MetadataSerializer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.tika.serialization.serdes;

import java.io.IOException;
import java.util.Arrays;
import java.util.Comparator;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

import org.apache.tika.metadata.Metadata;
import org.apache.tika.metadata.TikaCoreProperties;

public class MetadataSerializer extends JsonSerializer<Metadata> {
    private static final String TIKA_CONTENT_KEY = TikaCoreProperties.TIKA_CONTENT.getName();

    //always sort the content at the end
    private static final Comparator<String> METADATA_KEY_COMPARATOR = new Comparator<String>() {
        @Override
        public int compare(String o1, String o2) {
            if (o1.equals(TIKA_CONTENT_KEY)) {
                return 1;
            }
            if (o2.equals(TIKA_CONTENT_KEY)) {
                return -1;
            }
            return o1.compareTo(o2);
        }
    };

    private boolean prettyPrint = false;

    public MetadataSerializer() {

    }

    public MetadataSerializer(boolean prettyPrint) {
        this.prettyPrint = prettyPrint;
    }
    @Override
    public void serialize(Metadata metadata, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        jsonGenerator.writeStartObject();
        String[] names = metadata.names();
        if (prettyPrint) {
            Arrays.sort(names, METADATA_KEY_COMPARATOR);
        }
        for (String n : names) {
            String[] v = metadata.getValues(n);
            if (v.length == 0) {
                continue;
            } else if (v.length == 1) {
                jsonGenerator.writeStringField(n, v[0]);
            } else {
                jsonGenerator.writeFieldName(n);
                jsonGenerator.writeArray(v, 0, v.length);
            }
        }
        jsonGenerator.writeEndObject();
    }
}