Configuring rules

Message and priority overriding

You can change a rule’s message by specifying a message attribute on the rule element. This will override the previous value and change the message the rule will print on the report.

Similarly, the priority of a rule can be changed via a nested element. Using priority, you can deactivate some rules based on a minimum priority threshold (set using the -min CLI option). Priority is an integer ranging from 1 to 5, with 1 being the highest priority.

Putting things together, the following rule reference lowers the priority of EmptyCatchBlock to 5, such that e.g. using the -min 4 CLI parameters will cause the rule to be ignored.

<rule ref="category/java/errorprone.xml/EmptyCatchBlock"
      message="Empty catch blocks should be avoided" >
      <priority>5</priority>
</rule>

Rule properties

Properties make it easy to customise the behaviour of a rule directly from the xml. They come in several types, which correspond to the type of their values. For example, NPathComplexity declares a property “reportLevel”, with an integer value type, and which corresponds to the threshold above which a method will be reported. If you believe that its default value of 200 is too high, you could lower it to e.g. 150 in the following way:

<rule ref="category/java/design.xml/NPathComplexity">
    <properties>
        <property name="reportLevel">150</property>
    </properties>
</rule>

Properties are assigned a value with a property element, which should mention the name of a property as an attribute. The value of the property can be specified either in the content of the element, like above, or in the value attribute, e.g.

<property name="reportLevel" value="150"/>

All property assignements must be enclosed in a properties element, which is itself inside a rule element.

Some properties take multiple values (a list), in which case you can provide them all by delimiting them with a delimiter character. It is usually a pipe (‘|’), or a comma (‘,’) for numeric properties, e.g.

 <property name="legalCollectionTypes"
           value="java.util.ArrayList|java.util.Vector|java.util.HashMap"/>

These properties are referred to as multivalued properties in this documentation.