com.google.appengine.api.datastore.KeyFactory Maven / Gradle / Ivy
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/*
* Copyright 2021 Google LLC
*
* 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
*
* https://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.appengine.api.datastore;
import static com.google.common.io.BaseEncoding.base64Url;
import com.google.common.base.CharMatcher;
import com.google.storage.onestore.v3.OnestoreEntity.Reference;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* This class enables direct creation of {@code Key} objects, both in the root entity group (no
* parent) and as the child of a given parent. Keys can also be created indirectly by putting named
* Entities into the datastore, which will allocate a new key. See {@link Entity#Entity(String,
* String)} for details.
*
* This class also has methods for encoding and decoding {@code Key} objects to and from strings.
* Clients should not make any assumptions about the encoding format, except that it is a websafe
* string that does not need to be quoted when used in HTML or in URLs.
*
* @see Entity
*/
public class KeyFactory {
/**
* Creates a new {@code Key} having no parent from its kind and ID.
*
* @param kind the kind of the key to create
* @param id the numeric identifier of the key in {@code kind}, unique across all root entities of
* this kind, must not be zero
*/
public static Key createKey(String kind, long id) {
return createKey(null, kind, id);
}
/**
* Creates a new {@code Key} with the provided parent from its kind and ID.
*
* @param parent the parent of the key to create, can be {@code null}
* @param kind the kind of the key to create
* @param id the numeric identifier of the key in {@code kind}, unique across all entities of this
* kind with the same parent, must not be zero
*/
public static Key createKey(@Nullable Key parent, String kind, long id) {
return createKey(parent, kind, id, null);
}
static Key createKey(
@Nullable Key parent, String kind, long id, @Nullable AppIdNamespace appIdNamespace) {
if (id == 0L) {
throw new IllegalArgumentException("id cannot be zero");
}
return new Key(kind, parent, id, appIdNamespace);
}
/**
* Creates a new {@code Key} having no parent from its kind and name.
*
* @param kind the kind of the key to create
* @param name the name of the key in {@code kind}, as an arbitrary string unique across all root
* entities of this {@code kind}
*/
public static Key createKey(String kind, String name) {
return createKey(null, kind, name);
}
/**
* Creates a new {@code Key} with the provided parent from its kind and name.
*
* @param parent the parent of the key to create, can be {@code null}
* @param kind the kind of the key to create
* @param name the name of the key in {@code kind}, as an arbitrary string unique across all
* entities of this {@code kind} with the same parent
*/
public static Key createKey(@Nullable Key parent, String kind, String name) {
return createKey(parent, kind, name, null);
}
static Key createKey(
@Nullable Key parent, String kind, String name, @Nullable AppIdNamespace appIdNamespace) {
if (name == null || name.length() == 0) {
throw new IllegalArgumentException("name cannot be null or empty");
}
return new Key(kind, parent, name, appIdNamespace);
}
/**
* Shorthand for invoking {@link #keyToString(Key)} on the result of {@link #createKey(String,
* long)}
*
* @param kind the kind of the key to create
* @param id the numeric identifier of the key in {@code kind}, unique across all root entities of
* this kind, must not be zero
* @return A websafe {@code String} representation of the {@link Key} that was created
*/
public static String createKeyString(String kind, long id) {
return keyToString(createKey(kind, id));
}
/**
* Shorthand for invoking {@link #keyToString(Key)} on the result of {@link #createKey(Key,
* String, long)}
*
* @param parent the parent of the key to create, can be {@code null}.
* @param kind the kind of the key to create
* @param id the numeric identifier of the key in {@code kind}, unique across entities of this
* kind with the same parent, must not be zero
* @return A websafe {@code String} representation of the {@link Key} that was created
*/
public static String createKeyString(@Nullable Key parent, String kind, long id) {
return keyToString(createKey(parent, kind, id));
}
/**
* Shorthand for invoking {@link #keyToString(Key)} on the result of {@link #createKey(String,
* String)}
*
* @param kind the kind of the key to create
* @param name the name of the key in {@code kind}, as an arbitrary string unique across root
* entities of this {@code kind}
* @return A websafe {@code String} representation of the {@link Key} that was created
*/
public static String createKeyString(String kind, String name) {
return keyToString(createKey(kind, name));
}
/**
* Shorthand for invoking {@link #keyToString(Key)} on the result of {@link #createKey(Key,
* String, String)}
*
* @param parent the parent of the key to create, can be {@code null}.
* @param kind the kind of the key to create
* @param name the name of the key in {@code kind}, as an arbitrary string unique across entities
* of this {@code kind} with the same parent
* @return A websafe {@code String} representation of the {@link Key} that was created
*/
public static String createKeyString(@Nullable Key parent, String kind, String name) {
return keyToString(createKey(parent, kind, name));
}
/**
* Converts a {@code Key} into a websafe string. For example, this string can safely be used as an
* URL parameter embedded in a HTML document. Note that
* key.equals(KeyFactory.stringToKey(KeyFactory.keyToString(key))
* should evaluate to {@code true}.
