如何从 Java 中的 txt 文件中读取 JSON 数据？
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How to Read JSON data from txt file in Java?
提问by Thomas Hu
I am now want to read a series of JSON data(Nodes data) from local txt file(shown below, NODES.txt). I use javax.json to do this.
我现在想从本地 txt 文件（如下所示NODES.txt）读取一系列 JSON 数据（节点数据）。我使用 javax.json 来做到这一点。
Currently, I have a Node classwhich contains the attributes:type, id, geometry class(contains type, coordinates), properties class (contains name);
目前，我有一个包含属性的Node 类：type, id, geometry class(contains type, coordinates), properties class (contains name);
Here is the data I need to retrieve, it contains more than 500 nodes in it, here I just list 3 of them, so I need to use a loop to do it, I am quite new to this, please help !!
这是我需要检索的数据，它包含500多个节点，这里我只列出其中的3个，所以我需要使用循环来完成，我对此很陌生，请帮忙！！
The sample JSON data in NODES.txt
NODES.txt 中的示例 JSON 数据
[
{
"type" : "Feature",
"id" : 8005583,
"geometry" : {
"type" : "Point",
"coordinates" : [
-123.2288,
48.7578
]
},
"properties" : {
"name" : 1
}
},
{
"type" : "Feature",
"id" : 8005612,
"geometry" : {
"type" : "Point",
"coordinates" : [
-123.2271,
48.7471
]
},
"properties" : {
"name" : 2
}
},
{
"type" : "Feature",
"id" : 8004171,
"geometry" : {
"type" : "Point",
"coordinates" : [
-123.266,
48.7563
]
},
"properties" : {
"name" : 3
}
},
****A Lot In the Between****
{
"type" : "Feature",
"id" : 8004172,
"geometry" : {
"type" : "Point",
"coordinates" : [
-113.226,
45.7563
]
},
"properties" : {
"name" : 526
}
}
]
回答by Joel Min
First, read in the file and store the content in ONEString:
首先，读入文件并将内容存储在ONE 中String：
BufferedReader reader = new BufferedReader(new FileReader("NODES.txt"));
String json = "";
try {
StringBuilder sb = new StringBuilder();
String line = reader.readLine();
while (line != null) {
sb.append(line);
sb.append("\n");
line = reader.readLine();
}
json = sb.toString();
} finally {
reader.close();
}
Then parse the Json data from the String:
然后从 String 解析 Json 数据：
JSONObject object = new JSONObject(json); // this will get you the entire JSON node
JSONArray array = object.getJSONArray("Node"); // put in whatever your JSON data name here, this will get you an array of all the nodes
ArrayList<Node> nodeList = new ArrayList(array.length())<Node>;
for(int i=0; i<array.length(); i++){ // loop through the nodes
JSONObject temp = array.getJSONObject(i);
nodeList.get(i).setType(temp.getString("type")); //start setting the values for your node...
....
....
}
回答by Alain O'Dea
Create classes to represent the entries:
创建类来表示条目：
Feature.java:
功能.java：
import java.util.Map;
public class Node {
public String type;
public String id;
public Geometry geometry;
public Properties properties;
}
Geometry.java:
几何.java：
import java.util.List;
public class Geometry {
public String type;
public List<Double> coordinates;
}
Properties.java:
属性.java：
public class Properties {
public String name;
}
And an application main class to drive the processing.
和一个应用程序主类来驱动处理。
Main.java:
主.java：
import com.google.gson.Gson;
import java.io.FileReader;
import java.io.Reader;
public class Main {
public static void main(String[] args) throws Exception {
try (Reader reader = new FileReader("NODES.txt")) {
Gson gson = new Gson();
Node[] features = gson.fromJson(reader, Node[].class);
// work with features
}
}
}
