Spring AsyncRestTemplate

类说明

AsyncRestTemplate 是 Spring中提供异步的客户端HTTP访问的核心类。与RestTemplate类相似，它提供了一些类似的方法，只不过返回类型不是具体的结果，而是ListenableFuture包装类。

通过getRestOperations()方法，对外提供了一个同步的RestTemplate对象，并且通过这个RestTemplate对象来共享错误处理和消息转换。

注意：默认情况下，AsyncRestTemplate依靠标准JDK工具来创建HTTP链接。通过使用构造函数来接收AsyncClientHttpRequestFactory接口的具体实现类对象，你可以选用不同的HTTP库，例如Apache HttpComponents，Netty，以及OkHttp。

* Spring's central class for asynchronous client-side HTTP access. Exposes similar methods as RestTemplate, but returns ListenableFuture wrappers as opposed to concrete results.

The AsyncRestTemplate exposes a synchronous RestTemplate via the getRestOperations() method and shares its error handler and message converters with that RestTemplate.

Note: by default AsyncRestTemplate relies on standard JDK facilities to establish HTTP connections. You can switch to use a different HTTP library such as Apache HttpComponents, Netty, and OkHttp by using a constructor accepting an AsyncClientHttpRequestFactory.

类图

类图中省略了一些参数类型及重载的方法，在不影响理解的情况下，保证各要素在一幅图中展现。

 

private String result = "";

@Test
public void testAsyncPost() throws Exception {
String posturl = "http://xxxxxx";
String params = "xxxxxx";

MultiValueMap<String, String> headers = new LinkedMultiValueMap<String, String>();
headers.add("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");

HttpEntity<Object> hpEntity = new HttpEntity<Object>(params, headers);
AsyncRestTemplate asyncRt = new AsyncRestTemplate();

ListenableFuture<ResponseEntity<String>> future = asyncRt.postForEntity(posturl, hpEntity, String.class);

future.addCallback(new ListenableFutureCallback<ResponseEntity<String>>() {
public void onSuccess(ResponseEntity<String> resp) {
result = resp.getBody();
}
public void onFailure(Throwable t) {
System.out.println(t.getMessage());
}
});
System.out.println(result);
}

package com.mlxs.common.server.asyncrest;

import org.apache.log4j.Logger;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.concurrent.ListenableFuture;
import org.springframework.util.concurrent.ListenableFutureCallback;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.client.AsyncRestTemplate;
import org.springframework.web.client.RestTemplate;

/**
* Asyncrest: AsyncRestTemplate 异步发生请求测试
*
* @author mlxs
* @since 2016/8/4
*/
@Controller
@RequestMapping("/async")
public class AsyncrestController {
Logger logger = Logger.getLogger(AsyncrestController.class);

@RequestMapping("/fivetime")
@ResponseBody
public String tenTime(){
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "5秒...";
}

/**
* 同步调用
* @return
*/
@RequestMapping("/sync")
@ResponseBody
public String sync(){
//同步调用
RestTemplate template = new RestTemplate();
String url = "http://localhost:8080/async/fivetime";//休眠5秒的服务
String forObject = template.getForObject(url, String.class);
return "同步调用结束, 结果：" + forObject;
}

/**
* 异步调用
* @return
*/
@RequestMapping("/async")
@ResponseBody
public String async(){
AsyncRestTemplate template = new AsyncRestTemplate();
String url = "http://localhost:8080/async/fivetime";//休眠5秒的服务
//调用完后立即返回（没有阻塞）
ListenableFuture<ResponseEntity<String>> forEntity = template.getForEntity(url, String.class);
//异步调用后的回调函数
forEntity.addCallback(new ListenableFutureCallback<ResponseEntity<String>>() {
//调用失败
@Override
public void onFailure(Throwable ex) {
logger.error("=====rest response faliure======");
}
//调用成功
@Override
public void onSuccess(ResponseEntity<String> result) {
logger.info("--->async rest response success----, result = "+result.getBody());
}
});
return "异步调用结束";
}

}

同步请求：

异步请求：