Este tópico descreve como usar o oss SDK for Go para defina e obter metadados de arquivo.
Precauções
O código de exemplo deste tópico usa a região China (Hangzhou), cujo ID de região é
cn-hangzhou. Por padrão, o SDK usa um endpoint público. Para acesse o oss a partir de outros serviços da Alibaba Cloud na mesma região, use um endpoint interno. Para saber mais sobre o mapeamento entre regiões e endpoints do oss, acesse Regions and endpoints.Este tópico traz exemplos de como obter credenciais de acesso por variáveis de ambiente. Para mais detalhes, configure as credenciais de acesso e acesse Configure access credentials.
Para defina metadados de arquivo, você precisa da permissão
oss:PutObject. Para obter metadados de arquivo, você precisa da permissãooss:GetObject. Para mais informações, consulte Grant custom permissions to a RAM user.
Defina metadados ao fazer o upload de um arquivo
Defina metadados ao fazer o upload de um arquivo
O exemplo de código a seguir demonstra como defina metadados ao chamar a operação PutObject. Defina metadados como a data de expiração de um arquivo, a lista de controle de acesso (ACL) do arquivo como public-read ou metadados personalizados para identificar a finalidade ou as propriedades do arquivo. Use esse mesmo método para defina metadados em outras operações de upload. Crie um cliente oss para executar a operação.
package main
import (
"context"
"flag"
"log"
"strings"
"time"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)
// Define global variables.
var (
region string // The storage region.
bucketName string // The bucket name.
objectName string // The object name.
)
// The init function is used to initialize command-line parameters.
func init() {
flag.StringVar(®ion, "region", "", "The region in which the bucket is located.")
flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
flag.StringVar(&objectName, "object", "", "The name of the object.")
}
func main() {
// Parse command-line parameters.
flag.Parse()
// Check whether the bucket name is empty.
if len(bucketName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, bucket name required")
}
// Check whether the region is empty.
if len(region) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, region required")
}
// Check whether the object name is empty.
if len(objectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, object name required")
}
// Define the content to upload.
content := "hi oss"
// Load the default configurations and set the credential provider and region.
cfg := oss.LoadDefaultConfig().
WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
WithRegion(region)
// Create an OSS client.
client := oss.NewClient(cfg)
// Create a request to upload an object.
request := &oss.PutObjectRequest{
Bucket: oss.Ptr(bucketName), // The bucket name.
Key: oss.Ptr(objectName), // The object name.
Body: strings.NewReader(content), // The content to upload.
Expires: oss.Ptr(time.Date(2038, 12, 31, 12, 0, 0, 0, time.UTC).Format(time.RFC1123)), // The expiration time of the object.
Acl: oss.ObjectACLPublicRead,
Metadata: map[string]string{ // Custom metadata.
"Author": "alibaba oss sdk", // The author of the object.
"Date": "2024-07-01", // The creation date of the object.
},
}
// Send the request to upload the object.
result, err := client.PutObject(context.TODO(), request)
if err != nil {
log.Fatalf("failed to put object %v", err)
}
// Print the result of the object upload.
log.Printf("put object result:%#v\n", result)
}
Obter metadados de arquivo
Usar o método HeadObject para obter todos os metadados de um objeto
Execute o código de exemplo a seguir para chamar o método HeadObject e obter todos os metadados de um objeto específico.
package main
import (
"context"
"flag"
"log"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)
// Define global variables.
var (
region string // The storage region.
bucketName string // The bucket name.
objectName string // The object name.
)
// The init function is used to initialize command-line parameters.
func init() {
flag.StringVar(®ion, "region", "", "The region in which the bucket is located.")
flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
flag.StringVar(&objectName, "object", "", "The name of the object.")
}
func main() {
// Parse command-line parameters.
flag.Parse()
// Check whether the bucket name is empty.
if len(bucketName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, bucket name required")
}
// Check whether the region is empty.
if len(region) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, region required")
}
// Check whether the object name is empty.
if len(objectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, object name required")
}
// Load the default configurations and set the credential provider and region.
cfg := oss.LoadDefaultConfig().
WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
WithRegion(region)
// Create an OSS client.
client := oss.NewClient(cfg)
// Create a HeadObject request.
request := &oss.HeadObjectRequest{
Bucket: oss.Ptr(bucketName), // The bucket name.
