Java中的 KeyStore containsAlias() 方法及示例

Java.security.KeyStore类的containsAlias()方法用于检查请求的别名是否存在。

句法：

public final boolean containsAlias(String alias)
  throws KeyStoreException

参数：该方法将别名的名称作为要检查其条目的字符串类型的参数。
返回值：此方法返回一个布尔值，说明结果。
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。

下面是说明containsAlias()方法的示例：

示例 1：

Java

// Java program to demonstrate
// getInstance() 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 MessageDigest
            // and getting instance
            // By using getInstance() method
            KeyStore sr = KeyStore.getInstance("JKS");
 
            // Keystore password is require
            // 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);
 
            // checking the presence of the aliases
            // using containsAlias() method
            boolean status
                = sr.containsAlias("ftpkey");
 
            // display the result
            if (status)
                System.out.println("This aliases is present");
            else
                System.out.println("This aliases is absent");
        }
 
        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：

This aliases is present

示例 2：对于KeyStoreException

Java

// Java program to demonstrate
// getInstance() 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 MessageDigest
            // and getting instance
            // By using getInstance() method
            KeyStore sr = KeyStore.getInstance("JKS");
 
            // initializing keystore object
            // sr.load(is, pass);
 
            // checking the presence of the aliases
            // using containsAlias() method
            boolean status = sr.containsAlias("gfg");
 
            // display the result
            if (status)
                System.out.println("This aliases is present");
            else
                System.out.println("This aliases is absent");
        }
        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#containsAlias-java.lang.String-