At a minimum, the Sonar plugin has to be applied to the project.

apply plugin: "sonar"

Unless Sonar is run locally and with default settings, it is also necessary to configure connection settings for the Sonar server and database.

sonar {
    server {
        url = "http://my.server.com"
    }
    database {
        url = "jdbc:mysql://my.server.com/sonar"
        driverClassName = "com.mysql.jdbc.Driver"
        username = "Fred Flintstone"
        password = "very clever"
    }
}

Project settings determine how the project is going to be analyzed. The default configuration works well for analyzing standard Java projects and can be customized in many ways.

sonar {
    project {
        coberturaReportPath = file("$buildDir/cobertura.xml")
    }
}

The sonar, server, database, and project blocks in the examples above configure objects of type SonarRootModel, SonarServer, SonarDatabase, and SonarProject, respectively. See their API documentation for further information.

The Sonar plugin is capable of analyzing a whole project hierarchy at once. This yields a hierarchical view in the Sonar web interface with aggregated metrics and the ability to drill down into subprojects. It is also faster and less likely to run into out-of-memory problems than analyzing each project separately.

To analyze a project hierarchy, the Sonar plugin needs to be applied to the top-most project of the hierarchy. Typically (but not necessarily) this will be the root project. The sonar block in that project configures an object of type SonarRootModel. It holds all global configuration, most importantly server and database connection settings.

apply plugin: "sonar"

sonar {
    server {
        url = "http://my.server.com"
    }
    database {
        url = "jdbc:mysql://my.server.com/sonar"
        driverClassName = "com.mysql.jdbc.Driver"
        username = "Fred Flintstone"
        password = "very clever"
    }
}

Each project in the hierarchy has its own project configuration. Common values can be set from a parent build script.

subprojects {
    sonar {
        project {
            sourceEncoding = "UTF-8"
        }
    }
}

The sonar block in a subproject configures an object of type SonarProjectModel.

Projects can also be configured individually. For example, setting the skip property to true prevents a project (and its subprojects) from being analyzed. Skipped projects will not be displayed in the Sonar web interface.

project(":project1") {
    sonar {
        project {
            skip = true
        }
    }
}

Another typical per-project configuration is the programming language to be analyzed. Note that Sonar can only analyze one language per project.

project(":project2") {
    sonar {
        project {
            language = "groovy"
        }
    }
}

When setting only a single property at a time, the equivalent property syntax is more succinct:

project(":project2").sonar.project.language = "groovy"

By default, the Sonar plugin will analyze the production sources in the main source set and the test sources in the test source set. This works independent of the project's source directory layout. Additional source sets can be added as needed.

sonar.project {
    sourceDirs += sourceSets.custom.allSource.srcDirs
    testDirs += sourceSets.integTest.allSource.srcDirs
}

Eventually, most configuration is passed to the Sonar code analyzer in the form of key-value pairs known as Sonar properties. The SonarProperty annotations in the API documentation show how properties of the plugin's object model get mapped to the corresponding Sonar properties. The Sonar plugin offers hooks to post-process Sonar properties before they get passed to the code analyzer. The same hooks can be used to add additional properties which aren't covered by the plugin's object model.

For global Sonar properties, use the withGlobalProperties hook on SonarRootModel:

sonar.withGlobalProperties { props ->
    props["some.global.property"] = "some value"
}

For per-project Sonar properties, use the withProjectProperties hook on SonarProject:

sonar.project.withProjectProperties { props ->
    props["some.project.property"] = "some value"
}

The Sonar documentation provides a complete list of Sonar properties. (Note that most of these properties are already covered by the plugin's object model.) For configuring third-party Sonar plugins, consult their documentation.

The Sonar plugin adds the following tasks to the project.