Question

我有以下Json文件：

{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
"features": [
{ "type": "Feature", "properties": { "PARK_ID": 393, "FACILITYID": 26249,  "coordinates": [ -75.73, 45.34 ] } },
{ "type": "Feature", "properties": { "PARK_ID": 161, "FACILITYID": 3510,  "coordinates": [ -75.73, 45.37 ] } },

我能够读取第一行“type”：“FeatureCollection”

但我不确定如何阅读“crs”和“features”。我试图使用“功能”中的坐标来制作一棵树。

我的代码因此：

    import javax.json.*;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;


public class Preprocess {

    public static void main (String [] args){

        InputStream fis = null;
        try {
            fis = new FileInputStream("wadepools.json");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        JsonReader reader = Json.createReader(fis);
        JsonObject wadepool = reader.readObject();
        reader.

        System.out.println (wadepool.getString("features"));//if i put "type" here i get the output "FeatureCollection"
    }
    }

最好将它保存到本地json库中，因为我没有使用Maven或Gradle的任何经验。

感谢。

Answer 1

您可以从数组中获取JSON obj。

JSON：

{
    "type": "FeatureCollection",
    "crs": {
        "type": "name",
        "properties": {
            "name": "urn:ogc:def:crs:OGC:1.3:CRS84"
        }
    },
    "features": [{
            "type": "Feature",
            "properties": {
                "PARK_ID": 393,
                "FACILITYID": 26249,
                "coordinates": [-75.73, 45.34]
            }
        },
        {
            "type": "Feature",
            "properties": {
                "PARK_ID": 161,
                "FACILITYID": 3510,
                "coordinates": [-75.73, 45.37]
            }
        }

    ]
}

Java：

    JSONArray jarray = (JSONArray) parser.parse(new FileReader("wadepools.json"));

      for (Object o : jarray )
      {
        JSONObject value= (JSONObject) o;

        String type= (String) value.get("type");
        System.out.println(type);

       JSONArray features= (JSONArray) value.get("features");
  for (Object features: features)
        {
          System.out.println(features+"");
        }

      }

希望这会有所帮助..！

Answer 2

如果您不了解任何构建工具，则可以忽略此答案。如果你学习任何构建工具maven，gradle等会更好。 https://maven.apache.org/ https://gradle.org/ 以下代码用于maven构建。将以下依赖项添加到构建文件pom.xml。

的pom.xml

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.9.0</version>
</dependency>

代码：

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Preprocess {

    private static ObjectMapper MAPPER = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

    public static void main (String [] args){

        File fis = null;
        try {
            // provide a proper path to wadepools.json file
            fis = new File("./src/wadepools.json");
            JsonNode jsonNode = MAPPER.readTree(fis);
            System.out.println(jsonNode.get("features"));
            System.out.println(jsonNode.get("features").get(0).get("properties"));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (JsonProcessingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    }

如何使用javax.json在JSON中读取数组

2 个答案: