要将DXF文件转换为JSON格式，您可以使用Java DXF解析器库。下面是一个简单的示例代码，演示如何使用Java DXF解析器库将DXF文件解析为JSON格式：

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.json.simple.JSONObject;

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

import org.kabeja.dxf.DXFDocument;
import org.kabeja.dxf.DXFLayer;
import org.kabeja.dxf.DXFLine;
import org.kabeja.parser.ParseException;
import org.kabeja.parser.Parser;
import org.kabeja.parser.ParserBuilder;

public class DxfToJsonConverter {

    public static void main(String[] args) throws ParseException, IOException {
        // Create a parser for DXF files
        Parser parser = ParserBuilder.createDefaultParser();

        // Specify the DXF file to be parsed
        File dxfFile = new File("sample.dxf");

        // Parse the DXF file and get the DXF document
        parser.parse(dxfFile.getAbsolutePath());
        DXFDocument document = parser.getDocument();

        // Convert the DXF document to JSON format
        JSONObject json = convertToJSON(document);

        // Print the JSON output to console
        System.out.println(json);
    }

    private static JSONObject convertToJSON(DXFDocument document) throws JsonProcessingException {
        // Create a JSON object to hold the DXF data
        JSONObject json = new JSONObject();

        // Create a map to store layer names and their corresponding line data
        Map<String, JSONArray> layerData = new HashMap<String, JSONArray>();

        // Loop through all the layers in the DXF document
        for (DXFLayer layer : document.getDXFLayerIterator()) {
            // Create a JSON array to store the line data for this layer
            JSONArray lines = new JSONArray();

            // Loop through all the lines in this layer
            for (DXFLine line : layer.getDXFEntities(DXFLine.TYPE)) {
                // Create a JSON object to store the line data
                JSONObject lineData = new JSONObject();

                // Add the line data to the JSON object
                lineData.put("startX", line.getStartPoint().getX());
                lineData.put("startY", line.getStartPoint().getY());
                lineData.put("endX", line.getEndPoint().getX());
                lineData.put("endY", line.getEndPoint().getY());

                // Add the line data to the JSON array
                lines.add(lineData);
            }

            // Add the layer data to the map
            layerData.put(layer.getName(), lines);
        }

        // Add the layer data map to the JSON object
        json.put("layers", layerData);

        // Convert the JSON object to a string and return it
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(json.toJSONString(), JSONObject.class);
    }
}

上述示例代码将DXF文件解析为JSON格式，并将其打印到控制台。您可以根据需要修改代码，以符合您的具体要求。