.NetCore下多个文件流生成压缩文件

原有系统的附件都是保存在服务器上的，占用了大量的磁盘空间，如今要切换到AWS S3上做文件存储管理。文件打包下载之前的做法是，后台将文件服务器上的多个文件打包到一个压缩文件中，存放在服务器，后端接口返回压缩文件地址供前端下载；为此，特写下这篇文章来记录此处是如何根据文件流来制作压缩包的。

AWS S3更多存取文件的demo需看官方源码，本文中有下载的实例。

需要引用：AWSSDK.Core、AWSSDK.S3，可从NuGet安装;
需要引用：System.IO.Compression，可从NuGet安装;

在ConfigureServices下单例注入AWS类

 

public void ConfigureServices(IServiceCollection services)
{
    .......
    services.AddSingleton();
    .........
}

Configure下获取AWS实例

 

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    //......//
    Aws.Instance = app.ApplicationServices.GetService();
}

AWS类

 

public class Aws
{
    #region Init
    private readonly IConfiguration _cfg;
    /// 

    /// 存储桶名称
    /// 
    private string bucketName;
    /// 

    /// aws Id
    /// 
    private readonly string awsAccessKeyId;
    /// 

    /// aws Id key
    /// 
    private readonly string awsSecretAccessKey;
    private IAmazonS3 client;
    private AmazonS3Config config = new AmazonS3Config()
    {
        ServiceURL = "http://s3.amazonaws.com",
        RegionEndpoint = Amazon.RegionEndpoint.CNNorth1 //账号在哪个区域就用哪个区域，不然会出现账号401的问题
    };

    #endregion

    public Aws(IConfiguration cfg)
    {
        _cfg = cfg;
        awsAccessKeyId = _cfg["AccessKeyId"];
        awsSecretAccessKey = _cfg["SecretAccessKey"];
        bucketName = _cfg["BucketName"];
        client = new AmazonS3Client(awsAccessKeyId, awsSecretAccessKey, config);
    }

    /// 

    /// AWS文件批量下载
    /// 
    /// 文件相对地址（aws key）
    /// 
    public async Task BatchDownload(List fileNames)
    {
        try
        {
            byte[] res;
            using (MemoryStream ms = new MemoryStream())
            {
                using (ZipArchive zip = new ZipArchive(ms, ZipArchiveMode.Create, true))
                {
                    foreach (var fileName in fileNames)
                    {
                        //通过aws下载文件流
                        var response = await client.GetObjectAsync(bucketName, newfileName);
                        var pdfStream=  response.ResponseStream;//得到文件流
                        var pdfBytes = StringHelper.StreamToBytes(pdfStream);//文件流转换成字节

                        ZipArchiveEntry entry = zip.CreateEntry("abc.pdf");//压缩文件内创建一个文件名为“abc.pdf”,流是什么文件格式就用什么格式，此处我的是pdf格式
                        using (Stream sw = entry.Open())
                        {
                            sw.Write(pdfBytes, 0, pdfBytes.Length);//将文件的字节写到abc.pdf中
                        }
                    }
                    InvokeWriteFile(zip);//重新计算压缩文件的大小，此处参考别人的
                    int nowPos = (int)ms.Position;
                    res = new byte[ms.Length];
                    ms.Position = 0;
                    ms.Read(res, 0, res.Length);
                    ms.Position = nowPos;
                }
                return res;
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    public void InvokeWriteFile(ZipArchive zipArchive)
    {
        foreach (MethodInfo method in zipArchive.GetType().GetRuntimeMethods())
        {
            if (method.Name == "WriteFile")
            {
                method.Invoke(zipArchive, new object[0]);
            }
        }
    }
}

控制器下载压缩文件

 

/// 

///     批量下载
/// 
/// 
/// 
public async Task Packing(List ids)
{
    var paths = new List();
    //根据Id查询本地对应的文件名称，Id换取文件名称
    var bytes = await Aws.Instance.BatchDownload(paths).ToList());

    Response.ContentType = "application/octet-stream";

    var contentDisposition = "attachment;" + "filename=" + HttpUtility.UrlEncode("XXXX.zip");
    Response.Headers.Add("Content-Disposition", new string[] { contentDisposition });

    Response.ContentLength = bytes.Length;
    Response.Body.Write(bytes, 0, bytes.Length);//发送读取的内容数据到客户端浏览器
    Response.Body.Flush();
    return new EmptyResult();
}

前端Ajax调用

 

//后端返回的是文件流
var ids = [1,2,3];
var url = "/PackingByAws";
var form = $("
").attr("action", url).attr("method", "post");
////后端为List参数
ids.forEach(function (value) {
    form.append($("").attr("type", "hidden").attr("name", "ids").attr("value", value));
})
form.appendTo('body').submit().remove();