JsonNode rootNode = mapper.readTree(packet.getDecryptRequestBody());
JsonNode targetNode = null;
targetNode = rootNode.findValue("rpcMsgId"); // 查找第一级的rpcMsgId属性,如果属性不存在,则返回null,属性值如果为明确的null，返回NullNode，否则返回正常的JsonNode// 注：JsonNode还提供了find/path/get等获取节点的方法，但是这三种方法都不能明确的区分节点不存在、为明确的null。所以，应该使用findValue方法。

public class PacketHead {
private String serviceId;private String rpcMsgId;private Map<String,String> spiderOpts;//此处getter/setter省去
}
public class SpiderRequest {private PacketHead spiderPacketHead;private String requestBody;private String resultInfo;public SpiderPacketHead getSpiderPacketHead() {return spiderPacketHead;}public void setSpiderPacketHead(SpiderPacketHead spiderPacketHead) {this.spiderPacketHead = spiderPacketHead;}public String getRequestBody() {return requestBody;}public void setRequestBody(String requestBody) {this.requestBody = requestBody;}@JsonIgnorepublic String getRequestId() {return spiderPacketHead.getRpcMsgId();}public String getResultInfo() {return resultInfo;}public void setResultInfo(String resultInfo) {this.resultInfo = resultInfo;}public static void main(String[] args) throws JsonProcessingException, IOException {SpiderRequest req = new SpiderRequest();req.setSpiderPacketHead(new SpiderPacketHead());String json = JsonUtils.toJson(req);System.out.println(json);JsonNode node = mapper.readTree(json);JsonNode node1 = node.findValue("spiderPacketHead");ObjectNode node2 = (ObjectNode) node1;node2.put("rpcMsgId", "abc");System.out.println(mapper.writeValueAsString(node));}