用java写服务程序时经常会涉及到监控某些配置文件,当配置文件发生变化时实时重新加载该文件的内容到内存.
实际上log4j里有现成的类FileWatchdog做了类似的工作.我们只需继承它,然后重写它的一些方法就可以了.
/**使用log4j的监控狗 */
public class IPAccessFileWatchdog extends FileWatchdog {
public IPAccessFileWatchdog(String filename){
super(filename);
}
public void doOnChange() {
List<String> list = IPAccessController.this.loadIPRule(new File(this.filename));
if (list != null) {
IPAccessController.this.ipRule = list.toArray(new String[list.size()]);
} else {
IPAccessController.this.ipRule = null;
}
LogLog.warn("ip access config load completed from file:" + filename);
}
}
}
public class IPAccessFileWatchdog extends FileWatchdog {
public IPAccessFileWatchdog(String filename){
super(filename);
}
public void doOnChange() {
List<String> list = IPAccessController.this.loadIPRule(new File(this.filename));
if (list != null) {
IPAccessController.this.ipRule = list.toArray(new String[list.size()]);
} else {
IPAccessController.this.ipRule = null;
}
LogLog.warn("ip access config load completed from file:" + filename);
}
}
}
FileWatchdog的代码也很简单,其实就是起一个线程,每隔固定的时间扫描一次监控的文件.我把代码也贴出来:
'
// Contributors: Mathias Bogaert
package org.apache.log4j.helpers;
import java.io.File;
import org.apache.log4j.helpers.LogLog;
public abstract class FileWatchdog extends Thread {
static final public long DEFAULT_DELAY = 60000;
protected String filename;
protected long delay = DEFAULT_DELAY;
File file;
long lastModif = 0;
boolean warnedAlready = false;
boolean interrupted = false;
protected
FileWatchdog(String filename) {
this.filename = filename;
file = new File(filename);
setDaemon(true);
checkAndConfigure();
}
public
void setDelay(long delay) {
this.delay = delay;
}
abstract
protected
void doOnChange();
protected
void checkAndConfigure() {
boolean fileExists;
try {
fileExists = file.exists();
} catch(SecurityException e) {
LogLog.warn("Was not allowed to read check file existance, file:["+
filename+"].");
interrupted = true; // there is no point in continuing
return;
}
if(fileExists) {
long l = file.lastModified(); // this can also throw a SecurityException
if(l > lastModif) { // however, if we reached this point this
lastModif = l; // is very unlikely.
doOnChange();
warnedAlready = false;
}
} else {
if(!warnedAlready) {
LogLog.debug("["+filename+"] does not exist.");
warnedAlready = true;
}
}
}
public
void run() {
while(!interrupted) {
try {
Thread.sleep(delay);
} catch(InterruptedException e) {
// no interruption expected
}
checkAndConfigure();
}
}
}
// Contributors: Mathias Bogaert
package org.apache.log4j.helpers;
import java.io.File;
import org.apache.log4j.helpers.LogLog;
public abstract class FileWatchdog extends Thread {
static final public long DEFAULT_DELAY = 60000;
protected String filename;
protected long delay = DEFAULT_DELAY;
File file;
long lastModif = 0;
boolean warnedAlready = false;
boolean interrupted = false;
protected
FileWatchdog(String filename) {
this.filename = filename;
file = new File(filename);
setDaemon(true);
checkAndConfigure();
}
public
void setDelay(long delay) {
this.delay = delay;
}
abstract
protected
void doOnChange();
protected
void checkAndConfigure() {
boolean fileExists;
try {
fileExists = file.exists();
} catch(SecurityException e) {
LogLog.warn("Was not allowed to read check file existance, file:["+
filename+"].");
interrupted = true; // there is no point in continuing
return;
}
if(fileExists) {
long l = file.lastModified(); // this can also throw a SecurityException
if(l > lastModif) { // however, if we reached this point this
lastModif = l; // is very unlikely.
doOnChange();
warnedAlready = false;
}
} else {
if(!warnedAlready) {
LogLog.debug("["+filename+"] does not exist.");
warnedAlready = true;
}
}
}
public
void run() {
while(!interrupted) {
try {
Thread.sleep(delay);
} catch(InterruptedException e) {
// no interruption expected
}
checkAndConfigure();
}
}
}