试试这个：

ObjectMapper mapper = new ObjectMapper();

JsonNode rootNode = mapper.createObjectNode();

JsonNode childNode1 = mapper.createObjectNode();

((ObjectNode) childNode1).put("name1", "val1");

((ObjectNode) childNode1).put("name2", "val2");

((ObjectNode) rootNode).set("obj1", childNode1);

JsonNode childNode2 = mapper.createObjectNode();

((ObjectNode) childNode2).put("name3", "val3");

((ObjectNode) childNode2).put("name4", "val4");

((ObjectNode) rootNode).set("obj2", childNode2);

JsonNode childNode3 = mapper.createObjectNode();

((ObjectNode) childNode3).put("name5", "val5");

((ObjectNode) childNode3).put("name6", "val6");

((ObjectNode) rootNode).set("obj3", childNode3);

String jsonString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(rootNode);

System.out.println(jsonString);