*
* @param key The {@code Key} to convert to a {@code String}.
* @return A websafe {@code String} representation of the provided {@code String}.
* @throws IllegalArgumentException If the specified {@code Key} is incomplete.
*/
public static String keyToString(Key key) {
// Note: This must be consistent across languages. If it changes,
// make sure that the similar logic in Python changes as well.
// There are also unit tests which need to be changed.
if (!key.isComplete()) {
throw new IllegalArgumentException("Key is incomplete.");
} else {
Reference reference = KeyTranslator.convertToPb(key);
return base64Url().omitPadding().encode(reference.toByteArray());
}
}
/**
* Converts a {@code String}-representation of a {@code Key} into the {@code Key} instance it
* represents. Note that
* str.equals(KeyFactory.keyToString(KeyFactory.stringToKey(str))
* should evaluate to {@code true} for all strings returned by {@link
* KeyFactory#keyToString}.
*
* @param encoded The {@code String} representation of a {@code Key}.
* @return The {@code Key} that the given {@code String} represents.
* @throws IllegalArgumentException If the string cannot be parsed.
*/
public static Key stringToKey(String encoded) {
// Note: This must be consistent across languages. If it changes,
// make sure that the similar logic in Python changes as well.
// There are unit tests which also need to be changed.
int modulo = encoded.length() % 4;
if (modulo != 0) {
// Pad the string to a 4-byte boundary.
encoded += "====".substring(modulo);
}
byte[] decodedBytes;
try {
decodedBytes = base64Url().decode(CharMatcher.whitespace().removeFrom(encoded));
} catch (IllegalArgumentException ex) {
throw new IllegalArgumentException("Cannot parse: " + encoded, ex);
}
Reference reference = new Reference();
boolean parsed = reference.parseFrom(decodedBytes);
if (!parsed) {
throw new IllegalArgumentException("Could not parse Reference");
}
// The validation in createFromPb should cover missing required fields, so no need for
// an isInitialized check.
return KeyTranslator.createFromPb(reference);
}
/**
* Helper class that aids in the construction of {@link Key Keys} with ancestors. Initialize the
* {@code Builder} with the topmost ancestor in your key path and then add children using the
* {@link #addChild} overload that best suits your needs. When finished adding children, call
* {@link #getKey()} to retrieve your {@link Key} or {@link #getString()} to retrieve your {@link
* Key} encoded as a websafe {@link String}.
*
*
Examples:
*
*
* import com.google.appengine.api.datastore.KeyFactory.Builder;
*
* ...
*
* Key key = new Builder("Person", 88).addChild("Address", 24).getKey();
* String keyStr = new Builder("Photo Album", "Vacation").addChild("Photo", 1424).getString();
*
*/
public static final class Builder {
private Key current;
/**
* Create a {@code Builder}, establishing a {@link Key} constructed from the provided kind and
* name as the topmost ancestor.
*
* @param kind the kind of the topmost ancestor
* @param name the name of the topmost ancestor in {@code kind}, as an arbitrary string unique
* across root entities of this {@code kind}
*/
public Builder(String kind, String name) {
current = createKey(null, kind, name);
}
/**
* Create a {@code Builder}, establishing a {@link Key} constructed from the provided kind and
* id as the topmost ancestor.
*
* @param kind the kind of the topmost ancestor
* @param id the numeric identifier of the topmost ancestor in {@code kind}, unique across root
* entities of this kind, must not be zero
*/
public Builder(String kind, long id) {
current = createKey(null, kind, id);
}
/**
* Create a {@code Builder}, establishing the provided {@link Key} as the topmost ancestor.
*
* @param key the topmost ancestor
*/
public Builder(Key key) {
current = key;
}
/**
* Add a {@link Key} constructed from the provided kind and name as the child of the {@link Key}
* most recently added to the {@code Builder}.
*
* @param kind the kind of the child
* @param name the name of the child in {@code kind}, as an arbitrary string unique across
* entities of this {@code kind} with the same parent
* @return {@code this}
*/
public Builder addChild(String kind, String name) {
current = createKey(current, kind, name);
return this;
}
/**
* Add a {@link Key} constructed from the provided kind and id as the child of the {@link Key}
* most recently added to the {@code Builder}.
*
* @param kind the kind of the child
* @param id the numeric identifier of the child in {@code kind}, unique across entities of this
* kind with the same parent, must not be zero
* @return {@code this}
*/
public Builder addChild(String kind, long id) {
current = createKey(current, kind, id);
return this;
}
/** Returns the most recently added {@link Key}. */
public Key getKey() {
return current;
}
/** Returns the most recently added {@link Key}, encoded as a websafe {@link String}. */
public String getString() {
return keyToString(current);
}
}
// All methods are static. Do not instantiate.
private KeyFactory() {}
}