Java Base64编码和解码

需要的 jar 包

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.12</version>
</dependency>

将pdf文件编码成Base64字符串

private static String base64Encoder(String reportFile) {
        File pdfFile = new File(reportFile); 
    FileInputStream fileInputStream = null;
    BufferedInputStream bufferedInputStream = null;
    try {
        fileInputStream = new FileInputStream(pdfFile);
        bufferedInputStream = new BufferedInputStream(fileInputStream);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(byteArrayOutputStream);
    byte[] buffer = new byte[1024];  // 字节数组
    int len;
    try {
        // 从输入流中读取数据到字节数组 buffer 中 -1 if there is no more data because the end of the stream has been reached
        len = bufferedInputStream.read(buffer);
        while (len != -1) {
            // 从字节数组 buffer 中读取 len 字节，然后写入缓存输出流中
            bufferedOutputStream.write(buffer, 0, len);
            len = bufferedInputStream.read(buffer);  // 
        }
        // 刷新缓冲的输出字节写入到基础输出流
        bufferedOutputStream.flush();
    } catch (IOException e) {
        e.printStackTrace();
    }
    // 创建一个字节数组，并将输出流中的字节存入到字节数组中
    byte [] bytes = byteArrayOutputStream.toByteArray();
    try {
        fileInputStream.close();
        bufferedInputStream.close();
        byteArrayOutputStream.close();
        bufferedOutputStream.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
    // 将字节转换为base64编码的字符串
    return Base64.encodeBase64String(bytes);
}

解码还原得到pdf文件

private static void base64Decoder(String fileBase64) {
    BufferedInputStream bufferedInputStream = null;
    FileOutputStream fileOutputStream = null;
    BufferedOutputStream bufferedOutputStream = null;
    // 对base64编码的字符串进行解析，并将结果放到字节数组中
    byte [] bytes = Base64.decodeBase64(fileBase64);
    ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
    bufferedInputStream = new BufferedInputStream(byteArrayInputStream);
    File file = new File("C:\Users\mail\test解析得到.pdf");
    try {
        fileOutputStream = new FileOutputStream(file);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
    byte[] buffers = new byte[1024];
    try {
        int len = bufferedInputStream.read(buffers);
        while(len != -1) {
            bufferedOutputStream.write(buffers, 0, len);
            len = bufferedInputStream.read(buffers);
        }
        bufferedOutputStream.flush();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            bufferedInputStream.close();
            fileOutputStream.close();
            bufferedOutputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}