LOG4J2-3407 Log4j 1.2 bridge Check for non-existent appender when parsing properties #761
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kennymacleod
commented
Feb 18, 2022
| if (className == null) { | ||
| LOGGER.debug("Appender \"" + appenderName + "\" does not exist."); | ||
| return null; | ||
| } |
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Without this null-check, there will be a NPE from the next line down.
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Remark also that Log4j 1.x behaves differently
- whenever any component has an empty property the error "Could not find value for key ..." is logged (cf. source code.
- then there is a message "Could not instantiate appender named ..." (cf. source code). This should probably be checked just before the return statement. Remark that appender instantiation can also fail if some other properties are missing (e.g.
Filefor the file appender).
kennymacleod
commented
Feb 18, 2022
| log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout | ||
| log4j.appender.CONSOLE.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n | ||
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| log4j.logger.org.apache.log4j.xml=trace, A1 |
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Here we have a logger referring to an appender (A1) that does not exist
kennymacleod
commented
Feb 18, 2022
| try (LoggerContext loggerContext = TestConfigurator.configure("target/test-classes/LOG4J2-3407.properties")) { | ||
| final Configuration configuration = loggerContext.getConfiguration(); | ||
| assertNotNull(configuration); | ||
| } |
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This test fails with an NPE without the fix
garydgregory
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ppkarwasz
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Mar 30, 2022
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This change will make
PropertiesConfigurationtolerant of attempts to resolve a non-existent Appender. See JIRA ticket for details.