环信添加好友时，出现错误

刚刚毕业，所以很多不懂。这是我做的一个例子。但是一直报500错误

public static String addfriend(String ownerName,String friendName) throws IOException{

		String url = https://a1.easemob.com/gzw-demo/test1/users/zs1/contacts/users/zs2;

		String body = ClientContext.sendPost(url, null);

		return body;

	}

 
 
 
 
 

public static String sendPost(String urlStr, String reqBody) throws IOException {

		String token = ClientContext.getToken();

		PrintWriter out = null;

		BufferedReader in = null;

		String result = "";

		try {

			URL realUrl = new URL(urlStr);

			// 打开和URL之间的连接

			URLConnection conn = realUrl.openConnection();

			// 设置通用的请求属性

			conn.setRequestProperty("accept", "*/*");

			conn.setRequestProperty("connection", "Keep-Alive");

			conn.setRequestProperty("Authorization", "Bearer " + token);

			conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");

			// 发送POST请求必须设置如下两行

			conn.setDoOutput(true);

			conn.setDoInput(true);

			// 获取URLConnection对象对应的输出流

			out = new PrintWriter(conn.getOutputStream());

			// 发送请求参数

			if (reqBody != null) {

				out.print(reqBody);

			}

			// flush输出流的缓冲

			out.flush();

			// 定义BufferedReader输入流来读取URL的响应

			in = new BufferedReader(new InputStreamReader(conn.getInputStream()));

			String line;

			while ((line = in.readLine()) != null) {

				result += line;

			}

		} catch (Exception e) {

			System.out.println("发送 POST 请求出现异常！" + e);

			e.printStackTrace();

		}

		// 使用finally块来关闭输出流、输入流

		finally {

			try {

				if (out != null) {

					out.close();

				}

				if (in != null) {

					in.close();

				}

			} catch (IOException ex) {

				ex.printStackTrace();

			}

		}

		return result;

	}

 
报错为：
java.io.IOException: Server returned HTTP response code: 500 for URL: https://a1.easemob.com/gzw-demo/test1/users/zs1/contacts/users/zs2

    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1840)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1441)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)
    at com.longcom.commmon.ClientContext.sendPost(ClientContext.java:141)
    at com.longcom.service.UsersOperation.addfriend(UsersOperation.java:106)
    at com.longcom.test.Test.main(Test.java:47)