Java从web服务器下载文件到本地

/*从服务器中下载文件到本地*/

/*url:文件存放在服务器的地址；target:要保存的路径*/     

public String DownloadFile(String url,String target){

          URLConnection con=null;

          URL theUrl=null;

          try {

              theUrl=new URL(url);//建立地址

              con = theUrl.openConnection();//打开连接

              con.setConnectTimeout(30000);

              con.connect();//连接

          } catch (MalformedURLException e) {

              Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, e);

              return "给定的URL地址有误，请查看";

          }

          catch (IOException e) {

              Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, e);

              return "无法连接到远程机器，请重试！";

          }

          jLabel5.setText("√");

          Process++;

          File file = new File(gbl_ParentPath+"/UpdateTemp");

          if(file.exists()==false){

              file.mkdir();

          }

          String type = con.getContentType();

          if (type != null) {

              byte[] buffer = new byte[4 * 1024];

              int read;

              try {

                  FileOutputStream os = new FileOutputStream(target);

                  InputStream in = con.getInputStream();//重定向输入

                  while ((read = in.read(buffer)) > 0) {//读取输出

                      os.write(buffer, 0, read);//写入本地文件

                  }

                  os.close();

                  in.close();

                  jLabel6.setText("√");

                  Process++;

              } catch (FileNotFoundException e) {

                  Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, e);

                  return "所要下载的文件不存在！";

              }catch (IOException e) {

                  Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, e);

                  return "读取远程文件时出错！";

              }

          } else {

              return "文件未找着:"+url;

          }

          return "";

      }