Using httpClient's POST method to call webservice service produces Chinese garbled characters

Today I encountered a project that needs to use httpClient to remotely call webservice services. In this project, both the service end and the server end are used

The org.springframework.web.filter.CharacterEncodingFilter filter is used to set the encoding format of the data submitted by POST, but the Chinese data obtained by the server is still garbled.

The following is a method of the httpClient tool class I wrote:

public static String doPost(String url, Map<String, String> param) {
		// 创建Httpclient对象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		CloseableHttpResponse response = null;
		String resultString = "";
		try {
			// 创建Http Post请求
			HttpPost httpPost = new HttpPost(url);
			// 创建参数列表
			if (param != null) {
				List<NameValuePair> paramList = new ArrayList<>();
				for (String key : param.keySet()) {
					paramList.add(new BasicNameValuePair(key, param.get(key)));
				}
				// 模拟表单,此时需要设置数据的编码格式，否则默认会以ISO_8859_1进行编码
				UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList,"UTF-8");
				httpPost.setEntity(entity);
			}
			// 执行http请求
			response = httpClient.execute(httpPost);
			resultString = EntityUtils.toString(response.getEntity(), "utf-8");
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				response.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}

		return resultString;
	}

If the encoding method is not specified in UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList,"UTF-8");, after checking the source code, it is found that iso-8859-1 will be used to encode the data by default, which is the cause of the garbled code.

Although this problem is solved, there is still a doubt. Why is it that the org.springframework.web.filter.CharacterEncodingFilter filter is used to encode the post data, but it still needs to be specified in httpCilent? If any master knows, please let me know! ! !