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📜  Java中的提供者 getProperty() 方法和示例

📅  最后修改于: 2022-05-13 01:54:41.637000             🧑  作者: Mango

Java中的提供者 getProperty() 方法和示例

Java.security.Provider类的getProperty()方法用于在该属性列表中搜索具有指定键的属性。如果在该属性列表中未找到该键，则递归地检查默认属性列表及其默认值。如果未找到该属性，则该方法返回 null。

句法： 

public String getProperty(String key)

参数：此方法将属性键作为参数。

返回值：此方法返回此属性列表中具有指定键值的值，如果未找到该属性，则返回null 。

以下是说明getProperty()方法的示例：

示例 1： 

// Java program to demonstrate
// getProperty() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        // Declaring int values
        int i = 10;
  
        try {
            // creating the object of  KeyPairGenerator
            KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA", "SUN");
  
            // getting the Provider of the KeyPairGenerator sr
            // by using method getProvider()
            Provider provider = sr.getProvider();
  
            // Declaring the variable of set type
            Set set;
  
            // getting unmodifiable Set view of the property entries
            set = provider.keySet();
  
            // Creating the object of iterator to iterate set
            Iterator iter = set.iterator();
  
            while (i > 0) {
  
                // getting the mapped value in element
                // using getProperty() method
                String property = provider.getProperty((String)iter.next());
  
                // printing the property of specified key
                System.out.println("value is : " + property);
                i--;
            }
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出： 
value is : SHA1withDSA
value is : SHA1withDSA
value is : SHA1withDSA
value is : Software
value is : sun.security.provider.JavaKeyStore$DualFormatJKS
value is : SHA
value is : sun.security.provider.SHA
value is : sun.security.provider.JavaKeyStore$CaseExactJKS
value is : Software
value is : sun.security.provider.DSA$SHA256withDSA

示例 2： 
// Java program to demonstrate
// getProperty() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        // Declaring int values
        int i = 10;
  
        try {
            // creating the object of  KeyPairGenerator
            KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA", "SUN");
  
            // getting the Provider of the KeyPairGenerator sr
            // by using method getProvider()
            Provider provider = sr.getProvider();
  
            // getting the mapped value in element
            // using getProperty() method
            System.out.println("Trying to search for unspecified key");
            String property = provider.getProperty("geeks");
  
            // printing the property of specified key
            System.out.println("value is : " + property);
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出： 
Trying to search for unspecified key
value is : null