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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.QuerySnapshot;
import com.google.cloud.firestore.WriteResult;
import java.util.ArrayList;
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 fs_retrieve_create_examples]
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)));
futures.add(cities.document("LA").set(new City("Los Angeles", "CA", "USA", false, 3900000L)));
futures.add(cities.document("DC").set(new City("Washington D.C.", null, "USA", true, 680000L)));
futures.add(cities.document("TOK").set(new City("Tokyo", null, "Japan", true, 9000000L)));
futures.add(cities.document("BJ").set(new City("Beijing", null, "China", true, 21500000L)));
// (optional) block on operation
ApiFutures.allAsList(futures).get();
// [END fs_retrieve_create_examples]
}
/**
* Retrieves document in collection as map.
*
* @return map (string => object)
*/
public Map<String, Object> getDocumentAsMap() throws Exception {
// [START fs_get_doc_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 fs_get_doc_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 fs_get_doc_as_entity]
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 fs_get_doc_as_entity]
return city;
}
/**
* Return multiple documents from a collection based on a query.
*
* @return list of documents of capital cities.
*/
public List<DocumentSnapshot> getQueryResults() throws Exception {
// [START fs_get_multiple_docs]
//asynchronously retrieve multiple documents
ApiFuture<QuerySnapshot> future =
db.collection("cities").whereEqualTo("capital", true).get();
// future.get() blocks on response
List<DocumentSnapshot> documents = future.get().getDocuments();
for (DocumentSnapshot document : documents) {
System.out.println(document.getId() + " => " + document.toObject(City.class));
}
// [END fs_get_multiple_docs]
return documents;
}
/**
* Return all documents in the cities collection.
*
* @return list of documents
*/
public List<DocumentSnapshot> getAllDocuments() throws Exception {
// [START fs_get_all_docs]
//asynchronously retrieve all documents
ApiFuture<QuerySnapshot> future = db.collection("cities").get();
// future.get() blocks on response
List<DocumentSnapshot> documents = future.get().getDocuments();
for (DocumentSnapshot document : documents) {
System.out.println(document.getId() + " => " + document.toObject(City.class));
}
// [END fs_get_all_docs]
return documents;
}
/**
* Return all subcollections of the cities/SF document.
*
* @return iterable of collection references.
*/
public Iterable<CollectionReference> getCollections() throws Exception {
// [START fs_get_collections]
Iterable<CollectionReference> collections =
db.collection("cities").document("SF").getCollections();
for (CollectionReference collRef : collections) {
System.out.println("Found subcollection with id: " + collRef.getId());
}
// [END fs_get_collections]
return collections;
}
}