java动态缓存技术：WEB缓存应用[转载]
CacheData.java 存放缓存数据的Bean
/** * */package com.cari.web.cache; /** *//*** @author zsy* */public class CacheData ...{private Object data; private long time; private int count; public CacheData() ...{}public CacheData(Object data, long time, int count) ...{this.data = data; this.time = time; this.count = count; }public CacheData(Object data) ...{this.data = data; this.time = System.currentTimeMillis(); this.count = 1; }public void addCount() ...{count++; }public int getCount() ...{return count; }public void setCount(int count) ...{this.count = count; }public Object getData() ...{return data; }public void setData(Object data) ...{this.data = data; }public long getTime() ...{return time; }public void setTime(long time) ...{this.time = time; }}package com.cari.web.cache;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.Arrays;import java.util.Hashtable;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;/** * @author zsy */public class CacheOperation { private static final Log log = LogFactory.getLog(CacheOperation.class); private static CacheOperation singleton = null; private Hashtable cacheMap;//存放缓存数据 private ArrayList threadKeys;//处于线程更新中的key值列表 public static CacheOperation getInstance() { if (singleton == null) { singleton = new CacheOperation(); } return singleton; } private CacheOperation() { cacheMap = new Hashtable(); threadKeys = new ArrayList(); } /** * 添加数据缓存 * 与方法getCacheData(String key, long intervalTime, int maxVisitCount)配合使用 * @param key * @param data */ public void addCacheData(String key, Object data) { addCacheData(key, data, true); } private void addCacheData(String key, Object data, boolean check) { if (Runtime.getRuntime().freeMemory() < 5L*1024L*1024L) {//虚拟机内存小于10兆，则清除缓存 log.warn("WEB缓存：内存不足，开始清空缓存！"); removeAllCacheData(); return; } else if(check && cacheMap.containsKey(key)) { log.warn("WEB缓存：key值= " + key + " 在缓存中重复, 本次不缓存！"); return; } cacheMap.put(key, new CacheData(data)); } /** * 取得缓存中的数据 * 与方法addCacheData(String key, Object data)配合使用 * @param key * @param intervalTime 缓存的时间周期，小于等于0时不限制 * @param maxVisitCount 访问累积次数，小于等于0时不限制 * @return */ public Object getCacheData(String key, long intervalTime, int maxVisitCount) { CacheData cacheData = (CacheData)cacheMap.get(key); if (cacheData == null) { return null; } if (intervalTime > 0 && (System.currentTimeMillis() - cacheData.getTime()) > intervalTime) { removeCacheData(key); return null; } if (maxVisitCount > 0 && (maxVisitCount - cacheData.getCount()) <= 0) { removeCacheData(key); return null; } else { cacheData.addCount(); } return cacheData.getData(); } /** * 当缓存中数据失效时，用不给定的方法线程更新数据 * @param o 取得数据的对像(该方法是静态方法是不用实例，则传Class实列) * @param methodName 该对像中的方法 * @param parameters 该方法的参数列表(参数列表中对像都要实现toString方法,若列表中某一参数为空则传它所属类的Class) * @param intervalTime 缓存的时间周期，小于等于0时不限制 * @param maxVisitCount 访问累积次数，小于等于0时不限制 * @return */ public Object getCacheData(Object o, String methodName,Object[] parameters, long intervalTime, int maxVisitCount) { Class oc = o instanceof Class ? (Class)o : o.getClass(); StringBuffer key = new StringBuffer(oc.getName());//生成缓存key值 key.append("-").append(methodName); if (parameters != null) { for (int i = 0; i < parameters.length; i++) { if (parameters[i] instanceof Object[]) { key.append("-").append(Arrays.toString((Object[])parameters[i])); } else { key.append("-").append(parameters[i]); } } } CacheData cacheData = (CacheData)cacheMap.get(key.toString()); if (cacheData == null) {//等待加载并返回 Object returnValue = invoke(o, methodName, parameters, key.toString()); return returnValue instanceof Class ? null : returnValue; } if (intervalTime > 0 && (System.currentTimeMillis() - cacheData.getTime()) > intervalTime) { daemonInvoke(o, methodName, parameters, key.toString());//缓存时间超时,启动线程更新数据 } else if (maxVisitCount > 0 && (maxVisitCount - cacheData.getCount()) <= 0) {//访问次数超出,启动线程更新数据 daemonInvoke(o, methodName, parameters, key.toString()); } else { cacheData.addCount(); } return cacheData.getData(); } /** * 递归调用给定方法更新缓存中数据据 * @param o * @param methodName * @param parameters * @param key * @return 若反射调用方法返回值为空则返回该值的类型 */ private Object invoke(Object o, String methodName,Object[] parameters, String key) { Object returnValue = null; try { Class[] pcs = null; if (parameters != null) { pcs = new Class[parameters.length]; for (int i = 0; i < parameters.length; i++) { if (parameters[i] instanceof MethodInfo) {//参数类型是MethodInfo则调用该方法的返回值做这参数 MethodInfo pmi = (MethodInfo)parameters[i]; Object pre = invoke(pmi.getO(), pmi.getMethodName(), pmi.getParameters(), null); parameters[i] = pre; } if (parameters[i] instanceof Class) { pcs[i] = (Class)parameters[i]; parameters[i] = null; } else { pcs[i] = parameters[i].getClass(); } } } Class