使用Java套接字發送字節數組

Question

我正在編寫一個允許從服務器下載pdf文件的應用程序。在我的服務器端，由於pdfview庫的原因，我得到了pdf文件的字節緩衝區。我使用字節緩衝區填充字節數組，然後使用DataOutputStream發送字節數組。

大多數情況下，我在客戶端獲得了很好的數據，但有時我得到的數組中填充了隨機數，所以我無法重建我的PDF文件。我通常有以下錯誤：「java.io.IOException：這可能不是一個PDF文件」

所以當我比較收到的數據與發送的數據，它是完全不同的。 我可以注意到，在服務器部分數據總是正確

任何幫助表示讚賞

//Server side 
this.in = new ObjectInputStream(this.socket.getInputStream()); 
this.out = new DataOutputStream(this.socket.getOutputStream()); 
this.outObject = new ObjectOutputStream(this.socket.getOutputStream()); 

this.res = this.in.readObject().toString();//I read the client order(GET home page, next page...) 

//I get the bytebuffer from the pdf file------ 
this.file = new File (name+this.numFile+".pdf"); 
RandomAccessFile raf; 
raf = new RandomAccessFile(this.file, "r"); 
FileChannel channel = raf.getChannel(); 
this.buf = channel.map(FileChannel.MapMode.READ_ONLY,0, channel.size()); 
//-------------------------------------------- 

int size = this.buf.capacity(); 
this.out.writeInt(size);//I send the size of my bytebuffer to the server 

int size_array = 1000; 
this.pack = new byte[size_array]; 
this.pack = clean_array();//I replace my variable by an array filled with zeros 

for(long i=0;i<(size/size_array);i++){ 
buf.get(this.pack); 
    this.out.write(this.pack); 
    this.pack = clean_array();//I replace my variable by an array filled with zeros 
} 

//I have not sent the whole bytebuffer, the last byte array could have a different size 
//I work out this size, I create the new bytearray and I send it--------------------- 
int byteLeft = size%size_array; 
if(byteLeft>0){ 
    this.pack = new byte[byteLeft]; 
buf.get(this.pack); 
this.out.write(this.pack); 
this.pack = clean_array();//I replace my variable by an array filled with zeros 
} 

//------------------------------------------------- 

//Client side 
int size_array = 1000; 

pack =new byte[size_array]; 
pack = clean_array(); 

for(int i=0;i<((size/size_array));i++){  
    in.read(pack); 
    buf.put(pack); 
     pack = clean_array(); 
} 

if(size%size_array>0){ 
//for the last loop, the number of bytes sent by the server is not equal to 1000 
//So I create a byte array with the good size 
    pack = new byte[size%size_array]; 
    in.read(pack); 
    buf.put(pack); 
    pack = clean_array(); 
    } 

Answer 1

this.in = new ObjectInputStream(this.socket.getInputStream()); 
this.out = new DataOutputStream(this.socket.getOutputStream()); 
this.outObject = new ObjectOutputStream(this.socket.getOutputStream()); 

你並不需要的是DataOutputStream在這裏，你必須在之前創建的ObjectOutputStream ObjectInputStream，否則你會遇到死鎖。

this.res = this.in.readObject().toString();//I read the client order(GET home page, next page...) 

Bzzt。如果下一個對象是一個String，這行代碼就可以工作，但它應該使用（String）強制轉換，而不是toString（）。如果下一個對象不是，則表示您已將其損壞爲其他字符串。

this.pack = new byte[size_array]; 
this.pack = clean_array();//I replace my variable by an array filled with zeros 

毫無意義。 （a）它已經滿了零，（b）如果你堅持第二項任務，第一項任務的重點是什麼？

其餘的代碼是一個冗長的，可能是錯誤的發送文件到套接字的方式。這是簡單的方法：

FileInputStream fin = new FileInputStream(file); 
int count; 
byte[] buffer = new byte[8192]; 
while ((count = fin.read(buffer)) > 0) 
    out.write(buffer, 0, count); // here 'out' is the socket output stream or whatever you want to wrap around it.