a json file dumper for a list of google structs - krickert/search-api GitHub Wiki

import com.google.protobuf.Struct;
import com.google.protobuf.util.JsonFormat;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public final class JsonFileDumper {

    private JsonFileDumper() {
        // Utility class; prevent instantiation.
    }

    /**
     * Converts a list of Protobuf Structs to a JSON array and writes it to the specified file.
     *
     * @param structs  the list of Struct objects to convert
     * @param filePath the file path where the JSON output will be written
     * @throws IOException if writing to the file fails
     */
    public static void dumpStructsToJsonFile(List<Struct> structs, String filePath) throws IOException {
        // Use Protobuf's JsonFormat to print each Struct as JSON.
        JsonFormat.Printer printer = JsonFormat.printer();

        // Build a JSON array string.
        StringBuilder sb = new StringBuilder();
        sb.append("[\n");

        for (int i = 0; i < structs.size(); i++) {
            String json = printer.print(structs.get(i));
            sb.append(json);
            if (i < structs.size() - 1) {
                sb.append(",\n"); // add a comma between objects
            }
        }
        sb.append("\n]");

        // Write the JSON array string to the specified file.
        Files.write(Paths.get(filePath), sb.toString().getBytes(StandardCharsets.UTF_8));
    }

    // Example usage:
    public static void main(String[] args) {
        try {
            // Create some sample Structs.
            Struct struct1 = Struct.newBuilder()
                    .putFields("name", com.google.protobuf.Value.newBuilder().setStringValue("Alice").build())
                    .putFields("age", com.google.protobuf.Value.newBuilder().setNumberValue(30).build())
                    .build();

            Struct struct2 = Struct.newBuilder()
                    .putFields("name", com.google.protobuf.Value.newBuilder().setStringValue("Bob").build())
                    .putFields("age", com.google.protobuf.Value.newBuilder().setNumberValue(25).build())
                    .build();

            List<Struct> structs = List.of(struct1, struct2);
            String outputPath = "output.json";

            dumpStructsToJsonFile(structs, outputPath);
            System.out.println("JSON file written to: " + outputPath);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}