如何使用 Jackson 在 Java 中删除空的 json 节点？
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How do I remove empty json nodes in Java with Hymanson?
提问by user2842643
I'm a beginning java programmer, so I'm sorry if my question is kind of dumb.
我是一个初学 Java 程序员，所以如果我的问题有点愚蠢，我很抱歉。
I have a JSON object that looks like this:
我有一个如下所示的 JSON 对象：
{
"element1" : {
"generated_name_1": {
"a" : {"isReady":false}
},
"generated_name_2":{},
"generated_name_3":{},
"generated_name_4":{}
},
"element2" : {
"generated_name_5" : {
"a" : {"isReady":false},
"g" : {"isReady":false}
}
},
"element3" : {
"a" : { "isReady":false},
"n":{}
}
}
I would like to go through and delete every element that has an empty value associated with it, like "generated_name_2" and "n". I have no idea what the names of those elements would be, and I have no idea how far nested into the JSON tree it is.
我想遍历并删除每个具有与之关联的空值的元素，例如“generated_name_2”和“n”。我不知道这些元素的名称是什么，也不知道它在 JSON 树中嵌套了多远。
I get that I have to write a recursive program, and this is what I came up with:
我知道我必须编写一个递归程序，这就是我想出的：
public static void cleanJsonNodes(ObjectNode myJsonNode){
for (JsonNode currentNode : myJsonNode){
if (currentNode.size() == 0){
myJsonNode.remove(currentNode);
} else {
cleanJsonNodes((ObjectNode)currentNode);
}
}
}
Of course, this doesn't work, but I'm not really sure where to go from here and I've scoured the internet to no avail.
当然，这行不通，但我不确定从哪里开始，我已经在互联网上搜索无济于事。
Please someone help me!
请有人帮助我！
回答by user2379020
Check this
检查这个
How to not send an empty collection in Hymanson
For empty node in Json you can use
对于 Json 中的空节点，您可以使用
Removing JSON elements with Hymanson
These can solve your problem.
这些可以解决您的问题。
回答by Maxim Shoustin
I want only to show direction how to do that with Json:
我只想说明如何使用 Json 做到这一点：
JSONObject jsonObj = new JSONObject(_message);
Map<String, JSONObject> map = jsonObj.getMap();
Iterator<String> it = map.keySet().iterator();
while(it.hasNext()){
String key = it.next();
JSONObject o = map.get(key);
if(o.length() == 0){
it.remove();
}
}
When JSONObjectloads {}its length is 0, therefore you can drop it.
当JSONObject加载时，{}其长度为 0，因此您可以删除它。
As A side note, you can use this method in recursion like:
作为旁注，您可以在递归中使用此方法，例如：
JSONObject jsonObj = new JSONObject(_message);
invoke(jsonObj);
...
private static void invoke(JSONObject jsonObj) {
Map<String, JSONObject> map = jsonObj.getMap();
Iterator<String> it = map.keySet().iterator();
while(it.hasNext()){
String key = it.next();
JSONObject o = map.get(key);
if(o.length() == 0){
it.remove();
}
else{
invoke(o);
}
}
}
I didn't add any validation but for sure , you need to verify instance of jsonObj.getMap()...
我没有添加任何验证，但可以肯定的是，您需要验证jsonObj.getMap()...的实例
回答by Neil
I haven't tested it, but you probably want something like this:
我还没有测试过，但你可能想要这样的东西：
public static void stripEmpty(JsonNode node) {
Iterator<JsonNode> it = node.iterator();
while (it.hasNext()) {
JsonNode child = it.next();
if (child.isObject() && child.isEmpty(null))
it.remove();
else
stripEmpty(child);
}
}
