a simple PMD ruleset for SLF4J

This ruleset helps you to code with SLF4J.

what this project contains

This project has 2 sub modules.

ruleset

Simple PMD rules and default ruleset for SLF4J. You can use default ruleset easily with Maven like below.

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-pmd-plugin</artifactId>
	<version>2.7.1</version>
	<dependencies>
		<dependency>
			<groupId>jp.skypencil</groupId>
			<artifactId>RuleSet-for-SLF4J</artifactId>
			<version>0.4</version>
		</dependency>
	</dependencies>
	<configuration>
		<linkXRef>false</linkXRef>
		<sourceEncoding>UTF-8</sourceEncoding>
		<targetJdk>1.6</targetJdk>
		<rulesets>
			<ruleset>slf4j.xml</ruleset><!-- to use default ruleset for SLF4J -->
		</rulesets>
	</configuration>
</plugin>

If you want to use a part of these rules, you have to create your ruleset XML file. Sample ruleset XML file is here.

sonar-plugin

An plugin for Sonar. Please put this plugin (.jar) to your ${sonar.home}/extensions/plugin directory. You can command mvn package to build jar file, or download it from Maven central.

rules

Currently, we've provided 5 rules.

Don't pass other class to LoggerFactory

Given argument for LoggerFactory#getLogger(Class) is wrong. You have to provide the Class which you're coding.

class Foo {
    // You have to avoid passing Bar.class in Foo.class
    private final Logger bad = LoggerFactory.getLogger(Bar.class);
    // This is OK
    private final Logger logger = LoggerFactory.getLogger(Foo.class);
}

Don't publish Logger

Logger should be private.

class Foo {
    // You have to avoid publishing Logger
    public final Logger bad = LoggerFactory.getLogger(Foo.class);
    // This is OK
    private final Logger logger = LoggerFactory.getLogger(Foo.class);
}

Logger should be final

Logger should be final.

class Foo {
    // Logger should be final
    private Logger bad = LoggerFactory.getLogger(Foo.class);
    // This is OK
    private final Logger logger = LoggerFactory.getLogger(Foo.class);
}

Don't use static logger

Sometimes using non-static logger is better than using static one. See official FAQ for detail. If you want to keep your logger static, please use default logging rule instead.

class Foo {
    // Logger has to be non-static
    private final static Logger bad = LoggerFactory.getLogger(Foo.class);
    // This is OK
    private final Logger logger = LoggerFactory.getLogger(Foo.class);
}

Number of placeholder should be equal to number of argument

class Foo {
    private final Logger logger = LoggerFactory.getLogger(getClass());
    void method() {
        // this logging method has 2 placeholders, but only 1 parameter
        logger.info("{}, {}.", new Object[]{ "Hello" });
        // this is OK
        logger.info("{}, {}.", new Object[]{ "Hello", "World" });
    }
}

• supported from version 0.2
• this rule has a trouble, please try findbugs-slf4j instead.

limitation to parse

• the 1st argument of logging method should be a literal
• if the 2nd argument is array, it should be an array initializer like new Object[]{ ... }

history

0.1

• first release

0.2

• added Number of placeholder should be equal to number of argument rule

0.3

• refactored
• downgrade XML schema to avoid warning in Eclipse (issue #1)
• added a test case and fixed a bug about exception which is out of CLASSPATH (issue #2)

0.4

• fixed wrong description for Don't use static logger rule
• fixed NPE (issue #3)

copyright and license

Copyright 2012 Kengo TODA (eller86)

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.