Java 中的 KeyPairGenerator getInstance()方法，带示例
原文:https://www . geeksforgeeks . org/keypairgenerator-getinstance-method-in-Java-with-examples/
字符串算法
Java . security . KeyPairGenerator类的 getInstance() 方法用于返回一个为指定算法生成公钥/私钥对的 KeyPairGenerator 对象。
此方法遍历注册的安全提供程序列表，从最首选的提供程序开始。返回一个新的密钥生成器对象，该对象封装了来自支持指定算法的第一个提供程序的密钥生成器。
语法:
public static KeyPairGenerator
getInstance(String algorithm)
throws NoSuchAlgorithmException
参数:该方法以算法的标准名称为参数。
返回值:该方法返回新的 KeyPairGenerator 对象。
异常:如果没有提供程序支持指定算法的签名实现，此方法将抛出 NoSuchAlgorithmException 。
以下是说明 getInstance() 方法的示例:
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
// KeyPairGenerator
// and getting instance
// using getInstance() method
KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA");
// getting the Algorithm
String algo = sr.getAlgorithm();
// printing the algo String
System.out.println("Algorithm : " + algo);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Output:
Algorithm : DSA
示例 2: 显示 NoSuchAlgorithmException 异常
// 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
// KeyPairGenerator
// and getting instance
// using getInstance() method
System.out.println("Trying to get"
+ " the instance of unknown Algorithm");
KeyPairGenerator sr = KeyPairGenerator
.getInstance("TAJMAHAL");
// getting the Algorithm
String algo = sr.getAlgorithm();
// printing the algo String
System.out.println("Algorithm : " + algo);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Output:
Trying to get the instance of unknown Algorithm
Exception thrown : java.security.NoSuchAlgorithmException: TAJMAHAL KeyPairGenerator not available
getInstance(字符串算法，提供程序提供程序)
java.security.KeyPairGenerator 类的 getInstance() 方法用于返回一个为指定算法生成公钥/私钥对的 KeyPairGenerator 对象。 返回一个新的密钥生成器对象，该对象封装了来自指定提供程序对象的密钥生成器。请注意，指定的提供程序对象不必在提供程序列表中注册。
语法:
public static KeyPairGenerator
getInstance(String algorithm, Provider provider)
throws NoSuchAlgorithmException
参数:该方法将以下参数作为参数:
- 算法:请求的算法名称。
- 提供者:提供者
返回值:该方法返回新的 KeyPairGenerator 对象。
异常:该方法抛出以下异常:
- no suchalgorithm exception–如果指定的提供程序对象中没有指定算法的 SignatureSpi 实现，则为。
-
IllegalArgumentException– if the provider is null.
以下是说明 getInstance() 方法的示例:
注意:以下程序不会在联机 IDE 上运行。
例 1:
```java // 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 // KeyPairGenerator // and getting instance // using getInstance() method KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA");
// creating Provider object Provider pd = sr.getProvider();
// getting algorithm name // by using getAlgorithm() mathod String algo = sr.getAlgorithm();
// creating the object of KeyPairGenerator and getting instance // By usng getInstance() method KeyPairGenerator sr1 = KeyPairGenerator.getInstance(algo, pd);
// getting the status of signature object KeyPair keypair = sr1.generateKeyPair();
// printing the keypair System.out.println("Keypair : " + keypair); }
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e); } catch (ProviderException e) {
System.out.println("Exception thrown : " + e); } } } ```
Output:
```java Keypair : java.security.KeyPair@12a3a380
```
示例 2: 显示 NoSuchAlgorithmException 异常
```java // 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 // KeyPairGenerator // and getting instance // using getInstance() method KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA");
// creating Provider object Provider pd = sr.getProvider();
// creating the object of KeyPairGenerator and getting instance // By usng getInstance() method KeyPairGenerator sr1 = KeyPairGenerator.getInstance("TAJMAHAL", pd);
// getting the status of signature object KeyPair keypair = sr1.generateKeyPair();
// printing the keypair System.out.println("Keypair : " + keypair); }
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e); } catch (ProviderException e) {
System.out.println("Exception thrown : " + e); } } } ```
Output:
```java Exception thrown : java.security.NoSuchAlgorithmException: no such algorithm: TAJMAHAL for provider SUN
```
示例 3: 显示 IllegalArgumentException
```java // 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 // KeyPairGenerator // and getting instance // using getInstance() method KeyPairGenerator sr = KeyPairGenerator .getInstance("RSA");
// creating Provider object System.out.println("Trying to assign null as a provider"); Provider pd = null;
// getting algorithm name // by using getAlgorithm() mathod String algo = sr.getAlgorithm();
// creating the object of KeyPairGenerator and getting instance // By usng getInstance() method KeyPairGenerator sr1 = KeyPairGenerator .getInstance(algo, pd);
// getting the status of signature object KeyPair keypair = sr1.generateKeyPair();
// printing the keypair System.out.println("Keypair : " + keypair); }
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e); } catch (ProviderException e) {
System.out.println("Exception thrown : " + e); } catch (IllegalArgumentException e) {
System.out.println("Exception thrown : " + e); } } } ```
Output:
```java Trying to assign null as a provider Exception thrown : java.lang.IllegalArgumentException: missing provider
```
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