com.google.gcloud.datastore.Cursor.java Source code

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Here is the source code for com.google.gcloud.datastore.Cursor.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.gcloud.datastore;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.api.services.datastore.DatastoreV1;
import com.google.api.services.datastore.DatastoreV1.Value;
import com.google.common.base.MoreObjects;
import com.google.common.base.MoreObjects.ToStringHelper;
import com.google.common.io.BaseEncoding;
import com.google.protobuf.ByteString;
import com.google.protobuf.InvalidProtocolBufferException;

/**
 * A Google Cloud Datastore cursor.
 * The cursor can be used to as a starting point or an ending point for a {@link Query}
 */
public final class Cursor extends Serializable<DatastoreV1.Value> {

    private static final long serialVersionUID = -1423744878777486541L;

    private final transient ByteString byteString;

    Cursor(ByteString byteString) {
        this.byteString = byteString;
    }

    @Override
    public int hashCode() {
        return byteString.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        return obj == this || obj instanceof Cursor && byteString.equals(((Cursor) obj).byteString);
    }

    @Override
    public String toString() {
        ToStringHelper toStringHelper = MoreObjects.toStringHelper(this);
        StringBuilder stBuilder = new StringBuilder();
        for (int i = 0; i < byteString.size(); i++) {
            stBuilder.append(String.format("%02x", byteString.byteAt(i)));
        }
        return toStringHelper.add("bytes", stBuilder.toString()).toString();
    }

    ByteString byteString() {
        return byteString;
    }

    /**
     * Returns the cursor in an encoded form that can be used as part of a URL.
     */
    public String toUrlSafe() {
        return BaseEncoding.base64Url().encode(byteString.toByteArray());
    }

    /**
     * Create a {@code Cursor} given its URL safe encoded form.
     */
    public static Cursor fromUrlSafe(String urlSafe) {
        try {
            return Cursor.copyFrom(BaseEncoding.base64Url().decode(urlSafe));
        } catch (IllegalArgumentException e) {
            throw new IllegalStateException("Unexpected decoding exception", e);
        }
    }

    public static Cursor copyFrom(byte[] bytes) {
        return new Cursor(ByteString.copyFrom(checkNotNull(bytes)));
    }

    @Override
    Value toPb() {
        return DatastoreV1.Value.newBuilder().setBlobValue(byteString).build();
    }

    @Override
    Object fromPb(byte[] bytesPb) throws InvalidProtocolBufferException {
        return fromPb(DatastoreV1.Value.parseFrom(bytesPb));
    }

    static Cursor fromPb(DatastoreV1.Value valuePb) {
        return new Cursor(valuePb.getBlobValue());
    }
}