1.Connection接口
public interface Connection { /** * @Author xuyangyang * @Describe 给定开始和结束位置， 读取数据， 返回值是字节数组 * @Date 2017/6/7 * @Params * @Return */ byte[] read(int startPos, int endPos) throws IOException ; /** * @Author xuyangyang * @Describe 得到数据内容的长度 * @Date 2017/6/7 * @Params * @Return */ int getContentLength(); /** * @Author xuyangyang * @Describe 关闭连接 * @Date 2017/6/7 * @Params * @Return */ void close(); }2.ConnectionManager管理接口
public interface ConnectionManager { /** * @Author xuyangyang * @Describe 给定一个url , 打开一个连接 * @Date 2017/6/7 * @Params * @Return */ Connection open(String url) throws ConnectionException; }3.实现ConnectionManager,根据url打开一个连接,返回Connection对象
public class ConnectionManagerImpl implements ConnectionManager { @Override public Connection open(String url) throws ConnectionException { return new ConnectionImpl(url); } }4.具体的实现类
public class ConnectionImpl implements Connection { URL url; static final int BUFFER_SIZE = 1024; public ConnectionImpl(String _url) { try { url = new URL(_url); } catch (MalformedURLException e) { e.printStackTrace(); } } @Override public byte[] read(int startPos, int endPos) throws IOException { HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection(); httpURLConnection.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos); InputStream in = httpURLConnection.getInputStream(); byte[] bytes = new byte[BUFFER_SIZE]; int totalLen = endPos - startPos + 1; ByteArrayOutputStream baos = new ByteArrayOutputStream(); while (baos.size() < totalLen) { int len = in.read(bytes); if (len < 0) { break; } baos.write(bytes, 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() { } }5.简单的测试
public class ConnectionTest { @Before public void setUp() throws Exception { } @After public void tearDown() throws Exception { } @Test public void testContentLength() throws Exception{ ConnectionManager connMan = new ConnectionManagerImpl(); Connection conn = connMan.open("http://www.hinews.cn/pic/0/13/91/26/13912621_821796.jpg"); Assert.assertEquals(35470, conn.getContentLength()); } @Test public void testRead() throws Exception{ ConnectionManager connMan = new ConnectionManagerImpl(); Connection conn = connMan.open("http://www.hinews.cn/pic/0/13/91/26/13912621_821796.jpg"); byte[] data = conn.read(0, 35469); Assert.assertEquals(35470, data.length); data = conn.read(0, 1023); Assert.assertEquals(1024, data.length); data = conn.read(1024, 2023); Assert.assertEquals(1000, data.length); // 测试不充分，没有断言内容是否正确 } }