com.google.cloud.bigtable.grpc.scanner.ResultQueueEntry.java Source code

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Here is the source code for com.google.cloud.bigtable.grpc.scanner.ResultQueueEntry.java

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/*
 * Copyright 2015 Google Inc. All Rights Reserved.
 *
 * 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.google.cloud.bigtable.grpc.scanner;

import com.google.cloud.bigtable.grpc.io.IOExceptionWithStatus;
import com.google.common.base.Preconditions;

import io.grpc.Status;

import java.io.IOException;
import java.util.Objects;

/**
 * An entry in the result queue which may be one of: A data message,
 * a Throwable or a marker indicating end-of-stream.
 * @param <T> The type of messages representing data.
 */
abstract class ResultQueueEntry<T> {

    /**
     * <p>fromResponse.</p>
     *
     * @param response a T object.
     * @param <T> a T object.
     * @return a {@link com.google.cloud.bigtable.grpc.scanner.ResultQueueEntry} object.
     */
    public static <T> ResultQueueEntry<T> fromResponse(T response) {
        Preconditions.checkArgument(response != null, "Response may not be null");
        return new ResponseResultQueueEntry<T>(response);
    }

    /**
     * <p>fromThrowable.</p>
     *
     * @param throwable a {@link java.lang.Throwable} object.
     * @param <T> a T object.
     * @return a {@link com.google.cloud.bigtable.grpc.scanner.ResultQueueEntry} object.
     */
    public static <T> ResultQueueEntry<T> fromThrowable(Throwable throwable) {
        Preconditions.checkArgument(throwable != null, "Throwable may not be null");
        return new ExceptionResultQueueEntry<T>(throwable);
    }

    /**
     * <p>completionMarker.</p>
     *
     * @param <T> a T object.
     * @return a {@link com.google.cloud.bigtable.grpc.scanner.ResultQueueEntry} object.
     */
    @SuppressWarnings("unchecked")
    public static <T> ResultQueueEntry<T> completionMarker() {
        return COMPLETION_ENTRY;
    }

    private static final class ExceptionResultQueueEntry<T> extends ResultQueueEntry<T> {
        private static final String EXCEPTION_MESSAGE = "Error in response stream";

        private final Throwable throwable;

        private ExceptionResultQueueEntry(Throwable throwable) {
            this.throwable = throwable;
        }

        @Override
        public boolean isCompletionMarker() {
            return false;
        }

        @Override
        public T getResponseOrThrow() throws IOException {
            throw new IOExceptionWithStatus(EXCEPTION_MESSAGE, throwable, Status.fromThrowable(throwable));
        }

        @Override
        @SuppressWarnings("rawtypes")
        public boolean equals(Object obj) {
            if (!(obj instanceof ExceptionResultQueueEntry) || obj == null) {
                return false;
            }
            ExceptionResultQueueEntry other = (ExceptionResultQueueEntry) obj;
            return Objects.equals(throwable, other.throwable);
        }
    }

    private static final class ResponseResultQueueEntry<T> extends ResultQueueEntry<T> {
        private final T response;

        private ResponseResultQueueEntry(T response) {
            this.response = response;
        }

        @Override
        public boolean isCompletionMarker() {
            return false;
        }

        @Override
        public T getResponseOrThrow() throws IOException {
            return response;
        }

        @Override
        @SuppressWarnings("rawtypes")
        public boolean equals(Object obj) {
            if (!(obj instanceof ResponseResultQueueEntry) || obj == null) {
                return false;
            }
            ResponseResultQueueEntry other = (ResponseResultQueueEntry) obj;
            return Objects.equals(response, other.response);
        }
    }

    @SuppressWarnings("rawtypes")
    private static final ResultQueueEntry COMPLETION_ENTRY = new ResultQueueEntry() {
        @Override
        public boolean isCompletionMarker() {
            return true;
        }

        @Override
        public Object getResponseOrThrow() throws IOException {
            throw new IOException("Attempt to interpret a result stream completion marker as a result");
        }

        @Override
        public boolean equals(Object obj) {
            if (!(obj instanceof ResultQueueEntry) || obj == null) {
                return false;
            }
            ResultQueueEntry other = (ResultQueueEntry) obj;
            return isCompletionMarker() == other.isCompletionMarker();
        }
    };

    /**
     * <p>isCompletionMarker.</p>
     *
     * @return a boolean.
     */
    public abstract boolean isCompletionMarker();

    /**
     * <p>getResponseOrThrow.</p>
     *
     * @return a T object.
     * @throws java.io.IOException if any.
     */
    public abstract T getResponseOrThrow() throws IOException;
}