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Showing content from http://pmd.sourceforge.net/pmd-5.1.0/rules/java/logging-jakarta-commons.html below:

Ruleset: Jakarta Commons Logging

The Jakarta Commons Logging ruleset contains a collection of rules that find questionable usages of that framework.

UseCorrectExceptionLogging

Since: PMD 3.2

To make sure the full stacktrace is printed out, use the logging statement with two arguments: a String and a Throwable.

//CatchStatement/Block/BlockStatement/Statement/StatementExpression
/PrimaryExpression[PrimaryPrefix/Name[starts-with(@Image,
concat(ancestor::ClassOrInterfaceDeclaration/ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/FieldDeclaration
[Type//ClassOrInterfaceType[@Image='Log']]
/VariableDeclarator/VariableDeclaratorId/@Image, '.'))]]
[PrimarySuffix/Arguments[@ArgumentCount='1']]
[PrimarySuffix/Arguments//Name/@Image = ancestor::CatchStatement/FormalParameter/VariableDeclaratorId/@Image]

Example(s):

public class Main {
   private static final Log _LOG = LogFactory.getLog( Main.class );
   void bar() {
     try {
     } catch( Exception e ) {
      _LOG.error( e ); //Wrong!
     } catch( OtherException oe ) {
      _LOG.error( oe.getMessage(), oe ); //Correct
     }
   }
}

ProperLogger

Since: PMD 3.3

A logger should normally be defined private static final and be associated with the correct class. Private final Log log; is also allowed for rare cases where loggers need to be passed around, with the restriction that the logger needs to be passed into the constructor.

     
//ClassOrInterfaceBodyDeclaration[FieldDeclaration//ClassOrInterfaceType[@Image='Log']
 and
 not(FieldDeclaration[@Final='true'][@Static='true'][@Private='true'][.//VariableDeclaratorId[@Image=$staticLoggerName]]
 //ArgumentList//ClassOrInterfaceType/@Image = ancestor::ClassOrInterfaceDeclaration/@Image)
 and
 not(FieldDeclaration[@Final='true'][@Private='true'][.//VariableDeclaratorId[@Image='log']]
 [count(.//VariableInitializer)=0]
 [ancestor::ClassOrInterfaceBody//StatementExpression[.//PrimaryExpression/descendant::*[@Image='log']][count(.//AllocationExpression)=0]]
 )]

Example(s):

 
public class Foo {

   private static final Log LOG = LogFactory.getLog(Foo.class);	   // proper way

   protected Log LOG = LogFactory.getLog(Testclass.class);			// wrong approach
}

This rule has the following properties:

Name Default Value Description staticLoggerName LOG Name of the static Logger variable GuardDebugLogging

Since: PMD 4.3

When log messages are composed by concatenating strings, the whole section should be guarded by a isDebugEnabled() check to avoid performance and memory issues.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.logging.GuardDebugLoggingRule

Example(s):

            
public class Test {
    private static final Log __log = LogFactory.getLog(Test.class);
    public void test() {
        // okay:
        __log.debug("log something");

        // okay:
        __log.debug("log something with exception", e);

        // bad:
        __log.debug("log something" + " and " + "concat strings");

        // bad:
        __log.debug("log something" + " and " + "concat strings", e);

        // good:
        if (__log.isDebugEnabled()) {
        __log.debug("bla" + "",e );
        }
    }
}

This rule has the following properties:

Name Default Value Description violationSuppressRegex Suppress violations with messages matching a regular expression violationSuppressXPath Suppress violations on nodes which match a given relative XPath expression. guardsMethods [] method use to guard the log statement logLevels [] LogLevels to guard GuardLogStatement

Since: PMD 5.1.0

Whenever using a log level, one should check if the loglevel is actually enabled, or otherwise skip the associate String creation and manipulation.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.logging.GuardLogStatementRule

Example(s):

 
 	// Add this for performance
	if (log.isDebugEnabled() { ...
 	    log.debug("This happens");

This rule has the following properties:

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