Java Servlet下载文件（二）

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.jmimemagic.Magic;
import net.sf.jmimemagic.MagicException;
import net.sf.jmimemagic.MagicMatch;
import net.sf.jmimemagic.MagicMatchNotFoundException;
import net.sf.jmimemagic.MagicParseException;

import org.apache.log4j.Logger;

import com.sun.xml.internal.fastinfoset.stax.events.Util;

public class DownloadServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;
	protected static final Logger logger=Logger.getLogger(DownloadServlet.class);
	
	private String enc = "utf-8";
	private String fileRoot = "";
	private int bufferSize=2048;


	/**
	 * 初始化  enc,fileRoot
	 */
	public void init(ServletConfig config) throws ServletException {
		// TODO Auto-generated method stub
		String tempStr=config.getInitParameter("enc");
		if(!Util.isEmptyString(tempStr)){
			enc=tempStr;
		}
		tempStr=config.getInitParameter("fileRoot");
		if(!Util.isEmptyString(tempStr)){
			fileRoot=tempStr;
		}
		tempStr=config.getInitParameter("bufferSize");
		if(!Util.isEmptyString(tempStr)){
			bufferSize=Integer.parseInt(tempStr);
		}
		
	}


	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doPost(request, response);
	}
	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setCharacterEncoding(enc);
		response.setContentType("text/html;charset="+enc);
		//获取 请求的参数
		String filePath=request.getParameter("path");
		String fileName=request.getParameter("filename");
		
		if(!Util.isEmptyString(filePath)){
			if(Util.isEmptyString(fileRoot)){
				fileRoot=request.getSession().getServletContext().getRealPath("/");
			}
			//获取文件的 绝对路径
			String absPath=fileRoot+filePath;
			//获取 文件名
			if(Util.isEmptyString(fileName)){
				fileName=getFileName(absPath);
			}
			//安全 校验不通过
			if(!checkFileSafe(filePath)){
				StringBuilder sb=new StringBuilder("fileName:").append(fileName).append(" is invalid!");
				if(logger.isDebugEnabled()){
					logger.debug(sb.toString());
				}
				response.setContentLength(sb.length());
				response.getWriter().print(sb.toString());
				return;
			}
			if(!Util.isEmptyString(absPath)){
				try {
					if(logger.isDebugEnabled()){
						StringBuilder sb=new StringBuilder("fileName:").append(fileName).append(",file absolute path:").append(absPath);
						logger.debug(sb.toString());
					}
         //下载文件 开始	
			downloadFile(response,absPath,fileName);
				} catch (Exception e) {
					StringBuilder sb=new StringBuilder("download file exception,fileName:").append(fileName).append(",file absolute path:").append(absPath);
					logger.debug(sb.toString(), e);
					sb.delete(0, sb.length());
					sb.append("<script type=\"text/javascript\">alert(\"download file err.\");</script>");
					response.setCharacterEncoding(enc);
					response.setContentLength(sb.length());
					response.getWriter().write(sb.toString());
					return;
				} 
			}
		}else{
			StringBuilder sb=new StringBuilder("fileName:").append(fileName).append(",file directory not exists!");
			logger.debug(sb.toString());
			response.setContentLength(sb.length());
			response.getWriter().print(sb.toString());
			return;
		}
	}
	/**
	 * 下载文件
	 * 
	 * @param response
	 * @param absPath 文件的绝对路径
	 * @param fileName  文件的名字 空时 默认为  绝对路径的文件名 可以有后缀 或无后缀
	 * @throws IOException
	 */
	private void downloadFile(HttpServletResponse response,String absPath,String fileName) throws IOException{
		File file=new File(absPath);
		//判断文件是否存在 和  可读性
		if(!file.exists()|| !file.canRead()){
			throw new RuntimeException(" File not exists or can not be read.");
		}
		
		String contentType="";
		String conentDisposition="attachment;";
		
		if(!Util.isEmptyString(fileName) || !fileName.contains(".")){  
			contentType=getContentType(file,false);
			if(Util.isEmptyString(contentType)){
				contentType="application/x-msdownload";
			}
		}
		response.reset();
		FileInputStream fis=new FileInputStream(file);
		int contentLengh = fis.available();
		if(Util.isEmptyString(fileName)){
			response.setHeader("Content-Disposition",conentDisposition);
			response.setContentType(contentType);
		}else if(fileName.contains(".")){  //如果文件有后缀名 可以不用设置 contentType 浏览器会自动判断文件类型
			response.setHeader("Content-Disposition",conentDisposition+"filename="+convertFileName(fileName));
		}
		else{ //如果文件名没有后缀名 需要设置contentType
			response.setContentType(contentType);
			response.setHeader("Content-Disposition",conentDisposition+"filename="+convertFileName(fileName));
		}
		if(contentLengh>0){
			response.setContentLength(contentLengh);
		}
		
		ServletOutputStream sops=response.getOutputStream();
		copyStream(fis,sops,true);
		fis.close();
		sops.close();
		fis=null;
		sops=null;
		file=null;
	}
	/**
	 * 复制流 到 前端浏览器
	 * @param source 源文件输入流
	 * @param dest 输出流
	 * @param flush 
	 * @return
	 */
	private final long copyStream(InputStream source,OutputStream dest,boolean flush){
		int bytes;
		long total=0l;
		byte [] buffer=new byte[bufferSize];
		try {
			while((bytes=source.read(buffer))!=-1){
				if(bytes==0){
					bytes=source.read();
					if(bytes<0)
						break;
					dest.write(bytes);
					if(flush)
					   dest.flush();
					total+=bytes;
				}
				dest.write(buffer,0,bytes);
				if(flush)
					dest.flush();
				total+=bytes;
			}
			
		} catch (IOException e) {
			throw  new RuntimeException("IOException caught while copying.",e);
		}
		return total;
	}
	
	/**
	 * 根据传入的路径获取文件名
	 * @param filePath
	 * @return
	 */
	private String getFileName(String filePath){
		if(Util.isEmptyString(filePath)){
			return "";
		}
		int index1=filePath.lastIndexOf("/");
		int index2=filePath.lastIndexOf("//");
		int index=index1 > index2 ?index1:index2;
		if(index==-1)
			return filePath;
		String fileName=filePath.substring(index+1);
		return fileName;
	}
	/**
	 * 转换中文文件名 
	 * @param cfilename 中文文件名
	 * @return
	 */
    private String convertFileName(String filename){  
        try {  
        	filename=URLEncoder.encode(filename,enc);
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        return filename;  
    } 
    
    /**
     * 获取文件的类型 
     * @param file
     * @return 
     * @throws MagicParseException
     * @throws MagicMatchNotFoundException
     * @throws MagicException
     */
    private String getContentType(File file,boolean extensionHints){
    	try {
    		 Magic parser = new Magic();  
    		 MagicMatch match = parser.getMagicMatch(file, extensionHints);
    		 return match.getMimeType();  
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
    }
    
    /** 
     * 文件名的安全检查，以免被人通过"../../../"的方式获取其它文件 
     * @param filePath 
     * @return false：不安全    ture:安全
     */ 
    private boolean checkFileSafe(String filePath){
    	return !filePath.contains("../");
    }
    
}