如何将使用HttpClient下载的文件保存到特定文件夹中

Question

我正在尝试使用HttpClient下载PDF文件.我能够获取文件,但我不知道如何将字节转换为PDF并将其存储在系统的某个位置

我有以下代码,如何将其存储为PDF？

 public ???? getFile(String url) throws ClientProtocolException, IOException{

            HttpGet httpget = new HttpGet(url);
            HttpResponse response = httpClient.execute(httpget);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                long len = entity.getContentLength();
                InputStream inputStream = entity.getContent();
                // How do I write it?
            }

            return null;
        }

Answer 1

InputStream is = entity.getContent();
String filePath = "sample.txt";
FileOutputStream fos = new FileOutputStream(new File(filePath));
int inByte;
while((inByte = is.read()) != -1)
     fos.write(inByte);
is.close();
fos.close();

编辑:

您还可以使用BufferedOutputStream和BufferedInputStream来加快下载速度:

BufferedInputStream bis = new BufferedInputStream(entity.getContent());
String filePath = "sample.txt";
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(new File(filePath)));
int inByte;
while((inByte = bis.read()) != -1) bos.write(inByte);
bis.close();
bos.close();

Answer 2

只是为了记录,有更好(更容易)的方法来做同样的事情

File myFile = new File("mystuff.bin");

CloseableHttpClient client = HttpClients.createDefault();
try (CloseableHttpResponse response = client.execute(new HttpGet("http://host/stuff"))) {
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        try (FileOutputStream outstream = new FileOutputStream(myFile)) {
            entity.writeTo(outstream);
        }
    }
}

或者如果人们更喜欢它,可以使用流畅的API

Request.Get("http://host/stuff").execute().saveContent(myFile);

Answer 3

这是一个简单的解决方案IOUtils.copy():

File targetFile = new File("foo.pdf");

if (entity != null) {
    InputStream inputStream = entity.getContent();
    OutputStream outputStream = new FileOutputStream(targetFile);
    IOUtils.copy(inputStream, outputStream);
    outputStream.close();
}

return targetFile;

IOUtils.copy()很棒,因为它处理缓冲.但是,此解决方案不是很可扩展:

• 您无法指定目标文件名和目录
• 您可能希望以不同的方式存储文件,例如在数据库中.在这种情况下不需要文件.

更具可扩展性的解决方案涉及两个功能:

public void downloadFile(String url, OutputStream target) throws ClientProtocolException, IOException{
    //...
    if (entity != null) {
    //...
        InputStream inputStream = entity.getContent();
        IOUtils.copy(inputStream, target);
    }
}

和辅助方法:

public void downloadAndSaveToFile(String url, File targetFile) {
    OutputStream outputStream = new FileOutputStream(targetFile);
    downloadFile(url, outputStream);
    outputStream.close();
}

Answer 4

使用依赖项org.apache.httpcomponents:fluent-hc：

Request.Get(url).execute().saveContent(file);

请求来自org.apache.http.client.fluent.Request.

就我而言，我需要一个流，这同样简单：

inputStream = Request.Get(url).execute().returnContent().asStream();