使用Java实现文件流转base64

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ImageServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 指定图像的URL地址
        String imgUrl = "https://example.com/image.jpg";

        // 使用URL类打开指定URL的输入流
        try (InputStream inputStream = new URL(imgUrl).openStream()) {

            // 设置响应的内容类型为图像
            response.setContentType("image/jpeg");

            // 获取响应输出流
            try (OutputStream outputStream = response.getOutputStream()) {

                // 将图像输入流写入响应输出流
                byte[] buffer = new byte[1024];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
            }
        } catch (IOException e) {
            // 处理异常
            e.printStackTrace();
            response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        }
    }
}

imgUrl="http:127.0.0.1:8080/img/20240305/1.png"
// 直接使用URL类获取图像流
InputStream inputStream = new URL(imgUrl).openStream();

private static String convertToBase64(InputStream inputStream) throws IOException {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int bytesRead;
    while ((bytesRead = inputStream.read(buffer)) != -1) {
        byteArrayOutputStream.write(buffer, 0, bytesRead);
    }

    // 使用Base64编码，并手动添加data:image/png;base64,前缀
    String base64Image = "data:image/png;base64," +
            Base64.getEncoder().encodeToString(byteArrayOutputStream.toByteArray());

    return base64Image;
}