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RetrieveDataSnippets.java
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RetrieveDataSnippets.java
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/*
* Copyright 2017 Google 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.example.firestore.snippets;
import com.example.firestore.snippets.model.City;
import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.cloud.firestore.CollectionReference;
import com.google.cloud.firestore.DocumentReference;
import com.google.cloud.firestore.DocumentSnapshot;
import com.google.cloud.firestore.Firestore;
import com.google.cloud.firestore.QueryDocumentSnapshot;
import com.google.cloud.firestore.QuerySnapshot;
import com.google.cloud.firestore.WriteResult;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
/** Snippets to demonstrate Firestore data retrieval operations. */
public class RetrieveDataSnippets {
private final Firestore db;
RetrieveDataSnippets(Firestore db) {
this.db = db;
}
/** Create cities collection and add sample documents. */
void prepareExamples() throws Exception {
// [START firestore_data_get_dataset]
CollectionReference cities = db.collection("cities");
List<ApiFuture<WriteResult>> futures = new ArrayList<>();
futures.add(
cities
.document("SF")
.set(
new City(
"San Francisco",
"CA",
"USA",
false,
860000L,
Arrays.asList("west_coast", "norcal"))));
futures.add(
cities
.document("LA")
.set(
new City(
"Los Angeles",
"CA",
"USA",
false,
3900000L,
Arrays.asList("west_coast", "socal"))));
futures.add(
cities
.document("DC")
.set(
new City(
"Washington D.C.", null, "USA", true, 680000L, Arrays.asList("east_coast"))));
futures.add(
cities
.document("TOK")
.set(
new City(
"Tokyo", null, "Japan", true, 9000000L, Arrays.asList("kanto", "honshu"))));
futures.add(
cities
.document("BJ")
.set(
new City(
"Beijing",
null,
"China",
true,
21500000L,
Arrays.asList("jingjinji", "hebei"))));
// (optional) block on operation
ApiFutures.allAsList(futures).get();
// [END firestore_data_get_dataset]
}
/**
* Retrieves document in collection as map.
*
* @return map (string => object)
*/
public Map<String, Object> getDocumentAsMap() throws Exception {
// [START firestore_data_get_as_map]
DocumentReference docRef = db.collection("cities").document("SF");
// asynchronously retrieve the document
ApiFuture<DocumentSnapshot> future = docRef.get();
// ...
// future.get() blocks on response
DocumentSnapshot document = future.get();
if (document.exists()) {
System.out.println("Document data: " + document.getData());
} else {
System.out.println("No such document!");
}
// [END firestore_data_get_as_map]
return (document.exists()) ? document.getData() : null;
}
/**
* Retrieves document in collection as a custom object.
*
* @return document data as City object
*/
public City getDocumentAsEntity() throws Exception {
// [START firestore_data_get_as_custom_type]
DocumentReference docRef = db.collection("cities").document("BJ");
// asynchronously retrieve the document
ApiFuture<DocumentSnapshot> future = docRef.get();
// block on response
DocumentSnapshot document = future.get();
City city = null;
if (document.exists()) {
// convert document to POJO
city = document.toObject(City.class);
System.out.println(city);
} else {
System.out.println("No such document!");
}
// [END firestore_data_get_as_custom_type]
return city;
}
/**
* Return multiple documents from a collection based on a query.
*
* @return list of documents of capital cities.
*/
public List<QueryDocumentSnapshot> getQueryResults() throws Exception {
// [START firestore_data_query]
// asynchronously retrieve multiple documents
ApiFuture<QuerySnapshot> future = db.collection("cities").whereEqualTo("capital", true).get();
// future.get() blocks on response
List<QueryDocumentSnapshot> documents = future.get().getDocuments();
for (DocumentSnapshot document : documents) {
System.out.println(document.getId() + " => " + document.toObject(City.class));
}
// [END firestore_data_query]
return documents;
}
/**
* Return all documents in the cities collection.
*
* @return list of documents
*/
public List<QueryDocumentSnapshot> getAllDocuments() throws Exception {
// [START firestore_data_get_all_documents]
// asynchronously retrieve all documents
ApiFuture<QuerySnapshot> future = db.collection("cities").get();
// future.get() blocks on response
List<QueryDocumentSnapshot> documents = future.get().getDocuments();
for (QueryDocumentSnapshot document : documents) {
System.out.println(document.getId() + " => " + document.toObject(City.class));
}
// [END firestore_data_get_all_documents]
return documents;
}
/**
* Return all subcollections of the cities/SF document.
*
* @return iterable of collection references.
*/
public Iterable<CollectionReference> listCollections() throws Exception {
// [START firestore_data_get_sub_collections]
Iterable<CollectionReference> collections =
db.collection("cities").document("SF").listCollections();
for (CollectionReference collRef : collections) {
System.out.println("Found subcollection with id: " + collRef.getId());
}
// [END firestore_data_get_sub_collections]
return collections;
}
/** Closes the gRPC channels associated with this instance and frees up their resources. */
void close() throws Exception {
db.close();
}
}