ConnectionImpl.java

package com.github.fei9009.coderising0305.download.impl;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Arrays;

import com.github.fei9009.coderising0305.download.api.Connection;
import com.github.fei9009.coderising0305.download.api.ConnectionException;


public class ConnectionImpl implements Connection{
	
	URL url;
	static final int BUFFER_SIZE = 1024;
	
	ConnectionImpl(String _url) throws ConnectionException{
		try {			
			url = new URL(_url);
		} catch (MalformedURLException e) {			
			throw new ConnectionException();
		}
	}
	
	@Override
	public byte[] read(int startPos, int endPos) throws IOException {
		
		HttpURLConnection httpConn = (HttpURLConnection)url.openConnection();
		httpConn.setRequestProperty("Range", "bytes=" + startPos + "-"+ endPos);
		InputStream is  = httpConn.getInputStream();
		//is.skip(startPos);		
		byte[] buff = new byte[BUFFER_SIZE];  
        int totalLen = endPos - startPos + 1;
        ByteArrayOutputStream baos = new ByteArrayOutputStream();        
      
        while(baos.size() < totalLen){  
        	int len = is.read(buff);           
            if (len < 0) {  
                break;  
            }             
            baos.write(buff,0, len);            
        }  
        if(baos.size() > totalLen){
        	byte[] data = baos.toByteArray();
        	return Arrays.copyOf(data, totalLen);
        }
		return baos.toByteArray();
	}

	@Override
	public int getContentLength() {
		
		URLConnection con;
		try {
			con = url.openConnection();
			return con.getContentLength(); 
			
		} catch (IOException e) {			
			e.printStackTrace();
		}  
		return -1;
	}

	@Override
	public void close() {
		
		
	}

}