java实现文件变化监控的方法(推荐)

一. spring配置文件：application.xml

二. spring上下文加载监听器：SpringContextLoaderListener.class

import javax.servlet.ServletContextEvent;

import org.springframework.web.context.ContextLoaderListener;

public class SpringContextLoaderListener extends ContextLoaderListener{
  
  @Override
  public void contextInitialized(ServletContextEvent event) {
    super.contextInitialized(event);
    
    FileMonitor scanner = getScanner();
    
    // 启动目录扫描器
    scanner.start();
  }
  
  @Override
  public void contextDestroyed(ServletContextEvent event) {
    FileMonitor scanner = getScanner();
    
    // 关闭目录扫描器
    scanner.stop();
    
    super.contextDestroyed(event);
  }
  
  
  private FileMonitor getScanner() {
    return getCurrentWebApplicationContext().getBean(FileMonitor.class);
  }
}

三. web工程配置文件：web.xml

 
  contextConfigLocation
  
      classpath:application.xml
  
 
 
   com.web.SpringContextLoaderListener
 
  

四. 文件监测器

1. 接口：FileMonitor.class

import org.apache.commons.io.monitor.FileAlterationObserver;


public interface FileMonitor {

  
  void addObserver(FileAlterationObserver observer);
    
  
  void removeObserver(FileAlterationObserver observer);  
  
  
  Iterable getObservers();  
  
  
  void start();  
  
  
  void stop();  
  
  
  long getInterval();  
  
}

2. 实现类：FileMonitorImpl.class

import java.util.concurrent.ThreadFactory;

import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;
import org.apache.commons.lang3.concurrent.BasicThreadFactory;


public class FileMonitorImpl implements FileMonitor{

  private final FileAlterationMonitor monitor;
  
  
  private static final String MONITOR_THREAD_NAME = "File MonITOR Daemon";
    
  
  private static final boolean DAEMON = false;
  
  
  
  FileMonitorImpl(int interval, final FileAlterationObserver observer) {
    this(interval, observer, 
      new BasicThreadFactory.Builder().
   namingPattern(MONITOR_THREAD_NAME).daemon(DAEMON).build());    
  }  
  
  
  FileMonitorImpl(int interval, final FileAlterationObserver observer, 
final ThreadFactory factory) {    
    this.monitor = new FileAlterationMonitor(interval, new FileAlterationObserver[] { observer });
    monitor.setThreadFactory(factory);    
  } 
  
  
  @Override
  public void addObserver(FileAlterationObserver observer) {
    monitor.addObserver(observer);
  }

  
  @Override
  public void removeObserver(FileAlterationObserver observer) {
    monitor.removeObserver(observer);
  }

  
  @Override
  public Iterable getObservers() {
    return monitor.getObservers();
  }

  
  @Override
  public void start() {
    try {
      monitor.start();
    } 
    catch (Exception e) {
      e.printStackTrace();
    }
  }

  
  @Override
  public void stop() {
    try {
      monitor.stop();
    } 
    catch (Exception e) {
      e.printStackTrace();
    }
  }

  
  @Override
  public long getInterval() {
    return monitor.getInterval(); 
  }

}

五. 文件观察器

1. 接口：FileObserver.class

import java.io.File;

import org.apache.commons.io.monitor.FileAlterationListener;


public interface FileObserver {
  
  
  void addListener(final FileAlterationListener listener);
    
  
  void removeListener(final FileAlterationListener listener);
    
  
  Iterable getListeners();  
  
  
  void initialize() throws Exception;  
  
  
  void destroy() throws Exception;  
  
  
  File getDirectory();
  
  
  public FileFilter getFilter();
}

2. 实现类：FileObserverImpl.class

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOCase;
import org.apache.commons.io.monitor.FileAlterationListener;
import org.apache.commons.io.monitor.FileAlterationObserver;


public class FileObserverImpl extends FileAlterationObserver implements FileObserver{
  
  private static final long serialVersionUID = -7239227289538993830L;
  
  
  private final FileFilter filter;
    
  
  public FileObserverImpl(String dir, final FileFilter filter, 
    FileAlterationListener listener) {
    super(dir, filter, (IOCase) null);
    addListener(listener); 
    
    this.filter = filter;
    
    File directory = new File(dir);
    
    // 如果目录不存在
    if(!directory.exists()) {
      try {
 FileUtils.forceMkdir(directory);
      } 
      catch (IOException e) {
 e.printStackTrace();
      }
    }
    // 如果存在的是文件
    else if(directory.exists() && directory.isFile()) {
      try {
 FileUtils.forceDelete(directory);
 FileUtils.forceMkdir(directory);
      } 
      catch (IOException e) {
 e.printStackTrace();
      }
    }
  }
  
  
  @Override
  public void addListener(final FileAlterationListener listener) {
    super.addListener(listener);
  }

  
  @Override
  public void removeListener(final FileAlterationListener listener) {
    super.removeListener(listener);
  }

  
  @Override
  public Iterable getListeners() {
    return super.getListeners();
  }
  
  
  @Override
  public void initialize() throws Exception {
    super.initialize();
  }

  
  @Override
  public void destroy() throws Exception {
    super.destroy();
  }
  
  
  @Override
  public File getDirectory() {
    return super.getDirectory();
  }

  
  public FileFilter getFilter() {
    return filter;
  }  
}

六. 文件监听器：FileListener.class

import java.io.File;

import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationObserver;


public final class FileListener extends FileAlterationListenerAdaptor {
  
  
  @Override
  public void onFileCreate(File file) {
    // To do something
  }
  
  
  @Override
  public void onFileDelete(File file) {
    // To do something
  }
  
  
  @Override
  public void onFileChange(File file) {
    // To do something
  }
  
  
  @Override
  public void onStart(FileAlterationObserver observer) {
    // To do something
  }
  
  
  @Override
  public void onStop(FileAlterationObserver observer) {
    // To do something
  }
}

七. 文件过滤器

1. 接口：FileFilter.class

public interface FileFilter extends java.io.FileFilter {
  
  
  String[] getExtensions();
}

2. 实现类：FileFilterImpl.class

import java.io.File;

import org.apache.commons.io.FilenameUtils;


public class FileFilterImpl implements FileFilter{
  
  private String[] extensions;
  
  public FileFilterImpl(String... extensions) {
    this.extensions = extensions;
  }
  
  
  @Override
  public boolean accept(File pathname) {
    return FilenameUtils.isExtension(pathname.getName(), extensions); 
  }

  
  @Override
  public String[] getExtensions() {
    return extensions;
  }

}

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