使用凯撒密码对字符串进行 Java 装饰器模式

Question

所以我尝试遵循装饰器模式来加密和解密字符串。我让加密部分工作得很好，但在从 main 调用解密时遇到问题。我想使用刚刚加密的字符串，而不是再次使用默认字符串。我怎样才能实现这个目标？下面是我的类(class)(类(class)很多，但很短)

字符串

// Blueprint for classes that will have decorators
public interface AString {

    public String getAString();
}

纯字符串

public class PlainString implements AString {

    String test = "thisIsATest";

    public PlainString(){
        System.out.println("Created plain string: " + test);
    }
    @Override
    public String getAString() {
        // TODO Auto-generated method stub
        return test;
    }
}

字符串装饰器

abstract class StringDecorator implements AString {

    protected AString tempString;
    public StringDecorator(AString newString){
        tempString = newString;
    }
    public String getAString(){
        return tempString.getAString();
    }
}

加密写入器

public class EncryptingWriter extends StringDecorator{

    public EncryptingWriter(AString newString) {
        super(newString);

        System.out.println("Adding Ceasar Cipher Encryption");

    }
    public String getAString(){

        return encryptString((PlainString)tempString); //decorated
    }

    public String encryptString(PlainString aString){
        String s = "";
        int len = aString.test.length();

        for(int i = 0; i < len; i++){
            char c = (char)(aString.test.charAt(i) + 3);
            if(c > 'z')
                s += (char)(aString.test.charAt(i)) - (26-3);
            else
                s += (char)(aString.test.charAt(i) + 3);
        }
        return s;
    }

}

解密阅读器

public class DecryptingReader  extends StringDecorator {

    public DecryptingReader(AString newString) {
        super(newString);

        System.out.println("Adding Ceasar Cipher Decryption");

    }
    public String getAString(){
        return decryptString((PlainString)tempString); //decorated
    }

    public String decryptString(PlainString aString){
        String s = "";
        int len = aString.test.length();
        for(int i = 0; i < len; i++){
            char c = (char)(aString.test.charAt(i) - 3);
            if(c > 'z')
                s += (char)(aString.test.charAt(i)) + (26+3);
            else
                s += (char)(aString.test.charAt(i) - 3);
        }
        return s;
    }
}

DecoratorTester(主要)

public class DecoratorTester {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        AString basicString = new EncryptingWriter(new PlainString());
        String encryptedString = basicString.getAString();
        System.out.println("EncryptedString: " + encryptedString);

        DecryptingReader d = new DecryptingReader(basicString);
        System.out.println(d.tempString.getAString());
        //d.decryptString(d.tempString.getAString()); // how can I decrypt the string?
    }

}

Answer 1

它应该是这样的(基于我的评论)。

我正在重命名您的类以使其更加合理，特别是在装饰器的上下文中:

interface StringProvider {  // an interface that will produce a String
    String getStringValue();
}

class PlainStringProvider implements StringProvider {
    private String stringValue;
    public PlainStringProvider(String stringValue) {
        this.stringValue = stringValue;
    }
    @Override
    public String getStringValue() {
        return this.stringValue;
    }
}

class StringProviderDecorator implements StringProvider {
    private StringProvider delegate;
    public StringProviderDecorator(StringProvider delegate) {
        this.delegate = delegate;
    }
    @Override
    public String getStringValue() {
        return this.delegate.getStringValue();
    }
}

class EncryptStringProvider extends StringProviderDecorator {
    public EncryptStringProvider(StringProviderDecorator delegate) {
        super(delegate);
    }
    // your stuff about encryption
}


class DecryptStringProvider extends StringProviderDecorator {
    public DecryptStringProvider (StringProviderDecorator delegate) {
        super(delegate);
    }
    // your stuff about decryption
}

因此使用它们的代码如下所示:

String originalValue = "this is a test";

String encryptedValue 
    = new EncryptStringProvider(new PlainStringProvider(originalValue));

String decryptedValue
    = new DecryptStringProvider(new PlainStringProvider(encryptedValue));

assert decryptedValue == originalValue;