IgnoreEmptyFieldsRecordReader.java

/*
 * Copyright 2013 NGDATA nv
 *
 * 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.lilyproject.tools.import_.json;

import org.joda.time.DateTime;
import org.joda.time.LocalDate;
import org.lilyproject.repository.api.Link;
import org.lilyproject.repository.api.Record;
import org.lilyproject.repository.api.RepositoryException;

import java.math.BigDecimal;
import java.net.URI;
import java.util.List;

/**
 * A specialized RecordReader which will drop fields containing empty strings, drop lists
 * containing zero entries, and drop nested records containing zero fields.
 * For fields in the root record, the fields are not just skipped, they are actively deleted
 * by adding them to the deleted fields (this last part is actually a feature of the
 * superclass, see {@link RecordReader#deleteNullFields()}).
 *
 * <p>This makes a lot of sense when the input jsons are generated by ETL jobs that don't
 * want to bother with having to change the structure of the JSON according to whether
 * a field has a value or not. Instead, they can use a fixed json structure into which
 * they just need to fill in the blanks.</p>
 */
public class IgnoreEmptyFieldsRecordReader extends RecordReader {
    public static final IgnoreEmptyFieldsRecordReader INSTANCE = new IgnoreEmptyFieldsRecordReader();

    @Override
    protected Record readNestedRecord(ValueHandle handle, ReadContext context)
            throws InterruptedException, RepositoryException, JsonFormatException {
        Record record = super.readNestedRecord(handle, context);
        return record.getFields().isEmpty() ? null : record;
    }

    @Override
    protected String readString(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readString(handle, context);
    }

    @Override
    protected List<Object> readList(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        List<Object> result = super.readList(handle, context);
        return result != null && result.isEmpty() ? null : result;
    }

    @Override
    protected List<Object> readPath(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        List<Object> result = super.readPath(handle, context);
        return result != null && result.isEmpty() ? null : result;
    }

    @Override
    protected LocalDate readDate(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readDate(handle, context);
    }

    @Override
    protected DateTime readDateTime(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readDateTime(handle, context);
    }

    @Override
    protected Link readLink(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readLink(handle, context);
    }

    @Override
    protected Integer readInteger(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readInteger(handle, context);
    }

    @Override
    protected Long readLong(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readLong(handle, context);
    }

    @Override
    protected Double readDouble(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readDouble(handle, context);
    }

    @Override
    protected BigDecimal readDecimal(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readDecimal(handle, context);
    }

    @Override
    protected Boolean readBoolean(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readBoolean(handle, context);
    }

    @Override
    protected URI readUri(ValueHandle handle, ReadContext context)
            throws JsonFormatException, RepositoryException, InterruptedException {
        return isBlank(handle) ? null : super.readUri(handle, context);
    }

    protected boolean isBlank(ValueHandle handle) {
        return handle.node.isTextual() && handle.node.getTextValue().isEmpty();
    }
}