[Java知识库]抽象工厂模式+反射

import java.util.concurrent.TimeUnit;

public interface CacheService {

	String get(final String key);
	void set(String key, String value);
	void set(String key, String value, long timeout, TimeUnit timeUnit);
	void del(String key);
}

import org.springframework.stereotype.Service;
import java.util.concurrent.TimeUnit;

@Service
public class CacheServiceImpl implements CacheService{

	private RedisUtils redisUtils = new RedisUtils();
	@Override
	public String get(String key) {
		return redisUtils.get(key);
	}
	@Override
	public void set(String key, String value) {
		redisUtils.set(key, value);
	}
	@Override
	public void set(String key, String value, long timeout, TimeUnit
			timeUnit) {
		redisUtils.set(key, value, timeout, timeUnit);
	}
	@Override
	public void del(String key) {
		redisUtils.del(key);
	}
}

import java.util.concurrent.TimeUnit;

public interface ICacheAdapter {
	String get(String key);
	void set(String key, String value);
	void set(String key, String value, long timeout, TimeUnit timeUnit);
	void del(String key);
}

import org.springframework.stereotype.Service;
import java.util.concurrent.TimeUnit;

@Service
public class EGMCacheAdapter implements ICacheAdapter {
	private EGM egm = new EGM();
	@Override
	public String get(String key) {
		return egm.gain(key);
	}
	@Override
	public void set(String key, String value) {
		egm.set(key, value);
	}
	@Override
	public void set(String key, String value, long timeout, TimeUnit
			timeUnit) {
		egm.setEx(key, value, timeout, timeUnit);
	}
	@Override
	public void del(String key) {
		egm.delete(key);
	}
}

import java.util.concurrent.TimeUnit;

public class EGM {
	public String gain(String key) {
		return "redis设置值";
	}

	public void set(String key, String value) {
		System.out.println("设置成功！");
	}

	public void setEx(String key, String value, long timeout, TimeUnit timeUnit) {
	}

	public void delete(String key) {
	}
}

import java.util.concurrent.TimeUnit;

public class RedisUtils {
	public String get(String key) {
		return null;
	}

	public void set(String key, String value) {
	}

	public void set(String key, String value, long timeout, TimeUnit timeUnit) {
	}

	public void del(String key) {
	}
}

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;

public class JDKProxy {

	public static <T> T getProxy(Class<T> interfaceClass, ICacheAdapter cacheAdapter) throws Exception {
		InvocationHandler handler = new JDKInvocationHandler(cacheAdapter);
		ClassLoader classLoader =
				Thread.currentThread().getContextClassLoader();
		Class<?>[] classes = interfaceClass.getInterfaces();
		return (T) Proxy.newProxyInstance(classLoader, new Class[]{classes[0]},
				handler);
	}
}

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class JDKInvocationHandler implements InvocationHandler {
	private ICacheAdapter cacheAdapter;

	public JDKInvocationHandler(ICacheAdapter cacheAdapter) {
		this.cacheAdapter = cacheAdapter;
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		return ICacheAdapter.class.getMethod(method.getName(),
				getClazzByArgs(args)).invoke(cacheAdapter, args);
	}

	public static Class<?>[] getClazzByArgs(Object[] args) {
		Class<?>[] classes = new Class<?>[args.length];
		for (int i = 0; i < args.length; i++) {
			classes[i] = args[i].getClass();
		}
		return classes;
	}

}

public class AbstractFactoryTest {

	public static void main(String[] args) throws Exception {
		CacheService proxy_EGM = JDKProxy.getProxy(CacheServiceImpl.class, new
				EGMCacheAdapter());
		proxy_EGM.set("user_name_01","?傅哥");
		String val01 = proxy_EGM.get("user_name_01");
		System.out.println(val01);
	}

}

我在debug的时候发现会出现 Method threw ‘java.lang.NullPointerException’ exception. Cannot evaluate com.sun.proxy.$Proxy0.toString()但是不影响程序的正常运行，应该是由于动态代理的时候生成的对象可能并没有toString()方法，而debug模式下是通过toString来打印信息的。所以也解释了为什么在invoke方法中可以返回真实的代理对象

可参考
https://blog.csdn.net/qq_21040559/article/details/118541395
https://blog.csdn.net/zixiao_YING/article/details/79358708

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