Java实现文件监控器FileMonitor的实例代码

2023-08-04 01:43:04 293

应用场景：

代码可以实现文件变化后的监听，如文件变化，自动重新加载文件内容，实现配置文件的热部署。

代码：

packagecom.yx.demo.filemonitor;

importjava.io.File;
importjava.lang.ref.WeakReference;
importjava.util.ArrayList;
importjava.util.Collection;
importjava.util.HashMap;
importjava.util.Iterator;
importjava.util.List;
importjava.util.Timer;
importjava.util.TimerTask;

/**
*FileMonitor
*文件监控器
*
*@authoryx
*@date2019/12/210:59
*/
publicclassFileMonitor{

/**
*每2秒更新的默认监控器
*/
privatestaticFileMonitordefaultFileMonitor=newFileMonitor(2*1000);

privateTimertimer_;
privateHashMapfiles_;//File->Long
privateListfileEntrys=newjava.util.concurrent.CopyOnWriteArrayList();
privateCollection>listeners_;//ofWeakReference(FileListener)

privatelongpollingInterval=10000;

publicstaticFileMonitorgetDefaultFileMonitor(){
returndefaultFileMonitor;
}

/**
*Createafilemonitorinstancewithspecifiedpollinginterval.
*
*@parampollingIntervalPollingintervalinmilliseconds.
*/
publicFileMonitor(longpollingInterval){
this.pollingInterval=pollingInterval;

files_=newHashMap();
listeners_=newArrayList>();

timer_=newTimer("FileMonitor",true);
timer_.schedule(newFileMonitorNotifier(),0,pollingInterval);
}

/**
*Stopthefilemonitorpolling.
*/
publicvoidstop(){
timer_.cancel();
timer_=null;
}

publicvoidstart(){
if(timer_==null){
timer_=newTimer(true);
timer_.schedule(newFileMonitorNotifier(),0,pollingInterval);
}
}

/**
*Addfiletolistenfor.Filemaybeanyjava.io.File(includinga
*directory)andmaywellbeanon-existingfileinthecasewherethe
*creatingofthefileistobetrepped.
*
*Morethanonefilecanbelistenedfor.Whenthespecifiedfileis
*created,modifiedordeleted,listenersarenotified.
*
*@paramfileFiletolistenfor.
*/
publicvoidaddFile(Stringid,Filefile){
if(!files_.containsKey(file)){

FileEntryentry=newFileEntry(id,file,file.exists()?file.lastModified():-1);
files_.put(file,entry);
}
}

/**
*添加监控文件实体。
*
*@paramfileEntry
*/
publicvoidaddFileEntry(FileEntryfileEntry){
if(!fileEntrys.contains(fileEntry)){
fileEntrys.add(fileEntry);
}
}

/**
*通过文件实体的标识判断监控文件实体是否存在。
*
*@paramid
*@return
*/
publicbooleanfileEntryExists(Stringid){
if(id==null){
returnfalse;
}

for(inti=0;i>i=listeners_.iterator();i.hasNext();){
WeakReferencereference=i.next();
FileListenerlistener=(FileListener)reference.get();
if(listener==fileListener){
return;
}
}

//UseWeakReferencetoavoidmemoryleakifthisbecomesthe
//solereferencetotheobject.
listeners_.add(newWeakReference(fileListener));
}

/**
*Removelistenerfromthisfilemonitor.
*
*@paramfileListenerListenertoremove.
*/
publicvoidremoveListener(FileListenerfileListener){
for(Iterator>i=listeners_.iterator();i.hasNext();){
WeakReferencereference=(WeakReference)i.next();
FileListenerlistener=(FileListener)reference.get();
if(listener==fileListener){
i.remove();
break;
}
}
}

/**
*Thisisthetimerthreadwhichisexecutedeverynmillisecondsaccording
*tothesettingofthefilemonitor.Itinvestigatesthefileinquestion
*andnotifylistenersifchanged.
*/
privateclassFileMonitorNotifierextendsTimerTask{
@Override
publicvoidrun(){
try{
for(Iteratori=fileEntrys.iterator();i.hasNext();){
try{
FileEntryentry=i.next();
if(entry==null||!entry.check()){
i.remove();
}
}catch(Throwablet){
t.printStackTrace();
System.out.println("执行文件监控发生错误:"+t.getMessage());
}
}

//Loopovertheregisteredfilesandseewhichhavechanged.
//Useacopyofthelistincaselistenerwantstoalterthe
//listwithinitsfileChangedmethod.
Collectionfiles=newArrayList(files_.keySet());

for(Iteratori=files.iterator();i.hasNext();){
Filefile=i.next();
try{
FileEntryfileEntry=files_.get(file);
longlastModifiedTime=fileEntry.getLastModified();
longnewModifiedTime=file.exists()?file.lastModified():-1;

//logger.debug(file.getAbsolutePath());
//logger.debug("{}=>{}",lastModifiedTime,newModifiedTime);
//Chekiffilehaschanged
if(newModifiedTime!=lastModifiedTime){
//logger.debug("filechanged{})",file.getAbsolutePath());
fileEntry.setLastModified(newModifiedTime);
//Registernewmodifiedtime
files_.put(file,fileEntry);

if(fileEntry.getFileListener()!=null){
fileEntry.getFileListener().fileChanged(fileEntry);
}else{
//Notifylisteners
for(Iterator>j=
listeners_.iterator();j.hasNext();){
WeakReferencereference=
(WeakReference)j.next();
FileListenerlistener=(FileListener)reference.get();

//Removefromlistiftheback-endobjecthasbeenGC'd
if(listener==null){
j.remove();
}else{
listener.fileChanged(fileEntry);
}
}
}
}
}catch(Throwablet){
if(file!=null){
t.printStackTrace();
System.out.println(
"filemonitorexecuteerror,file="+file.getAbsolutePath()+
t.getMessage());
}else{
System.out.println(
"filemonitorexecuteerror,file=null"+t.getMessage());
}
}
}
}catch(Throwablet){
System.out.println("执行文件监控发生错误"+t.getMessage());
}
}
}
}
packagecom.yx.demo.filemonitor;

/**
*FileListener
*
*@authoryx
*@date2019/12/210:55
*/
publicinterfaceFileListener{
/**
*
*@paramfileEntry
*/
publicvoidfileChanged(FileEntryfileEntry);
}

packagecom.yx.demo.filemonitor;

importjava.io.File;
importjava.lang.ref.WeakReference;
/**
*FileEntry
*文件Entry，如果FileEntry指定了FileListener，那么当文件发生变动时只触发指定的FileListener
*
*@authoryx
*@date2019/12/210:56
*/
publicclassFileEntry{
Stringid;
Filefile;
longlastModified;
FileListenerfileListener=null;
ObjectuserData;
WeakReference

Java实现文件监控器FileMonitor的实例代码

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