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https://blog.csdn.net/itguangit/article/details/78825505
https://www.cnblogs.com/tomcatandjerry/p/5899722.html
通过RestTemplate可以进行http接口的调用，例如如下是POST方式：
public ResponseEntity<JsonNode> Post(String url, Map<String, Object> params, HttpHeaders headers){
org.apache.commons.httpclient.HttpMethod httpMethod = new PostMethod(url);
headers.setContentType(MediaType.APPLICATION_JSON);
httpMethod.getParams().setParameter(
HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, false));
HttpEntity<Map<String, Object>> entity = new HttpEntity<>(params, headers);
logger.info("addRole entity : " + entity);
logger.info("addRole data : " + restTemplate.postForEntity(url, entity, JsonNode.class));
return restTemplate.postForEntity(url, entity, JsonNode.class);
}GET方式（这有个坑，就是getForEntity方法并不能携带请求头信息，因此，对于需要BA认证的REST资源获取，使用execute方法）：
public ResponseEntity<JsonNode> Get(String url, HttpHeaders headers){
org.apache.commons.httpclient.HttpMethod httpMethod = new GetMethod(url);
httpMethod.getParams().setParameter(
HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, false));
HttpEntity entity = new HttpEntity(headers);
return restTemplate.exchange(url, HttpMethod.GET, entity, JsonNode.class );
}