我正在尝试实现服务器端缓存，以避免一直进入数据库进行查询。
我已经构建了我的缓存，可以与数百个用户一起使用，但是当数量达到数千时，构建需要很长时间。为了提高性能，我可以对此做些什么的优化。
由于
/**
*
* Get a user profile
*
* @param userid
* the userid of the profile to get
*
* @param serialized
* true if you want the profile string serialized
*
* @return the user profile as a string or an Object
*/
private static ConcurrentMap<String, Profile> getUserProfiles() {
final String select = "SELECT ua.userid, ua.displayname, ua.major, ua.minor,ua.profileimage,ua.genderpreference,"
+ "ad.devicetoken,pf.optionalImageOne, pf.optionalImageTwo, pf.optionalImageThree, "
+ "pf.optionalImagefour,pp.created,hon.numhots,hon.numnots "
+ "FROM UserAccount ua "
+ "LEFT OUTER JOIN ApnsDevices ad ON ad.userid = ua.userid "
+ "LEFT OUTER JOIN ProfileImages pf ON pf.userid = ua.userid "
+ "LEFT OUTER JOIN PendingProfile pp ON pp.userid = ua.userid "
+ "LEFT OUTER JOIN HotOrNot hon ON hon.userid = ua.userid";
final String friendsList = "SELECT * FROM Shortlist WHERE userid = ?";
String displayName = "";
String userid = null;
String genderpreference = null;
Profile userProfile;
int majorid = 0;
int minorid = 0;
int hots = 0;
int nots = 0;
byte[][] images = new byte[4][];
byte[] image = null;
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
ResultSet rs2 = null;
Timestamp onDemandTimeSent = null;
long origianlStartTime = System.nanoTime();
ConcurrentMap<String, Profile> results = new ConcurrentHashMap<String, Profile>();
try {
conn = source.getConnection();
st = conn.prepareStatement(select);
rs = st.executeQuery(select);
while (rs.next()) {
byte[] imageOne = null;
byte[] imageTwo = null;
byte[] imageThree = null;
byte[] imageFour = null;
long startTime = System.nanoTime();
userid = rs.getString("userid");
genderpreference = rs.getString("genderpreference");
majorid = rs.getInt("major");
minorid = rs.getInt("minor");
image = rs.getBytes("profileimage");
displayName = rs.getString("displayname");
hots = rs.getInt("numhots");
nots = rs.getInt("numnots");
onDemandTimeSent = rs.getTimestamp("created");
if (rs.getBlob("optionalImageOne") != null){
imageOne = rs.getBlob("optionalImageOne").getBytes(1,(int) rs.getBlob("optionalImageOne").length());
}
if (rs.getBlob("optionalImageTwo") != null){
imageTwo = rs.getBlob("optionalImageTwo").getBytes(1,(int) rs.getBlob("optionalImageTwo").length());
}
if (rs.getBlob("optionalImageThree") != null){
imageThree = rs.getBlob("optionalImageThree").getBytes(1,(int) rs.getBlob("optionalImageThree").length());
}
if (rs.getBlob("optionalImageFour") != null){
imageFour = rs.getBlob("optionalImageFour").getBytes(1,(int) rs.getBlob("optionalImageFour").length());
}
images[0] = imageOne;
images[1] = imageTwo;
images[2] = imageThree;
images[3] = imageFour;
String deviceToken = rs.getString("devicetoken");
// get friends list
List<String> friends = new ArrayList<String>();
st = conn.prepareStatement(friendsList);
st.setString(1, userid);
rs2 = st.executeQuery();
String friend;
while (rs2.next()) {
friend = rs2.getString("friend");
if (friend != null) {
friends.add(friend);
}
}
if (onDemandTimeSent != null) {
userProfile = new Profile(image, onDemandTimeSent.toString(), userid, displayName, hots, nots, majorid, minorid, deviceToken, genderpreference, friends);
} else {
userProfile = new Profile(image, null, userid, displayName, hots, nots, majorid, minorid, deviceToken, genderpreference, friends);
}
userProfile.setAlternativeImages(images);
long endTime = System.nanoTime();
double totalTime = TimeUnit.SECONDS.convert((endTime - startTime), TimeUnit.NANOSECONDS);
System.out.println("Total time to generate user profile for "+ userid + " was : " + totalTime + " seconds : " + userProfile);
logger.info("Generated user profile for " + userid);
results.put(userid, userProfile);
}
} catch (Exception e) {
e.printStackTrace();
logger.warn("An error occured when getting user profile for "+ userid, e);
} finally {
closeConnection(conn);
closeResultSet(rs);
closeResultSet(rs2);
closePreparedStatement(st);
}
long endTime = System.nanoTime();
double totalTime = TimeUnit.SECONDS.convert((endTime - origianlStartTime), TimeUnit.NANOSECONDS);
System.out.println("Total time to generate all user profiles for " + results.size() + " users was " + totalTime + " seconds");
return results;
}