ConnectionImpl.java

package week3_0312.impl;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import java.io.InputStream;

import week3_0312.api.Connection;

public class ConnectionImpl implements Connection{
	
	private URL url = null;
	private HttpURLConnection conn = null;
	
	public ConnectionImpl(String url){
		try{
			this.url = new URL(url);
		} catch(MalformedURLException e) {
			e.printStackTrace();
		}
	}

	@Override
	public byte[] read(int startPos, int endPos) throws IOException {
		try {
			conn = (HttpURLConnection) url.openConnection();
		} catch (IOException e) {
			e.printStackTrace();
		}
		conn.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos);
		InputStream inputStream = (InputStream) conn.getInputStream();
		byte[] result = new byte[endPos - startPos + 1];
		byte[] data = new byte[1024];
		int read = -1;
		int i = 0;
		while ((read = inputStream.read(data,0, data.length)) != -1) {
			System.arraycopy(data, 0, result, i, read);
			i += read;
		}
		return result;
	}

	@Override
	public int getContentLength() {
		HttpURLConnection openConnection = null;
		try {
			openConnection = (HttpURLConnection) url.openConnection();
		} catch(IOException e) {
			e.printStackTrace();
		}
		int contentLength = openConnection.getContentLength();
		openConnection.disconnect();
		return contentLength;
	}

	@Override
	public void close() {
		conn.disconnect();
		conn = null;
	}

}