JSP文件下载的实现

<%@ page import="com.jstrd.htgl.common.Htglcommon" %>
<%@ page import="java.net.*" %>
<% 
    String mineType = "text/plain";
    
    String subject = request.getParameter("subject");
    String name = new String(request.getParameter("name").getBytes("ISO8859-1"));
    if( subject != null )
    {
        Htglcommon bigText = new Htglcommon();
        byte[] bts = bigText.selectText(subject,name);
        if( bts != null )
        {
            String ext = bigText.docType;
            if( ext != null )
            {
                mineType = "";
                if( "pdf".equalsIgnoreCase(ext))
                {
                    mineType = "application/pdf";
                }
                else if( "xls".equalsIgnoreCase(ext))
                {
                    mineType = "application/vnd.ms-excel";
                }
                else if( "doc".equalsIgnoreCase(ext))
                {
                    mineType = "application/msword";
                }
                else if( "gif".equalsIgnoreCase(ext))
                {
                    mineType = "image/gif";
                }
                else if( "jpg".equalsIgnoreCase(ext))
                {
                    mineType = "image/jpeg";
                }
                else if( "bmp".equalsIgnoreCase(ext))
                {
                    mineType = "image/x-bmp";
                }
                else if( "png".equalsIgnoreCase(ext))
                {
                    mineType = "image/png";
                }
                else if( "ppt".equalsIgnoreCase(ext))
                {
                    mineType = "application/vnd.ms-powerpoint";
                }
                else if( "txt".equalsIgnoreCase(ext))
                {
                    mineType = "text/plain";
                }
                else if( "zip".equalsIgnoreCase(ext))
                {
                    mineType = "application/zip";
                }
                else if( "rar".equalsIgnoreCase(ext))
                {
                    mineType = "application/zip";
                }
                if( mineType.equals("") )
                {
                    mineType = application.getMimeType("temp." + ext);
                }
                response.reset();
                ServletOutputStream stream = response.getOutputStream();
                //response.addHeader("Content-Disposition","attachment; filename="+ URLEncoder.encode(bigText.docName,"gb2312"));
                response.setContentType(mineType + "; charset=gb2312");                
                stream.write(bts);
                stream.flush();
                stream.close();
                bts = null;
            }
        }
    }
    
%>

package com.jstrd.htgl.common;

import java.util.Calendar;
import java.util.GregorianCalendar;


import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.exp.dao.DBConnection;
import com.exp.dao.DBConnectionFactory;
import com.exp.dao.EXPSQLException;
import com.exp.dao.dialect.Dialect;
import com.exp.dao.dialect.OracleDialect;

public class Htglcommon {
    
    public transient String docType = "";
    public transient String docName = "";    
    
    public Htglcommon() {    
    }

/** *//**
     * 查询数据（正文）
     * 
     * @param subject
     *            数据对应主题
     * @return 如果数据不存在，则返回null
     * @throws EXPSQLException
     */
    public byte[] selectText(String subject,String strName) throws EXPSQLException {
        DBConnection dbConnection = this.getDBConnection();
        Connection con = dbConnection.getConnection();
        PreparedStatement ps = null;
        ResultSet rs = null;
        String strString = "";
        try {
            Dialect dialect = dbConnection.getDialect();
            if (dialect instanceof OracleDialect) {
                ps = con.prepareStatement("select file_body,file_name from sys_file f,flow_inst s where f.flow_inid=s.flow_inid and f.file_name=s.doc_name and f.flow_inid=? and f.file_name=?");
                ps.setString(1, subject);
                ps.setString(2, strName);
                rs = ps.executeQuery();
                if (rs.next()) {
                    byte[] bts = rs.getBytes(1);
                    //Blob blob = rs.getBytes(1);
                    strString = rs.getString(2);
                    this.docName = strString;
                    this.docType = strString.substring(strString.lastIndexOf(".")+1);
                    //byte[] bts = blob.getBytes((long) 1, (int) blob.length());
                    rs.close();
                    ps.close();
                    return bts;
                }
                rs.close();
                ps.close();
            } else {
                ps = con.prepareStatement("select file_body,file_name from sys_file f,flow_inst s where f.flow_inid=s.flow_inid and f.file_name=s.doc_name and f.flow_inid=? and f.file_name=?");
                ps.setString(1, subject);
                ps.setString(2, strName);
                rs = ps.executeQuery();
                if (rs.next()) {
                    byte[] bts = rs.getBytes(1);
                    strString = rs.getString(2);
                    this.docName = strString;
                    this.docType = strString.substring(strString.lastIndexOf(".")+1);
                    rs.close();
                    ps.close();
                    return bts;
                }
                rs.close();
                ps.close();
            }
            return null;
        } catch (SQLException sqlE) {
            throw new EXPSQLException(sqlE);
        } finally {
            dbConnection.close();
        }
    }

    protected DBConnection getDBConnection() throws EXPSQLException {
        return DBConnectionFactory
                .createDBConnection("WorkFlow");
    }

}