文档章节

How to log in Spring with SLF4J and Logback

perfectspr
 perfectspr
发布于 2014/11/19 16:21
字数 1641
阅读 1097
收藏 9

1. Introduction

1.1. Simple Logging Facade for Java(SL4J)

The  SLF4J serves as a simple facade or abstraction for various logging frameworks, such as java.util.logging, logback and log4j. SLF4J allows the end-user to plug in the desired logging framework at deployment time. Note that SLF4J-enabling your library/application implies the addition of only a single mandatory dependency, namely slf4j-api-x.x.x.jar.

1.2. Logback

From Logback’s official documentation:

“Logback is intended as a successor to the popular log4j project, picking up where log4j leaves off.

Logback’s architecture is sufficiently generic so as to apply under different circumstances. At present time, logback is divided into three modules, logback-core, logback-classic and logback-access.

The logback-core module lays the groundwork for the other two modules. The logback-classic module can be assimilated to a significantly improved version of log4j. Moreover, logback-classic natively implements the SLF4J API so that you can readily switch back and forth between logback and other logging frameworks such as log4j or java.util.logging (JUL).

The logback-access module integrates with Servlet containers, such as Tomcat and Jetty, to provide HTTP-access log functionality. Note that you could easily build your own module on top of logback-core.”

1.3.  Spring

Spring is using by default Jakarta Commons Logging, but in the blog post Logging Dependencies in Spring from Spring.io it says “if we could turn back the clock and start Spring now as a new project it would use a different logging dependency. Probably the first choice would be the Simple Logging Facade for Java (SLF4J)

2. Configuration

To use SLF4J with Spring you need to replace the commons-logging dependency with the SLF4J-JCL bridge. Once you have done that, then logging calls from within Spring will be translated into logging calls to the SLF4J API, so if other libraries in your application use that API, then you have a single place to configure and manage logging.

2.1. Spring

2.1.1. Exclude commons-logging

To switch off commons-logging, the commons-logging dependency mustn’t be present in the classpath at runtime. If you are using maven like me, you can simply exclude it from the spring-context artifact:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>${spring.version}</version>
    <exclusions>
       <exclusion>
          <groupId>commons-logging</groupId>
          <artifactId>commons-logging</artifactId>
       </exclusion>
    </exclusions>            
</dependency>


2.1.2. Required libraries

Because I am using LogBack, which implements SLF4J directly, you will need to depend on two libraries (jcl-over-slf4j and logback):

<!-- LogBack dependencies --> 
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>${logback.version}</version>
</dependency>
<dependency>                                    
    <groupId>org.slf4j</groupId>                
    <artifactId>jcl-over-slf4j</artifactId>     
    <version>${jcloverslf4j.version}</version>  
</dependency>

Note: You might also want to exclude the slf4j-api depedency from other external dependencies, besides Spring, to avoid having more than one version of that API on the classpath.

Code tip:
All dependencies required for the projects can be found on GitHub in the  pom.xml  file.

2.2. Logback

To configure Logback all you have to do is place the file logback.xml in the classpath.

2.1. logback.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <Pattern>.%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg %n
            </Pattern>
        </encoder>
        <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
            <level>TRACE</level>
        </filter>
    </appender>
      <appender name="dailyRollingFileAppender" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <File>c:/tmp/rest-demo.log</File>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- daily rollover -->
            <FileNamePattern>rest-demo.%d{yyyy-MM-dd}.log</FileNamePattern>
            <!-- keep 30 days' worth of history -->
            <maxHistory>30</maxHistory>            
        </rollingPolicy>
        <encoder>
            <Pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{35} - %msg %n</Pattern>
        </encoder>         
      </appender>
      <appender name="minuteRollingFileAppender" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- rollover every minute -->
            <FileNamePattern>c:/tmp/minutes/rest-demo-minute.%d{yyyy-MM-dd_HH-mm}.log</FileNamePattern>
            <!-- keep 30 minutes' worth of history -->
            <maxHistory>30</maxHistory>            
        </rollingPolicy>
        <encoder>
            <Pattern>%-4relative [%thread] %-5level %logger{35} - %msg %n</Pattern>
        </encoder>         
      </appender>      
    <logger name="org.codingpedia" additivity="false">
        <level value="DEBUG" />
        <appender-ref ref="dailyRollingFileAppender"/>
        <appender-ref ref="minuteRollingFileAppender"/>
        <appender-ref ref="consoleAppender" />
    </logger>
    <root>
        <level value="INFO" />
        <appender-ref ref="consoleAppender" />
    </root>
</configuration>

Logback uses appenders , which are components Logback delegates the task of writing logging events to. 

