保存图片到数据库

/**
	 * 新增广告
	 */
	public boolean saveAdvertise(Advertisement advertisement,String webUrl,String url) throws Exception {
		// TODO Auto-generated method stub
		boolean b = false;
		PreparedStatement pstmt = null;
		Connection conn = null;
		ResultSet rset = null;
		try {
			conn = this.getJdbcTemplate().getDataSource().getConnection();
			conn.setAutoCommit(false);   
            BLOB blob = null;   
            String sql = "insert into HOLIDAY_ADVERTISEMENT(ADVERTISEID,ADVERTISENAME,PIC,LINKURL,HOTELADDNUM,HOLIDAYADDNUM,HOLIDAYTYPEADDNUM,PUBLISHSTATE,CHOREN) values (SEQ_ADVERTISE.nextval,?,empty_blob(),?,?,?,?,?,?)";
            /** 新增广告策略
             * 如果新增的广告频道位置在对应频道已经存在，需先将存在的频道位置设为null，然后新增就ok啦。
             * 开始-----
             **/
            String sql2 = "";
            if(advertisement.getHoteladdnum()!=null){
            	sql2 = "update HOLIDAY_ADVERTISEMENT set HOTELADDNUM = null where HOTELADDNUM = "+advertisement.getHoteladdnum()+" and CHOREN = '"+advertisement.getChoren()+"'";
            	pstmt = conn.prepareStatement(sql2);
            	pstmt.executeUpdate();
            	if(pstmt!=null){
            		pstmt.close();
            	}
            }
            if(advertisement.getHolidayaddnum()!=null){
            	sql2 = "update HOLIDAY_ADVERTISEMENT set HOLIDAYADDNUM = null where HOLIDAYADDNUM = "+advertisement.getHolidayaddnum()+" and CHOREN = '"+advertisement.getChoren()+"'";
            	pstmt = conn.prepareStatement(sql2);
            	pstmt.executeUpdate();
            	if(pstmt!=null){
            		pstmt.close();
            	}
            }
            if(advertisement.getHolidaytypeaddnum()!=null){
            	sql2 = "update HOLIDAY_ADVERTISEMENT set HOLIDAYTYPEADDNUM = null where HOLIDAYTYPEADDNUM = "+advertisement.getHolidaytypeaddnum()+" and CHOREN = '"+advertisement.getChoren()+"'";
            	pstmt = conn.prepareStatement(sql2);
            	pstmt.executeUpdate();
            	if(pstmt!=null){
            		pstmt.close();
            	}
            }
            /** 结束 **/
            pstmt = conn.prepareStatement(sql);   
            pstmt.setString(1, advertisement.getAdvertisename());
            pstmt.setString(2, advertisement.getLinkurl());
            if(advertisement.getHoteladdnum()!=null){
            	pstmt.setLong(3, advertisement.getHoteladdnum());
            }else {
//            	pstmt.setNull(3, Types.NULL);
            	pstmt.setNull(3, java.sql.Types.INTEGER);
			}
            if(advertisement.getHolidayaddnum()!=null){
            	pstmt.setLong(4, advertisement.getHolidayaddnum());
            }else {
//            	pstmt.setNull(4, Types.NULL);
            	pstmt.setNull(4, java.sql.Types.INTEGER);
			}
            if(advertisement.getHolidaytypeaddnum()!=null){
            	pstmt.setLong(5, advertisement.getHolidaytypeaddnum());
            }else {
//            	pstmt.setNull(5, Types.NULL);
            	pstmt.setNull(5, java.sql.Types.INTEGER);
			}
            pstmt.setLong(6, advertisement.getPublishstate());
            pstmt.setString(7, advertisement.getChoren());
            pstmt.executeUpdate();   
            if(pstmt!=null){
        		pstmt.close();
        	}  
  
            pstmt = conn   
                    .prepareStatement("select PIC from HOLIDAY_ADVERTISEMENT where ADVERTISENAME= ? for update");   
            pstmt.setString(1, advertisement.getAdvertisename());   
            rset = pstmt.executeQuery();   
            if (rset.next())   
                blob = (BLOB) rset.getBlob(1);   
            System.out.println(url);
            String fileName = url;
            File f = new File(webUrl+fileName);   
            FileInputStream fin = new FileInputStream(f);   
            System.out.println("file size = " + fin.available());   
            pstmt = conn   
                    .prepareStatement("update HOLIDAY_ADVERTISEMENT set PIC=? where ADVERTISENAME=?");   
            OutputStream out = blob.getBinaryOutputStream();   
            byte[] data = new byte[(int) fin.available()];   
            fin.read(data);   
            out.write(data);   
            fin.close();   
            out.close();   
            pstmt.setBlob(1, blob);   
            pstmt.setString(2, advertisement.getAdvertisename());   
  
            pstmt.executeUpdate();   
            conn.commit(); 
            /** 删除上传的文件 **/
	        File file = new File(webUrl+url);
	        if(file.exists()){
	        	file.delete();
	        }
            b = true;
        } catch (Exception e) {   
            e.printStackTrace();
        } finally{
        	if(rset!=null){
            	rset.close();
        	}
        	if(pstmt!=null){
            	pstmt.close();
        	}
        	 if(conn!=null){
             	conn.close();
         	} 
        }
		return b;
	}

 上面的代码是实际工作中的逻辑，总结一下保存图片到数据库的步骤：

一、insert into 保存数据到数据库，对应的blob地方使用empty_blob()；

二、select PIC from HOLIDAY_ADVERTISEMENT where ADVERTISENAME= ? for update 查询出blob的字段，用blob保存起来。

三、update HOLIDAY_ADVERTISEMENT set PIC=? where ADVERTISENAME=? 将要保存的图片的文件流读取到blob中，替换原来的blob字段内容。具体代码在上面的程序中寻找。