java 使用静态hashmap实现简单缓存
因项目需要的数据查询较多，数量大，所以要用到缓存，在未引用redis的情况下，仅仅只做一个速度的提升
1、Cache类
public class Cache<E> {
private String key;//缓存ID，根据iD往hashmap存放值
private E value;//缓存数据 ，需要缓存的对象实体
private long timeOut;//更新时间
private boolean expired; //是否过期
public Cache() {
super();
}
public Cache(String key, E value, long timeOut, boolean expired) {
this.key = key;
this.value = value;
this.timeOut = timeOut+System.currentTimeMillis();
this.expired = expired;
}
public String getKey() {
return key;
}
public long getTimeOut() {
return timeOut;
}
public E getValue() {
return value;
}
public void setKey(String string) {
key = string;
}
public void setTimeOut(long l) {
timeOut = l;
}
public void setValue(E object) {
value = object;
}
public boolean isExpired() {
return expired;
}
public void setExpired(boolean b) {
expired = b;
}
}
2、CacheManager类
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
/**
* Created by admin on 2018/1/2.
*/
public class CacheManager {
private static HashMap cacheMap = new HashMap();
//单实例构造方法
private CacheManager() {
super();
}
//获取布尔值的缓存
public static boolean getSimpleFlag(String key){
try{
return (Boolean) cacheMap.get(key);
}catch(NullPointerException e){
return false;
}
}
public static long getServerStartdt(String key){
try {
return (Long)cacheMap.get(key);
} catch (Exception ex) {
return 0;
}
}
//设置布尔值的缓存
public synchronized static boolean setSimpleFlag(String key,boolean flag){
if (flag && getSimpleFlag(key)) {//假如为真不允许被覆盖
return false;
}else{
cacheMap.put(key, flag);
return true;
}
}
public synchronized static boolean setSimpleFlag(String key,long serverbegrundt){
if (cacheMap.get(key) == null) {
cacheMap.put(key,serverbegrundt);
return true;
}else{
return false;
}
}
//得到缓存。同步静态方法
private synchronized static Cache getCache(String key) {
return (Cache) cacheMap.get(key);
}
//判断是否存在一个缓存
private synchronized static boolean hasCache(String key) {
return cacheMap.containsKey(key);
}
//清除所有缓存
public synchronized static void clearAll() {
cacheMap.clear();
}
//清除某一类特定缓存,通过遍历HASHMAP下的所有对象，来判断它的KEY与传入的TYPE是否匹配
public synchronized static void clearAll(String type) {
Iterator i = cacheMap.entrySet().iterator();
String key;
ArrayList<String> arr = new ArrayList();
try {
while (i.hasNext()) {
java.util.Map.Entry entry = (java.util.Map.Entry) i.next();
key = (String) entry.getKey();
if (key.startsWith(type)) { //如果匹配则删除掉
arr.add(key);
}
}
for (int k = 0; k < arr.size(); k++) {
clearOnly(arr.get(k));
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
//清除指定的缓存
public synchronized static void clearOnly(String key) {
cacheMap.remove(key);
}
//载入缓存
public synchronized static void putCache(String key, Cache obj) {
cacheMap.put(key, obj);
}
//获取缓存信息
public static Cache getCacheInfo(String key) {
if (hasCache(key)) {
Cache cache = getCache(key);
if (cacheExpired(cache)) { //调用判断是否终止方法
cache.setExpired(true);
cacheMap.remove(key);
return null;
}
return cache;
}else{
return null;
}
}
//载入缓存信息
public static void putCacheInfo(String key, Cache obj, long dt,boolean expired) {
Cache cache = new Cache();
cache.setKey(key);
cache.setTimeOut(dt + System.currentTimeMillis()); //设置多久后更新缓存
cache.setValue(obj);
cache.setExpired(expired); //缓存默认载入时，终止状态为FALSE
cacheMap.put(key, cache);
}
//重写载入缓存信息方法
public static void putCacheInfo(String key,Cache obj,long dt){
Cache cache = new Cache();
cache.setKey(key);
cache.setTimeOut(dt+System.currentTimeMillis());
cache.setValue(obj);
cache.setExpired(false);
cacheMap.put(key,cache);
}
//判断缓存是否终止
public static boolean cacheExpired(Cache cache) {
if (null == cache) { //传入的缓存不存在
return false;
}
long nowDt = System.currentTimeMillis(); //系统当前的毫秒数
long cacheDt = cache.getTimeOut(); //缓存内的过期毫秒数
if (cacheDt <= 0||cacheDt>nowDt) { //过期时间小于等于零时,或者过期时间大于当前时间时，则为FALSE
return false;
} else { //大于过期时间 即过期
return true;
}
}
//获取缓存中的大小
public static int getCacheSize() {
return cacheMap.size();
}
//获取指定的类型的大小
public static int getCacheSize(String type) {
int k = 0;
Iterator i = cacheMap.entrySet().iterator();
String key;
try {
while (i.hasNext()) {
java.util.Map.Entry entry = (java.util.Map.Entry) i.next();
key = (String) entry.getKey();
if (key.indexOf(type) != -1) { //如果匹配则删除掉
k++;
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
return k;
}
//获取缓存对象中的所有键值名称
public static ArrayList getCacheAllkey() {
ArrayList a = new ArrayList();
try {
Iterator i = cacheMap.entrySet().iterator();
while (i.hasNext()) {
java.util.Map.Entry entry = (java.util.Map.Entry) i.next();
a.add((String) entry.getKey());
}
} catch (Exception ex) {} finally {
return a;
}
}
//获取缓存对象中指定类型 的键值名称
public static ArrayList getCacheListkey(String type) {
ArrayList a = new ArrayList();
String key;
try {
Iterator i = cacheMap.entrySet().iterator();
while (i.hasNext()) {
java.util.Map.Entry entry = (java.util.Map.Entry) i.next();
key = (String) entry.getKey();
if (key.indexOf(type) != -1) {
a.add(key);
}
}
} catch (Exception ex) {} finally {
return a;
}
}
}
3、调用
@Override
public DcJqrfbView getMap(String qlinkId, String country, String online, String devtype, String devtype1, String beautify,String adminQLinkId) throws Exception {
DcJqrfbView viewRespons=new DcJqrfbView();
String cache_key=new StringBuilder().append(qlinkId).append(country).append(online).append(devtype).append(devtype1).append(beautify).append(adminQLinkId).toString();
Cache<DcJqrfbView> c = CacheManager.getCacheInfo(cache_key);
if(c!=null&&!c.isExpired()){
return c.getValue();
}else{
c = new Cache(cache_key,viewRespons,10*60*1000,false);
}
int positionFialdNum=0;
int noActivityNum=0;
List<DcJqrfb> allData=new ArrayList<DcJqrfb>();
List<DcJqrfb> data=new ArrayList<DcJqrfb>();
DcWebResponse<List<DcJqrfb>> response=new DcWebResponse<List<DcJqrfb>>();
Map<String,DcJqrfb> map=new HashMap<String,DcJqrfb>();
response.setSuccess(true);
response.setData(data);
viewRespons.setResponse(response);
viewRespons.setPositionFialdNum(positionFialdNum);
viewRespons.setNoActivityNum(noActivityNum);
CacheManager.putCache(cache_key,c);
return viewRespons;
}
