java 从对象创建 Jackson ObjectNode
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Create Hymanson ObjectNode from Object
提问by Chris
I need to add a new item to an existing ObjectNode, given a key and a value. The value is specified as an Objectin the method sig and shouldbe 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 Objectand of course I get a "not applicable for the arguments (String, Object)"error.
ObjectNode给定一个键和一个值，我需要将一个新项目添加到现有的。该值被指定为Object在该方法中SIG和应该是ObjectNode.set（）接受（的类型之一String，Integer，Boolean等等）。但我不能这样做，myObjectNode.set(key, value);因为值只是一个Object，当然我得到一个“不适用于参数（字符串，对象）”的错误。
My make-it-work solution is to create a function to check the instanceofand cast it to create a ValueNode:
我的让它工作的解决方案是创建一个函数来检查instanceof并转换它以创建一个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
}
..and then I can use myObjectNode.set(key, getValueNode(value));
..然后我可以使用 myObjectNode.set(key, getValueNode(value));
There must be a better waybut I'm having trouble finding it.
一定有更好的方法，但我找不到它。
I'm guessing that there is a way to use ObjectMapperbut how isn't clear to me at this point. For example I can write the value out as a stringbut 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).
我猜有一种方法可以使用，ObjectMapper但此时我不清楚如何使用。例如，我可以将值作为字符串写出，但我需要它作为我可以在 ObjectNode 上设置的东西，并且需要是正确的类型（即所有东西都不能只是转换为字符串）。
回答by Alexey Gavrilov
Use ObjectMapper#convertValuemethod to covert object to a JsonNode instance. Here is an example:
使用ObjectMapper#convertValue方法将对象转换为 JsonNode 实例。下面是一个例子：
public class HymansonConvert {
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);
}
}
Output:
输出：
{"integer":1,"string":"string","bool":true,"array":["a","b","c"]}
回答by Gili
Using the put()methods is a lot easier:
使用这些put()方法要容易得多：
ObjectMapper mapper = new ObjectMapper();
ObjectNode root = mapper.createObjectNode();
root.put("name1", 1);
root.put("name2", "someString");
ObjectNode child = root.putObject("child");
child.put("name3", 2);
child.put("name4", "someString");
