日常开发中，常用spring的aop机制来拦截方法，记点日志、执行结果、方法执行时间啥的，很是方便，比如下面这样：（以spring-boot项目为例）
一、先定义一个Aspect
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;
@Aspect
@Component("logAspect")
public class LogAspect {
@Pointcut("execution(* com.cnblogs.yjmyzz..service..*(..))")
private void logPointCut() {
}
@Around("logPointCut()")
public Object doAround(ProceedingJoinPoint pjp) {
Object result = null;
StringBuilder sb = new StringBuilder();
long start = 0;
try {
//记录线程id、方法签名
sb.append("thread:" + Thread.currentThread().getId() + ", method:" + pjp.getSignature() + ",");
//记录参数
if (pjp.getArgs() != null) {
sb.append("args:");
for (int i = 0; i < pjp.getArgs().length; i++) {
sb.append("[" + i + "]" + pjp.getArgs()[i] + ",");
}
}
start = System.currentTimeMillis();
result = pjp.proceed();
//记录返回结果
sb.append("result:" + result);
} catch (Throwable e) {
sb.append(",error:" + e.getMessage());
throw e;
} finally {
long elapsedTime = System.currentTimeMillis() - start;
//记录执行时间
sb.append(",elapsedTime:" + elapsedTime + "ms");
System.out.println(sb.toString());
return result;
}
}
}
二、定义一个service
import org.springframework.stereotype.Service;
@Service("sampleService")
public class SampleService {
public String hello(String name) {
return "你好," + name;
}
}
三、跑一把
@SpringBootApplication
@EnableAspectJAutoProxy
@ComponentScan(basePackages = {"com.cnblogs.yjmyzz"})
public class AopThreadApplication {
public static void main(String[] args) throws InterruptedException {
ApplicationContext context = SpringApplication.run(AopThreadApplication.class, args);
SampleService sampleService = context.getBean(SampleService.class);
System.out.println("main thread:" + Thread.currentThread().getId());
System.out.println(sampleService.hello("菩提树下的杨过"));
System.out.println();
}
}
输出：
main thread:1 thread:1, method:String com.cnblogs.yjmyzz.aop.thread.service.SampleService.hello(String),args:[0]菩提树下的杨过,result:你好,菩提树下的杨过,elapsedTime:6ms 你好,菩提树下的杨过
第2行即aop拦截后输出的内容。但有些时候，我们会使用多线程来调用服务，这时候aop还能不能拦到呢？
四、多线程
4.1 场景1：Runnable中传入了Spring上下文
public class RunnableA implements Runnable {
private ApplicationContext context;
public RunnableA(ApplicationContext context) {
this.context = context;
}
@Override
public void run() {
SampleService sampleService = context.getBean(SampleService.class);
System.out.println("thread:" + Thread.currentThread().getId() + "," + sampleService.hello("菩提树下的杨过-2"));
}
}
把刚才的main方法，改成用线程池调用（即：多线程）
public static void main(String[] args) throws InterruptedException {
ApplicationContext context = SpringApplication.run(AopThreadApplication.class, args);
System.out.println("main thread:" + Thread.currentThread().getId());
System.out.println();
ExecutorService executorService = Executors.newSingleThreadExecutor();
executorService.submit(new RunnableA(context));
}
输出如下：
main thread:1 thread:23, method:String com.cnblogs.yjmyzz.aop.thread.service.SampleService.hello(String),args:[0]菩提树下的杨过-2,result:你好,菩提树下的杨过-2,elapsedTime:4ms thread:23,你好,菩提树下的杨过-2
很明显，仍然正常拦截到了，而且从线程id上看，确实是一个新线程。
4.2 场景2：Runnable中没传入Spring上下文
public class RunnableB implements Runnable {
public RunnableB() {
}
@Override
public void run() {
SampleService sampleService = new SampleService();
System.out.println("thread:" + Thread.currentThread().getId() + "," + sampleService.hello("菩提树下的杨过-2"));
}
}
