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# 检索证书和证书链
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以下示例演示了如何使用 [GetCertificate](https://docs.amazonaws.cn/acm/latest/APIReference/API_GetCertificate.html) 函数。

```
package com.amazonaws.samples;

import com.amazonaws.regions.Regions;
import com.amazonaws.services.certificatemanager.AWSCertificateManagerClientBuilder;
import com.amazonaws.services.certificatemanager.AWSCertificateManager;
import com.amazonaws.services.certificatemanager.model.GetCertificateRequest;
import com.amazonaws.services.certificatemanager.model.GetCertificateResult;

import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.AWSCredentials;

import com.amazonaws.services.certificatemanager.model.InvalidArnException;
import com.amazonaws.services.certificatemanager.model.ResourceNotFoundException;
import com.amazonaws.services.certificatemanager.model.RequestInProgressException;
import com.amazonaws.AmazonClientException;

/**
 * This sample demonstrates how to use the GetCertificate function in the Amazon Certificate
 * Manager service.
 *
 * Input parameter:
 *   CertificateArn - The ARN of the certificate to retrieve.
 *
 * Output parameters:
 *   Certificate - A base64-encoded certificate in PEM format.
 *   CertificateChain - The base64-encoded certificate chain in PEM format.
 *
 */

public class AWSCertificateManagerExample {

   public static void main(String[] args) throws Exception{

      // Retrieve your credentials from the C:\Users\name\.aws\credentials file in Windows
      // or the ~/.aws/credentials file in Linux.
      AWSCredentials credentials = null;
      try {
          credentials = new ProfileCredentialsProvider().getCredentials();
      }
      catch (Exception ex) {
          throw new AmazonClientException("Cannot load the credentials from the credential profiles file.", ex);
      }

      // Create a client.
      AWSCertificateManager client = AWSCertificateManagerClientBuilder.standard()
              .withRegion(Regions.US_EAST_1)
              .withCredentials(new AWSStaticCredentialsProvider(credentials))
              .build();

      // Create a request object and set the ARN of the certificate to be described.
      GetCertificateRequest req = new GetCertificateRequest();
      req.setCertificateArn("arn:aws:acm:region:account:certificate/12345678-1234-1234-1234-123456789012");

      // Retrieve the certificate and certificate chain. 
      // If you recently requested the certificate, loop until it has been created.
      GetCertificateResult result = null;
      long totalTimeout = 120000l;
      long timeSlept = 0l;
      long sleepInterval = 10000l;
      while (result == null && timeSlept < totalTimeout) {
         try {
            result = client.getCertificate(req);
         }
         catch (RequestInProgressException ex) {
            Thread.sleep(sleepInterval);
         }
         catch (ResourceNotFoundException ex)
         {
            throw ex;
         }
         catch (InvalidArnException ex)
         {
            throw ex;
         }

         timeSlept += sleepInterval;
      }

      // Display the certificate information.
      System.out.println(result);
   }
}
```

前面的示例将创建类似于以下内容的输出。

```
{Certificate: -----BEGIN CERTIFICATE-----
    base64-encoded certificate
-----END CERTIFICATE-----,
CertificateChain: -----BEGIN CERTIFICATE-----
    base64-encoded certificate chain 
-----END CERTIFICATE-----
}
```