是否可以使用任何Spring
库来“限制”方法的并发调用次数?像:
@RestController
public class MyRest {
@RequestMethod
public void call() {
someLongRunningSyncTask();
return "finished";
}
public void someLongRunningSyncTask() {
}
}
假设我已经希望这个方法延迟任何执行(以及其余的webservice响应),如果已有5个其他线程正在运行此方法。
是否有任何注释或其他抽象层已经给我这种行为?
答案 0 :(得分:1)
可以实现一个接口HandlerInterceptorAdapter
来拦截spring mvc请求。 Spring还在HandlerInterceptorAdapter
中提供了它的抽象实现,因此您可以扩展它并覆盖您需要的任何方法。从您的描述中看起来您只需要覆盖preHandle
和postHandle
方法。您可以查看this帖子以获取更多示例。以下是如何实现您需要的任何锁定策略,您觉得方便;
public class CustomInterceptor extends HandlerInterceptorAdapter {
private final Semaphore semaphore;
private final long waitTime;
public CustomInterceptor() {
// Hardcode this values or inject through spring as preferred.
semaphore = new Semaphore(5);
waitTime = 10;
}
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
try {
boolean acquired = semaphore.tryAcquire(1, waitTime, TimeUnit.SECONDS);
if (!acquired) {
//TODO Do something with the response or keep waiting or whatever
}
} catch (InterruptedException e) {
// Do something with this exception. Write custom message to response and then return false.
// TODO write custom message to response i.e interrupted or something
return false;
}
return super.preHandle(request, response, handler);
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
ModelAndView modelAndView) throws Exception {
semaphore.release();
super.postHandle(request, response, handler, modelAndView);
}
}
然后在spring xml或java config中实例化,并将其注入SimpleUrlHandlerMapping
的拦截器属性,如下所示;
<bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="mappings">
<props>
<prop key="/welcome">welcomeController</prop>
</props>
</property>
<property name="interceptors">
<list>
<ref bean="customInterceptor" />
</list>
</property>
</bean>
<bean id="customInterceptor" class="com.common.mvc.interceptors.CustomInterceptor" />
PS: Haven未对代码进行测试,但您应该了解基本知识。