JAVA - 从Webserver下载二进制文件（例如PDF）文件 [英] JAVA - Download Binary File (e.g. PDF) file from Webserver
问题描述
我需要将一个pdf文件从网络服务器下载到我的电脑并在本地保存。
I need to download a pdf file from a webserver to my pc and save it locally.
我使用Httpclient连接到网络服务器并获取内容正文： / p>
I used Httpclient to connect to webserver and get the content body:
HttpEntity entity=response.getEntity();
InputStream in=entity.getContent();
String stream = CharStreams.toString(new InputStreamReader(in));
int size=stream.length();
System.out.println("stringa html page LENGTH:"+stream.length());
System.out.println(stream);
SaveToFile(stream);
然后我将内容保存在一个文件中：
Then i save content in a file:
//check CRLF (i don't know if i need to to this)
String[] fix=stream.split("\r\n");
File file=new File("C:\\Users\\augusto\\Desktop\\progetti web\\test\\test2.pdf");
PrintWriter out = new PrintWriter(new FileWriter(file));
for (int i = 0; i < fix.length; i++) {
out.print(fix[i]);
out.print("\n");
}
out.close();
我还尝试将String内容直接保存到文件中：
I also tried to save a String content to file directly:
OutputStream out=new FileOutputStream("pathPdfFile");
out.write(stream.getBytes());
out.close();
但结果总是一样的：我可以打开pdf文件，但我只能看到白页。错误是围绕pdf流和endstream charset编码？ stream和endStream之间的pdf内容是否需要以其他方式进行操作？
But the result is always the same: I can open pdf file but i can see white pages only. Does the mistake is around pdf stream and endstream charset encoding? Does pdf content between stream and endStream need to be manipulate in some others way?
希望这有助于避免一些误解我想做什么：
Hope this helps to avoid some misunderstanding about what i want to do:
这是我的登录（完美地运作）：
This is my login (works perfectly):
public static void postForm(){
String cookie="";
try {
System.out.println("POSTFORM ###################################");
String postURL = "http://login.libero.it/logincheck.php";
HttpPost post = new HttpPost(postURL);
post.setHeader("User-Agent", "Chrome/14.0.835.202");
post.setHeader("Referer","http://login.libero.it/?layout=m&service_id=m_mail&ret_url=http://m.mailbeta.libero.it/m/wmm/auth/check");
if(cookieVector.size()>0){
for(int i=0;i<cookieVector.size();i++){
cookie=cookie+cookieVector.elementAt(i).toString().replace("Set-Cookie:", "")+";";
}
post.setHeader("Cookie",cookie);
}
//System.out.println("sequenza cookie post:"+cookie);
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("SERVICE_ID", "m_mail"));
params.add(new BasicNameValuePair("LAYOUT", "m"));
params.add(new BasicNameValuePair("DEVICE", ""));
params.add(new BasicNameValuePair("RET_URL","http://m.mailbeta.libero.it/m/wmm/auth/check"));
params.add(new BasicNameValuePair("LOGINID", "secret"));
params.add(new BasicNameValuePair("PASSWORD", "secret"));
UrlEncodedFormEntity ent = new UrlEncodedFormEntity(params,HTTP.UTF_8);
System.out.println("stringa urlPost:"+ent.toString());
post.setEntity(ent);
HttpResponse responsePOST = client.execute(post);
System.out.println("Response postForm: " + responsePOST.getStatusLine());
Header[] allHeaders = responsePOST.getAllHeaders();
String location = "";
for (Header header : allHeaders) {
if("location".equalsIgnoreCase(header.getName())) location = header.getValue();
responsePOST.addHeader(header.getName(), header.getValue());
}
cookieVector.clear();
Header[] headerx=responsePOST.getHeaders("Set-Cookie");
System.out.println("array header:"+headerx.length);
for(int i=0;i<headerx.length;i++){
System.out.println("restituito cookie POST:"+headerx[i].getValue());
cookieVector.add(headerx[i]);
//System.out.println("cookie trovato POST:"+cookieVector.elementAt(i));
}
//System.out.println("inseriti"+cookieVector.size()+""+"elements");
//HttpEntity resEntity = responsePOST.getEntity();
// populate redirect information in response
//CONTROLLO ESITO LOGIN
if(location.contains("https://login.libero.it/logincheck.php")){
loginError=1;
}
System.out.println("Redirecting to: " + location);
//EntityUtils.consume(resEntity);
responsePOST.getEntity().consumeContent();
System.out.println("torno a GET:"+"url:"+location+"cookieVector size:"+cookieVector.size());
get(location,"http://login.libero.it/logincheck.php");
} catch (IOException ex) {
Logger.getLogger(LiberoLoginNew.class.getName()).log(Level.SEVERE, null, ex);
}
}
一旦记录我能够访问文件的链接（pdf，image，doc，exc。）。在这种情况下，我们以pdf文件为例：
Once logged i'm able to access to the file's link (pdf,image,doc, exc.). In this case we take for example a pdf file:
public static void httpConnection(String url,String referer,String cookieAuth){
try {
String location="";
String cookie="";
HttpResponse response;
HttpGet get;
HttpEntity respEntity;
