org.kiji.scoring.server.KijiScoringServerCell.java Source code

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Here is the source code for org.kiji.scoring.server.KijiScoringServerCell.java

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/**
 * (c) Copyright 2013 WibiData, Inc.
 *
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * 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 org.kiji.scoring.server;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.Charset;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericContainer;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.io.JsonEncoder;
import org.apache.avro.specific.SpecificDatumWriter;
import org.apache.avro.specific.SpecificRecord;

import org.kiji.annotations.ApiAudience;
import org.kiji.schema.impl.AvroCellEncoder;

/**
 * Models what a Kiji cell looks like when returned to the client. If the value set in the cell
 * is an Avro record, then the value will be serialized into a JSON string (so the client can
 * deserialize this back to an Avro object). Otherwise the object's toString() method will be used
 * to serialize the value. If the value is not an Avro type (subclass of GenericContainer) or a Java
 * primitive, serialization will fail.
 */
@ApiAudience.Private
@JsonPropertyOrder({ "timestamp", "value" })
public class KijiScoringServerCell {

    /**
     * Returns an encoded JSON string for the given object.
     *
     * @param input datum to encode as a JSON string.
     * @return the JSON string representing this object.
     *
     * @throws IOException if there is an error encoding the datum.
     */
    private static String getJsonString(final Object input) throws IOException {

        final String jsonString;
        if (input instanceof GenericContainer) {
            final GenericContainer record = (GenericContainer) input;
            final ByteArrayOutputStream baos = new ByteArrayOutputStream();
            try {
                final JsonEncoder encoder = EncoderFactory.get().jsonEncoder(record.getSchema(), baos);
                if (record instanceof SpecificRecord) {
                    new SpecificDatumWriter<GenericContainer>(record.getSchema()).write(record, encoder);
                } else {
                    new GenericDatumWriter<GenericContainer>(record.getSchema()).write(record, encoder);
                }
                encoder.flush();
                jsonString = new String(baos.toByteArray(), Charset.forName("UTF-8"));
            } finally {
                baos.close();
            }
        } else {
            jsonString = input.toString();
        }

        return jsonString;
    }

    /**
     * Returns the Avro Schema for this value.
     *
     * @param value is the record whose schema to return
     * @return the Schema object of the input value.
     */
    private static Schema getSchema(final Object value) {
        if (value instanceof GenericContainer) {
            return ((GenericContainer) value).getSchema();
        }
        final Schema primitiveSchema = AvroCellEncoder.PRIMITIVE_SCHEMAS.get(value.getClass().getCanonicalName());
        if (null != primitiveSchema) {
            return primitiveSchema;
        }
        throw new RuntimeException(
                String.format("Unsupported output type found." + "Class: %s", value.getClass().getCanonicalName()));
    }

    @JsonProperty("family")
    private String mFamily;

    @JsonProperty("qualifier")
    private String mQualifier;

    @JsonProperty("timestamp")
    private Long mTimestamp;

    @JsonProperty("value")
    private String mValue;

    @JsonProperty("schema")
    private String mSchema;

    /**
     * Initialize a new KijiScoringServerCell.
     *
     * @param family column family of the cell.
     * @param qualifier column qualifier of the cell.
     * @param timestamp timestamp of the cell.
     * @param value is the cell's value. If this is an Avro object, then it will be serialized
     *        to JSON and returned as a string literal containing JSON data.
     * @throws IOException if there is a problem serializing the value into JSON.
     */
    public KijiScoringServerCell(final String family, final String qualifier, final Long timestamp,
            final Object value) throws IOException {
        mTimestamp = timestamp;
        mValue = getJsonString(value);
        mSchema = getSchema(value).toString();
        mFamily = family;
        mQualifier = qualifier;
    }

    /** Default constructor for Jackson. **/
    public KijiScoringServerCell() {
    }

    /**
     * Get the cell's column family.
     *
     * @return the cell's column family.
     */
    public String getFamily() {
        return mFamily;
    }

    /**
     * Get the cell's column qualifier.
     *
     * @return the cell's column qualifier.
     */
    public String getQualifier() {
        return mQualifier;
    }

    /**
     * Get the cell's timestamp.
     *
     * @return the cell's timestamp
     */
    public Long getTimestamp() {
        return mTimestamp;
    }

    /**
     * Get the cell's datum value as a JSON encoded string.
     *
     * @return the cell's datum value.
     */
    public String getValue() {
        return mValue;
    }
}