One possibility is to run mvn package, it may bring some errors at run time depending on the Giraph-Hadoop version you're using. A safe (but dirty) alternative is the following.
Upload the graph:
$HADOOP_HOME/bin/hdfs dfs -copyFromLocal src/main/resources/graph.txt /user/giraph/input/graph.txt
Enter the correct folder:
cd src/main/java
Copy the Giraph examples jar (which contains all the dependencies needed to run the project)
cp /usr/local/giraph/giraph-examples/target/giraph-examples-1.3.0-hadoop2-for-hadoop-2.10.1-jar-with-dependencies.jar ./msmcs.jar
Compile the code with the proper dependencies
javac -cp /usr/local/giraph/giraph-examples/target/giraph-examples-1.3.0-hadoop2-for-hadoop-2.10.1-jar-with-dependencies.jar:$($HADOOP_HOME/bin/hadoop classpath) $(find . -name '*.java')
Merge the Giraph examples and the project jars
jar uf msmcs.jar it/unitn/msmcs/common/io it/unitn/msmcs/common/messages it/unitn/msmcs/common/writables it/unitn/msmcs/kecc
Remove old Giraph files (if it is not the first run)
$HADOOP_HOME/bin/hdfs dfs -rm /user/giraph/aggregatorValues_0
$HADOOP_HOME/bin/hdfs dfs -rm -r /user/giraph/output/connectivity
Run the project
$HADOOP_HOME/bin/hadoop jar msmcs.jar org.apache.giraph.GiraphRunner it.unitn.msmcs.kecc.InitComputation -op /user/giraph/output/connectivity -vof it.unitn.msmcs.common.io.ConnectivityOutputFormat -mc it.unitn.msmcs.kecc.ConnectivityMaster -aw org.apache.giraph.aggregators.TextAggregatorWriter -ca giraph.textAggregatorWriter.frequency=1 -eip /user/giraph/input/graph.txt -eif it.unitn.msmcs.common.io.ConnectivityInputFormat -w 1 -ca giraph.SplitMasterWorker=false,giraph.logLevel=error,giraph.useSuperstepCounters=false,input.k=3
Check the results
$HADOOP_HOME/bin/hdfs dfs -text /user/giraph/output/connectivity/p* | less