io.wcm.caravan.pipeline.impl.operators.ExtractOperator.java Source code

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Here is the source code for io.wcm.caravan.pipeline.impl.operators.ExtractOperator.java

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/*
 * #%L
 * wcm.io
 * %%
 * Copyright (C) 2014 wcm.io
 * %%
 * 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.
 * #L%
 */
package io.wcm.caravan.pipeline.impl.operators;

import static org.apache.commons.lang3.StringUtils.isNotBlank;
import io.wcm.caravan.pipeline.JsonPipelineOutput;
import io.wcm.caravan.pipeline.impl.JacksonFunctions;
import io.wcm.caravan.pipeline.impl.JsonPathSelector;
import rx.Observable.Operator;
import rx.Subscriber;
import rx.exceptions.Exceptions;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.MissingNode;

/**
 * An operator that evaluates a JSONPath expression on the pipeline's JSON output and extracts the first result.
 * If any result is missing, Jackson {@link MissingNode} will be returned as an extraction result.
 */
public class ExtractOperator implements Operator<JsonPipelineOutput, JsonPipelineOutput> {

    private final String jsonPath;
    private final String targetProperty;

    /**
     * @param jsonPath the JSONPath to evaluate
     * @param targetProperty the name of the property to store the first result of the JSONpath expression in
     */
    public ExtractOperator(String jsonPath, String targetProperty) {
        this.jsonPath = jsonPath;
        this.targetProperty = targetProperty;
    }

    @Override
    public Subscriber<? super JsonPipelineOutput> call(Subscriber<? super JsonPipelineOutput> subscriber) {
        return new Subscriber<JsonPipelineOutput>() {

            @Override
            public void onCompleted() {
                subscriber.onCompleted();
            }

            @Override
            public void onError(Throwable e) {
                Exceptions.throwIfFatal(e);
                subscriber.onError(e);
            }

            @Override
            public void onNext(JsonPipelineOutput output) {
                ArrayNode result = new JsonPathSelector(jsonPath).call(output.getPayload());

                JsonNode extractedPayload = result.size() == 0 ? MissingNode.getInstance() : result.get(0);

                if (isNotBlank(targetProperty)) {
                    extractedPayload = JacksonFunctions.wrapInObject(targetProperty, extractedPayload);
                }

                JsonPipelineOutput extractedOutput = output.withPayload(extractedPayload);
                subscriber.onNext(extractedOutput);
            }
        };
    }
}