sg.atom.utils.datastructure.parser.JSONParser.java Source code

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Here is the source code for sg.atom.utils.datastructure.parser.JSONParser.java

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/*
 * Copyright 2011,2012 Metamarkets Group Inc.
 *
 * 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 sg.atom.utils.datastructure.parser;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Function;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.metamx.common.exception.FormattedException;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class JSONParser implements Parser<String, Object> {

    private final ObjectMapper jsonMapper = new ObjectMapper();
    private ArrayList<String> fieldNames = null;

    private static final Function<JsonNode, String> valueFunction = new Function<JsonNode, String>() {
        @Override
        public String apply(JsonNode node) {
            // use getValueAsText for compatibility with older jackson implementations on EMR
            return (node == null || node.isMissingNode() || node.isNull()) ? null : node.asText();
        }
    };

    public JSONParser() {
    }

    public JSONParser(Iterable<String> fieldNames) {
        setFieldNames(fieldNames);
    }

    @Override
    public List<String> getFieldNames() {
        return fieldNames;
    }

    @Override
    public void setFieldNames(Iterable<String> fieldNames) {
        ParserUtils.validateFields(fieldNames);
        this.fieldNames = Lists.newArrayList(fieldNames);
    }

    @Override
    public Map<String, Object> parse(String input) throws FormattedException {
        try {
            Map<String, Object> map = new LinkedHashMap<String, Object>();
            JsonNode root = jsonMapper.readTree(input);

            Iterator<String> keysIter = (fieldNames == null ? root.fieldNames() : fieldNames.iterator());

            while (keysIter.hasNext()) {
                String key = keysIter.next();
                JsonNode node = root.path(key);

                if (node.isArray()) {
                    final List<String> nodeValue = Lists.newArrayListWithExpectedSize(node.size());
                    for (final JsonNode subnode : node) {
                        final String subnodeValue = valueFunction.apply(subnode);
                        if (subnodeValue != null) {
                            nodeValue.add(subnodeValue);
                        }
                    }
                    map.put(key, nodeValue);
                } else {
                    final String nodeValue = valueFunction.apply(node);
                    if (nodeValue != null) {
                        map.put(key, nodeValue);
                    }
                }
            }
            return map;
        } catch (Exception e) {
            Throwables.propagateIfPossible(e, FormattedException.class);
            throw new FormattedException.Builder().withErrorCode(FormattedException.ErrorCode.UNPARSABLE_ROW)
                    .withMessage(e.getMessage()).build();
        }
    }
}