gov.nasa.pds.harvest.util.out.NDJsonDocUtils Maven / Gradle / Ivy

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package gov.nasa.pds.harvest.util.out;

import java.io.StringWriter;
import java.io.Writer;
import java.util.Collection;
import com.google.gson.stream.JsonWriter;


/**
 * Utility class to write NJSON (new-line delimited JSON) documents.
 *  
 * @author karpenko
 *
 */
public class NDJsonDocUtils
{
    private static final String REPLACE_DOT_WITH = "/";


    /**
     * Create primary key JSON (first line in NJSON record)
     * @param id primary key
     * @return primary key JSON
     * @throws Exception Generic exception
     */
    public static String createPKJson(String id) throws Exception
    {
        StringWriter sw = new StringWriter();
        JsonWriter jw = new JsonWriter(sw);
        
        jw.beginObject();
        
        jw.name("index");
        jw.beginObject();
        jw.name("_id").value(id);
        jw.endObject();
        
        jw.endObject();
        
        jw.close();
        
        return sw.getBuffer().toString();
    }

    
    /**
     * Write primary key (first line in NJSON record)
     * @param writer Generic writer
     * @param id primary key
     * @throws Exception Generic exception
     */
    public static void writePK(Writer writer, String id) throws Exception
    {
        writer.write(createPKJson(id));
    }

    
    /**
     * Write a field.
     * @param jw JSON writer
     * @param key a key / field name
     * @param value a value
     * @throws Exception Generic exception
     */
    public static void writeField(JsonWriter jw, String key, String value) throws Exception
    {
        if(value == null) return;
        
        key = toEsFieldName(key);
        jw.name(key).value(value);
    }


    /**
     * Write a field.
     * @param jw JSON writer
     * @param key a key / field name
     * @param value a value
     * @throws Exception Generic exception
     */
    public static void writeField(JsonWriter jw, String key, long value) throws Exception
    {
        key = toEsFieldName(key);
        jw.name(key).value(value);
    }

    
    /**
     * Write a field.
     * @param jw JSON writer
     * @param key a key / field name
     * @param value a value
     * @throws Exception Generic exception
     */
    public static void writeField(JsonWriter jw, String key, float value) throws Exception
    {
        key = toEsFieldName(key);
        jw.name(key).value(value);
    }

    
    /**
     * Write a field.
     * @param jw JSON writer
     * @param key a key / field name
     * @param values collection of values
     * @throws Exception Generic exception
     */
    public static void writeField(JsonWriter jw, String key, Collection values) throws Exception
    {
        if(values == null || values.isEmpty()) return;

        key = toEsFieldName(key);
        jw.name(key);

        if(values.size() == 1)
        {
            jw.value(values.iterator().next());
        }
        else
        {
            jw.beginArray();
            for(String value: values)
            {
                jw.value(value);
            }
            jw.endArray();
        }
    }


    /**
     * Write multivalued field as an array
     * @param jw JSON writer
     * @param key key / field name
     * @param values collection of values
     * @throws Exception an exception
     */
    public static void writeArray(JsonWriter jw, String key, Collection values) throws Exception
    {
        if(values == null || values.isEmpty()) return;

        key = toEsFieldName(key);
        jw.name(key);

        jw.beginArray();
        for(String value: values)
        {
            jw.value(value);
        }
        jw.endArray();
    }

        
    /**
     * Convert registry field name to the valid Elasticsearch field name. 
     * (Replace '.' with '/').
     * @param fieldName a field name
     * @return valid Elasticsearch field name
     */
    public static String toEsFieldName(String fieldName)
    {
        return fieldName.replaceAll("\\.", REPLACE_DOT_WITH);
    }
}