java http请求获取tocken

可以使用如下代码获取Java中的token：

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class TokenUtil {

    public static String getToken(String clientId, String clientSecret) {

        String plainCreds = clientId + ":" + clientSecret;
        byte[] plainCredsBytes = plainCreds.getBytes(StandardCharsets.UTF_8);
        String base64Creds = Base64.getEncoder().encodeToString(plainCredsBytes);

        String tokenUrl = "http://your.auth.server/oauth/token"; //your auth server url
        String grantType = "client_credentials"; //the type of grant
        String scope = "read write"; //the scope of the access token

        String url = tokenUrl + "?grant_type=" + grantType + "&scope=" + scope;
        URL obj;
        InputStream in = null;
        try {
            obj = new URL(url);
            URLConnection conn = obj.openConnection();
            HttpURLConnection httpConn = (HttpURLConnection) conn;
            httpConn.setRequestMethod("POST");
            httpConn.setRequestProperty("Authorization", "Basic " + base64Creds);

            in = new BufferedInputStream(httpConn.getInputStream());
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            StringBuffer buffer = new StringBuffer();

            String line;
            while ((line = reader.readLine()) != null) {
                buffer.append(line);
            }

            return buffer.toString();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        return null;
    }

}

该方法使用了Basic认证方式，将client id和client secret进行base64编码后传递给token server。同时，也传递了`grant_type`和`scope`参数，用于指定授权方式和访问权限范围。在token server验证完成后，会返回一个JSON格式字符串，里面包括了access_token等信息。