An example of how to safely combine GeoTools component jars into a single (uber) jar. It uses the Maven shade plugin to properly combine the META-INF/services entries of the individual GeoTools jars.

pom.xml to create GeoTools uber-jar

<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>org.geotools</groupId>
    
    <artifactId>gt-uber</artifactId>
    
    <!-- The version of the GeoTools jars to combine -->
    <version>10.2</version>
    
    <packaging>jar</packaging>
    <name>Combined GeoTools jar</name>
    
    <description>
        Creates a single jar containing all GeoTools modules required by
        your project. You can then reference this jar from your project pom.xml
        rather than individual GeoTools jars.
    </description>
    
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <artifactSet>
                                <!--                                                           -->
                                <!-- We only want to include GeoTools dependencies and not the -->
                                <!-- large number of third party transitive dependencies       -->
                                <!--                                                           -->
                                <includes>
                                    <include>org.geotools:gt-*</include>
                                </includes>
                            </artifactSet>
                            <transformers>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                    <resource>META-INF/registryFile.jai</resource>
                                </transformer>
                            </transformers>
                            <createSourcesJar>true</createSourcesJar>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    
    <dependencies>
        <!--                                                   -->
        <!-- GeoTools modules to include in the uber-jar       -->
        <!-- (other moduels which are transitive dependencies  -->
        <!-- will also be pulled in)                           -->
        <!--                                                   -->
        <dependency>
            <groupId>${project.groupId}</groupId>
            <artifactId>gt-shapefile</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>${project.groupId}</groupId>
            <artifactId>gt-swing</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>${project.groupId}</groupId>
            <artifactId>gt-epsg-hsql</artifactId>
            <version>${project.version}</version>
        </dependency>
        
    </dependencies>
  
</project>