springmvc callable处理异步请求
使用业务场景: 对于有的请求业务处理流程可能比较耗时，比如长查询，远程调用等，主线程会被一直占用，而tomcat线程池线程有限，处理量就会下降
servlet3.0以后提供了对异步处理的支持，springmvc封装了异步处理，满足用户请求后，主线程很快结束，并开启其它线程处理任务，并将处理结果响应用户，而主线程就可以接收更多请求。
参考官方解释:
https://spring.io/blog/2012/05/07/spring-mvc-3-2-preview-introducing-servlet-3-async-support
原理简介:对于一次请求，比如front/test
1,springmvc开启副线程处理业务(将Callable 提交到 TaskExecutor)
2,DispatcherServlet和所有的Filter退出web容器的线程，但是response 保持打开状态
3,Callable返回结果，SpringMVC将请求front/test重新派发给容器(再重新请求一次front/test)，恢复之前的处理；
4,DispatcherServlet重新被调用，将结果返回给用户
使用条件:mvc4.0以上，servlet3.0以上
使用示例
1 import java.util.concurrent.Callable;
2 import java.util.concurrent.TimeUnit;
3
4 import org.slf4j.Logger;
5 import org.slf4j.LoggerFactory;
6 import org.springframework.web.bind.annotation.RequestMapping;
7 import org.springframework.web.bind.annotation.RestController;
8 @RestController
9 public class RestfulAsync {
10 private Logger logger = LoggerFactory.getLogger(getClass());
11 @RequestMapping("/front/test")
12 public Callable<String> order() {
13 logger.info("主线程开始");
14 Callable<String> result = () -> {
15 logger.info("副线程开始");
16 TimeUnit.SECONDS.sleep(1);
17 logger.info("副线程返回");
18 return "success";
19 };
20 logger.info("主线程返回");
21 return result;
22 }
23 }
配置文件:
1,web.xml 3.0以上
<!--mvc配置--> <servlet> <servlet-name>springMVC</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring/spring-mvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> <!--在此处增加异步支持--> <async-supported>true</async-supported> </servlet> <servlet-mapping> <servlet-name>springMVC</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> 注意所有的过滤器filter也必须增加异步支持<async-supported>true</async-supported>如： <filter> <filter-name>shiroFilter</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> <init-param> <!-- 该值缺省为false,表示生命周期由SpringApplicationContext管理,设置为true则表示由ServletContainer管理 --> <param-name>targetFilterLifecycle</param-name> <param-value>true</param-value> </init-param> <async-supported>true</async-supported> </filter> <filter-mapping> <filter-name>shiroFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 2,spring-mv.xml配置 注意必须指定所需的命名空间 xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation=" http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd"> <!-- spring mvc 异步处理基于任务线程池 --> <bean id="taskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor"> <property name="corePoolSize" value="10" /><!--核心线程数 --> <property name="maxPoolSize" value="100" /><!--最大线程数 --> <property name="queueCapacity" value="1024" /><!--缓冲队列大小 --> <property name="threadNamePrefix" value="http-do-business-pool-" /><!--线程池中产生的线程名字前缀 --> <property name="keepAliveSeconds" value="30" /><!--线程池中空闲线程的存活时间单位秒 --> </bean> <mvc:annotation-driven> <mvc:async-support task-executor="taskExecutor" //此处指定自定义线程池，否则异步处理会使用默认线程池SimpleAsyncTaskExecutor，这个线程大小无限制，会有问题 // 会提示:An Executor is required to handle java.util.concurrent.Callable return values.Please, configure a TaskExecutor in the MVC config under "async support".The SimpleAsyncTaskExecutor currently in use is not suitable under load default-timeout="1000"> //超时时间，单位毫秒 <mvc:callable-interceptors> <bean class="com.ronglian.bms.commons.interceptor.MyCallableInterceptor" /> // 指定异步处理超时拦截器 </mvc:callable-interceptors> </mvc:async-support> </mvc:annotation-driven>
3,异步处理超时拦截器示例:
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Callable;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.CallableProcessingInterceptor;
import com.google.gson.Gson;
import com.ronglian.bms.restful.ResultEnum;
/**
* 异步处理超时拦截器,处理业务超时的情况,xml配置见
* <mvc:annotation-driven>
<mvc:async-support task-executor="taskExecutor"
default-timeout="1000">
<mvc:callable-interceptors>
<bean class="com.ronglian.bms.commons.interceptor.MyCallableInterceptor" />
</mvc:callable-interceptors>
</mvc:async-support>
</mvc:annotation-driven>
* @author zli
* @Date 2019-03-06
*/
public class MyCallableInterceptor implements CallableProcessingInterceptor{
public <T> Object handleTimeout(NativeWebRequest request, Callable<T> task) throws Exception {
HttpServletResponse servletResponse = request.getNativeResponse(HttpServletResponse.class);
if (!servletResponse.isCommitted()) {
//return "service time out";
servletResponse.setContentType("application/json;charset=utf-8");
String obj = this.buildResult(ResultEnum.ERROR_TIME_OUT.getCode(), ResultEnum.ERROR_TIME_OUT.getMsg(), null);
servletResponse.getWriter().write(obj);
servletResponse.getWriter().close();
}
return null;
}
private String buildResult(String headerCode, String headMsg, Object bodyResult) {
Map<String, Object> resultMap = new HashMap<String, Object>();
Map<String, String> headMap = new HashMap<String, String>();
headMap.put("retCode", headerCode);
headMap.put("retMsg", headMsg);
resultMap.put("header", headMap);
resultMap.put("body", bodyResult);
Gson g = new Gson();
return g.toJson(resultMap);
}
}
另外一种带超时处理的Callable,即WebAsyncTask,示例代码如下
/**
* WebAsyncTask示例,带处理超时的Callable
* @return
*/
@RequestMapping("/front/testwithtimeout")
public WebAsyncTask<String> test2() {
logger.info("主线程开始");
Callable<String> result = () -> {
logger.info("副线程开始");
try {
TimeUnit.SECONDS.sleep(4);
} catch (Exception e) {
// TODO: handle exception
}
logger.info("副线程返回");
return "success";
};
logger.info("主线程返回");
WebAsyncTask<String> wat = new WebAsyncTask<String>(3000L, result);
wat.onTimeout(new Callable<String>() {
@Override
public String call() throws Exception {
// TODO Auto-generated method stub
return "超时";
}
});
return wat;
}
