XPathFilter.java

/*
 * Copyright 2013 Netflix, 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 com.netflix.suro.routing;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.netflix.suro.message.MessageContainer;
import com.netflix.suro.routing.filter.MessageFilter;
import com.netflix.suro.routing.filter.MessageFilterCompiler;
import com.netflix.suro.routing.filter.lang.InvalidFilterException;

/**
 * An implementation of {@link Filter} that coerced message payload to a string, and applies
 * regex to the coerced string. The match is partial.
 *
 */
public class XPathFilter implements Filter {
    public static final String TYPE = "xpath";
    public static final String JSON_PROPERTY_FILTER = "filter";
    public static final String JSON_PROPERTY_CONVERTER = "converter";

    private final MessageFilter filter;
    private final String expression;
    private final MessageConverter converter;

    @JsonCreator
    public XPathFilter(
        @JsonProperty(JSON_PROPERTY_FILTER) String expression,
        @JsonProperty(JSON_PROPERTY_CONVERTER) MessageConverter converter) {
        this.expression = expression;
        try {
            filter = MessageFilterCompiler.compile(expression);
        } catch (InvalidFilterException e) {
            throw new IllegalArgumentException(String.format("Can't compile expression %s into a message filter: %s", expression, e.getMessage()), e);
        }

        this.converter = converter == null ? new JsonMapConverter() : converter;
    }

    /**
     *
     * @param message The message that is to be matched against the filter's regex pattern
     * @return true if the message's string representation contains the regex pattern. False otherwise.
     * @throws Exception If filtering fails. For example, if the given message can't be coerced into a string.
     */
    @Override
    public boolean doFilter(MessageContainer message) throws Exception {
        return filter.apply(converter.convert(message));
    }

    @JsonProperty(JSON_PROPERTY_CONVERTER)
    public MessageConverter getConverter() {
        return converter;
    }

    @JsonProperty(JSON_PROPERTY_FILTER)
    public String getExpression() {
        return expression;
    }
}