The application I am working with has log calls in the catch blocks auto-generated by NetBeans only and no other kind of logging:
Logger.getLogger(SomeClass.class.getName()).log(Level.SEVERE, null, ex);
What steps should be taken to redirect log output from the console to for example a text file?
I read Lars Vogel tutoriral http://www.vogella.com/tutorials/Logging/article.html and for the most part understand what he is doing, but apparently when he wanted to log an event, he would call a method from an instance of his own logger LOGGER.
NetBeans developers probably intended to auto-generate the log calls the way they did for a reason. Does their logging have to be replaced as in the tutorial, or can it be simply configured to use another logging destination?
My confusion stems from the fact that Logger.getLogger is a static method.
What steps should be taken to redirect log output from the console to for example a text file?
From the Java Logging Overview Examples:
public static void main(String[] args) {
Handler fh = new FileHandler("%t/wombat.log");
Logger.getLogger("").addHandler(fh);
Logger.getLogger("com.wombat").setLevel(Level.FINEST);
...
}
That example creates a wombat.log file in the temp directory.
Otherwise you can modify or specify a logging.properties entry to install a FileHandler. Here is a modified entry of the 'lib/logging.properties' located in your Java Home directory.
############################################################
# Global properties
############################################################
# "handlers" specifies a comma separated list of log Handler
# classes. These handlers will be installed during VM startup.
# Note that these classes must be on the system classpath.
# By default we only configure a ConsoleHandler, which will only
# show messages at the INFO and above levels.
#
#handlers= java.util.logging.ConsoleHandler
# To also add the FileHandler, use the following line instead.
handlers=java.util.logging.FileHandler, java.util.logging.ConsoleHandler
You can use the 'java.util.logging.config.file' system property on launch to specify alternate log configuration files.
if getLogger() is a static method, which executes without an instance of Logger class being created,
Contained in the Java Logging Overview listed above there is a link to the Java SE API Specification. That is the contract for how all this works.
If you look up Logger.getLogger you'll see:
Find or create a logger for a named subsystem. If a logger has already been created with the given name it is returned. Otherwise a new logger is created.
If a new logger is created its log level will be configured based on the LogManager configuration and it will configured to also send logging output to its parent's Handlers. It will be registered in the LogManager global namespace.
The getLogger method is creating or locating a logger.
than where does addHandler() persist its result?
Handlers are store on the logger instance. The output type depends on the handler. The properties of each handler are described in the API spec.
The Logging Hierarchy and Record Forwarding might help you understand what is happening in the example code.
I have a simple question where I still can not find any answer. I want to log messages into a separate log file. I am using Java logging and not log4j.
I have the following class:
package org.imixs.workflow;
public class MailPlugin {
....
private static Logger logger = Logger.getLogger(MailPlugin.class.getName());
...
logger.info("some info...");
}
I am using GlassFish server. So I need to customize the settings in the logger.properties file from GlassFish.
What entries need to be added to the GlassFish logger.properties file to log all messages from my class 'MailPlugin' into a separate log file?
You can create a file appender and apply a Filter to it that only returns true when it the logging is coming from the MailPlugin
Say I have the following config for the java util logger I am using
handlers=java.util.logging.ConsoleHandler
.level=INFO
java.util.logging.ConsoleHandler.level=ALL
Now I want to restrict all classes that are in the package org.apache.solr.* to only log WARNING or higher levels. How to I do this through configuration only? ( similar to how we use category in log4j)
Try org.apache.solr.level=WARNING
By default slf4j, when using with jdk (slf4j-jdk14-1.6.1.jar), does not log debug messages.
How do I enable them?
I can’t find info neither in the official docs, the web or here on how to enable it.
I found some info on (failed though) creating a file in %JDK_HOME%/lib and defining the level there, in a config file.
However, I would like to define the level at compile-/run-time so I can both run and debug my app from my IDE with different logging levels.
Isn’t there some environment variable I can set, or VM arg?
Why do you think it does not log DEBUG messages?
If you mean that your log.debug(String) logging calls do not end up in java.util.logging log files, then I guess you have to configure the logging.properties configuration file to allow log messages at FINE level.
If you do not want to mess with the global %JRE_HOME%/lib/logging.properties, then you can just pass in -Djava.util.logging.config.file=logging.properties on the command line - this will force the logging system to look for that configuration file in the current directory.
Or use some other (programmatic) way to configure java.util.logging, see below for tutorial.
This has nothing to do with configuring SLF4J; in fact, SLF4J does not have any configuration, everything is configured by simply swapping JAR files.
For your reference:
JDK14LoggerAdapter
Java Logging API tutorial
If you are using slf4j SimpleLogger implementation read this.
There you can see that simpleLogger use INFO as default log level. You can change it by using a system property. This is usefull for non-production evironments:
static {
System.setProperty("org.slf4j.simpleLogger.defaultLogLevel", "trace");
}
You can add -Dorg.slf4j.simpleLogger.defaultLogLevel=debug to the VM options.
I just put my logging.properties file in my applications WEB-INF/classes file (or use the command line argument identified by Neeme Praks if you're not deploying in a war), and have the properties file open in eclipse so I can fine tune it to log the packages and at the level I'm interested in.
In the logging.properties file, you need to make sure that both the logger level and the handler level are set to the level you want. For example, if you want your output to go to the console, you need to have at least the following:
#logging.properties file contents
#Define handlers
handlers=java.util.logging.ConsoleHandler
#Set handler log level
java.util.logging.ConsoleHandler.level=FINE
#Define your logger level
com.company.application.package.package.level=FINE
#Assign your handler to your logger
com.company.application.package.package.handlers=java.util.logging.ConsoleHandler
You mentioned the slf4j-jdk14-1.6.1.jar. This provides the slf4j binding to java.util.logging. You need to have that in your classpath, but make sure you also have the slf4j api (slf4j-api-1.7.12.jar) in your classpath as well.
I find the example logging.properties file in this link useful for creating a variety of loggers and handlers, to give you fine-grained control over what logs go to the console, and what logs go to a file:.
And here's the slf4j manual.
if you are using lombok Slf4j
package com.space.slf4j;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* #author anson
* #date 2019/6/18 16:17
*/
#Slf4j
#RestController
public class TestController {
#RequestMapping("/log")
public String testLog(){
log.info("######### info #########");
log.debug("######### debug #########");
log.error("######### error #########");
return null;
}
}
application.yml
logging:
level:
root: debug
In runtime with the default configuration you can enable it with this code:
public class MyTest {
static {
Logger rootLogger = Logger.getLogger("");
rootLogger.setLevel(Level.ALL);
rootLogger.getHandlers()[0].setLevel(Level.ALL);
}
I'm using this code inside TestNG Unit.
Hi I'm using log4j api for logging purpose. When I use the following code to append to the appender, it's showing "addAppender() is undefined for the type Logger" error
FileAppender myAppender = new FileAppender(new PatternLayout(),"output.log");
Logger.getLogger(ConfigFileReader.class.getName()).addAppender(myAppender);
Can anyone tell me what should I do to debug this error?
Are you sure that you are importing the correct Logger class? A common error is to import java.util.Logger instead of the Logger from the log4j package.