tomcat管理執行緒數量有限，當達到一定請求數量時，無法繼續接受請求，使用多執行緒的方式，可以呼叫一個非同步執行緒來執行。
執行邏輯如下圖，tomcat就收http請求，呼叫一個副執行緒進行處理，副執行緒處理後，將結果返回給主執行緒。在副執行緒處理整個業務邏輯的過程中，主執行緒可以空閒出來，去處理其他請求。使得伺服器的吞吐量可以有一個很大的提升。
package com.ustc.reed.controller.async;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @author xuanxuan
*
*/
import java.util.concurrent.Callable;
@RestController
public class AsyncController {
private static Logger logger = LoggerFactory.getLogger(AsyncController.class);
@GetMapping("/sync")
public String sync() throws Exception{
logger.info("主執行緒開始");
Thread.sleep(1000);
logger.info("主執行緒結束");
return "success";
}
@GetMapping("/async")
public Callable<String> async() throws Exception{
logger.info("主執行緒開始");
Callable<String> result = new Callable<String>() {
@Override
public String call() throws Exception {
logger.info("副執行緒開始");
Thread.sleep(1000);
logger.info("副執行緒返回");
return "success";
}
};
logger.info("主執行緒結束");
return result;
}
}
複製程式碼在瀏覽器中輸入http://localhost:8082/reed/sync
可以使用 DeferredResult來處理此類業務場景。
執行緒1和執行緒2是完全隔離的，誰也不知道對方的存在。
限於篇幅，新建一個MockQueue，來模擬下單處理。
package com.ustc.reed.service.sync;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
/**
* created by xuanxuan on 2019/1/6
*/
@Component
public class MockQueue {
private String placeOrder; //下單訊息
private String completeOrder; //下單成功訊息
private Logger logger = LoggerFactory.getLogger(getClass());
public String getPlaceOrder() {
return placeOrder;
}
public void setPlaceOrder(String placeOrder) throws Exception {
new Thread(() -> {
logger.info("接到下單請求, " + placeOrder);
try {
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
}
this.completeOrder = placeOrder;
logger.info("下單請求處理完畢," + placeOrder);
}).start();
}
public String getCompleteOrder() {
return completeOrder;
}
public void setCompleteOrder(String completeOrder) {
this.completeOrder = completeOrder;
}
}
複製程式碼每個訂單號會有一個處理結果。DeferredResultHolder可以在圖示的執行緒1和執行緒2之間傳遞DeferredResult這個物件map的key可以理解為訂單號。
package com.ustc.reed.service.sync;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.async.DeferredResult;
import java.util.HashMap;
import java.util.Map;
/**
* created by xuanxuan on 2019/1/6
*/
@Component
public class DeferredResultHolder {
private Map<String,DeferredResult<String>> map = new HashMap<>();
public Map<String, DeferredResult<String>> getMap() {
return map;
}
public void setMap(Map<String, DeferredResult<String>> map) {
this.map = map;
}
}
複製程式碼監聽下單是否完成，完成則返回訂單結果。
package com.ustc.reed.service.sync;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
/**
* created by xuanxuan on 2019/1/6
*/
@Component
public class QueueListener implements ApplicationListener<ContextRefreshedEvent> {
private Logger logger = LoggerFactory.getLogger(QueueListener.class);
@Autowired
private MockQueue mockQueue;
@Autowired
private DeferredResultHolder deferredResultHolder;
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
new Thread(
new Runnable() {
@Override
public void run() {
while (true){
if(StringUtils.isNotBlank(mockQueue.getCompleteOrder())){
String orderNumber = mockQueue.getCompleteOrder();
logger.info("返回訂單結果："+orderNumber);
deferredResultHolder.getMap().get(orderNumber).setResult("place order success");
mockQueue.setCompleteOrder(null);
}else {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
).start();
}
}
複製程式碼請求程式碼如下。
package com.ustc.reed.controller.async;
import com.ustc.reed.service.sync.DeferredResultHolder;
import com.ustc.reed.service.sync.MockQueue;
import org.apache.commons.lang3.RandomStringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.async.DeferredResult;
/**
* @author xuanxuan
*
*/
import java.util.concurrent.Callable;
@RestController
public class AsyncController {
private static Logger logger = LoggerFactory.getLogger(AsyncController.class);
@Autowired
private MockQueue mockQueue;
@Autowired
private DeferredResultHolder deferredResultHolder;
@GetMapping("/mqasync")
public DeferredResult<String> mqasync() throws Exception{
logger.info("主執行緒開始");
String orderNumber = RandomStringUtils.randomNumeric(8);
mockQueue.setPlaceOrder(orderNumber);
DeferredResult<String> result = new DeferredResult<>();
deferredResultHolder.getMap().put(orderNumber, result);
return result;
}
}
複製程式碼在瀏覽器中輸入http://localhost:8082/reed/mqasync ，模擬出編號為05804777的訂單的處理過程，結果如下。
