Java中的 KeyStore getCertificate() 方法及示例

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

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：此方法返回所请求别名的证书（如果存在）。
异常：如果您不初始化此密钥库，此方法将引发KeyStoreException 。
注意：本文中的所有程序都不会在在线 IDE 上运行，因为不存在“privatekey”密钥库。您可以在系统上的Java编译器上检查此代码。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以访问该密钥库。
以下是说明getCertificate()方法的示例：
示例 1：

Java

// 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);
        }
    }
}

输出：

Certificate version : 3

示例 2：对于KeyStoreException

Java

// 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);
        }
    }
}

输出：

Exception thrown :
 java.security.KeyStoreException:
 Uninitialized keystore

参考： https://docs.oracle.com/javase/9/docs/api/ Java/security/KeyStore.html#getCertificate-java.lang.String-