Java KeyFactory getInstance()用法及代碼示例

getInstance(String algorithm)

java.security.KeyFactory類的getInstance()方法返回一個KeyFactory類型的對象，該對象應用分配的KeyFactory算法。

用法:

public static KeyFactory
  getInstance(String algorithm)
  throws NoSuchAlgorithmException

參數：此方法將標準算法視為要為其實例創建此KeyFactory實例的參數。

返回值：此方法返回一個新的 key 工廠對象。

異常：此方法引發以下異常：

NoSuchAlgorithmException：如果沒有提供者可用於支持特定算法的關鍵工廠spi應用程序。
NullPointerException ：如果algorithm為null。

下麵是說明getInstance()方法的示例：

示例1:

// Java program to demonstrate 
// getInstance() method 
  
import java.security.*; 
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
    { 
  
        try { 
  
            // creating the object of KeyFactory 
            // and getting instance 
            // By usng getInstance() method 
            KeyFactory sr 
                = KeyFactory.getInstance("DSA"); 
  
            // getting the algoritm of KeyFactory object 
            String str = sr.getAlgorithm(); 
  
            // printing the status 
            System.out.println("algorithm : " + str); 
        } 
  
        catch (NoSuchAlgorithmException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
        catch (NullPointerException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

algorithm : DSA

示例2:顯示NoSuchAlgorithmException

// Java program to demonstrate 
// getInstance() method 
  
import java.security.*; 
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
    { 
  
        try { 
  
            // creating the object of KeyFactory 
            // and getting instance 
            // By usng getInstance() method 
            KeyFactory sr = KeyFactory.getInstance("GEEKS"); 
  
            // getting the algoritm of KeyFactory object 
            String str = sr.getAlgorithm(); 
  
            // printing the status 
            System.out.println("algorithm : " + str); 
        } 
  
        catch (NoSuchAlgorithmException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
        catch (NullPointerException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

Exception thrown :
 java.security.NoSuchAlgorithmException:
 GEEKS KeyFactory not available

getInstance(String algorithm, String provider)

java.security.KeyFactory類的getInstance()方法返回一個KeyFactory類型的對象，該對象應用分配的KeyFactory算法和分配的提供程序對象。

用法:

public static KeyFactory
  getInstance(String algorithm, String provider)
  throws NoSuchAlgorithmException

參數：此方法尋求以下參數作為參數：

algorithm：這是為獲取實例而指定的算法的名稱。
provider：這是要指定的提供者的名稱

返回值：此方法返回一個新的 key 工廠對象。

異常：此方法引發以下異常：

NoSuchAlgorithmException：–如果沒有提供者可用於支持特定算法的關鍵工廠spi應用程序。
IllegalArgumentException：–如果提供者為null。
NullPointerException ：–如果算法為null

下麵是說明getInstance()方法的示例：

示例1:

// Java program to demonstrate 
// getInstance() method 
  
import java.security.*; 
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
    { 
        try { 
            // creating the object of KeyFactory 
            // and getting instance 
            // By usng getInstance() method 
            KeyFactory sr 
                = KeyFactory.getInstance( 
                    "DSA", "SUN"); 
  
            // getting the algoritm of KeyFactory object 
            String str = sr.getAlgorithm(); 
  
            // printing the status 
            System.out.println("algorithm : " + str); 
        } 
  
        catch (NoSuchAlgorithmException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
        catch (NullPointerException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
        catch (NoSuchProviderException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

algorithm : DSA

示例2:顯示NoSuchAlgorithmException

// Java program to demonstrate 
// getInstance() method 
  
import java.security.*; 
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
    { 
        try { 
            // creating the object of KeyFactory 
            // and getting instance 
            // By usng getInstance() method 
            KeyFactory sr 
                = KeyFactory.getInstance( 
                    "RSA", "SUN"); 
  
            // getting the algoritm of KeyFactory object 
            String str = sr.getAlgorithm(); 
  
            // printing the status 
            System.out.println("algorithm : " + str); 
        } 
  
        catch (NoSuchAlgorithmException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
        catch (NullPointerException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
        catch (NoSuchProviderException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

Exception thrown :
 java.security.NoSuchAlgorithmException:
 no such algorithm: RSA for provider SUN

參考： https://docs.oracle.com/javase/9/docs/api/java/security/KeyFactory.html#getInstance-java.lang.String-

相關用法

注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 KeyFactory getInstance() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。