概述
使用动态代理使得在不影响打印日志的类的情况下进行日志打印，也就解耦业务逻辑和日志打印
代码
代码执行流程：Proxy->获取代理ProxyCalculator.getProxy，代理执行对应的方法，并打印日志
测试类ProxyTest
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| import xyz.lyhcc.calculate.Calculator;
import xyz.lyhcc.calculate.MathCalculator;
import xyz.lyhcc.proxy.ProxyCalculator;
public class ProxyTest {
@Test
public void test() {
Calculator proxy = (Calculator) ProxyCalculator.getProxy(new MathCalculator());
proxy.add(1,2);
proxy.div(10, 2);
}
}
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代理获取类ProxyCalculator
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| import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import xyz.lyhcc.calculate.Calculator;
import xyz.lyhcc.logger.LoggerUtils;
public class ProxyCalculator {
public static Calculator getProxy(Calculator calculator) {
ClassLoader loader = calculator.getClass().getClassLoader();
Class<?>[] interfaces = calculator.getClass().getInterfaces();
InvocationHandler h = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result = null;
try {
LoggerUtils.logStart(method, args);
result = method.invoke(calculator, args);
LoggerUtils.logFinished(method, result);
} catch (Exception e) {
LoggerUtils.logError(method, e);
}
return result;
}
};
Object proxy = Proxy.newProxyInstance(loader, interfaces, h);
return (Calculator) proxy;
}
}
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日志类 LoggerUtils
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| import java.lang.reflect.Method;
import java.util.Arrays;
public class LoggerUtils {
public static void logStart(Method method, Object... args) {
System.out.println("[" + method.getName() + " is running..] args=" + Arrays.asList(args));
}
public static void logFinished(Method method, Object result) {
System.out.println("[" + method.getName() + " is Finished...] result=" +result);
}
public static void logError(Method method, Exception e) {
System.out.println("[" + method.getName() + " has errors] error is " + e.getCause());
}
}
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计算器类和接口
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| public interface Calculator {
public int add(int x, int y);
public int sub(int x, int y);
public int multi(int x, int y);
public int div(int x, int y);
}
public class MathCalculator implements Calculator{
@Override
public int add(int x, int y) {
return x + y;
}
@Override
public int sub(int x, int y) {
return x - y;
}
@Override
public int multi(int x, int y) {
return x * y;
}
@Override
public int div(int x, int y) {
return x / y;
}
}
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动态代理的问题
- 当没有实现任何接口时无法使用动态代理，代理对象和被代理对唯一能产生的关联就是实现了同一接口
- 实现起来困难
