參數： 請求路徑， 請求參數， 返回類型， 擴展模板變量
參數： 請求參數， 返回類型
HttpEntityRequestCallback構造器
HttpEntityRequestCallback是RestTemplate的私有內部類，繼承了RestTemplate私有內部類 AcceptHeaderRequestCallback,AcceptHeaderRequestCallback實現了RequestCallback接口，重寫了doWithRequest方法
HttpEntity是 HTTP請求或響應實體
public void doWithRequest(ClientHttpRequest httpRequest) throws IOException {
//調用父類方法
super.doWithRequest(httpRequest);
Object requestBody = this.requestEntity.getBody();
//判斷內部類中的HttpEntity是否有參數
if (requestBody == null) {
HttpHeaders httpHeaders = httpRequest.getHeaders();
HttpHeaders requestHeaders = this.requestEntity.getHeaders();
if (!requestHeaders.isEmpty()) {
//如果header不為空，將header的值賦給方法接收的參數ClientHttpRequest
requestHeaders.forEach((key, values) -> {
httpHeaders.put(key, new LinkedList(values));
});
}
//添加content長度
if (httpHeaders.getContentLength() < 0L) {
httpHeaders.setContentLength(0L);
}
} else {
Class<?> requestBodyClass = requestBody.getClass();
Type requestBodyType = this.requestEntity instanceof RequestEntity ? ((RequestEntity)this.requestEntity).getType() : requestBodyClass;
HttpHeaders httpHeadersx = httpRequest.getHeaders();
HttpHeaders requestHeadersx = this.requestEntity.getHeaders();
MediaType requestContentType = requestHeadersx.getContentType();
//消息轉換器列表
Iterator var8 = RestTemplate.this.getMessageConverters().iterator();
while(var8.hasNext()) {
//策略接口，指定可以從HTTP請求和響應轉換的轉換器
HttpMessageConverter<?> messageConverter = (HttpMessageConverter)var8.next();
if (messageConverter instanceof GenericHttpMessageConverter) {
//可以將HTTP請求轉換為指定泛型類型的目標對象，將指定泛型類型的源對象轉換為HTTP響應
GenericHttpMessageConverter<Object> genericConverter = (GenericHttpMessageConverter)messageConverter;
//判斷 指示此轉換器是否可以寫入給定的類
if (genericConverter.canWrite((Type)requestBodyType, requestBodyClass, requestContentType)) {
if (!requestHeadersx.isEmpty()) {
requestHeadersx.forEach((key, values) -> {
httpHeadersx.put(key, new LinkedList(values));
});
}
//打印debug日志
this.logBody(requestBody, requestContentType, genericConverter);
將給定對象寫入給定的輸出消息
genericConverter.write(requestBody, (Type)requestBodyType, requestContentType, httpRequest);
return;
}
} else if (messageConverter.canWrite(requestBodyClass, requestContentType)) {
if (!requestHeadersx.isEmpty()) {
requestHeadersx.forEach((key, values) -> {
httpHeadersx.put(key, new LinkedList(values));
});
}
this.logBody(requestBody, requestContentType, messageConverter);
messageConverter.write(requestBody, requestContentType, httpRequest);
return;
}
}
String message = "No HttpMessageConverter for [" + requestBodyClass.getName() + "]";
if (requestContentType != null) {
message = message + " and content type [" + requestContentType + "]";
}
throw new RestClientException(message);
}
}
private void logBody(Object body, @Nullable MediaType mediaType, HttpMessageConverter<?> converter) {
if (RestTemplate.this.logger.isDebugEnabled()) {
if (mediaType != null) {
RestTemplate.this.logger.debug("Writing [" + body + "] as \"" + mediaType + "\"");
} else {
String classname = converter.getClass().getName();
RestTemplate.this.logger.debug("Writing [" + body + "] with " + classname);
}
}
}
響應提取器，它使用給定的實體轉換器 將響應轉換為類型T
最后的execute方法
@Nullable
public <T> T execute(String url, HttpMethod method, @Nullable RequestCallback requestCallback, @Nullable ResponseExtractor<T> responseExtractor, Object... uriVariables) throws RestClientException {
//使用URI變量映射展開給定的URI模板
URI expanded = this.getUriTemplateHandler().expand(url, uriVariables);
return this.doExecute(expanded, method, requestCallback, responseExtractor);
}
參數：url - 要連接的完全擴展的URL， method - 要執行的HTTP方法（GET，POST等）， requestCallback- 准備請求的對象（可以null）， responseExtractor- 從響應中提取返回值的對象（可以null）
@Nullable
protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback, @Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
Assert.notNull(url, "URI is required");
Assert.notNull(method, "HttpMethod is required");
ClientHttpResponse response = null;
Object var14;
try {
//通過工廠模式創建ClientHttpRequest對象
ClientHttpRequest request = this.createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
//執行請求
response = request.execute();
//處理給定的響應，執行適當的日志記錄並在ResponseErrorHandler必要時調用
this.handleResponse(url, method, response);
//extractData 從給定數據中提取數據ClientHttpResponse並將其返回
var14 = responseExtractor != null ? responseExtractor.extractData(response) : null;
} catch (IOException var12) {
String resource = url.toString();
String query = url.getRawQuery();
resource = query != null ? resource.substring(0, resource.indexOf(63)) : resource;
throw new ResourceAccessException("I/O error on " + method.name() + " request for \"" + resource + "\": " + var12.getMessage(), var12);
} finally {
if (response != null) {
response.close();
}
}
return var14;
}