# Configuring rules

Learn how to configure your rules directly from the ruleset XML.

## 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">
                  <value>150</value>
            </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 assignments must be enclosed in a `properties` element, which is itself inside a `rule` element.

Tip: The properties of a rule are documented with the rule, e.g. here for NPathComplexity. Note that assigning a value to a property that does not exist throws an error!

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.

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