如何从HTTP响应中获取mongodb objectId

我正在测试在数据库中保存对象的端点。Post方法按预期工作,对象转到数据库。我正试图找出如何从得到的HTTP响应中获取mongo objectID,这样就可以使用Put和Delete方法进行进一步的测试,因为我需要用于URI的objectID。

@Test
public void saveRule() throws URISyntaxException, IOException {

    RuleDTO ruleDTO = new RuleDTO();
    ruleDTO.setTitle("My rule");
    ruleDTO.setIndex(666);

    ObjectMapper mapper = new ObjectMapper();
    String json = mapper.writeValueAsString(ruleDTO);

    String target = "http://localhost:8090" + "/v2/rules"; // fix
    URI uri = new URI(target);
    HttpPost httpPost = new HttpPost(uri.toASCIIString());
    StringEntity entity = new StringEntity(json);
    httpPost.setHeader("Accept", "application/json");
    httpPost.setHeader("Content-type", "application/json");
    httpPost.setEntity(entity);
    HttpResponse response = httpClient.execute(httpPost);

    int HTTPcode = response.getStatusLine().getStatusCode();
    HttpEntity getEntity = response.getEntity();
    String getJson = EntityUtils.toString(getEntity);

    ObjectMapper objectMapper = new ObjectMapper();
    Rule rule = objectMapper.readValue(getJson, Rule.class);
    boolean isMyRule = false;

    if (rule.getTitle().equals("My rule")) {
        isMyRule = true;
    }

    boolean correctStatus = HTTPcode >= 200 && HTTPcode <= 300 ? true : false;

    assertTrue(correctStatus);
    assertTrue(isMyRule);
}