log4j configuration file error detection
I'开发者_如何学运维m currently writing a logger utilizing log4j. Once I load in a log4j.properties or a log4j.xml file, I was wondering if there was a way to detect if the logger configuration file is valid. If it isn't valid, I was hoping to load a default setting (that's located in another file) instead.
Thanks
We solved this problem by redirecting System.err before loading the configuration and checking if errors were logged to the stream:
class ConfigurationLoader {
class Log4jConfigStderrStream extends ByteArrayOutputStream {
private int lineCount;
private StringBuilder output;
private PrintStream underlying;
public Log4jConfigStderrStream(PrintStream underlying) {
this.lineCount = 0;
this.output = new StringBuilder("");
this.underlying = underlying;
}
@Override
public void flush() throws IOException {
String[] buffer;
synchronized (this) {
buffer = this.toString().split("\n");
super.flush();
super.reset();
for (int i = 0; i < buffer.length; i++) {
String line = buffer[i].replace("\n", "").replace("\r",
"");
if (line.length() > 0) {
this.lineCount++;
this.output.append(line);
this.output.append("\n");
}
}
}
}
public String getOutput() {
return this.output.toString();
}
public PrintStream getUnderlying() {
return this.underlying;
}
public boolean hasErrors() {
return this.lineCount == 0 ? false : true;
}
}
private String output;
public void flushOutput() {
if (!"".equals(this.output))
System.err.print(this.output);
}
public boolean loadConfiguration(String filename) {
Log4jConfigStderrStream confErr;
confErr = new Log4jConfigStderrStream(System.err);
System.setErr(new PrintStream(confErr, true));
LogManager.resetConfiguration();
DOMConfigurator.configure(filename);
System.setErr(confErr.getUnderlying());
this.output = confErr.getOutput();
return !confErr.hasErrors();
}
}
You can only try to check manually for a logger being existent or not.
http://svn.apache.org/viewvc/logging/log4j/trunk/src/main/java/org/apache/log4j/LogManager.java?view=markup
Like: LogManager.exists("your logger name");
Additionally you can check if your xml is valid or not with validating it against the DTD.
But what is the definition for a "valid" log file? If its only syntax based use DTD validation and check if the property file is in a good format.
If a file is valid if it has a specific constellation use the manual approach above.
Hope that helps, Christian
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