Classes from required Eclipse plugins are missing when building with Maven - maven

Question

I want to do the simplest Maven build with Tycho, but couldn't get it working. My project has only one pom.xml file, there are no parent or sibling POMs.
When I run mvn clean install I get lots of compilation errors which entries such as:
[ERROR] /dir/file.java:[8,33] package org.eclipse.core.commands does not exist
This is how my POM file looks like:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mygroup</groupId>
<artifactId>myartifact</artifactId>
<version>1.0.0-SNAPSHOT</version>
<name>myartifact</name>
<description>Maven stuff</description>
<properties>
<tycho.version>0.20.0</tycho.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<luna-repo.url>http://download.eclipse.org/releases/luna</luna-repo.url>
<kepler-repo.url>http://download.eclipse.org/releases/kepler</kepler-repo.url>
</properties>
<repositories>
<repository>
<id>luna</id>
<url>${luna-repo.url}</url>
<layout>p2</layout>
</repository>
<repository>
<id>kepler</id>
<url>${kepler-repo.url}</url>
<layout>p2</layout>
</repository>
</repositories>
<build>
<sourceDirectory>src</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-eclipse-plugin</artifactId>
<version>2.9</version>
<configuration>
<pde>true</pde>
</configuration>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
<plugin>
<groupId>org.eclipse.tycho</groupId>
<artifactId>tycho-maven-plugin</artifactId>
<version>${tycho.version}</version>
<extensions>true</extensions>
</plugin>
<plugin>
<groupId>org.eclipse.tycho</groupId>
<artifactId>target-platform-configuration</artifactId>
<version>${tycho.version}</version>
<configuration>
<environments>
<environment>
<os>linux</os>
<ws>gtk</ws>
<arch>x86</arch>
</environment>
<environment>
<os>linux</os>
<ws>gtk</ws>
<arch>x86_64</arch>
</environment>
<environment>
<os>win32</os>
<ws>win32</ws>
<arch>x86</arch>
</environment>
<environment>
<os>win32</os>
<ws>win32</ws>
<arch>x86_64</arch>
</environment>
<environment>
<os>macosx</os>
<ws>cocoa</ws>
<arch>x86_64</arch>
</environment>
</environments>
</configuration>
</plugin>
</plugins>
</build>
</project>
This is how my manifest file looks like:
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: pluginname
Bundle-SymbolicName: pluginname;singleton:=true
Bundle-Version: 1.0.0.SNAPSHOT
Bundle-Activator: com.mygroup.pluginname.ui.Activator
Require-Bundle: org.eclipse.ui,
org.eclipse.core.runtime,
org.eclipse.core.resources,
org.eclipse.ui.ide,
org.apache.commons.io;bundle-version="2.0.1"
Bundle-RequiredExecutionEnvironment: JavaSE-1.7
Bundle-ActivationPolicy: lazy
Bundle-ClassPath: .
I don't really know what I am missing here.

Answer 1

Your project doesn't specify a packaging type, so it defaults to jar. For jar projects, Tycho doesn't do anything, so all your otherwise correct configuration has no effect.
To activate Tycho, you need to add the configuration
<packaging>eclipse-plugin</packaging>
Then, Tycho will resolve the build class path according to the dependencies you have declared in the OSGi manifest.
Note that Tycho doesn't use the maven-compiler-plugin, so after activating Tycho this configuration has no effect. Also, I have no experience with the maven-eclipse-plugin in combination with Tycho. Instead of that plugin, I would recommend to use M2Eclipse for importing the project in Eclipse.

Answer 2

You need to add a dependency for the set of libraries you are using in your source code.
Maven isn't being told to obtain or manage them, so Eclipse doesn't know they exist. When you are trying to import them in your source code and compile, it's generating the error you are seeing.
Ex:
<dependencies>
...
<dependency>
<groupId>org.eclipse.core</groupId>
<artifactId>commands</artifactId>
<version>3.3.0-I20070605-0010</version>
</dependency>
...
</dependencies>
See the eclipse repository for the info required for other libraries.
EDIT: To fix your SWT compilation error, follow the steps shown on the SWT-repo project's webpage. An example for the win32 Intel x86/x64 architecture:
<dependency>
<groupId>org.eclipse.swt</groupId>
<artifactId>org.eclipse.swt.win32.win32.x86_64</artifactId>
<version>4.4</version>
</dependency>
Change yours based on your platform.