2.1.1. ConsoleAppender

As the name says it, this appender logs to the console. It has an encoder property - encoders are responsible for transforming an incoming event into a byte array and writing out the resulting byte array onto the appropriate OutputStream.

Note: Until logback version 0.9.19, many appenders relied on the Layout instances to control the format of log output. Since then encoders are the standard – encoders are assigned the type of ch.qos.logback.classic.encoder.PatternLayoutEncoder by default.

The PatternLayoutEncoder wraps instances of PatternLayout - this takes a logging event and returns a String, which you can customize by using PatternLayout’s conversion pattern.

From Logaback’s documentation:
The conversion pattern of PatternLayout is closely related to the conversion pattern of the printf() function in the C programming language. A conversion pattern is composed of literal text and format control expressions calledconversion specifiers. You are free to insert any literal text within the conversion pattern. Each conversion specifier starts with a percent sign ‘%’ and is followed by optional format modifiers, a conversion word and optional parameters between braces. The conversion word controls the data field to convert, e.g. logger name, level, date or thread name. The format modifiers control field width, padding, and left or right justification.”

You can find below a short explanation of the the conversion specifiers used in the example:

  • %d{HH:mm:ss.SSS} - Used to output the date of the logging event.

  • %thread- outputs the name of the thread that generated the logging event

  • %-5level - means the level of the logging event should be left justified to a width of five characters

  • %logger{36}  - outputs the name of the logger at the origin of the logging event. It takes an integer as parameter. This specifies the length the converter’s algorithm  will shorten the logger name to.

  • %msg – outputs the application-supplied message associated with the logging event.

  • %n – outputs the platform dependent line separator character or characters.

  • %relative – outputs the number of milliseconds elapsed since the start of the application until the creation of the logging event

The result looks something like this:

10:12:51.012 [qtp231719230-45] DEBUG o.c.d.r.util.LoggingResponseFilter

1

10:12:51.012 [qtp231719230-45] DEBUG o.c.d.r.util.LoggingResponseFilter

 or

102662 [qtp1790106082-48] DEBUG o.c.d.r.dao.PodcastDao.getPodcasts

1

102662 [qtp1790106082-48] DEBUG o.c.d.r.dao.PodcastDao.getPodcasts

2.1.2. RollingFileAppender

The RollingFileAppender extends FileAppender with the capability to rollover log files. In the example, the RollingFileAppender will log to a file named rest-demo.log file and, once a certain condition (every day and every minute) is met, change its logging target to another file.

There are two important sub-components that interact with RollingFileAppender. The first RollingFileAppender sub-component, namely RollingPolicy, is responsible for undertaking the actions required for a rollover. A second sub-component of RollingFileAppender, namely TriggeringPolicy, will determine if and exactly when rollover occurs. Thus, RollingPolicy is responsible for the what and TriggeringPolicy is responsible for the when.

To be of any use, a RollingFileAppender must have both a RollingPolicy and a TriggeringPolicy set up. However, if its  RollingPolicy also implements the TriggeringPolicy interface, then only the former needs to be specified explicitly – this is exactly the case in the example, where TimeBasedRollingPolicy is used. This assumes the responsibility for rollover as well as for the triggering of said rollover, by implementing both RollingPolicy and TriggeringPolicy interfaces.

In the example the rollover occurs daily and every minute.  For the “daily”-appender, the file property is set to rest-demo.log: During today (March 21th, 2014), logging will go to the file c:/temp/rest-demo.log. At midnight, the rest-demo.log will be renamed to c:/rest-demo.2014-03-21.log and a new c:/temp/rest-demo.log will be created and for the rest of March 22th logging output will be redirected to rest-demo.log.

Note:
The file property in 
RollingFileAppender (the parent of TimeBasedRollingPolicy) can be either set or omitted. By setting the file property of the containing FileAppender, you can decouple the location of the active log file and the location of the archived log files.

3. Integration in code

To use SLF4J in code is pretty easy – you just have to get a logger, and then on that logger you can log messages at the different logging levels (TRACE, DEBUG, INFO, WARN, ERROR).