Key: oss.Ptr(objectName), // The object name.
}
// Execute the HeadObject operation and process the result.
result, err := client.HeadObject(context.TODO(), request)
if err != nil {
log.Fatalf("failed to head object %v", err)
}
// Print the result of the HeadObject operation.
log.Printf("head object result:%#v\n", result)
}
Usar o método GetObjectMeta para obter metadados parciais de um objeto
Nota
Chame o método GetObjectMeta para obter apenas um subconjunto dos metadados de um objeto, como o tamanho do conteúdo (ContentLength), ETag, data e hora da última modificação (LastModified), data e hora do último acesso (LastAccessTime), ID da versão (VersionId) e o valor CRC de 64 bits (HashCRC64) do objeto.
Execute o exemplo de código a seguir para chamar o método GetObjectMeta e obter metadados parciais de um objeto específico.
package main
import (
"context"
"flag"
"log"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)
// Define global variables.
var (
region string // The storage region.
bucketName string // The bucket name.
objectName string // The object name.
)
// The init function is used to initialize command-line parameters.
func init() {
flag.StringVar(®ion, "region", "", "The region in which the bucket is located.")
flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
flag.StringVar(&objectName, "object", "", "The name of the object.")
}
func main() {
// Parse command-line parameters.
flag.Parse()
// Check whether the bucket name is empty.
if len(bucketName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, bucket name required")
}
// Check whether the region is empty.
if len(region) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, region required")
}
// Check whether the object name is empty.
if len(objectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, object name required")
}
// Load the default configurations and set the credential provider and region.
cfg := oss.LoadDefaultConfig().
WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
WithRegion(region)
// Create an OSS client.
client := oss.NewClient(cfg)
// Create a request to obtain the object metadata.
request := &oss.GetObjectMetaRequest{
Bucket: oss.Ptr(bucketName), // The bucket name.
Key: oss.Ptr(objectName), // The object name.
}
// Execute the operation to obtain the object metadata and process the result.
result, err := client.GetObjectMeta(context.TODO(), request)
if err != nil {
log.Fatalf("failed to get object meta %v", err)
}
// Print the result of obtaining the object metadata.
log.Printf("get object meta result:%#v\n", result)
}
Modifique os metadados de um arquivo existente
Usar o método **CopyObject** para modifique metadados de objeto
O exemplo de código a seguir demonstra como chamar o método CopyObject para defina os metadados do objeto de destino durante a operação de cópia. Especifique os metadados do objeto de destino.
package main
import (
"context"
"flag"
"log"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)
// Define global variables.
var (
region string // The storage region.
srcBucketName string // The source bucket name.
srcObjectName string // The source object name.
destBucketName string // The destination bucket name.
destObjectName string // The destination object name.
)
// The init function is used to initialize command-line parameters.
func init() {
flag.StringVar(®ion, "region", "", "The region in which the bucket is located.")
flag.StringVar(&srcBucketName, "src-bucket", "", "The name of the source bucket.")
flag.StringVar(&srcObjectName, "src-object", "", "The name of the source object.")
flag.StringVar(&destBucketName, "dest-bucket", "", "The name of the destination bucket.")
flag.StringVar(&destObjectName, "dest-object", "", "The name of the destination object.")
}
func main() {
// Parse command-line parameters.
flag.Parse()
// Check whether the source bucket name is empty.
if len(srcBucketName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, source bucket name required")
}
// Check whether the region is empty.
if len(region) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, region required")
}
// If the destination bucket name is not specified, the source bucket name is used.
if len(destBucketName) == 0 {
destBucketName = srcBucketName
}
// Check whether the source object name is empty.
if len(srcObjectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, source object name required")
}
// Check whether the destination object name is empty.
if len(destObjectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, destination object name required")
}
// Load the default configurations and set the credential provider and region.
cfg := oss.LoadDefaultConfig().
WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
WithRegion(region)
// Create an OSS client.
client := oss.NewClient(cfg)
// Create metadata.
metaData := map[string]string{
"x-oss-meta-tag1": "value1", // The metadata key is x-oss-meta-tag1, and the value is value1.
"x-oss-meta-tag2": "value2", // The metadata key is x-oss-meta-tag2, and the value is value2.
