# Project facets

Facets define characteristics and requirements for Java EE projects and are used as part of the runtime configuration.

When you add a facet to a project, that project is configured to perform a certain task, fulfill certain requirements, or have certain characteristics. For example, the EAR facet sets up a project to function as an enterprise application by adding a deployment descriptor and setting up the project's classpath.

You can add facets only to Java EE projects and other types of projects that are based on J2EE projects, such as enterprise application projects, dynamic Web projects, and EJB projects. You cannot add facets to a Java™ project or plug-in project, for example. Typically, a facet-enabled project has at least one facet when it is created, allowing you to add more facets if necessary. For example, a new EJB project has the EJB Module facet. You can then add other facets to this project like the EJBDoclet (XDoclet) facet. To add a facet to a project, see Adding a facet to a Java EE project.

Some facets require other facets as prerequisites. Other facets cannot be in the same project together. For example, you cannot add the Dynamic Web Module facet to an EJB project because the EJB project already has the EJB Module facet. Some facets can be removed from a project and others cannot.

Facets also have version numbers. You can change the version numbers of facets as long as you stay within the requirements for the facets. To change the version number of a facet, see Changing the version of a facet.

Related concepts
Enterprise application projects
Related tasks
Creating an enterprise application project
Creating an application client project
Creating a connector project
Adding a facet to a Java EE project
Changing the Java compiler version for a Java EE project
Changing the version of a facet