# Java를 사용한 URL 서명 생성
<a name="CFPrivateDistJavaDevelopment"></a>

다음 코드 예제 외에도 [AWS SDK for Java(버전 1)의 `CloudFrontUrlSigner` 유틸리티 클래스](https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/cloudfront/CloudFrontUrlSigner.html)를 사용하여 [CloudFront 서명 URL](private-content-signed-urls.md)을 만들 수 있습니다.

자세한 예제는 AWS SDK Code Examples Code Library에서 [AWS SDK를 사용하여 서명된 URL 및 쿠키 만들기](https://docs.aws.amazon.com/code-library/latest/ug/cloudfront_example_cloudfront_CloudFrontUtilities_section.html)를 참조합니다.**

**참고**  
서명된 URL 생성은 [CloudFront를 통해 프라이빗 콘텐츠를 제공](PrivateContent.md)하는 프로세스의 한 부분에 불과합니다. 전체 프로세스에 대한 자세한 내용은 [서명된 URL 사용](private-content-signed-urls.md)을 참조하세요.
`Signature.getInstance` 직접 호출에서 `SHA1withRSA`를 `SHA256withRSA`로 바꿀 수 있습니다.

**Example Java 정책 및 서명 암호화 메서드**  <a name="ExampleJavaPolicyAndSignatureEncryptionMethods"></a>

```
package org.example;

import java.time.Instant;
import java.time.temporal.ChronoUnit;
import software.amazon.awssdk.services.cloudfront.CloudFrontUtilities;
import software.amazon.awssdk.services.cloudfront.model.CannedSignerRequest;
import software.amazon.awssdk.services.cloudfront.url.SignedUrl;

public class Main {

    public static void main(String[] args) throws Exception {
        CloudFrontUtilities cloudFrontUtilities = CloudFrontUtilities.create();
        Instant expirationDate = Instant.now().plus(7, ChronoUnit.DAYS);
        String resourceUrl = "https://a1b2c3d4e5f6g7.cloudfront.net";
        String keyPairId = "K1UA3WV15I7JSD";
        CannedSignerRequest cannedRequest = CannedSignerRequest.builder()
                .resourceUrl(resourceUrl)
                .privateKey(new java.io.File("/path/to/private_key.pem").toPath())
                .keyPairId(keyPairId)
                .expirationDate(expirationDate)
                .build();
        SignedUrl signedUrl = cloudFrontUtilities.getSignedUrlWithCannedPolicy(cannedRequest);
        String url = signedUrl.url();
        System.out.println(url);

    }
}
```

**Example Java에서 SHA256을 사용한 준비된 정책 서명 예제**  <a name="ExampleJavaPolicySHA256AndSignatureEncryptionMethods"></a>

```
package org.example;

import java.io.File;
import java.nio.file.Files;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.spec.PKCS8EncodedKeySpec;
import java.time.Instant;
import java.time.temporal.ChronoUnit;
import java.util.Base64;

public class Main {

    public static void main(String[] args) throws Exception {
        String resourceUrl = "https://a1b2c3d4e5f6g7.cloudfront.net/myfile.html";
        String keyPairId = "K1UA3WV15I7JSD";
        Instant expiration = Instant.now().plus(7, ChronoUnit.DAYS);
        PrivateKey privateKey = loadPrivateKey("/path/to/private_key.der");

        System.out.println(createSignedUrl(resourceUrl, keyPairId, privateKey, expiration, "SHA1"));
        System.out.println(createSignedUrl(resourceUrl, keyPairId, privateKey, expiration, "SHA256"));
    }

    static String createSignedUrl(String resourceUrl, String keyPairId,
                                  PrivateKey privateKey, Instant expiration,
                                  String hashAlgorithm) throws Exception {
        long epochSeconds = expiration.getEpochSecond();

        String policy = "{\"Statement\":[{\"Resource\":\"" + resourceUrl
                + "\",\"Condition\":{\"DateLessThan\":{\"AWS:EpochTime\":" + epochSeconds + "}}}]}";

        String jcaAlgorithm = hashAlgorithm.equals("SHA256") ? "SHA256withRSA" : "SHA1withRSA";

        Signature sig = Signature.getInstance(jcaAlgorithm);
        sig.initSign(privateKey);
        sig.update(policy.getBytes("UTF-8"));
        String signature = base64UrlEncode(sig.sign());

        String url = resourceUrl
                + (resourceUrl.contains("?") ? "&" : "?")
                + "Expires=" + epochSeconds
                + "&Signature=" + signature
                + "&Key-Pair-Id=" + keyPairId;

        if (hashAlgorithm.equals("SHA256")) {
            url += "&Hash-Algorithm=SHA256";
        }

        return url;
    }

    static String base64UrlEncode(byte[] bytes) {
        return Base64.getEncoder().encodeToString(bytes)
                .replace('+', '-')
                .replace('=', '_')
                .replace('/', '~');
    }

    static PrivateKey loadPrivateKey(String path) throws Exception {
        byte[] keyBytes = Files.readAllBytes(new File(path).toPath());
        return KeyFactory.getInstance("RSA")
                .generatePrivate(new PKCS8EncodedKeySpec(keyBytes));
    }
}
```

추가 참고:
+ [Perl을 사용한 URL 서명 생성](CreateURLPerl.md)
+ [PHP를 사용한 URL 서명 생성](CreateURL_PHP.md)
+ [C\# 및 .NET Framework를 사용한 URL 서명 생성](CreateSignatureInCSharp.md)