使用 Java 从 JSON 中提取名称/值对
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Extracting name/value pairs from JSON with Java
提问by Mislav Javor
I have this JSON code:
我有这个 JSON 代码：
{
"success": 1,
"item": [
{
"itemId": "jogurt123",
"name": "Jogurt",
"description": "kajmak",
"pictureUrl": "https://www.google.hr/images/srpr/logo11w.png",
"categoryId": "mlijeko"
}
],
"specs": [
{
"specId": "volumen",
"value": "1",
"unit": "litra"
},
{
"specId": "mast",
"value": "50",
"unit": "%"
}
]
}
}
I wonder how to extract name/value pairs into Strings using Java. I would like to get the end result:
我想知道如何使用 Java 将名称/值对提取到字符串中。我想得到最终结果：
String name = "Jogurt"
String description = "kajmak"
etc...
I tried using JSONObject to create an object that contains this name/value pairs and I wanted to extract them then but in the following code
我尝试使用 JSONObject 创建一个包含此名称/值对的对象，然后我想提取它们，但在以下代码中
String getParam(String code, String element){
try {
String base = this.getItembyID(code);
JSONObject product = new JSONObject(base);
String param = product.getString("name");
return param;
} catch (JSONException e) {
e.printStackTrace();
return "error";
}
}
I get an exception saying that there is not an element "name" in the JSONObject when clearly there is. Any suggestions?
我收到一个异常，说 JSONObject 中没有元素“名称”，但显然存在。有什么建议？
EDIT: The getItembyID method returns the JSON code written above in a string form. JSON code has been validated
编辑：getItembyID 方法以字符串形式返回上面编写的 JSON 代码。JSON 代码已通过验证
采纳答案by Nambi
{ ->JSONObject
{ -> JSONObject
[-> JSONArray
[-> JSONArray
You need to get the jsonObject inside the Jsonarray
您需要在 Jsonarray 中获取 jsonObject
Do like this
这样做
String getParam(String code, String element){
try {
String base = this.getItembyID(code);
JSONObject product = new JSONObject(base);
JSONArray jarray = product.getJSONArray("item");
String param = jarray.getJSONObject(0).getString("name");
return param;
} catch (JSONException e) {
e.printStackTrace();
return "error";
}
}
回答by Sotirios Delimanolis
Assuming baseis the JSON you posted in your question, then your assumptions stated here
假设base是您在问题中发布的 JSON，那么您的假设在此处说明
I get an exception saying that there is not an element "name" in the JSONObject when clearly there is.
我收到一个异常，说 JSONObject 中没有元素“名称”，但显然存在。
are wrong. The JSON object you've shown contains only 3 elements: success, item, and specs. itemis a JSON array with a single element, another JSON object. That JSON object contains a value named name.
错了。还有你的JSON对象仅包含三个元素：success，item，和specs。item是一个带有单个元素的 JSON 数组，另一个 JSON 对象。该 JSON 对象包含一个名为 的值name。
You need to get thatJSON object so that you can retrieve thatvalue.
您需要获取该JSON 对象，以便您可以检索该值。
Or consider using a different JSON parsing library like Hymanson or Gson that mostly does this for you based on some POJO class.
或者考虑使用不同的 JSON 解析库，如 Hymanson 或 Gson，它们主要基于某些 POJO 类为您执行此操作。
回答by ravi.patel
If u have java classes for particular data u are getting in form of json. Then it would be easy to extract data by using Hymanson library. [ Download: http://repo1.maven.org/maven2/com/fasterxml/Hymanson/core/Hymanson-core/2.2.3/Hymanson-core-2.2.3.jar]
如果你有特定数据的 java 类，你会以 json 的形式获得。然后使用 Hymanson 库很容易提取数据。[下载：http: //repo1.maven.org/maven2/com/fasterxml/Hymanson/core/Hymanson-core/2.2.3/Hymanson-core-2.2.3.jar]
then Your code will be:
那么你的代码将是：
public String getParam(String code, String element) {
String base = this.getElementById(code);
ObjectMapper mapper = new ObjectMapper();
Product product = mapper.readValue(base, Product.class);
// this will return name of product
return product.getItem()[0].getName();
}
