用java代码写一个下载pdf的restfull api接口

以下是一个使用Java编写的RESTful API接口，用于从指定URL下载PDF文件：

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

@Path("/pdf-download")
public class PdfDownloadApi {

    @GET
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    public Response downloadPdf() {
        try {
            URL url = new URL("http://www.example.com/example.pdf"); // Replace with your PDF file URL
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            InputStream inputStream = conn.getInputStream();

            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

            byte[] buffer = new byte[4096];
            int bytesRead = -1;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }

            byte[] bytes = outputStream.toByteArray();

            Response.ResponseBuilder response = Response.ok(bytes);
            response.header("Content-Disposition", "attachment; filename=example.pdf"); // Replace with desired file name
            return response.build();

        } catch (IOException e) {
            e.printStackTrace();
            return Response.serverError().build();
        }
    }
}

请注意，该代码仅供参考，需要根据具体情况进行修改和适应。例如，您需要将URL替换为您要下载的实际PDF文件的URL，并将Content-Disposition标头中的文件名替换为所需的名称。此外，还需要处理异常和错误情况以及其他可能的细节和安全性考虑。