JAVA断点续传(B/S)（1）

说明：

SiteFileFetch.java 负责整个文件的抓取，控制内部线程(FileSplitterFetch类)。  
FileSplitterFetch.java 负责部分文件的抓取。  
FileAccess.java 负责文件的存储。  
SiteInfoBean.java 要抓取的文件的信息，如文件保存的目录，名字，抓取文件的URL等。  
Utility.java 工具类，放一些简单的方法。

*
 **SiteFileFetch.java
 */
package NetFox;

import java.io.*;
import java.net.*;

public class SiteFileFetch extends Thread {
    SiteInfoBean siteInfoBean = null; // 文件信息Bean
    long[] nStartPos; // 开始位置
    long[] nEndPos; // 结束位置
    FileSplitterFetch[] fileSplitterFetch; // 子线程对象
    long nFileLength; // 文件长度
    boolean bFirst = true; // 是否第一次取文件
    boolean bStop = false; // 停止标志
    File tmpFile; // 文件下载的临时信息
    DataOutputStream output; // 输出到文件的输出流
    
    public SiteFileFetch(SiteInfoBean bean) throws IOException {
        siteInfoBean = bean;
        // tmpFile = File.createTempFile ("zhong","1111",new
        // File(bean.getSFilePath()));
        tmpFile = new File(bean.getSFilePath() + File.separator
                + bean.getSFileName() + ".info");
        if (tmpFile.exists()) {
            bFirst = false;
            read_nPos();
        } else {
            nStartPos = new long[bean.getNSplitter()];
            nEndPos = new long[bean.getNSplitter()];
        }
    }

    public void run() {
        // 获得文件长度
        // 分割文件
        // 实例FileSplitterFetch
        // 启动FileSplitterFetch线程
        // 等待子线程返回
        try {
            if (bFirst) {
                nFileLength = getFileSize();
                if (nFileLength == -1) {
                    System.err.println("File Length is not known!");
                } else if (nFileLength == -2) {
                    System.err.println("File is not access!");
                } else {
                    for (int i = 0; i < nStartPos.length; i++) {
                        nStartPos[i] = (long) (i * (nFileLength / nStartPos.length));
                    }
                    for (int i = 0; i < nEndPos.length - 1; i++) {
                        nEndPos[i] = nStartPos[i + 1];
                    }
                    nEndPos[nEndPos.length - 1] = nFileLength;
                }
            }
            // 启动子线程
            fileSplitterFetch = new FileSplitterFetch[nStartPos.length];
            for (int i = 0; i < nStartPos.length; i++) {
                fileSplitterFetch[i] = new FileSplitterFetch(siteInfoBean
                        .getSSiteURL(), siteInfoBean.getSFilePath()
                        + File.separator + siteInfoBean.getSFileName(),
                        nStartPos[i], nEndPos[i], i);
                Utility.log("Thread " + i + " , nStartPos = " + nStartPos[i]
                        + ", nEndPos = " + nEndPos[i]);
                fileSplitterFetch[i].start();
            }
            // fileSplitterFetch[nPos.length-1] = new
            // FileSplitterFetch(siteInfoBean.getSSiteURL(),siteInfoBean.getSFilePath()
            // + File.separator +
            // siteInfoBean.getSFileName(),nPos[nPos.length-1],nFileLength,nPos.length-1);
            // Utility.log("Thread " + (nPos.length-1) + " , nStartPos = " +
            // nPos[nPos.length-1] + ",nEndPos = " + nFileLength);
            // fileSplitterFetch[nPos.length-1].start();
            // 等待子线程结束
            // int count = 0;
            // 是否结束while循环
            boolean breakWhile = false;
            while (!bStop) {
                write_nPos();
                Utility.sleep(500);
                breakWhile = true;
                for (int i = 0; i < nStartPos.length; i++) {
                    if (!fileSplitterFetch[i].bDownOver) {
                        breakWhile = false;
                        break;
                    }
                }
                if (breakWhile)
                    break;
                // count++;
                // if(count>4)
                // siteStop();
            }
            System.err.println("文件下载结束！");
        } catch (Exception e) {
            e.printStackTrace();
        }
    } // 获得文件长度

    public long getFileSize() {
        int nFileLength = -1;
        try {
            URL url = new URL(siteInfoBean.getSSiteURL());
            HttpURLConnection httpConnection = (HttpURLConnection) url
                    .openConnection();
            httpConnection.setRequestProperty("User-Agent", "NetFox");
            int responseCode = httpConnection.getResponseCode();
            if (responseCode >= 400) {
                processErrorCode(responseCode);
                return -2; // -2 represent access is error
            }
            String sHeader;
            for (int i = 1;; i++) {
                // DataInputStream in = new
                // DataInputStream(httpConnection.getInputStream ());
                // Utility.log(in.readLine());
                sHeader = httpConnection.getHeaderFieldKey(i);
                if (sHeader != null) {
                    if (sHeader.equals("Content-Length")) {
                        nFileLength = Integer.parseInt(httpConnection
                                .getHeaderField(sHeader));
                        break;
                    }
                } else
                    break;
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        Utility.log(nFileLength);
        return nFileLength;
    }

    // 保存下载信息（文件指针位置）
    private void write_nPos() {
        try {
            output = new DataOutputStream(new FileOutputStream(tmpFile));
            output.writeInt(nStartPos.length);
            for (int i = 0; i < nStartPos.length; i++) {
                // output.writeLong(nPos[i]);
                output.writeLong(fileSplitterFetch[i].nStartPos);
                output.writeLong(fileSplitterFetch[i].nEndPos);
            }
            output.close();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 读取保存的下载信息（文件指针位置）
    private void read_nPos() {
        try {
            DataInputStream input = new DataInputStream(new FileInputStream(
                    tmpFile));
            int nCount = input.readInt();
            nStartPos = new long[nCount];
            nEndPos = new long[nCount];
            for (int i = 0; i < nStartPos.length; i++) {
                nStartPos[i] = input.readLong();
                nEndPos[i] = input.readLong();
            }
            input.close();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void processErrorCode(int nErrorCode) {
        System.err.println("Error Code : " + nErrorCode);
    }

    // 停止文件下载
    public void siteStop() {
        bStop = true;
        for (int i = 0; i < nStartPos.length; i++)
            fileSplitterFetch[i].splitterStop();
    }
}