路过 Map<String, List<Request>> lists 在控制器请求主体中。我的问题解决了。我得到了预期的json。

只需删除第二和第三个列表。只保留一个列表，让它保留它的名字，比如 list 或者 requests . 然后把它添加到列表中。

Root root = new Root(); // whatever
root.getRequests().add(myFirstRequest); // index 0 in the array
root.getRequests().add(mySecondRequest); // index 1 in the array
root.getRequests().add(myThirdRequest); // index 2 in the array

String json = // however you were making json out of Root before

使用 @JsonAnySetter .
示例，使用 public 为简单起见，字段：

class Root {
    @JsonAnySetter
    public Map<String, List<Request>> lists = new LinkedHashMap<>();
}

class Request {
    public int id;
    public String title;
    public int level;
    public List<Request> children;
    @JsonProperty("parent_id")
    public Integer parentId; // 'Integer', not 'int', since it can be null
}

测试

ObjectMapper mapper = new ObjectMapper();
Root root = mapper.readValue(new File("test.json"), Root.class);
for (Entry<String, List<Request>> entry : root.lists.entrySet()) {
    System.out.println(entry.getKey() + ":");
    for (Request request : entry.getValue()) {
        System.out.println("  id=" + request.id +
                        ", title=" + request.title +
                        ", level=" + request.level +
                     ", children=" + request.children +
                     ", parentId=" + request.parentId);
    }
}

输出

0:
  id=12123, title=sfsdf, level=0, children=[], parentId=null
1:
  id=213, title=d, level=1, children=[], parentId=1212312
  id=3232, title=dfsdf, level=1, children=[], parentId=42
  id=234, title=tder, level=1, children=[], parentId=122
2:
  id=452, title=Blll, level=2, children=[], parentId=322
  id=123, title=trrr, level=11, children=[], parentId=1221
  id=33, title=sdfw, level=2123, children=[], parentId=10