Question

Eclipse’s “problems” tab is displaying this error:

Description: Java compiler level does not match the version of the installed Java project facet.
Resource: groupping
Path: [blank]
Location: Unknown
Type: Faceted Project Problem (Java Version Mismatch)

My pom.xml has this setting:

<plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
            <source>1.6</source>
            <target>1.6</target>
        </configuration>
    </plugin>
</plugins>

Where else could the settings be mismatched?

Answer 1

Did you check your Project Properties -> Project Facets panel? (From that post)

A WTP project is composed of multiple units of functionality (known as
facets).

The Java facet version needs to always match the java compiler compliance
level.
The best way to change java level is to use the Project Facets
properties panel as that will update both places at the same time.

The “Project->Preferences->Project Facets” stores its configuration in this file, “org.eclipse.wst.common.project.facet.core.xml“, under the “.settings” directory.

The content might look like this

<?xml version="1.0" encoding="UTF-8"?>
<faceted-project>
  <runtime name="WebSphere Application Server v6.1"/>
  <fixed facet="jst.java"/>
  <fixed facet="jst.web"/>
  <installed facet="jst.java" version="5.0"/>
  <installed facet="jst.web" version="2.4"/>
  <installed facet="jsf.ibm" version="7.0"/>
  <installed facet="jsf.base" version="7.0"/>
  <installed facet="web.jstl" version="1.1"/>
</faceted-project>

Check also your Java compliance level: