spring boot

RestTemplate 源码的简单分析

//使用示例 
    @PostMapping("/judge")
    public boolean judge() {
        RestTemplate restTemplate = new RestTemplate();
        String fooResourceUrl
                = "http://localhost:8080/spring-rest/foos";
        ResponseEntity<String> response
                = restTemplate.getForEntity(fooResourceUrl + "/1", String.class);
        return  false;
    }

	@Override
	public <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request,
			Class<T> responseType, Object... uriVariables) throws RestClientException {

		RequestCallback requestCallback = httpEntityCallback(request, responseType);
		ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
		return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables));
	} 


	...


	@Nullable
	protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback,
			@Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {

		...

		ClientHttpResponse response = null;
		try {
			ClientHttpRequest request = createRequest(url, method);
			if (requestCallback != null) {
				requestCallback.doWithRequest(request);
			}
			response = request.execute();
			handleResponse(url, method, response);
			return (responseExtractor != null ? responseExtractor.extractData(response) : null);
		}
		catch (IOException ex) {
			...
		}
		finally {
			...
		}
	}

到了 HttpAccessor 的 createRequest 方法

	protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
		ClientHttpRequest request = getRequestFactory().createRequest(url, method);
		initialize(request);
		if (logger.isDebugEnabled()) {
			logger.debug("HTTP " + method.name() + " " + url);
		}
		return request;
	}


	/**
	 * Return the request factory that this accessor uses for obtaining client request handles.
	 */
	public ClientHttpRequestFactory getRequestFactory() {
		return this.requestFactory;
	}

    而 ClientHttpRequestFactory 是什么。

    这张图就可以看出 ClientHttpRequestFactory 的实现有多个，而 RestTemplate则封装了组装、发送 HTTP消息，以及解析响应的底层细节。

    spring 很多也进行这样的封装，比如log 。

参考资料

• https://www.baeldung.com/rest-template （template 使用）