For demonstration purposes I created a special logging filter LoggingResponseFilter (didn’t want the REST facade cluttered with logging code) in the REST content, that will log

  • input – the HTTP method used + the relative path called of the REST resource

  • output – a pretty print of the response entities in JSON format

package org.codingpedia.demo.rest.util;
import java.io.IOException;
import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.container.ContainerResponseContext;
import javax.ws.rs.container.ContainerResponseFilter;
import org.codehaus.jackson.map.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class LoggingResponseFilter
        implements ContainerResponseFilter {
    private static final Logger logger = LoggerFactory.getLogger(LoggingResponseFilter.class);
    public void filter(ContainerRequestContext requestContext,
            ContainerResponseContext responseContext) throws IOException {
        String method = requestContext.getMethod();
        logger.debug("Requesting " + method + " for path " + requestContext.getUriInfo().getPath());
        Object entity = responseContext.getEntity();
        if (entity != null) {
            logger.debug("Response " + new ObjectMapper().writerWithDefaultPrettyPrinter().writeValueAsString(entity));
        }
    }
}

So you I am just getting the “LoggingResponseFilter ” logger  and on that, I will log messages at DEBUG level and upwards.

Well, that’s it! I would like to use this opportunity once again to thank the people who have developed and documented these wonderful frameworks. To name a few Dave Syer, Ceki Gülcü, Sébastien Pennec, Carl Harris . Thank you guys and keep up the good work!

4. Resources

4.1. Source code

4.1. Codingpedia

4.3. Web


本文转载自:http://www.codingpedia.org/ama/how-to-log-in-spring-with-slf4j-and-logback/#2_Configuration

共有 人打赏支持
perfectspr
粉丝 5
博文 43
码字总数 1198
作品 0
大连
技术主管
Java混乱的日志体系(logback)(转)

作为一名 Java 程序员,日常开发工作中肯定会接触日志系统,但是众多的框架,包括 Log4j、Log4j2、Logback、Slf4j、Apache Common logging 等等,引用的 maven 依赖众多,到底可以去掉哪些,...

easonjim
2017/12/27
0
0
Java日志框架:SLF4J, Apache Common-Logging, Log4J和Logba

Log4j Apache的一个开放源代码项目,通过使用Log4j,我们可以控制日志信息输送的目的地是控制台、文件、GUI组件、甚至是套接口服务 器、NT的事件记录器、UNIX Syslog守护进程等;用户也可以控...

凯文加内特
2015/05/08
0
0
Failed to load class org.slf4j.impl.StaticLogger 的解决方案

在hibernate + spring + struts 框架下,布署在weblogic9下的时候报Failed to load class org.slf4j.impl.StaticLogger错误,最后问题解决。 分析问题,由于是找不包slf4j相应的jar包,因此是...

曾赛
2009/11/12
0
0
spring boot(8)默认日志logback配置

1 日志简介 Spring Boot使用Commons Logging记录所有内部日志,但是它将底层日志实现打开,为Java.Util.Logging,Log4J2和Logback提供默认配置。 在每个案例中,loggers都预先配置,以使用控...

刘胜球
2017/10/31
0
0
ClassCastException Log4jLoggerFactory LoggerContex

今天调试web项目,使用Spring+各种组件。 其中用到了slf4j-core,slf4j-simple,slf4j-api,logback-classic,slf4j-log4j12。。。 运行后报一下错误: SEVERE: Exception sending context ...

白凡
2014/01/14
0
1

没有更多内容

加载失败,请刷新页面

加载更多

storm drpc实例

序 本文主要演示一下storm drpc实例 配置 version: '2'services: supervisor: image: storm container_name: supervisor command: storm supervisor -c storm.......

go4it
28分钟前
0
0
官宣 | Chrome 70正式向所有HTTP网站发出红色“不安全”警告!

10月17日,坐拥10亿用户的Chrome浏览器正式上线70版本。作为第一个采用TLS1.3正式版的Chrome版本,在安全新功能方面,Chrome 70进一步升级了HTTP页面“不安全”显示标识,即当用户输入数据时...

亚洲诚信
29分钟前
4
0
mysql 数据类型及占用字节数

数字类型 TINYINT                           1 字节 SMALLINT                          2 个字节 MEDIUMINT                         3 个字节...

会游泳的鱼_
今天
6
0
高性能mysql:创建高性能的索引

性能优化简介 MySQL性能定义为完成某件任务所需要的时间量度,换句话说,性能即响应时间,这是一个非常重要的原则。我们通过任务和时间而不是资源来测量性能。数据库服务器的目的是执行SQL语...

背后的辛酸
今天
8
0
HTTP get、post 中请求json与map传参格式

import java.io.IOException;import java.net.URI;import java.net.URISyntaxException;import java.nio.charset.Charset;import java.util.ArrayList;import java.util.List;im......

寒风中的独狼
今天
9
0

没有更多内容

加载失败,请刷新页面

加载更多

返回顶部
顶部