• 客户端不知道它要创建的具体是哪一个子类。
• 一个类想要由自己的子类来定义某对象的创建过程。
• 类将创建某对象的职责代理给一些帮助子类中的一个，并且你想要将哪一个子类作为代理的信息进行局部化。

• 简单工厂又称"静态工厂"，顾名思义，这是工厂方法和简单工厂最大的不同，这也是最容易区分开这两种模式的特征。
• 虽然两者都志在对象创建的局部封装，但简单工厂侧重于创建对象的代码复用，或者已创建实例的复用，或者创建实例的统一性；而工厂方法侧重于子类自己特定创建逻辑的实现。
• 简单工厂模式中的工厂类是为产品类实例化的核心，而工厂方法模式把初始化工作交给子类实现。换句话讲，如果有新产品添加，简单工厂需要修改自己的工厂类，而工厂方法只需增加新工厂子类 - 简单工厂对 OCP 原则的支持力度不如工厂方法。

package com.defonds.cloud.tool.config.util;


import com.defonds.cloud.tool.config.encrypt.Encryptor;
import com.defonds.cloud.tool.config.encrypt.factory.EncryptorFactory;
import com.defonds.cloud.tool.config.encrypt.factory.EncryptorFactoryLinux;
import com.defonds.cloud.tool.config.encrypt.factory.EncryptorFactoryMac;
import com.defonds.cloud.tool.config.encrypt.factory.EncryptorFactoryWindows;


public class EncryptorUtil {
	private static String osName = System.getProperties().getProperty("os.name");
	private static Encryptor encryptor;
	static {
		EncryptorFactory encryptorFactory;
		if (osName.equals("Linux")) { // os is linux
			encryptorFactory = new EncryptorFactoryLinux();
		} else if (osName.contains("Windows")) { // os is windows
			encryptorFactory = new EncryptorFactoryWindows();
		} else { // os is mac
			encryptorFactory = new EncryptorFactoryMac();
		}
		encryptor = encryptorFactory.getEncryptor();
	}
	
	/**
	 * 
	 * @param content - the string to be encrypt or decrypt
	 * @param flag - encrypt flag, true is encrypt, false is decrypt
	 * @return - string after encrypt or decrypt
	 */
	public static String encryptorStr(String content, boolean flag) {
		return EncryptorUtil.encryptor.encrypt(content, flag);
	}
	
}

package com.defonds.cloud.tool.config.encrypt;


public interface Encryptor {
	/**
	 * @param content str to be encrypted
	 * @param flag true:encrypt false:decrypt
	 * @return
	 */
	public String encrypt(String content, boolean flag);
}

package com.defonds.cloud.tool.config.encrypt;


import java.io.IOException;


import com.defonds.cloud.tool.config.util.NativeUtils;


public class EncryptorLinuxAmd64 implements Encryptor {
	// Native method declaration
    // use the keyword "native" indicate this is an ‘unsafe‘ mtehod for java
    native String encryptStr(String content, boolean flag);
    
    // Load the library
    static {
        try {
    		System.loadLibrary("libaesjni");
    	}catch (UnsatisfiedLinkError e) {
            try {
				NativeUtils.loadLibraryFromJar("/com/defonds/cloud/tool/config/encrypt/native/linux/amd64/libaesjni.so");
			} catch (IOException e1) {
				throw new RuntimeException(e1);
			} // during runtime. .DLL within .JAR
    	}
    }


	@Override
	public String encrypt(String content, boolean flag) {
		// TODO Auto-generated method stub
		return this.encryptStr(content, flag);
	}
}

package com.defonds.cloud.tool.config.encrypt.factory;


import com.defonds.cloud.tool.config.encrypt.Encryptor;


public interface EncryptorFactory {
	public Encryptor getEncryptor();
}

package com.defonds.cloud.tool.config.encrypt.factory;


import com.defonds.cloud.tool.config.encrypt.Encryptor;
import com.defonds.cloud.tool.config.encrypt.EncryptorLinuxAmd64;
import com.defonds.cloud.tool.config.encrypt.EncryptorLinuxI386;


public class EncryptorFactoryLinux implements EncryptorFactory {
	private static String osArch = System.getProperties().getProperty("os.arch");
	
	@Override
	public Encryptor getEncryptor() {
		if (osArch.equals("amd64")) { // os is linux amd64
			return new EncryptorLinuxAmd64();
		} else { // os is linux i386
			return new EncryptorLinuxI386();
		}
	}


}

		String abc = "abc";
		System.out.println("before encrypt:" + abc);
		String abcEncrypted = EncryptorUtil.encryptorStr(abc, true);
		System.out.println("after encrypt:" + abcEncrypted);
		String abc2 = EncryptorUtil.encryptorStr(abcEncrypted, false);
		System.out.println("after decrypt:" + abc2);

public class EncryptorFactory {
	private static Properties sp = System.getProperties(); 
	private static String osName = sp.getProperty("os.name");
	private static String osArch = sp.getProperty("os.arch");
	private static int index2 = osName.indexOf("indows");
	private static boolean isWindows = false;
	static {
		if (index2 != -1) {
			isWindows = true;
		} 
    }
	
	public static Encryptor getEncryptor() {
		if (isWindows) { // os is windows
			if (osArch.equals("amd64")) { // os is windows amd64
				return new EncryptorWindowsAmd64();
			} else { // os is windows x86
				return new EncryptorWindowsX86();
			}
		} else { // os is linux
			if (osArch.equals("amd64")) { // os is linux amd64
				return new EncryptorLinuxAmd64();
			} else { // os is linux i386
				return new EncryptorLinuxI386();
			}
		}
	}
}

• C++ 与 Java 混合编程