oc = o instanceof Class ? (Class)o : o.getClass(); // Method m = oc.getDeclaredMethod(methodName, pcs); Method m = matchMethod(oc, methodName, pcs); returnValue = m.invoke(o, parameters); if (key != null && returnValue != null) { addCacheData(key, returnValue, false); } if (returnValue == null) { returnValue = m.getReturnType(); } } catch(Exception e) { log.error("调用方法失败,methodName=" + methodName); if (key != null) { removeCacheData(key); log.error("更新缓存失败，缓存key=" + key); } e.printStackTrace(); } return returnValue; } /** * 找不到完全匹配的方法时,对参数进行向父类匹配 * 因为方法aa(java.util.List) 与 aa(java.util.ArrayList)不能自动匹配到 * * @param oc * @param methodName * @param pcs * @return * @throws NoSuchMethodException * @throws NoSuchMethodException */ private Method matchMethod(Class oc, String methodName, Class[] pcs ) throws NoSuchMethodException, SecurityException { try { Method method = oc.getDeclaredMethod(methodName, pcs); return method; } catch (NoSuchMethodException e) { Method[] ms = oc.getDeclaredMethods(); aa:for (int i = 0; i < ms.length; i++) { if (ms[i].getName().equals(methodName)) { Class[] pts = ms[i].getParameterTypes(); if (pts.length == pcs.length) { for (int j = 0; j < pts.length; j++) { if (!pts[j].isAssignableFrom(pcs[j])) { break aa; } } return ms[i]; } } } throw new NoSuchMethodException(); } } /** * 新启线程后台调用给定方法更新缓存中数据据 * @param o * @param methodName * @param parameters * @param key */ private void daemonInvoke(Object o, String methodName,Object[] parameters, String key) { if (!threadKeys.contains(key)) { InvokeThread t = new InvokeThread(o, methodName, parameters, key); t.start(); } } /** * 些类存放方法的主调对像,名称及参数数组 * @author zsy * */ public class MethodInfo { private Object o; private String methodName; private Object[] parameters; public MethodInfo(Object o, String methodName,Object[] parameters) { this.o = o; this.methodName = methodName; this.parameters = parameters; } public String getMethodName() { return methodName; } public void setMethodName(String methodName) { this.methodName = methodName; } public Object getO() { return o; } public void setO(Object o) { this.o = o; } public Object[] getParameters() { return parameters; } public void setParameters(Object[] parameters) { this.parameters = parameters; } public String toString() { StringBuffer str = new StringBuffer(methodName); if (parameters != null) { str.append("("); for (int i = 0; i < parameters.length; i++) { if (parameters[i] instanceof Object[]) { str.append(Arrays.toString((Object[])parameters[i])).append(","); } else { str.append(parameters[i]).append(","); } } str.append(")"); } return str.toString(); } } /** * 线程调用方法 * @author zsy * */ private class InvokeThread extends Thread { private Object o; private String methodName; private Object[] parameters; private String key; public InvokeThread(Object o, String methodName,Object[] parameters, String key) { this.o = o; this.methodName = methodName; this.parameters = parameters; this.key = key; } public void run() { threadKeys.add(key); invoke(o, methodName, parameters, key); threadKeys.remove(key); } } /** * 移除缓存中的数据 * @param key */ public void removeCacheData(String key) { cacheMap.remove(key); } /** * 移除所有缓存中的数据 * */ public void removeAllCacheData() { cacheMap.clear(); } public String toString() { StringBuffer sb = new StringBuffer("************************ "); sb.append("正在更新的缓存数据： "); for (int i = 0; i < threadKeys.size(); i++) { sb.append(threadKeys.get(i)).append(" "); } sb.append("当前缓存大小：").append(cacheMap.size()).append(" "); sb.append("************************"); return sb.toString(); }}public class Test { String rulStr=....; String encoding=....; public void getData() { DataCreator c = new DataCreator(); String result = c.initUrlData(urlStr,encoding); System.out.println(result); }}public void getData() { DataCreator data = new DataCreator(); CacheOperation co = CacheOperation.getInstance(); String str = (String)co.getCacheData(data, "initUrlData",new Object[]{urlStr, encoding}, 120000, 100); System.out.println(result); }............String province = request.getParameter("province");String city= request.getParameter("city");String county= request.getParameter("county");Document doc = XMLBuilder.buildLatelyKeyword(kwm.latelyKeyword(province, city, county));out.write(doc);......做缓存并两分钟更新一次,如下：......String province = request.getParameter("province");String city= request.getParameter("city");String county= request.getParameter("county");CacheOperation co = CacheOperation.getInstance();MethodInfo mi = co.new MethodInfo(kwm, "latelyKeyword", new Object[]{province, city, county}); Document doc = (Document )co.getCacheData(XMLBuilder.class,"buildLatelyKeyword",new Object[]{mi}, 120000, 0);out.write(doc);......