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RateLimit.java
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112 lines (80 loc) · 2.98 KB
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package utils;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.concurrent.ConcurrentHashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
public class RateLimit {
private static final int MAX_REQUESTS = 3;
private static final int INTERVAL = 1 * 60 * 1000; // 1min
private static final int BLOCKED_TIME = 2 * 60 * 1000; // 2min
private Map<String, ArrayList<Calendar>> requestsList;
private Map<String, Calendar> blockedList;
private static RateLimit instance;
public RateLimit() {
requestsList = new ConcurrentHashMap<String, ArrayList<Calendar>>();
blockedList = new ConcurrentHashMap<String, Calendar>();
}
public static synchronized RateLimit getInstance() {
if (instance == null) {
instance = new RateLimit();
}
return instance;
}
public boolean doFilter(HttpServletRequest request) {
String ipAddress = request.getRemoteAddr();
System.out.println(ipAddress);
Calendar currentTime = this.getCurrentTime();
if (requestsList.containsKey(ipAddress)) {
if (isInBlockedList(ipAddress)) {
return false;
}
if (isAnExceedingRequest(ipAddress)) {
return false;
}
requestsList.get(ipAddress).add(currentTime);
} else {
ArrayList<Calendar> calendarList = new ArrayList<Calendar>();
calendarList.add(currentTime);
requestsList.put(ipAddress, calendarList);
}
return true;
}
public Boolean isAnExceedingRequest(String ipAddress) {
ArrayList<Calendar> requestsListArray = requestsList.get(ipAddress);
int requestsListArraySize = requestsListArray.size();
Calendar currentTime = getCurrentTime();
if (requestsListArraySize < MAX_REQUESTS) {
return false;
}
int countRequestLessThanOneMinute = 0;
// getting the last items from list
for (int i = 0; i < MAX_REQUESTS; i++) {
if ((currentTime.getTimeInMillis()
- requestsListArray.get(requestsListArraySize - (i + 1)).getTimeInMillis()) < INTERVAL) {
countRequestLessThanOneMinute++;
}
}
if (countRequestLessThanOneMinute == MAX_REQUESTS) {
blockedList.put(ipAddress, currentTime);
return true;
}
return false;
}
public Boolean isInBlockedList(String ipAddress) {
Calendar currentTime = getCurrentTime();
Calendar blockTime = blockedList.get(ipAddress);
if (blockTime == null) {
return false;
}
if ((currentTime.getTimeInMillis() - blockTime.getTimeInMillis()) < BLOCKED_TIME) {
return true;
}
blockedList.remove(ipAddress);
return false;
}
public Calendar getCurrentTime() {
Calendar now = Calendar.getInstance();
return now;
}
}