Examination bonus point projects

Read about reading from files by using instances of java.io.BufferedReader.

Reading from standard input may be achieved by:

final BufferedReader source = new BufferedReader(new InputStreamReader(System.in));
...

You may create an executable jar archive using Maven. Starting from the mi-mavem-archetype-quickstart your pom.xml already contains a blueprint. Just insert your class containing the entry main(...) method (i.e. de.hdm_stuttgart.mi.sd1.grep.Grep in the current example) accordingly:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-shade-plugin</artifactId>
  <version>2.4.1</version>
  <configuration>
    <transformers>
      <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
        <manifestEntries>
          <Main-Class>de.hdm_stuttgart.mi.sd1.grep.Grep</Main-Class>
        </manifestEntries>
      </transformer>
    </transformers>
  </configuration>
  <executions>
    <execution>
      <phase>package</phase>
        <goals>
          <goal>shade</goal>
        </goals>
     </execution>
  </executions>
</plugin>

Running mvn install will create an executable jar file like e.g. ~/.m2/repository/de/hdm-stuttgart/mi/sd1/grep/0.9/grep-0.9.jar with “~” denoting your home directory:

> mvn install
[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building grep 0.9
[INFO] ------------------------------------------------------------------------

...
-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running de.hdm_stuttgart.mi.sd1.grep.CommandLineTest
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.757 sec

Results :

Tests run: 5, Failures: 0, Errors: 0, Skipped: 0

...
[INFO] Installing /home/goik/workspace/sd-project-summer/grep/target/grep-0.9.jar to 
     /home/goik/.m2/repository/de/hdm-stuttgart/mi/sd1/grep/0.9/grep-0.9.jar
...

Due to our <Main-Class>de.hdm_stuttgart.mi.sd1.grep.Grep</Main-Class> declaration in pom.xml this jar file is executable:

> java -jar ~/.m2/repository/de/hdm-stuttgart/mi/sd1/grep/0.9/grep-0.9.jar
No search string given
Usage: grep [-i] [-l] searchString [file 1] [file 2] ...

There are further simplification steps:

Testing requires capturing of output being generated by e.g. System.out.println(...) calls. Consider the following code writing the string “Hello World!” to standard output:

public class App {
    /**
     * @param args Unused
     */
    public static void main( String[] args ) {
        System.out.print( "Hello World!" );
    }
}

We want to set up a Junit test which captures the output to compare it with the expected string value "Hello World!". Following http://stackoverflow.com/questions/1119385/junit-test-for-system-out-println we redefine the standard output stream by a private instance of java.io.ByteArrayOutputStream. Due to Junit's @Before and @After annotations this instance replaces System.out during our tests:

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

import org.junit.After;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

/**
 * Unit test for simple App.
 */
public class AppTest {
   private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();

   @Before
   public void setUpStreams() {
       System.setOut(new PrintStream(outContent));
   }

   @After
   public void cleanUpStreams() {
       System.setOut(null);
       outContent.reset();
   }
   
    /**
     * Test method accessing output generated by System.out.println(...) calls.
     */
    @Test
    public void testApp() {
       App.main(new String[]{}); // Calling main() method printing "Hello World!"
       Assert.assertEquals("Hello World!", outContent.toString());
    }
}