            idToObject = new HashMap();
        }
        idToObject.put( id, instance );
    }

    public Object getObjectWithId( IdKey id ) {
        if ( null != idToObject ) {
            return idToObject.get( id );
        }
        return null;
    }
}