如何使用WebClient发送POST请求正文

Question

我有使用String的方法。我想使用WebClient在主体中发送此字符串。

一块块下面。

public String JsonMethod(User user) {
        String jsonUserRegister = "{\n" +
                "    \"variables\":\n" +
                "        {\n" +
                "           \"user\": \n" +
                "           {\n" +
                "               \"value\":\n" +
                "                   {\n" +
                "                \"username\": \"" + user.getUsername() + "\",\n" +
                "                \"email\": \"" + user.getEmail() + "\",\n" +
                "                \"address\": \"" + user.getAddress() + "\",\n" +
                "                \"number\": \"" + user.getNumber() + "\"\n" +
                "               } }\n" +
                "        }\n" +
                "}";

        return jsonUserRegister;
    }

WebClient webClient;

public Mono<Boolean> registerUser(User user) {
    return webClient
            .post()
            .uri(URL + ":" + PORT + REST_API_REGISTER_PROCESS)
            .contentType(MediaType.APPLICATION_JSON)
            .body(WHAT SHOULD BE THERE?)

我不知道如何从方法到.body调用此字符串