How log spring boot jar file exceptions

Question

When you create Tomcat embedded JAR file and install it on a server, how can access to the Exceptions? Recently my server and process stops suddenly and I do not know what is going on. I checked Windows Event viewer but could not find anything. Is there any place that exception writes for example on a file?

Answer 1

By default, Spring Boot will only log to the console and will not write log files. If you want to write log files in addition to the console output you need to set a logging.file or logging.path property (for example in your application.properties).

java -Dlogging.file=target/my_logfile.log -jar spring_boot_app.jar
or 
java -Dlogging.path=target/logs -jar spring_boot_app.jar
(Will create spring.log file inside target/logs)

Ref: http://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-logging.html#boot-features-logging-file-output

To make life easier you can use logback.xml or logback-spring.xml

Following is a sample of logback.xml. Include it inside src/main/resources directory.

<?xml version="1.0" encoding="UTF-8"?>

<configuration scan="true">
    <include resource="org/springframework/boot/logging/logback/base.xml"/>

<!-- The FILE and ASYNC appenders are here as examples for a production configuration -->

    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>logFile.%d{yyyy-MM-dd}.log</fileNamePattern>
            <maxHistory>90</maxHistory>
        </rollingPolicy>
        <encoder>
            <charset>utf-8</charset>
            <Pattern>%d %-5level [%thread] %logger{0}: %msg%n</Pattern>
        </encoder>
    </appender>

    <appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
        <queueSize>512</queueSize>
        <appender-ref ref="FILE"/>
    </appender>


    <!-- your project package -->
    <logger name="com.test" level="INFO"/>

    <!-- <logger name="javax.activation" level="WARN"/>
    <logger name="javax.mail" level="WARN"/>
    <logger name="javax.xml.bind" level="WARN"/>
    <logger name="ch.qos.logback" level="WARN"/>
    <logger name="com.codahale.metrics" level="WARN"/>
    <logger name="com.ryantenney" level="WARN"/>
    <logger name="com.sun" level="WARN"/>
    <logger name="com.zaxxer" level="WARN"/>
    <logger name="io.undertow" level="WARN"/>
    <logger name="io.undertow.websockets.jsr" level="ERROR"/>
    <logger name="org.apache" level="WARN"/>
    <logger name="org.apache.catalina.startup.DigesterFactory" level="OFF"/>
    <logger name="org.bson" level="WARN"/>
    <logger name="org.hibernate.validator" level="WARN"/>
    <logger name="org.hibernate" level="WARN"/>
    <logger name="org.hibernate.ejb.HibernatePersistence" level="OFF"/>
    <logger name="org.springframework" level="WARN"/>
    <logger name="org.springframework.web" level="WARN"/>
    <logger name="org.springframework.security" level="WARN"/>
    <logger name="org.springframework.cache" level="WARN"/>
    <logger name="org.thymeleaf" level="WARN"/>
    <logger name="org.xnio" level="WARN"/>
    <logger name="springfox" level="WARN"/>
    <logger name="sun.rmi" level="WARN"/>
    <logger name="liquibase" level="WARN"/>
    <logger name="LiquibaseSchemaResolver" level="INFO"/>
    <logger name="sun.rmi.transport" level="WARN"/> -->

    <contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator">
        <resetJUL>true</resetJUL>
    </contextListener>

    <root level="INFO">
        <appender-ref ref="CONSOLE"/>
        <appender-ref ref="FILE"/>
    </root>

</configuration>

Above configuration will generate the logs to the the working directory of the JAR file with the names like logFile.yyyy.MM.dd.log

Answer 2

You should add the application.properties file in your classpath and set logging properties there.

If the only change you need to make to logging is to set the levels of various loggers then you can do that in application.properties using the "logging.level" prefix, e.g.

logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR
logging.file=C:\myapplication.log

You can also set the location of a file to log to (in addition to the console) using "logging.file".

See here