ttools: add some programmatic invocation example classes

ttools/src/main/uk/ac/starlink/ttools/example/Calculator.java

@@ -0,0 +1,41 @@
+package uk.ac.starlink.ttools.example;
+
+import java.io.IOException;
+import uk.ac.starlink.task.Task;
+import uk.ac.starlink.task.TaskException;
+import uk.ac.starlink.ttools.task.MapEnvironment;
+import uk.ac.starlink.ttools.task.Calc;
+
+/**
+ * Minimal example of invoking a stilts task programmatically
+ * using the parameter system.
+ *
+ * @author   Mark Taylor
+ * @since    3 Oct 2014
+ */
+public class Calculator {
+    public static void main( String[] args ) throws TaskException, IOException {
+
+        /* Get expression from command line. */
+        if ( args.length != 1 ) {
+            System.err.println( "\n   Usage: " + Calculator.class.getName()
+                                               + " <expression>\n" );
+            System.exit( 1 );
+        }
+        String expr = args[ 0 ];
+
+        /* Set up and populate an execution environment with parameter
+         * values. */
+        MapEnvironment env = new MapEnvironment();
+        env.setValue( "expression", expr );
+
+        /* Create and execute a task of the right kind with these parameters.
+         * The Calc class is the one used by the stilts calc command. */
+        Task calcTask = new Calc();
+        calcTask.createExecutable( env ).execute();
+
+        /* Retrieve the result from the environment, and output it. */
+        String result = env.getOutputText();
+        System.out.println( expr + "\t=\t" + result );
+    }
+}

ttools/src/main/uk/ac/starlink/ttools/example/Head10.java

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+package uk.ac.starlink.ttools.example;
+
+import java.io.IOException;
+import uk.ac.starlink.table.StarTable;
+import uk.ac.starlink.table.StarTableOutput;
+import uk.ac.starlink.task.Task;
+import uk.ac.starlink.task.TaskException;
+import uk.ac.starlink.ttools.task.MapEnvironment;
+import uk.ac.starlink.ttools.task.TablePipe;
+
+/**
+ * Minimal example of invoking a stilts table processing task
+ * programmatically using the parameter system.
+ *
+ * @author   Mark Taylor
+ * @since    3 Oct 2014
+ */
+public class Head10 {
+    public static void main( String[] args ) throws TaskException, IOException {
+
+        /* Get input table file name from the command line. */
+        if ( args.length != 1 ) {
+            System.err.println( "\n   Usage: " + Head10.class.getName() 
+                                               + " <table>\n" );
+        }
+        String fileName = args[ 0 ];
+
+        /* Set up and populate an execution environment
+         * with parameter values.  An alternative to setting the value
+         * of the "in" parameter with a string would be to use a StarTable
+         * object. */
+        MapEnvironment env = new MapEnvironment();
+        env.setValue( "in", fileName );
+        env.setValue( "cmd", "head 10" );
+
+        /* Create and execute a task of the right kind with these parameters. 
+         * The TablePipe class is the one used by the stilts tpipe command. */
+        Task task = new TablePipe();
+        task.createExecutable( env ).execute();
+
+        /* Retrieve the output table from the execution environment.
+         * The output parameter is "omode", which is the parameter of
+         * type ProcessingMode in the tpipe task. */
+        StarTable outTable = env.getOutputTable( "omode" );
+
+        /* Write the result to standard output. */
+        new StarTableOutput().writeStarTable( outTable, "-", "ascii" );
+    }
+}