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# GetCertificateAuthorityCsr
<a name="JavaApi-GetCertificateAuthorityCsr"></a>

以下 Java 示例显示了如何使用该[GetCertificateAuthorityCsr](https://docs.aws.amazon.com/privateca/latest/APIReference/API_GetCertificateAuthorityCsr.html)操作。

此操作可检索您的私有证书颁发机构 (CA) 的证书签名请求 (CSR)。CSR 是在您调用[CreateCertificateAuthority](https://docs.aws.amazon.com/privateca/latest/APIReference/API_CreateCertificateAuthority.html)操作时创建的。将 CSR 放至您的本地 X.509 基础设施，并使用根或从属 CA 对其进行签名。然后通过调用操作将签名的证书重新导入 ACM PCA。[ImportCertificateAuthorityCertificate](https://docs.aws.amazon.com/privateca/latest/APIReference/API_ImportCertificateAuthorityCertificate.html)以 PEM 格式的 base64 编码字符串形式返回 CSR。

```
package com.amazonaws.samples;

import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.client.builder.AwsClientBuilder.EndpointConfiguration;
import com.amazonaws.auth.AWSStaticCredentialsProvider;

import com.amazonaws.services.acmpca.AWSACMPCA;
import com.amazonaws.services.acmpca.AWSACMPCAClientBuilder;

import com.amazonaws.services.acmpca.model.GetCertificateAuthorityCsrRequest;
import com.amazonaws.services.acmpca.model.GetCertificateAuthorityCsrResult;

import com.amazonaws.AmazonClientException;
import com.amazonaws.services.acmpca.model.ResourceNotFoundException;
import com.amazonaws.services.acmpca.model.InvalidArnException;
import com.amazonaws.services.acmpca.model.RequestInProgressException;
import com.amazonaws.services.acmpca.model.RequestFailedException;
import com.amazonaws.services.acmpca.model.AWSACMPCAException;

import com.amazonaws.waiters.Waiter;
import com.amazonaws.waiters.WaiterParameters;
import com.amazonaws.waiters.WaiterTimedOutException;
import com.amazonaws.waiters.WaiterUnrecoverableException;

public class GetCertificateAuthorityCsr {

   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("default").getCredentials();
      } catch (Exception e) {
         throw new AmazonClientException("Cannot load your credentials from disk", e);
      }

      // Define the endpoint for your sample.
      String endpointRegion = "region";  // Substitute your region here, e.g. "us-west-2"
      String endpointProtocol = "https://acm-pca." + endpointRegion + ".amazonaws.com/";
      EndpointConfiguration endpoint =
            new AwsClientBuilder.EndpointConfiguration(endpointProtocol, endpointRegion);

      // Create a client that you can use to make requests.
      AWSACMPCA client = AWSACMPCAClientBuilder.standard()
         .withEndpointConfiguration(endpoint)
         .withCredentials(new AWSStaticCredentialsProvider(credentials))
         .build();
         
      // Create the request object and set the CA ARN.
      GetCertificateAuthorityCsrRequest req = new GetCertificateAuthorityCsrRequest();
      req.withCertificateAuthorityArn("arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566");

      // Create waiter to wait on successful creation of the CSR file.
      Waiter<GetCertificateAuthorityCsrRequest> waiter = client.waiters().certificateAuthorityCSRCreated();
      try {
         waiter.run(new WaiterParameters<>(req));
      } catch (WaiterUnrecoverableException e) {
          //Explicit short circuit when the recourse transitions into
          //an undesired state.
      } catch (WaiterTimedOutException e) {
          //Failed to transition into desired state even after polling.
      } catch (AWSACMPCAException e) {
          //Unexpected service exception.
      }

      // Retrieve the CSR.
      GetCertificateAuthorityCsrResult result = null;
      try {
         result = client.getCertificateAuthorityCsr(req);
      } catch (RequestInProgressException ex) {
         throw ex;
      } catch (ResourceNotFoundException ex) {
         throw ex;
      } catch (InvalidArnException ex) {
         throw ex;
      } catch (RequestFailedException ex) {
         throw ex;
      }

      // Retrieve and display the CSR;
      String Csr = result.getCsr();
      System.out.println(Csr);
   }
}
```

对于您指定的证书颁发机构 (CA)，您的输出应类似如下。证书签名请求 (CSR) 采用 PEM 格式进行 base64 编码。将它保存到本地文件中，然后将它置于本地 X.509 基础设施，并使用根或从属 CA 对它进行签名。

```
-----BEGIN CERTIFICATE REQUEST----- base64-encoded request -----END CERTIFICATE REQUEST-----
```