我需要为用 Java 编写的 Web 应用程序实现 OAuth2 以访问 Gmail。不幸的是，谷歌的文档只有一个关于这个主题的 Python 示例： https://developers.google.com/gmail/api/auth/web-server
我已经用谷歌搜索了几个小时，但找不到一个很好的例子来解释这个主题 - 我是 OAuth2 的新手，因此 Java 中的分步示例会非常有用。
提前致谢:)
【问题讨论】：
我已尝试为 Gmail 快速入门指南做出贡献。我认为阻力最小的路径是复制我这里的内容。
假设你有你的秘密，并且你已经在之前的授权过程中获得了一个 refresh_token。你可以试试这个。
/**
* Assuming the user of this application has already obtained an refresh_token, this will create a Credential object
* using the provided secrets and the provided refresh_token.
*
* @param refreshToken Refresh Token obtained in previous authorization process
* @param HTTP_TRANSPORT The network HTTP Transport.
* @return An authorized Credential object.
* @throws IOException If the credentials.json file cannot be found.
*/
private static Credential getCredentials(final String refreshToken, final NetHttpTransport HTTP_TRANSPORT) throws IOException {
GoogleClientSecrets clientSecrets = getGoogleClientSecrets();
return new GoogleCredential.Builder()
.setJsonFactory(JSON_FACTORY)
.setTransport(HTTP_TRANSPORT)
.setClientSecrets(clientSecrets)
.build().setRefreshToken(refreshToken);
}
完整版：GmailQuickstart.java
// Copyright 2018 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
//
// 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.
// [START gmail_quickstart]
import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.util.store.FileDataStoreFactory;
import com.google.api.services.gmail.Gmail;
import com.google.api.services.gmail.GmailScopes;
import com.google.api.services.gmail.model.Label;
import com.google.api.services.gmail.model.ListLabelsResponse;
import java.io.*;
import java.security.GeneralSecurityException;
import java.util.Collections;
import java.util.List;
public class GmailQuickstart {
private static final String APPLICATION_NAME = "Gmail API Java Quickstart";
private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();
private static final String TOKENS_DIRECTORY_PATH = "tokens";
/**
* Global instance of the scopes required by this quickstart.
* If modifying these scopes, delete your previously saved tokens/ folder.
*/
private static final List<String> SCOPES = Collections.singletonList(GmailScopes.GMAIL_LABELS);
private static final String CREDENTIALS_FILE_PATH = "credentials.json";
private static GoogleClientSecrets getGoogleClientSecrets() throws IOException {
// Load client secrets.
File credentialJson = new File(CREDENTIALS_FILE_PATH);
if (!credentialJson.exists()) {
throw new FileNotFoundException("Resource not found: " + CREDENTIALS_FILE_PATH);
}
return GoogleClientSecrets.load(JSON_FACTORY, new InputStreamReader(new FileInputStream(credentialJson)));
}
/**
* Launches a small local server on 8888 which facilitates the authorization process from scratch. In turn creates
* an authorized Credential object when the user proceeds with the authorization.
*
* @param HTTP_TRANSPORT The network HTTP Transport.
* @return An authorized Credential object.
* @throws IOException If the credentials.json file cannot be found.
*/
private static Credential getCredentials(final NetHttpTransport HTTP_TRANSPORT) throws IOException {
// Load client secrets.
GoogleClientSecrets clientSecrets = getGoogleClientSecrets();
// Build flow and trigger user authorization request.
GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
HTTP_TRANSPORT, JSON_FACTORY, clientSecrets, SCOPES)
.setDataStoreFactory(new FileDataStoreFactory(new java.io.File(TOKENS_DIRECTORY_PATH)))
.setAccessType("offline")
.build();
LocalServerReceiver receiver = new LocalServerReceiver.Builder().setPort(8888).build();
return new AuthorizationCodeInstalledApp(flow, receiver).authorize("user");
}
/**
* Assuming the user of this application already has an refresh_token handy, this will create a Credential object
* using the provided secrets and the provided refresh_token.
*
* @param refreshToken Refresh Token obtained in previous authorization process
* @param HTTP_TRANSPORT The network HTTP Transport.
* @return An authorized Credential object.
* @throws IOException If the credentials.json file cannot be found.
*/
private static Credential getCredentials(final String refreshToken, final NetHttpTransport HTTP_TRANSPORT) throws IOException {
GoogleClientSecrets clientSecrets = getGoogleClientSecrets();
return new GoogleCredential.Builder()
.setJsonFactory(JSON_FACTORY)
.setTransport(HTTP_TRANSPORT)
.setClientSecrets(clientSecrets)
.build().setRefreshToken(refreshToken);
}
private static Credential getCredential(NetHttpTransport HTTP_TRANSPORT) throws IOException {
Credential credentials;
switch (getAuthPreference()) {
case FULL_AUTH:
credentials = getCredentials(HTTP_TRANSPORT);
break;
case REFRESH_AUTH:
System.out.print("please provide refresh_token:");
String refreshToken = getUserInput();
credentials = getCredentials(refreshToken, HTTP_TRANSPORT);
break;
default:
credentials = getCredentials(HTTP_TRANSPORT);
}
return credentials;
}
private static WhatToDo getAuthPreference() throws IOException {
// Enter data using BufferReader
System.out.println("You can choose how to authorize your request.");
System.out.println("\t1) Need to do full authorization");
System.out.println("\t2) Already have refresh_token handy. Can provide this next.");
String userInput = getUserInput();
if (userInput.equals("1")) {
return WhatToDo.FULL_AUTH;
}
if (userInput.equals("2")) {
return WhatToDo.REFRESH_AUTH;
}
System.err.println("Your Input was incorrect! ");
return getAuthPreference();
}
private static String getUserInput() throws IOException {
BufferedReader reader = new BufferedReader(
new InputStreamReader(System.in));
// Reading data using readLine
String userInput = reader.readLine();
return userInput;
}
enum WhatToDo {
FULL_AUTH,
REFRESH_AUTH
}
public static void main(String... args) throws IOException, GeneralSecurityException {
// Build a new authorized API client service.
final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
Gmail service = new Gmail.Builder(HTTP_TRANSPORT, JSON_FACTORY, getCredential(HTTP_TRANSPORT))
.setApplicationName(APPLICATION_NAME)
.build();
// Print the labels in the user's account.
String user = "me";
ListLabelsResponse listResponse = service.users().labels().list(user).execute();
List<Label> labels = listResponse.getLabels();
if (labels.isEmpty()) {
System.out.println("No labels found.");
} else {
System.out.println("Labels:");
for (Label label : labels) {
System.out.printf("- %s\n", label.getName());
}
}
}
}
// [END gmail_quickstart]
【讨论】：