我尝试实现GmailAPI的代码，但代码找不到credentials.jar。我在谷歌默认代码中放置了 file.exists() 验证，然后我在该位置找到了它们。那么为什么我在执行中看到“找不到文件”错误？

这是带有我的文件验证的 Google 默认代码:

private static Credential getCredentials(final NetHttpTransport HTTP_TRANSPORT) throws IOException { 
        //Verify if the directory of credentials exists: 
        File credentials = new File(CREDENTIALS_FILE_PATH); 
        if(credentials.exists()){ 
            System.out.print("The credentials directory exists! --> "+credentials.getAbsolutePath()); 
        } 
        // Load client secrets. 
        InputStream in = GmailAPI.class.getResourceAsStream(CREDENTIALS_FILE_PATH); 
        if (in == null) { 
            throw new FileNotFoundException("Resource not found: " + CREDENTIALS_FILE_PATH); 
        } 
        GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY, new InputStreamReader(in)); 
 
        // 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"); 
    } 

这是执行的输出:

The credentials directory exists! --> C:\rfp\GymSoft\Google\credentials.json 
Exception in thread "main" java.io.FileNotFoundException: Resource not found: Google/credentials.json 
    at apoio.GmailAPI.getCredentials(GmailAPI.java:43) 
    at apoio.GmailAPI.main(GmailAPI.java:61) 
C:\rfp\GymSoft\nbproject\build-impl.xml:1340: The following error occurred while executing this line: 
C:\rfp\GymSoft\nbproject\build-impl.xml:981: Java returned: 1 
BUILD FAILED (total time: 1 second) 

请您参考如下方法:

您必须将 credentials.json 文件放入项目的资源文件夹中，然后声明一个常量并在代码中实现它:

private static final String CREDENTIALS_FILE_PATH = "/credentials.json"; 
InputStream in = GmailAPI.class.getResourceAsStream(CREDENTIALS_FILE_PATH); 

默认情况下，GmailAPI 会在此处搜索 credentials.json 文件，除非您设置绝对路径，但为了避免麻烦，最好将其放在资源文件夹中。

您可以查看使用 Java 的快速入门 Gmail API 示例 here 。