java笔记——多线程下载

java 实现一个多线程下载程序，暂时还有部分bug需要修改，先做些笔记

将网络资源Resource .划分成不通的part对象，然后用不通线程去下载part 最后下载完的线程负责合并文件

其实这个过程还有很多优化的地方，能否三个线程同时合并文件，同时删除下载的附件，或者不生成这么多的临时文件，还可以改进成断点下载，还可以写一个爬虫

获得很多url 然后批量下载之类。

先贴下暂时的代码 设计到一些细节的东西，

UUID  之前没遇到过的

package download.object;import java.io.RandomAccessFile;import java.util.UUID;public class Part {private int begin;//下载总长度private int length;//已下载长度private int currentLength;//private String partName;/** * 构造Part对象 * @param begin * @param length * @param currentLength */public Part(int begin,int length,int currentLength){this.begin=begin;this.length=length;this.currentLength=currentLength;this.partName=UUID.randomUUID().toString()+".part";}public int getBegin() {return begin;}public void setBegin(int begin) {this.begin = begin;}public int getLength() {return length;}public void setLength(int length) {this.length = length;}public int getCurrentLength() {return currentLength;}public void setCurrentLength(int currentLength) {this.currentLength = currentLength;}public String getPartName() {return partName;}public void setPartName(String partName) {this.partName = partName;}}

Resource.java

package download.object;import java.io.IOException;import java.net.MalformedURLException;import java.net.URL;import java.util.ArrayList;import java.util.Date;import java.util.List;import java.util.UUID;public class Resource {private List<Part> parts ;private int threadNum;private String id;private String url;private String savePath;private String saveFileName;private Date startDate;private float costTime;private float spareTime;private int size;public int getCurrentLength(){int result=0;for(Part part:parts){result+=part.getCurrentLength();}return result;}public int getSize() throws IOException {if(size==0){URL u=new URL(url);size=u.openConnection().getContentLength();}return size;}public List<Part> getParts() {return parts;}public void setParts(List<Part> parts) {this.parts = parts;}public int getThreadNum() {return threadNum;}public void setThreadNum(int threadNum) {this.threadNum = threadNum;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public String getSavePath() {return savePath;}public void setSavePath(String savePath) {this.savePath = savePath;}public String getSaveFileName() {return saveFileName;}public void setSaveFileName(String saveFileName) {this.saveFileName = saveFileName;}public Date getStartDate() {return startDate;}public void setStartDate(Date startDate) {this.startDate = startDate;}public float getCostTime() {return costTime;}public void setCostTime(float costTime) {this.costTime = costTime;}public float getSpareTime() {return spareTime;}public void setSpareTime(float spareTime) {this.spareTime = spareTime;}public Resource(String url,String savePath,String saveFileName,int threadNum){this.id=UUID.randomUUID().toString();this.url=url;this.savePath=savePath;this.saveFileName=saveFileName;this.threadNum=threadNum;this.parts=new ArrayList<Part>();}}

DownloadThread.java

package download.thread;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.io.OutputStreamWriter;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import download.object.Part;import download.object.Resource;import download.util.FileUtil;public class DownloadThread extends Thread{private Resource rs;private Part p;private RandomAccessFile raf ;public DownloadThread(Resource rs,Part p ,RandomAccessFile raf){this.rs=rs;this.p=p;this.raf=raf;}@Overridepublic void run() {try {if(p.getCurrentLength()>=p.getLength()){return;}int begin=p.getBegin()+p.getCurrentLength();int end=p.getBegin()+p.getLength();System.out.println(getName()+":"+begin+" "+end);URL url=new URL(rs.getUrl());HttpURLConnection conn=(HttpURLConnection)url.openConnection();conn.addRequestProperty("Range", "bytes="+begin+"-"+end);int temp=0;byte[] buffer=new byte[1024];InputStream is=url.openStream();raf.seek(begin);while((temp=is.read(buffer))!=-1){raf.write(buffer,0,temp);p.setCurrentLength(p.getCurrentLength()+temp);}if (isFinished(rs)){mergeFile(rs);}} catch (MalformedURLException e) {// TODO Auto-generated catch blocke.printStackTrace();}catch(IOException e){e.printStackTrace();}}private void mergeFile(Resource rs) throws IOException {OutputStream out=new FileOutputStream(new File(rs.getSavePath()+File.separator+rs.getSaveFileName()));InputStream in=null;System.out.println("合并图片");byte[] buf=new byte[1024];int tempRead=0;for(Part part:rs.getParts()){File raf=FileUtil.getPartFile(rs, part);in=new FileInputStream(raf);while((tempRead=in.read(buf))!=-1){out.write(buf,0,tempRead);}}if(out!=null){out.close();}if(in!=null){in.close();}}private boolean isFinished(Resource rs) throws IOException {if(rs.getCurrentLength()>=rs.getSize()){return true;}return false;}}

DownloadHandler.java

package download.thread;import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;import download.object.Part;import download.object.Resource;public class DownloadHandler {                 public void doDownload(Resource rs){      try {int preLength=rs.getSize()/rs.getThreadNum()+1;  for(int i=0;i<rs.getThreadNum();i++){  int length=preLength;  if(i==rs.getThreadNum()-1){   length=rs.getSize()-i*preLength;  }  System.out.println(length);    Part p =new Part(i*preLength,length, 0);    rs.getParts().add(p);    RandomAccessFile raf=new RandomAccessFile(rs.getSavePath()+File.separator+p.getPartName(),"rw");    new DownloadThread(rs,p,raf).start();      }} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}          }      }

FileUtil

package download.util;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.FileWriter;import java.io.IOException;import java.io.OutputStream;import java.io.OutputStreamWriter;import download.object.Part;import download.object.Resource;public class FileUtil {public static File getPartFile(Resource rs,Part p){return new File(rs.getSavePath()+File.separator+p.getPartName());}public static void deletePartFile(Resource rs) throws IOException{for(Part part:rs.getParts()){File file=  getPartFile(rs,part);System.out.println(file.getName());if(!file.exists()) continue;//delete}}}