获取Access Token报code: 400, body is mandatory

代码是按官方给的示例写的
// This file is auto-generated, don't edit it. Thanks.
package com.aliyun.sample;

import com.aliyun.tea.*;

public class Sample {

/**
 * <b>description</b> :
 * <p>使用 Token 初始化账号Client</p>
 * @return Client
 * 
 * @throws Exception
 */
public static com.aliyun.dingtalkoauth2_1_0.Client createClient() throws Exception {
    com.aliyun.teaopenapi.models.Config config = new com.aliyun.teaopenapi.models.Config();
    config.protocol = "https";
    config.regionId = "central";
    return new com.aliyun.dingtalkoauth2_1_0.Client(config);
}

public static void main(String[] args_) throws Exception {
    java.util.List<String> args = java.util.Arrays.asList(args_);
    com.aliyun.dingtalkoauth2_1_0.Client client = Sample.createClient();
    com.aliyun.dingtalkoauth2_1_0.models.GetTokenRequest getTokenRequest = new com.aliyun.dingtalkoauth2_1_0.models.GetTokenRequest()
            .setClientId("suite123")
            .setClientSecret("********")
            .setGrantType("client_credentials");
    try {
        client.getToken("ding9f****41", getTokenRequest);
    } catch (TeaException err) {
        if (!com.aliyun.teautil.Common.empty(err.code) && !com.aliyun.teautil.Common.empty(err.message)) {
            // err 中含有 code 和 message 属性，可帮助开发定位问题
        }

    } catch (Exception _err) {
        TeaException err = new TeaException(_err.getMessage(), _err);
        if (!com.aliyun.teautil.Common.empty(err.code) && !com.aliyun.teautil.Common.empty(err.message)) {
            // err 中含有 code 和 message 属性，可帮助开发定位问题
        }

    }        
}

}