要通过签名URL将文件上传到Google Cloud存储，您可以使用以下代码示例：

import com.google.auth.oauth2.GoogleCredentials;
import com.google.cloud.storage.Blob;
import com.google.cloud.storage.BlobInfo;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

import java.io.FileInputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.concurrent.TimeUnit;

public class GCSUploader {
    private static final String BUCKET_NAME = "your-bucket-name";
    private static final String OBJECT_NAME = "your-object-name";
    private static final String CREDENTIALS_PATH = "/path/to/your/credentials.json";

    public static void uploadFileWithSignedUrl() throws IOException {
        // 从JSON凭据文件中获取Google Cloud Storage凭据
        GoogleCredentials credentials = GoogleCredentials.fromStream(new FileInputStream(CREDENTIALS_PATH));

        // 设置Google Cloud Storage选项
        StorageOptions options = StorageOptions.newBuilder().setCredentials(credentials).build();
        Storage storage = options.getService();

        // 创建用于上传的BlobInfo对象
        BlobInfo blobInfo = BlobInfo.newBuilder(BUCKET_NAME, OBJECT_NAME).build();

        // 生成签名URL
        String signedUrl = storage.signUrl(blobInfo, 5, TimeUnit.MINUTES);

        // 上传文件
        Path filePath = Paths.get("/path/to/your/local/file");
        byte[] fileBytes = Files.readAllBytes(filePath);
        Blob blob = storage.create(blobInfo, fileBytes);

        System.out.println("文件上传成功！签名URL: " + signedUrl);
    }

    public static void main(String[] args) {
        try {
            uploadFileWithSignedUrl();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

请确保替换示例代码中的以下值：

• your-bucket-name：您的Google Cloud存储桶名称。
• your-object-name：要上传的对象在存储桶中的名称。
• /path/to/your/credentials.json：您的Google Cloud凭据JSON文件的路径。
• /path/to/your/local/file：要上传的本地文件的路径。

您可以在Google Cloud Console中创建一个存储桶，并在其中上传文件，然后使用上述代码示例生成签名URL并将文件上传到存储桶中。