图像需要花费大量时间才能加载到JSP中

Question

I have a scenario where I am fetching multiple images from the Oracle database through the loop. But it's taking a lot of time to fetch the images and display it on the browser. Through, this code I am calling my method with some parameters.

for(Object[] obj: memberDetails)
{
    System.out.println("String.valueOf(obj[0])"+String.valueOf(obj[0]));

    try{
        memberImage=dtSrvc.getQueImageForQC(Id,String.valueOf(obj[0]));
    }
    catch(Exception e)
    {}

    map.put("memImage"+count, memberImage);
    key.add("memImage"+count);
    hmap.put("memImage"+count, memberImage);
    count++;
}  

and here is my query through which I am fetching images

ps = conn.prepareStatement("select photo from member_photo where ID='"
                        + Id + "' and que_id=" + QueId);

Please, let me know how can I speed up this process. I am unable to fetch all images if the network is slow. My application is currently used by many peoples.

Answer 1

The problem is that you use individual query to fetch each image from the db. It makes a network overhead. You can try many of the solutions described here to change your code to do one query instead of many. See how to Batching Select Statements in JDBC .

ps = conn.prepareStatement("select photo from member_photo where ID in (" + inClause.toString() + ')');

you don't need que_id if ID is a primary key in the table.

Answer 2

My suggestion is about fetching images first and keep them as pure file(temp) on a accessible and public folder of your application, and then simply point them out with simple image resource using img tag.
The process would be like this.
1. Query images and keep them under /a_public_folder/images/... which each images is going be named as 1.jpeg , 2.jpeg where 1 and 2 are ids(unique).
2. keep the ids retrieved from the database with a simple context such as list_id:List<Long>
3. your final servlet would be like the following

for(long idx:list_id){
  out.print("<img src=\"/a_public_folder/images/"+idx+".jpeg\"/>");
}

4. you may also apply a filter for /a_public_folder/images/* path in order to just allow users who have permission to view content/images
5. have a session listener in order to remove associated(fetched) images to the particular user session, or have a daemon thread for cleaning up the directory(images have no links longer) interval.

But I suggest extract images from database to simple pure file and just keep the images path into the database.