Java 中的 KeyStore getCertificate()方法，示例

原文:https://www . geesforgeks . org/keystore-get certificate-in-Java-method-with-examples/

java.security.KeyStore 类的 getCertificate() 方法用于为请求的别名提供证书。。 语法:

public final Certificate
  getCertificate(String alias)
  throws KeyStoreException

参数:此方法接受别名的名称作为要获取其证书的参数。 返回值:该方法返回所请求别名的证书(如果存在)。 异常:如果不初始化这个密钥库，这个方法抛出密钥库异常。 注意:本文中的所有程序都不会在联机 IDE 上运行，因为不存在“privatekey”密钥库。您可以在系统的 Java 编译器上检查这些代码。要检查此代码，请在您的系统上创建一个密钥库“privatekey”，并设置您自己的密钥库密码来访问该密钥库。 以下是举例说明 getCertificate() 方法: 例 1:

Java 语言(一种计算机语言，尤用于创建网站)

// Java program to demonstrate
// getCertificate() method

import java.security.*;
import java.security.cert.*;
import java.util.*;
import java.io.*;

public class GFG {
    public static void main(String[] argv)
    {
        try {

            // creating the object of KeyStore
            // and getting instance
            // By using getInstance() method
            KeyStore sr = KeyStore.getInstance("JKS");

            // keystore password is required to access keystore
            char[] pass = ("123456").toCharArray();

            // creating and initializing object of InputStream
            InputStream is
                = new FileInputStream(
                    "f:/java/private key.store");

            // initializing keystore object
            sr.load(is, pass);

            // getting the certificate
            // using getCertificate() method
            X509Certificate cert
                = (X509Certificate)sr
                      .getCertificate("ftpkey");

            // display the result
            System.out.println("Certificate version : "
                               + cert.getVersion());
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (KeyStoreException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (FileNotFoundException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (IOException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (CertificateException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

Output: 

Certificate version : 3

例 2: 为钥匙库异常为

Java 语言(一种计算机语言，尤用于创建网站)

// Java program to demonstrate
// getCertificate() method

import java.security.*;
import java.security.cert.*;
import java.util.*;
import java.io.*;

public class GFG {
    public static void main(String[] argv)
    {
        try {

            // creating the object of KeyStore
            // and getting instance
            // By using getInstance() method
            KeyStore sr = KeyStore.getInstance("JKS");

            // initializing keystore object
            // sr.load(is, pass);

            // getting the certificate
            // using getCertificate() method
            X509Certificate cert
                = (X509Certificate)sr
                      .getCertificate("ftpkey");

            // display the result
            System.out.println("Certificate version : "
                               + cert.getVersion());
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (KeyStoreException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

Output: 

Exception thrown :
 java.security.KeyStoreException:
 Uninitialized keystore

参考:T2【https://docs . Oracle . com/javase/9/docs/API/Java/security/keystore . html # getCertificate-Java . lang . string-T4】

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