【Spring-web】AsyncRestTemplate源码学习

2017-01-23 by 安静的下雪天 http://www.cnblogs.com/quiet-snowy-day/p/6343347.html

 

本篇概要

• 类说明
• 类图
• 简单例子
• 精辟的内部类

 

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。

 

 

 

简单例子

    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);
    }

 

精辟的内部类

    /**
     * Adapts a {@link RequestCallback} to the {@link AsyncRequestCallback} interface.
     */
    private static class AsyncRequestCallbackAdapter implements AsyncRequestCallback {

        private final RequestCallback adaptee;

        /**
         * Create a new {@code AsyncRequestCallbackAdapter} from the given
         * {@link RequestCallback}.
         * @param requestCallback the callback to base this adapter on
         */
        public AsyncRequestCallbackAdapter(RequestCallback requestCallback) {
            this.adaptee = requestCallback;
        }

        @Override
        public void doWithRequest(final AsyncClientHttpRequest request) throws IOException {
            if (this.adaptee != null) {
                this.adaptee.doWithRequest(new ClientHttpRequest() {
                    @Override
                    public ClientHttpResponse execute() throws IOException {
                        throw new UnsupportedOperationException("execute not supported");
                    }
                    @Override
                    public OutputStream getBody() throws IOException {
                        return request.getBody();
                    }
                    @Override
                    public HttpMethod getMethod() {
                        return request.getMethod();
                    }
                    @Override
                    public URI getURI() {
                        return request.getURI();
                    }
                    @Override
                    public HttpHeaders getHeaders() {
                        return request.getHeaders();
                    }
                });
            }
        }
    }

AsyncRequestCallbackAdapter源码