从对象创建Jackson对象节点 [英] Create Jackson ObjectNode from Object

问题描述

我需要在给定键和值的情况下将新项添加到现有的ObjectNode中.该值在方法sig中指定为Object，并且应该是ObjectNode.set()接受的类型之一(String，Integer，Boolean等).但是我不能只做myObjectNode.set(key, value);，因为值只是一个Object，当然我会得到一个不适用于参数(字符串，对象)" 错误.

I need to add a new item to an existing ObjectNode, given a key and a value. The value is specified as an Object in the method sig and should be one of the types that ObjectNode.set() accepts (String, Integer, Boolean, etc). But I can't just do myObjectNode.set(key, value); because value is just an Object and of course I get a "not applicable for the arguments (String, Object)" error.

我的工作解决方案是创建一个函数来检查instanceof并将其强制转换为创建ValueNode:

My make-it-work solution is to create a function to check the instanceof and cast it to create a ValueNode:

private static ValueNode getValueNode(Object obj) {
  if (obj instanceof Integer) {
    return mapper.createObjectNode().numberNode((Integer)obj);
  }
  if (obj instanceof Boolean) {
    return mapper.createObjectNode().booleanNode((Boolean)obj);
  }
  //...Etc for all the types I expect
}

..然后我可以使用myObjectNode.set(key, getValueNode(value));

..and then I can use myObjectNode.set(key, getValueNode(value));

必须有更好的方法，但我很难找到它.

There must be a better way but I'm having trouble finding it.

我猜想有一种使用ObjectMapper的方法，但是目前我还不清楚.例如我可以将值写为字符串，但我需要它是我可以在ObjectNode上设置的东西，并且必须是正确的类型(即，不能将所有内容都转换为String).

I'm guessing that there is a way to use ObjectMapper but how isn't clear to me at this point. For example I can write the value out as a string but I need it as something I can set on my ObjectNode and needs to be the correct type (ie everything can't just be converted to a String).

推荐答案

使用

Use ObjectMapper#convertValue method to covert object to a JsonNode instance. Here is an example:

public class JacksonConvert {
    public static void main(String[] args) {
        final ObjectMapper mapper = new ObjectMapper();
        final ObjectNode root = mapper.createObjectNode();
        root.set("integer", mapper.convertValue(1, JsonNode.class));
        root.set("string", mapper.convertValue("string", JsonNode.class));
        root.set("bool", mapper.convertValue(true, JsonNode.class));
        root.set("array", mapper.convertValue(Arrays.asList("a", "b", "c"), JsonNode.class));
        System.out.println(root);
    }
}

输出:

{"integer":1,"string":"string","bool":true,"array":["a","b","c"]}

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