log4j

I have a large web project that uses log4j directly, together with many 3rd-party libraries and a mix of logging libraries. our code base - uses log4j directly. Hibernate - uses slf4j, and the slf4j-log4j binding. Spring - uses commons-loggings. Thus, it uses the jcl-over-slf4j bridge api, slf4j itself, and slf4j-log4j binding. Other numerous libraries, using either commons loggings or log4j. I am considering migrating our own code base to slf4j api, but I am not sure if the benefits are strong enough and worth the effort. Currently I am aware of the following benefits: Cleaner api.

日 志，源于log，有航海日志的意思。指记录海员记录每天的行程，生活及发生的事件。在软件开发领域，用来监控代码中变量变化，跟踪 代码运行的轨迹，在开发环境中担当调试器作用，向控制台或文件输出信息。 几乎所有的软件开发语言（平台）都有自己的日志系统， java ，.net，ruby，php等。在 java 领 域，存在大量的日志组件， open-open 收 录了21个日志组件。 从 功能上讲，这些可以分为三类，一是日志工具类，它实现了日志的记录，格式化和级别的划分，代表为 logback，simplelog。二是日志系统，提供了完整的框架功能并实现了日志记录。代表为jul（jdk提供的日志框 架），log4j（apache开源项目）。三是抽象整合类，它提供了一组接口，完成日志功能，通过包装其他日志工具或系统来工作jcl（apache开 源组件），slf4j。 从历史上讲，log4j出现最早， Ceki Gülcü 是其创造者。自java1.4开始，jdk提供了 java .util.logging 类库，提供了一个完整的日志框架，在设计上要比log4j要更清晰。 这个时候，除此之外，还有一些其他日志组件， java 领域从来不缺少轮子，总是有人在发明轮 子，轮子多了，就会产生混乱，就会有人站出来，要一统江湖，于是，jcl，apache一个开源的日志组件诞生了

I am using a third party library (cannot modify it) that uses for logging system.out.println statements. The output shows fine in the console but I am not able to retrieve those information in the catalina[...].log file? Is it possible to send those to log4j? System.out.println() prints out to stdout. Therefore, if you want to see these statements in a log file, you can just redirect stdout where you want it in the Tomcat startup script. When running Tomcat on unixes, the console output is usually redirected to the file named catalina.out . The name is configurable using an environment

Given the Java argument evaluation mechanism , how does Log4j implement lazy evaluation when formatting the message with curly brackets "to avoid the cost of parameter construction" when log is disabled? e.g. logger.debug("Entry number: {} is {}", i, entry[i]); I guess what Log4j means, is that with the curly brackets, they avoid constructing a String when its not necessary (e.g. the Level is not Debug): With logger.debug("Entry number: " + i + " is " + String.valueOf(entry[i])); The String is always calculated even when its not logged. with logger.debug("Entry number: {} is {}", i, entry[i]);

in log4j I could specify a class in the properties file to log at the debug level like this: log4j.logger.com.mycompany.mypackage.ClassName=DEBUG How do I do this in log4j2? Note I still need to use the new property file (not xml or json). TIA As the log4j2 configuration documentation states As of version 2.4, Log4j now supports configuration via properties files. Note that the property syntax is NOT the same as the syntax used in Log4j 1. It then provides a substantial example for all types of configuration elements. Concerning your question, you need to specify your loggers in a loggers

There is a pattern that happens every now and then. I have a method called many times, and it contains this snippet: Foo foo = getConfiguredFoo(); if (foo == null) { logger.warn("Foo not configured"); foo = getDefaultFoo(); } Then my log file is cluttered with this warning a hundred times. I know I can grep it out, but I wonder if there is a better way to see this warning only once. Note: the duplication of messages is a correct behavior by default, so this is not about avoiding unintentional duplicate log message . I tagged my question as log4j, but I'm open to other java logging frameworks.

一、背景 　　最近由于项目的需要，我们把log4j 1.x的版本全部迁移成log4j 2.x 的版本，那随之而来的slf4j整合log4j的配置（ 使用Slf4j集成Log4j2构建项目日志系统的完美解决方案 ）以及log4j2配置文件的详解，就需要我们来好好聊一聊了。本文就专门来讲解下log4j2.xml配置文件的各项标签的意义。 二、配置全解 　　1.关于配置文件的名称以及在项目中的存放位置 　　　　log4j 2.x版本不再支持像1.x中的.properties后缀的文件配置方式，2.x版本配置文件后缀名只能为".xml",".json"或者".jsn". 　　　　系统选择配置文件的优先级(从先到后)如下： 　　　　　　(1).classpath下的名为log4j2-test.json 或者log4j2-test.jsn的文件. 　　　　　　(2).classpath下的名为log4j2-test.xml的文件. 　　　　　　(3).classpath下名为log4j2.json 或者log4j2.jsn的文件. 　　　　　　(4).classpath下名为log4j2.xml的文件. 　　　　　我们一般默认使用log4j2.xml进行命名。如果本地要测试，可以把log4j2-test.xml放到classpath，而正式环境使用log4j2.xml

I have crearte log4j.properties file like below: log4j.logger.org.hibernate=INFO, hb log4j.logger.org.hibernate.SQL=DEBUG log4j.logger.org.hibernate.type=TRACE log4j.logger.org.hibernate.hql.ast.AST=info log4j.logger.org.hibernate.tool.hbm2ddl=warn log4j.logger.org.hibernate.hql=debug log4j.logger.org.hibernate.cache=info log4j.logger.org.hibernate.jdbc=debug log4j.appender.hb=org.apache.log4j.ConsoleAppender log4j.appender.hb.layout=org.apache.log4j.PatternLayout log4j.appender.hb.layout.ConversionPattern=HibernateLog --> %d{HH:mm:ss} %-5p %c - %m%n log4j.appender.hb.Threshold=TRACE Can

So we have our J2EE application using Log4j like this public class CustomerController { private static Logger logger = Logger.getLogger(CustomerController.class); public CustomerService customerservice = null; public CustomerController() throws Exception { PropertyConfigurator.configureAndWatch("c:\log4j.property", 50000); customerservice = ServiceManagerSingleton.getCustomerServiceInstance(); } } This way we can change the log-level realtime. Very handy. Most of our classes are set up just like this controller. We use the singleton-pattern so that we only have one instance of eash class; one