GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. It would be nice to remove the requirement for log4j with out loosing any of the benefits of logging, and still allowing the use of log4j for those that use it, while still opening the doors for others not using it to use what they already use maybe java.
Thanks for fixing this issue. I just noticed this problem in a project of mine, and was curious if there was any plans to backport this into a bug fix release. The main issue with explicitly specifying which implementation is that if there are two dependencies and both are pulling different slf4j implementations you get into a bind, and one gets randomly chosen.
What exactly did I do wrong mbap? If you want just send over a pull request with the fix. This change is only in the 6. I understand that the 6. To clarify my original post, what I was trying to say is that I use yavijava in one of my projects, which has this log4j dependency. Log4j is an implementation of the slf4j implementation.
SLF4J with Log4j example
The problem I have is that I have another dependency that pulls in a different slf4j implementation, specifically logback. What happens when both log4j and logback 2 different implementations of slf4j are in the classpath is that slf4j will print warnings and then randomly pick one of implementations that are in the classpath.
If there is no configuration for the randomly chosen logger implementation, then logging will just be a noop. TLDR;; yavijava brings in log4j which might conflict with loggers of projects that depend on yavijava. If your patch makes it into a sooner release than the 6. I am happy to send in a patch if the work is incomplete, but it looks like you handled all of it in a7efb Oh I see. I thought you were saying I might have done the wrong thing in the gradle file for how I declare the compile time dep.
I do not plan to back port that work into a 6. I do agree I shouldnt have done it this way to begin with by using log4j but I didnt know about slf4j when I did all the log4j stuff, and I think to change how the lib would work fundamentally like that is best done in a major release not a minor revision.
I would be open to cutting a separate release labeled as like 6. I guess if I did that I would have to be sure to patch 6. Ya I agree with it being a larger amount of work, and your solution would definitely work for me. I def don't want to create a maintenance headache for you though, but if you feel it wouldn't be too tough that would be great.
It only takes a minute to sign up. I have seen this question but does not answer me. It have a brand new project. Is it really an upgrade.
Should I use it in a project which will also have an API for other to extend upon? SLF4J is basically an abstraction layer. It is not a logging implementation. It means that if you're writing a library and you use SLF4J, you can give that library to someone else to use and they can choose which logging implementation to use with SLF4J e. It helps prevent projects from being dependent on lots of logging APIs just because they use libraries that are dependent on them. So, to summarise: SLF4J does not replace log4j, they work together.
Which one you use, is then decided at deployment timenot when you write your code. Best practice today is to use slf4j to for your own log statements, and then choose the appropriate backend for it. Here log4j. SLF4j can be configured to use log4j as a logging backend so they can work together. Sign up to join this community.
The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 8 years, 7 months ago. Active 6 years, 8 months ago. Viewed k times. Shahzeb Shahzeb 1 1 gold badge 4 4 silver badges 7 7 bronze badges. Active Oldest Votes. The Overflow Blog.
Featured on Meta. Feedback on Q2 Community Roadmap. Linked Related 4. Hot Network Questions.If you want to generate your logging information in a particular format based on a pattern, then you can use org.
PatternLayout to format your logging information. The PatternLayout class extends the abstract org. Layout class and overrides the format method to structure the logging information according to a supplied pattern. PatternLayout is also a simple Layout object that provides the following- Bean Property which can be set using the configuration file:.
The following table explains the characters used in the above pattern and all other characters that you can use in your custom pattern:.
By default, the relevant information is displayed as output as is. However, with the aid of format modifiers, it is possible to change the minimum field width, the maximum field width, and justification. Compile and run the above program. It would create a log. Previous Page.
Next Page. Previous Page Print Page. Used to output the category of the logging event. For example, for the category name "a. Used to output the fully qualified class name of the caller issuing the logging request.
SLF4J Vs Log4j
For example, for the class name "org. Used to output the date of the logging event. Used to output the number of milliseconds elapsed from the construction of the layout until the creation of the logging event. Used to output the NDC nested diagnostic context associated with the thread that generated the logging event.
The X conversion character is followed by the key for the MDC. Left pad with spaces if the category name is shorter than 20 characters. However, if the category name is longer than 30 characters, then truncate from the beginning. Right pad with spaces if the category name is shorter than 20 characters.
However, if category name is longer than 30 characters, then truncate from the beginning.You may also assume that these components will not switch to SLF4J in the immediate future. The figure below illustrates the idea. Please note that for source code under your control, you really should use the slf4j-migrator. The binary-based solutions described in this page are appropriate for software beyond your control.
This jar file is intended as a drop-in replacement for JCL version 1. You can immediately enjoy the benefits of SLF4J's reliability and preserve backward compatibility at the same time. Just replace commons-logging. The underlying logging framework can be any of the frameworks supported by SLF4J.
Often times, replacing commons-logging. Thus, if for some reason an existing application must use JCL, your part of that application can still code against the SLF4J API in a manner transparent to the larger application environment. On the other hand, slf4j-jcl. Indeed, slf4j-jcl. Please note that jcl-over-slf4j. SLF4J ship with a module called log4j-over-slf4j. It allows log4j users to migrate existing applications to SLF4J without changing a single line of code but simply by replacing the log4j.