}
// Create a request to copy the object.
copyRequest := &oss.CopyObjectRequest{
Bucket: oss.Ptr(destBucketName), // The destination bucket name.
Key: oss.Ptr(destObjectName), // The destination object name.
SourceKey: oss.Ptr(srcObjectName), // The source object name.
SourceBucket: oss.Ptr(srcBucketName), // The source bucket name.
Metadata: metaData, // Specify the metadata of the destination object.
MetadataDirective: oss.Ptr("Replace"), // Do not copy the metadata of the source object.
}
// Execute the copy object operation and process the result.
copyResult, err := client.CopyObject(context.TODO(), copyRequest)
if err != nil {
log.Fatalf("failed to copy object: %v", err)
}
log.Printf("copy object result versionId:%#v\n", copyResult)
}
Usar o método **Copier.Copy** do gerenciador de cópia para modifique metadados de objeto
O exemplo de código a seguir demonstra como chamar o método Copier.Copy do gerenciador de cópia para defina os metadados do objeto de destino ao copiar o objeto source. Substitua os metadados originais, limpe-os ou atualize partes deles. Após concluir a operação de cópia, escolha se deseja exclua o objeto source.
package main
import (
"context"
"flag"
"log"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)
// Define global variables.
var (
region string // The storage region.
srcBucketName string // The source bucket name.
srcObjectName string // The source object name.
destBucketName string // The destination bucket name.
destObjectName string // The destination object name.
)
// The init function is used to initialize command-line parameters.
func init() {
flag.StringVar(®ion, "region", "", "The region in which the bucket is located.")
flag.StringVar(&srcBucketName, "src-bucket", "", "The name of the source bucket.")
flag.StringVar(&srcObjectName, "src-object", "", "The name of the source object.")
flag.StringVar(&destBucketName, "dest-bucket", "", "The name of the destination bucket.")
flag.StringVar(&destObjectName, "dest-object", "", "The name of the destination object.")
}
func main() {
// Parse command-line parameters.
flag.Parse()
// Check whether the source bucket name is empty.
if len(srcBucketName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, bucket name required")
}
// Check whether the storage region is empty.
if len(region) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, region required")
}
// If the destination bucket name is not specified, the source bucket name is used.
if len(destBucketName) == 0 {
destBucketName = srcBucketName
}
// Check whether the source object name is empty.
if len(srcObjectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, src object name required")
}
// Check whether the destination object name is empty.
if len(destObjectName) == 0 {
flag.PrintDefaults()
log.Fatalf("invalid parameters, destination object name required")
}
// Configure the OSS client.
cfg := oss.LoadDefaultConfig().
WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
WithRegion(region)
// Create an OSS client.
client := oss.NewClient(cfg)
// Create a file copier.
c := client.NewCopier()
// Set the metadata of the destination object.
metaData := map[string]string{
"x-oss-meta-tag1": "value1",
"x-oss-meta-tag2": "value2",
}
// Build a request to copy the object.
copyRequest := &oss.CopyObjectRequest{
Bucket: oss.Ptr(destBucketName), // The destination bucket name.
Key: oss.Ptr(destObjectName), // The destination object name.
SourceKey: oss.Ptr(srcObjectName), // The source object name.
SourceBucket: oss.Ptr(srcBucketName), // The source bucket name.
Metadata: metaData, // Specify the metadata of the destination object.
MetadataDirective: oss.Ptr("Replace"), // Do not copy the metadata of the source object.
}
// Execute the copy object operation.
result, err := c.Copy(context.TODO(), copyRequest)
if err != nil {
log.Fatalf("failed to copy object %v", err) // If the copy fails, log the error and exit.
}
// Build a request to delete the object.
deleteRequest := &oss.DeleteObjectRequest{
Bucket: oss.Ptr(srcBucketName), // The bucket name.
Key: oss.Ptr(srcObjectName), // The name of the object to delete.
}
// Execute the delete object operation.
deleteResult, err := client.DeleteObject(context.TODO(), deleteRequest)
if err != nil {
log.Fatalf("failed to delete multiple objects %v", err)
}
// Print the result of the copy object operation.
log.Printf("copy object result:%#v\n", result)
// Print the result of the delete object operation.
log.Printf("delete objects result:%#v\n", deleteResult)
}