ConnectionManagerImpl.java

package com.coderising.download.impl;

import java.io.IOException;

import java.net.HttpURLConnection;

import java.net.URL;

import com.coderising.download.api.Connection;

import com.coderising.download.api.ConnectionException;

import com.coderising.download.api.ConnectionManager;



public class ConnectionManagerImpl implements ConnectionManager {



    @Override

    public Connection open(String fileURL, int startPos, int endPos) throws ConnectionException {

        try {

            System.out.println("try to open file url: " + fileURL);



            URL url = new URL(fileURL);

            HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();



            // 设定读取range

            httpConn.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos);

            System.out.println("Range: bytes=" + startPos + "-" + endPos);



            int responseCode = httpConn.getResponseCode();



            System.out.println("server replied HTTP code: " + responseCode);

            if (responseCode == HttpURLConnection.HTTP_OK || responseCode == HttpURLConnection.HTTP_PARTIAL) {

                System.out.println("return new ConnectionImpl");

                return new ConnectionImpl(httpConn, fileURL);

            } else {

                throw new ConnectionException("server replied HTTP code: " + responseCode);

            }

        } catch (IOException e) {

            throw new ConnectionException(e);

        }

    }



    @Override

    public int getContentLength(String fileURL) throws ConnectionException {

        try {

            System.out.println("try to open file url: " + fileURL);



            URL url = new URL(fileURL);

            HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();

            int responseCode = httpConn.getResponseCode();



            System.out.println("server replied HTTP code: " + responseCode);

            if (responseCode == HttpURLConnection.HTTP_OK) {

                System.out.println("return contentLength: " + httpConn.getContentLength());

                int contentLength = httpConn.getContentLength();

                httpConn.disconnect();

                return contentLength;

            } else {

                throw new ConnectionException("server replied HTTP code: " + responseCode);

            }

        } catch (IOException e) {

            throw new ConnectionException(e);

        }

    }

}