Referer=referer;
System.out.println("HTTPCONNECTION ################################");
System.out.println("connessione a:"+url+"............");
get = new HttpGet(url);
if(referer.length()>0){
//httpget.setHeader("Referer",referer );
}
if(attachmentURL.size()==0){
get.setHeader("User-Agent", "Chrome/14.0.835.202");
}else{
get.setHeader("Accept-charset", "UTF-8");
get.setHeader("Content-type", "application/pdf");
}
if(cookieVector.size()>0){
System.out.println("iserisco cookie da vector");
for(int i=0;i<cookieVector.size();i++){
cookie=cookie+cookieVector.elementAt(i).toString().replace("Set-Cookie:", "")+";";
}
get.setHeader("Cookie", cookie);
}else if(cookieAuth.length()>0){
System.out.println("inserisco cookieAuth....");
System.out.println("valore cookieSession:"+cookieAuth);
get.setHeader("Cookie",cookieAuth.replace("Set-Cookie:", "")+";");
}
response = client.execute(get);
cookieVector.clear();//reset cookie
System.out.println("home get: " + response.getStatusLine());
Header[] headery=response.getAllHeaders();
for(int j=0;j<headery.length;j++){
System.out.println(headery[j].getName()+" "+" VALUE:"+" "+headery[j].getValue());
}
Header[] headerx=response.getHeaders("Set-Cookie");
System.out.println("array header:"+headerx.length);
System.out.print("httpconnection SERVER HEADERS ###############");
for(int i=0;i<headerx.length;i++){
if("location".equalsIgnoreCase(headerx[i].getName())){
location = headerx[i].getValue();
//ResponseGET.addHeader(headerx[i].getName(), header.getValue());
}
//System.out.println(headerx[i].getValue());
cookieVector.add(headerx[i]);
}
//STREAM CONTENT BODY
HttpEntity entity2=response.getEntity();
InputStream in=entity2.getContent(); <==THIS IS THE WAY I GET STREAM RESPONSE
if(attachmentURL.size()>0){
saveAttachment(in);//SAVE FILE <==
}else{
from(in,htmlpage);//Parse and grab: message title,subject,attachments. If attachments are found then come back here and execute the method saveAttachment.
in.close();
}
} catch (IOException ex) {
Logger.getLogger(LiberoLoginNew.class.getName()).log(Level.SEVERE, null, ex);
}
}
方法http连接有效，我可以下载文件!!
Method httpConnection works and i can download the file!!
服务器响应：
Date VALUE: Fri, 18 Nov 2011 13:09:46 GMT
Server VALUE: Apache/2.2.21 (Unix) mod_jk/1.2.23
Set-Cookie VALUE: MST_PVP=tiQZO3nbl9_5f_OQXtJP32YiqQx_5f_kSh6F6Io7r3xS; Domain=m.libero.it; Path=/
Content-Type VALUE: application/octet-stream
Expires VALUE: Fri, 18 Nov 2011 15:09:46 GMT
Transfer-Encoding VALUE: chunked
回应正文示例：
%PDF-1.7
1 0 obj % entry point
<<
/Type /Catalog
/Pages 2 0 R
>
endobj
> endobj
2 0 obj
<<
/Type /Pages
/MediaBox [ 0 0 200 200 ]
/Count 1
/Kids [ 3 0 R ]
>>
endobj
3 0 obj
<<
/Type /Page
/Parent 2 0 R
/Resources <<
/Font <<
/F1 4 0 R
>>
>>
/Contents 5 0 R
>>
endobj
4 0 obj
<<
/Type /Font
/Subtype /Type1
/BaseFont /Times-Roman
>>
endobj
5 0 obj % page content
<<
/Length 44
>>
stream
BT
70 50 TD
/F1 12 Tf
(Hello, world!) Tj
ET
endstream
endobj
xref
0 6
0000000000 65535 f
0000000010 00000 n
0000000079 00000 n
0000000173 00000 n
0000000301 00000 n
0000000380 00000 n
trailer
<<
/Size 6
/Root 1 0 R
>>
startxref
492
%%EOF
现在，让我们开始从这里。
请你告诉我在将文件保存到文件中需要做些什么？
Now,let starts from here. Can you,please, tell me what i have to do to save the stream in a file?
要从Stream数据本地保存文件，请尊重二进制数据大自然，我喜欢这样：
To save a file locally from the Stream data, respecting the binary data nature, i did like this:
public void saveFile(InputStream is){
try {
DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(new File("test.pdf"))));
int c;
while((c = is.read()) != -1) {
out.writeByte(c);
}
out.close();
is.close();
}catch(IOException e) {
System.err.println("Error Writing/Reading Streams.");
}
}
如果你想要一个更有效的方法，你可以使用java .IOUtils并且这样做：
If you want a more efficent method you can use java.IOUtils and do like this:
public void saveFile(InputStream is){
OutputStream os=new FileOutputStream(new File("test.pdf"));
byte[] bytes = IOUtils.toByteArray(is);
os.write(bytes);
os.close();
}
推荐答案
从不 将二进制数据存储到字符串。
从不 使用 PrintWriter 获取二进制数据。
从不 逐行写二进制文件。
Never write binary files line by line.
我不想苛刻或不礼貌但这三个从来没有必须扎根于你的脑海！ ：）
I don't want to be harsh or impolite but these three never's have to take roots in your mind! :)
你可以看到此页面有关如何下载二进制文件的示例。我不喜欢这个例子，因为它将整个文档缓存在内存中（如果它的大小为5GB会发生什么？）但你可以从这开始。 ：）
You can see this page for an example on how to download a binary file. I don't like this example because it caches the whole document in memory (what happens if its size is 5GB?) but you can start from this. :)
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