Java实现缓存，类似于Redis的实现，可以缓存对象到内存中，提高访问效率。代码如下：
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator; /**
* <p>Description: 管理缓存</p>
* 可扩展的功能：当cache到内存溢出时必须清除掉最早期的一些缓存对象，这就要求对每个缓存对象保存创建时间
* 目前该缓存管理器仅仅支持IOS客户端访问时的登录状态管理，如果进行它用，请防止key冲突
* @author zhanglp
*/
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<String>();
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);
}
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<String> 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<String> 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;
}
} }
/**
* <p>Description: 缓存DTO</p>
* @author zhanglp
*/
public class Cache {
private String key;//缓存ID
private Object value;//缓存数据
private long timeOut;//更新时间
private boolean expired; //是否终止
public Cache() {
super();
} public Cache(String key, Object value, long timeOut, boolean expired) {
this.key = key;
this.value = value;
this.timeOut = timeOut;
this.expired = expired;
} public String getKey() {
return key;
} public long getTimeOut() {
return timeOut;
} public Object getValue() {
return value;
} public void setKey(String string) {
key = string;
} public void setTimeOut(long l) {
timeOut = l;
} public void setValue(Object object) {
value = object;
} public boolean isExpired() {
return expired;
} public void setExpired(boolean b) {
expired = b;
}
}
如何使用：
public static void main(String[] args) {
//Demo1
Cache c1 = new Cache();
c1.setKey("China");
c1.setValue("*");
Cache c2 = new Cache();
c2.setKey("American");
c2.setValue("美利坚合众国");
CacheManager.putCache("one", c1);
CacheManager.putCache("two", c2);
System.out.println("缓存大小："+CacheManager.getCacheSize());
System.out.println("key为one的缓存对象Value："+CacheManager.getCacheInfo("one").getValue());
System.out.println("-----------------------------------");
//Demo2
Cache c3 = new Cache();
c3.setKey("小客车品牌列表");
List<String> list1 = new ArrayList<String>();
list1.add("奔驰");
list1.add("宝马");
list1.add("奥迪");
list1.add("现代");
c3.setValue(list1);
CacheManager.putCache("car", c3);
List<String> list2 = new ArrayList<String>();
Object obCar = CacheManager.getCacheInfo("car").getValue();
if(obCar instanceof List){
list2 = (List<String>) obCar;
}
for(String brand : list2){
System.out.println("Key为car的品牌："+brand);
}
System.out.println("-----------------------------------");
//Demo3
Cache c4 = new Cache();
c4.setKey("朗行-自动1.8T");
Cache c5 = new Cache();
c5.setKey("朗境-双离合2.0T");
Cache c6 = new Cache();
c6.setKey("夏朗-自动1.8T");
Cache c7 = new Cache();
c7.setKey("朗逸-双离合2.0T");
Cache c8 = new Cache();
c8.setKey("速腾-自动1.8T");
Cache c9 = new Cache();
c9.setKey("迈腾-双离合2.0T");
Cache c10 = new Cache();
c10.setKey("辉腾-双离合2.0T");
Map<String,String> map1 = new HashMap<String,String>();
map1.put("全景天窗", "是");
map1.put("发动机排量", "2.0L");
map1.put("排放标准", "国5");
c10.setValue(map1);
Cache c11 = new Cache();
c11.setKey("英菲尼迪-1.8T都市精英版");
CacheManager.putCache("朗行", c4);
CacheManager.putCache("朗境", c5);
CacheManager.putCache("朗逸", c6);
CacheManager.putCache("夏朗", c7);
CacheManager.putCache("速腾", c8);
CacheManager.putCache("迈腾", c9);
CacheManager.putCache("辉腾", c10);
//得到朗系家族的车产品
Object carObj2 = CacheManager.getCacheListLikekey("朗");
List<String> list3 = new ArrayList<String>();
if(carObj2 instanceof List){
list3 = (List<String>) carObj2;
}
for(String product : list3){
System.out.println("朗系家族："+product);
}
System.out.println("-----------------------------------");
//得到X腾系列的车产品
Object carObj3 = CacheManager.getCacheListLikekey("腾");
List<String> list4 = new ArrayList<String>();
if(carObj2 instanceof List){
list4 = (List<String>) carObj3;
}
for(String product : list4){
System.out.println("腾系家族："+product);
}
System.out.println("-----------------------------------");
System.out.println("此时的缓存大小："+CacheManager.getCacheSize());
}