The log4j-over-slf4j module contains replacements of most widely used log4j classes, namely org. Categoryorg. Loggerorg. Priorityorg. Levelorg. MDCand org.The following is a list of compile dependencies for this project. These dependencies are required to compile and run the application:.
The following is a list of runtime dependencies for this project. These dependencies are required to run the application:. The following is a list of test dependencies for this project. These dependencies are only required to compile and run unit tests for the application:. The following is a list of transitive dependencies for this project. Transitive dependencies are the dependencies of the project dependencies.
Project Licenses: Apache License, Version 2. Description: Apache Commons Lang, a package of Java utility classes for the classes that are in java. Project Licenses: Eclipse Public License 1. Description: This is the core API of hamcrest matcher framework to be used by third-party framework providers. This includes the a foundation set of matcher implementations for common operations.
Apache License, Version 2. Project Dependencies compile The following is a list of compile dependencies for this project. These dependencies are only required to compile and run unit tests for the application: GroupId ArtifactId Version Classifier Type Licenses junit junit 4. Hamcrest Core Description: This is the core API of hamcrest matcher framework to be used by third-party framework providers.
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I currently am starting a new Webapp running on tomcat 6 I have components using slf4j and components using commons logging I plan to use log4j 2. Now my questions are: - To which interface do I program my new classes? What's the preferred way to deploy the jars? If you're going to use SLF4J, program to that interface. It offers the most flexibility for underlying logging implementation.
The point of slf4j is to be an interface that you can program to, so in the future if you decide to switch to, say, logback, you won't have to rewrite your code.
The only reason imo to put JARs in the Tomcat libs directory is if they need to load a native library. Since Java won't allow you to load the same native library from two different classloaders, you need to put then in a common location.
But that doesn't apply here. Some people think of the lib directory as a way to save space. And avoiding lib means you avoid most of the hard-to-debug classloading issues. If not, and all you care about is dealing with code that uses Log4J internally, there's log4j-over-slf4jwhich will intercept Log4J calls.
Then you need to pick a framework, such as Logback. Please note that I have not used Log4J 2. With that being said, I would answer your questions as follows:. Learn more. How to use log4j 2. Asked 7 years, 1 month ago. Active 4 years, 10 months ago.
Viewed 23k times. Active Oldest Votes. To which interface do I program my new classes? Put them in your WAR. Haven't used log4j 2. But that should be available on the SLF4J site. As for keeping your configuration external so you can modify it on the fly: you can still do this, putting just the config file in the lib directory and nothing in the WAR.
It'll be found by a classpath scan from within the WAR. However, I much prefer using JMX to adjust logging levels. This solution does not use log4j2, but 1. I am using slf4j with log4j2 and using slf4j-api Kalpesh Soni Kalpesh Soni 4, 1 1 gold badge 34 34 silver badges 44 44 bronze badges.
It has a nice, simple API that is everything you will probably need from a logging framework. Plus, if you decide for some reason that you want to switch to logback or Log4J 1. Definitely put the jars in the application war. You should almost never put jars into the application server's lib directory. Otherwise, they will affect all web applications on that application server, not just yours.If you are a developer then you have written a logging statement frequently in your career.
We in this article have covered two of the most commonly used logging mechanism — Log4j and Slf4j. In this topic, we are going to learn about Slf4j vs Log4j.
The loggings can be categorized into various levels like trace, debug, info, error, fatal and several other modes. These loggings details are sharable to different platforms like other databases and file consoles. They also hold every kind of interaction details that a user had with the system either be transaction detail, information or also if something goes wrong I mean to say if the particular activity does not perform the execution.
Ssl4j is just an abstraction or it provides an abstraction layer and we are not using it whereas Log4j is a logging framework that has different implementations. Talking of the components within this two Sl4j does not have any components as such it has a list of implementations like logback or NOPloggers and several others whereas in case of log4j it has 3 main components within namely —. Talking of preferences we would like to say there is no direct comparison between ssl4j and log4j but there can be preferences based on particular situations and when to use either of them, follows below the list —.
Slf4j can be configured to use Log4j as a logging backend for working together but the later conversion of not possible. Logging is an essential part of application troubleshooting is concerned, it is a development parameter of finding issues during the development cycle. About logging, we have witnessed two crucial players i. Essentially they are used by developers for logging and have some specific usage guidelines. This is a guide to Slf4j vs Log4j. Here we discuss the Slf4j vs Log4j key differences with infographics and comparison table.
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Please provide your Email ID. Email ID is incorrect. The Slf4j is compatible with all its previous versions. A user can easily migrate from slf4j to any version without any issue. There are several hindrances as one has to look after for the migration, talking of the Log4j2 the backward compatibility is not possible. Libraries and embedded components should prefer ssl4j for their logging needs because these libraries do not have their choice of logging framework upon end-user.