import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class RequestLimitCache {
private static final ConcurrentHashMap> map = new ConcurrentHashMap>();
private static final long EXPIRE_TIME = 1000 * 5L;
private static final int MAX_REFRESH_COUNT = 10;
private static final RequestLimitCache cache = new RequestLimitCache();
private RequestLimitCache() {
Executors.newSingleThreadScheduledExecutor().scheduleWithFixedDelay(new ClearCacheRunnable(), 1000L, 500L, TimeUnit.MILLISECONDS);
}
public static RequestLimitCache getInstance() {
return cache;
}
// 增加指定key的访问次数
public void increment(String key) {
CopyOnWriteArrayList list = map.get(key);
if (list == null) {
map.put(key, new CopyOnWriteArrayList());
}
map.get(key).add(System.currentTimeMillis());
}
// 是否到达指定数量
public boolean isUpCount(String key) {
CopyOnWriteArrayList list = map.get(key);
if (list == null) {
return false;
}
return list.size() > MAX_REFRESH_COUNT;
}
// 清理过期数据线程
private static class ClearCacheRunnable implements Runnable {
@Override
public void run() {
try {
clear();
} catch (Exception e) {
e.printStackTrace();
}
}
private void clear() {
for (String key : map.keySet()) {
CopyOnWriteArrayList list = map.get(key);
for (Long date : list) {
if ((System.currentTimeMillis() - date) > RequestLimitCache.EXPIRE_TIME) {
list.remove(date);
}
}
}
}
}
}
import java.io.IOException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class RefreshFilter implements Filter {
public void init(FilterConfig config) throws ServletException {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
String ip = req.getRemoteAddr(); //得到客户端IP地址
String requestURI = req.getRequestURI();//得到客户请求的uri
String cache_key=ip+requestURI;
Cache cache = Cache.getInstance();
if (cache.isUpCount(cache_key)) {
res.setContentType("text/html; charset=UTF-8");// 响应类型
res.sendRedirect(req.getContextPath() + "/error.html");
} else {
cache.increment(cache_key);
chain.doFilter(request, response);
}
}
public void destroy() {
}
// 缓存
private static class Cache {
private static final ConcurrentHashMap> map = new ConcurrentHashMap>();
private static final long EXPIRE_TIME = 1000 * 5L;
private static final long CLEAR_TIME = 500L;
private static final int MAX_REFRESH_COUNT = 10;
private static final Cache cache = new Cache();
private Cache() {
new Thread(new ClearCacheRunnable()).start();
}
public static Cache getInstance() {
return cache;
}
// 增长指定url的点击次数
public void increment(String key) {
CopyOnWriteArrayList list = map.get(key);
if (list == null) {
map.put(key, new CopyOnWriteArrayList());
}
map.get(key).add(new Long(System.currentTimeMillis()));
}
// 是否到达指定数量
public boolean isUpCount(String key) {
CopyOnWriteArrayList list = map.get(key);
if (list == null) {
return false;
}
return list.size() > MAX_REFRESH_COUNT;
}
// 清理过期数据线程
private static class ClearCacheRunnable implements Runnable {
@Override
public void run() {
while (true) {
try {
Thread.sleep(Cache.CLEAR_TIME);
clear();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void clear() {
for (String key : map.keySet()) {
CopyOnWriteArrayList list = map.get(key);
for (Long date : list) {
if ((System.currentTimeMillis() - date) > Cache.EXPIRE_TIME) {
list.remove(date);
}
}
}
}
}
}
}
