java缓存技术_java缓存技术
最近在做java緩存,了解了一下.
以下僅是對map對方式討論。沒有對點陣圖陣討論。
作緩存要做以下2點:
1:清理及更新緩存時機的處理:
. 虛擬機內存不足,清理緩存
.. 緩存時間超時,或訪問次數超出, 啟動線程更新
2:類和方法的反射 (線程嵌套調用)
reflect.invoke的使用。
代碼如下：
package atest.hiyaCache;
/**
*
* @author hiyachen
* @version $Revision$
*/
public class AddrDetail {
public String latelyKeyword(String province, String city, String county){
System.out.println("AddrDetail.latelyKeyword=" + province + city + county);
return province + city + county;
}
public String buildCache(String latelyKeyword){
System.out.println("AddrDetail.buildCache=" + latelyKeyword);
return latelyKeyword;
}
}
package atest.hiyaCache;
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 atest.hiyaCache;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Hashtable;
import org.apache.commons.logging.Log;?? //commons-loggings-1.1.1.jar
import org.apache.commons.logging.LogFactory;
public class CacheOperation {
private static final Log log = LogFactory.getLog(CacheOperation.class);
private static CacheOperation singleton = null;
private Hashtable cacheMap;//存放緩存數據
private ArrayList threadKeys;//處于線程更新中的key值列表
public static CacheOperation getInstance() {
if (singleton == null) {
singleton = new CacheOperation();
}
return singleton;
}
private CacheOperation() {
cacheMap = new Hashtable();
threadKeys = new ArrayList();
}
/**
* 添加數據緩存
* 與方法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) {//虛擬機內存小于10兆，則清除緩存
log.warn("WEB緩存：內存不足，開始清空緩存！");
removeAllCacheData();
return;
} else if(check && cacheMap.containsKey(key)) {
log.warn("WEB緩存：key值= " + key + " 在緩存中重復, 本次不緩存！");
return;
}
cacheMap.put(key, new CacheData(data));
}
/**
* 取得緩存中的數據
* 與方法addCacheData(String key, Object data)配合使用
* @param key
* @param intervalTime 緩存的時間周期，小于等于0時不限制
* @param maxVisitCount 訪問累積次數，小于等于0時不限制
* @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();
}
/**
* 當緩存中數據失效時，用不給定的方法線程更新數據
* @param o 取得數據的對像(該方法是靜態方法是不用實例，則傳Class實列)
* @param methodName 該對像中的方法
* @param parameters 該方法的參數列表(參數列表中對像都要實現toString方法,若列表中某一參數為空則傳它所屬類的Class)
* @param intervalTime 緩存的時間周期，小于等于0時不限制
* @param maxVisitCount 訪問累積次數，小于等于0時不限制
* @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());//生成緩存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) {//等待加載并返回
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());//緩存時間超時,啟動線程更新數據
} else if (maxVisitCount > 0 && (maxVisitCount - cacheData.getCount()) <= 0) {//訪問次數超出,啟動線程更新數據
daemonInvoke(o, methodName, parameters, key.toString());
} else {
cacheData.addCount();
}
return cacheData.getData();
}
/**
* 遞歸調用給定方法更新緩存中數據據
* @param o
* @param methodName
* @param parameters
* @param key
* @return 若反射調用方法返回值為空則返回該值的類型
*/
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) {
//參數類型是MethodInfo則調用該方法的返回值做這參數
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);
Object o1 = oc.newInstance();? // add by chf
returnValue = m.invoke(o1, parameters);
if (key != null && returnValue != null) {
addCacheData(key, returnValue, false);
}
if (returnValue == null) {
returnValue = m.getReturnType();
}
} catch(Exception e) {
log.error("調用方法失敗,methodName=" + methodName);
if (key != null) {
removeCacheData(key);
log.error("更新緩存失敗，緩存key=" + key);
}
e.printStackTrace();
}
return returnValue;
}
/**
* 找不到完全匹配的方法時,對參數進行向父類匹配
* 因為方法aa(java.util.List) 與 aa(java.util.ArrayList)不能自動匹配到
*
* @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();
}
}
/**
* 新啟線程后臺調用給定方法更新緩存中數據據
* @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();
}
}
/**
* 些類存放方法的主調對像,名稱及參數數組
* @author hiya
*
*/
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();
}
}
/**
* 線程調用方法
* @author hiya
*
*/
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);
}
}
/**
* 移除緩存中的數據
* @param key
*/
public void removeCacheData(String key) {
cacheMap.remove(key);
}
/**
* 移除所有緩存中的數據
*
*/
public void removeAllCacheData() {
cacheMap.clear();
}
public String toString() {
StringBuffer sb = new StringBuffer("************************ ");
sb.append("正在更新的緩存數據： ");
for (int i = 0; i < threadKeys.size(); i++) {
sb.append(threadKeys.get(i)).append(" ");
}
sb.append("當前緩存大小：").append(cacheMap.size()).append(" ");
sb.append("************************");
return sb.toString();
}
}
實際使用：
package atest.hiyaCache;
//import javax.swing.text.Document;
import atest.hiyaCache.CacheOperation.MethodInfo;
public class CacheExec {
/**
* [メソッドの説明を書きましょう]
* @param args
*/
public static void main(String[] args) {
// TODO 自動生成されたメソッド?スタブ
//??????? 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);
String province = "Jiangsu ";
String city= "Nanjing ";
String county= "Jiangning";
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);
while (true){
// chf@tsinghua.org.cn
MethodInfo mi = co.new MethodInfo(AddrDetail.class, "latelyKeyword", new Object[]{province, city, county});
// 120000 毫秒(2分鐘)更新緩存
String aa = (String)co.getCacheData(AddrDetail.class,"buildCache",new Object[]{mi}, 120000, 5);
System.out.println("CacheExec:main=" + aa);
}??? }
}
當緩存次數超過5時，重新執行。看一下執行結果。
AddrDetail.latelyKeyword=Jiangsu Nanjing Jiangning
AddrDetail.buildCache=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
AddrDetail.latelyKeyword=Jiangsu Nanjing Jiangning
AddrDetail.buildCache=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
CacheExec:main=Jiangsu Nanjing Jiangning
AddrDetail.latelyKeyword=Jiangsu Nanjing Jiangning
AddrDetail.buildCache=Jiangsu Nanjing Jiangning
總結
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