与RunnableA的区别在于，完全与spring上下文没有任何关系，服务实例是手动new出来的。
修改main方法：
public static void main(String[] args) throws InterruptedException {
ApplicationContext context = SpringApplication.run(AopThreadApplication.class, args);
System.out.println("main thread:" + Thread.currentThread().getId());
System.out.println();
ExecutorService executorService = Executors.newSingleThreadExecutor();
executorService.submit(new RunnableB());
}
输出：
main thread:1 thread:22,你好,菩提树下的杨过-2
全都是手动new出来的对象，与spring没半毛钱关系，aop不起作用也符合预期。这种情况下该怎么破？
轮到CGLib出场了，其实spring的aop机制，跟它就有密切关系，大致原理：CGLib会从被代理的类，派生出一个子类，然后在子类中覆写所有非final的public方法，从而达到"方法增强"的效果。为此，我们需要写一个代理类：
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import org.apache.commons.lang3.ArrayUtils;
import java.lang.reflect.Method;
public class AopProxy implements MethodInterceptor {
private final static int MAX_LEVEL = 3;
private final static String DOT = ".";
public static String getMethodName(Method method) {
if (method == null) {
return null;
}
String[] arr = method.toString().split(" ");
String methodName = arr[2].split("\(")[0] + "()";
String[] arr2 = methodName.split("\.");
if (arr2.length > MAX_LEVEL) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < arr2.length; i++) {
if (i <= MAX_LEVEL) {
sb.append(arr2[i].substring(0, 1) + DOT);
} else {
sb.append(arr2[i] + DOT);
}
}
String temp = sb.toString();
if (temp.endsWith(DOT)) {
temp = temp.substring(0, temp.length() - 1);
}
return temp;
}
return methodName;
}
@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
StringBuilder sb = new StringBuilder();
Object result = null;
long start = System.currentTimeMillis();
boolean hasError = false;
try {
sb.append("thread[" + Thread.currentThread().getId() + "] " + getMethodName(method) + " =>args:");
if (ArrayUtils.isNotEmpty(objects)) {
for (int i = 0; i < objects.length; i++) {
sb.append("[" + i + "]" + objects[i].toString() + ",");
}
} else {
sb.append("null,");
}
result = methodProxy.invokeSuper(o, objects);
sb.append(" result:" + result);
} catch (Exception e) {
sb.append(", error:" + e.getMessage());
hasError = true;
} finally {
long execTime = System.currentTimeMillis() - start;
sb.append(", execTime:" + execTime + " ms");
}
System.out.println(sb.toString());
return result;
}
}
关键点都在intercept方法里，被代理的类有方法调用时，在intercept中处理拦截逻辑，为了方便使用这个代理类，再写一个小工具：
import net.sf.cglib.proxy.Enhancer;
public class ProxyUtils {
/**
* 创建代理对象实例
*
* @param type
* @param <T>
* @return
*/
public static <T> T createProxyObject(Class<T> type) {
AopProxy factory = new AopProxy();
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(type);
enhancer.setCallback(factory);
//注意：被代理的类，必须有默认无参的空构造函数
T instance = (T) enhancer.create();
return instance;
}
}
有了它就好办了：
public class RunnableB implements Runnable {
public RunnableB() {
}
@Override
public void run() {
//注：这里改成用CGLib来创建目标的代理类实例
SampleService sampleService = ProxyUtils.createProxyObject(SampleService.class);
System.out.println("thread:" + Thread.currentThread().getId() + "," + sampleService.hello("菩提树下的杨过-2"));
}
}
手动new的地方，改成用ProxyUtils生成代理类实例，还是跑刚才的main方法：
main thread:1 thread[24] c.c.y.a.thread.service.SampleService.hello() =>args:[0]菩提树下的杨过-2, result:你好,菩提树下的杨过-2, execTime:9 ms thread:24,你好,菩提树下的杨过-2
第2行的输出，便是AopProxy类拦截的输出，成功拦截，皆大欢喜！
注意事项：
1. 被代理的类，不能是内部类（即嵌套在类中的类），更不能是final类
2. 要拦截的方法，不能是private方法或final方法