http发送post请求中文乱码问题

package com.lwl.util;

import sun.misc.BASE64Encoder;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;

/**
 * post请求
 *
 * @author liuwenlong
 * @create 2021-11-30 22:25:00
 */
@SuppressWarnings("all")
public class SendPost {

    /**
     * Post请求一个地址
     *
     * @param URL         请求地址
     * @param requestBody 请求的body
     * @return
     */
    public String doPost(String URL, String requestBody) {
        OutputStreamWriter out = null;
        BufferedReader in = null;
        StringBuilder result = new StringBuilder();
        HttpURLConnection conn = null;
        String username = "账号";
        String password = "密码";
        String input = username + ":" + password;
        try {
            java.net.URL url = new URL(URL);
            conn = (HttpURLConnection) url.openConnection();
            BASE64Encoder base = new BASE64Encoder();
            String encodedPassword = base.encode(input.getBytes("UTF-8"));
            System.out.println("加密后的密码：" + encodedPassword);
            //将加密的账号密码放到请求头里，这里注意Basic后面要加空格
            conn.setRequestProperty("Authorization", "Basic " + encodedPassword);
            conn.setRequestMethod("POST");
            //发送POST请求必须设置为true
            conn.setDoOutput(true);
            conn.setDoInput(true);
            //设置连接超时时间和读取超时时间
            conn.setConnectTimeout(3000);
            conn.setReadTimeout(3000);
            conn.setRequestProperty("Content-Type","application/json;charset=UTF-8");
            conn.setRequestProperty("Accept", "application/json");
            //获取输出流，写入请求的json报文
            out = new OutputStreamWriter(conn.getOutputStream(),"utf-8");
            System.out.println(requestBody);

            out.write(requestBody); //获取请求的body,
            out.flush();
            out.close();
            //取得输入流，并使用Reader读取
            if (200 == conn.getResponseCode()) {
                in = new BufferedReader(new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8));
                String line;
                while ((line = in.readLine()) != null) {
                    result.append(line);
                    System.out.println(line);
                }
            } else {
                System.out.println("ResponseCode is an error code:" + conn.getResponseCode());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }
        return result.toString();
    }

}

注意，OutputStreamWriter 后面要添加 utf-8