通过geoserver2.18版的rest api向postgis图层表中插入geojson数据，请给出java代码

以下是通过 GeoServer 2.18 版本的 REST API 向 PostGIS 图层表中插入 GeoJSON 数据的 Java 代码示例：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class AddGeoJSONToPostGIS {

    public static void main(String[] args) {
        try {
            // Set up the HTTP connection
            URL url = new URL("http://localhost:8080/geoserver/rest/workspaces/{workspace}/datastores/{datastore}/featuretypes/{featuretype}/insertFeatures");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/json");
            conn.setRequestProperty("Accept", "application/json");
            conn.setDoOutput(true);

            // Set the JSON data to be sent in the request body
            String jsonData = "{\"feature\": {\"type\": \"FeatureCollection\", \"features\": [{\"type\": \"Feature\", \"geometry\": {\"type\": \"Point\", \"coordinates\": [30, 10]}, \"properties\": {\"name\": \"My Point\"}}]}}";

            // Write the JSON data to the output stream
            conn.getOutputStream().write(jsonData.getBytes());

            // Read the response from the server
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    (conn.getInputStream())));

            String output;
            while ((output = br.readLine()) != null) {
                // Print the response to the console
                System.out.println(output);
            }

            conn.disconnect();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

注意替换 URL 中的 `{workspace}`、`{datastore}` 和 `{featuretype}` 参数为实际的工作区、数据存储和要插入数据的图层名称。此外，还需替换 `jsonData` 字符串为实际的 GeoJSON 数据。