[#182] added convenience method for annotated interface, added tests

src/main/java/picocli/CommandLine.java

@@ -498,6 +498,34 @@ public static <T> T populateCommand(T command, String... args) {
         return command;
     }
 
+    /**
+     * <p>
+     * Convenience method that derives the command specification from the specified interface class, and returns an
+     * instance of the specified interface. The interface is expected to have annotated getter methods. Picocli will
+     * instantiate the interface and the getter methods will return the option and positional parameter values matched on the command line.
+     * </p><p>
+     * This is equivalent to
+     * </p><pre>
+     * CommandLine cli = new CommandLine(spec);
+     * cli.parse(args);
+     * return cli.getCommand();
+     * </pre>
+     *
+     * @param spec the interface that defines the command specification. This object contains getter methods annotated with
+     *          {@code @Option} or {@code @Parameters}.
+     * @param args the command line arguments to parse
+     * @param <T> the type of the annotated object
+     * @return an instance of the specified annotated interface
+     * @throws InitializationException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
+     * @throws ParameterException if the specified command line arguments are invalid
+     * @since 3.1
+     */
+    public static <T> T populateSpec(Class<T> spec, String... args) {
+        CommandLine cli = toCommandLine(spec, new DefaultFactory());
+        cli.parse(args);
+        return cli.getCommand();
+    }
+
     /** Parses the specified command line arguments and returns a list of {@code CommandLine} objects representing the
      * top-level command and any subcommands (if any) that were recognized and initialized during the parsing process.
      * <p>

src/test/java/picocli/CommandLineAnnotatedMethodImplTest.java

@@ -83,10 +83,10 @@ static class Objects {
         @Option(names = "-string") void setString(String val) { aString = val; }
         @Option(names = "-list")   void setList(List<String> val) { aList = val; }
 
-        @Option(names = "-map", type = {Integer.class, Double.class})
+        @Option(names = "-map")
         void setMap(Map<Integer, Double> val) { aMap = val; }
 
-        @Option(names = "-set", type = Short.class)
+        @Option(names = "-set")
         void setSortedSet(SortedSet<Short> val) { aSet = val; }
     }
 

src/test/java/picocli/CommandLineAnnotatedMethodSpecTest.java

@@ -107,10 +107,10 @@ interface Objects {
         @Option(names = "-list")
         List<String> getList();
 
-        @Option(names = "-map", type = {Integer.class, Double.class})
+        @Option(names = "-map")
         Map<Integer, Double> getMap();
 
-        @Option(names = "-set", type = Short.class)
+        @Option(names = "-set")
         SortedSet<Short> getSortedSet();
     }
 
@@ -189,4 +189,26 @@ public void testAnnotatedMutableFieldsOnInterfaceAreValid() {
             assertEquals("Invalid picocli annotation on interface field", ok.getMessage());
         }
     }
+
+    @Test
+    public void testPopulateSpec() {
+        Objects objects = CommandLine.populateSpec(Objects.class, "-b -y1 -s2 -i3 -l4 -f5 -d6 -bigint=7 -string abc -list a -list b -map 1=2.0 -set 33 -set 22".split(" "));
+        assertTrue(objects.aBoolean());
+        assertEquals(Byte.valueOf((byte) 1), objects.aByte());
+        assertEquals(Short.valueOf((short) 2), objects.aShort());
+        assertEquals(Integer.valueOf(3), objects.anInt());
+        assertEquals(Long.valueOf(4), objects.aLong());
+        assertEquals(5f, objects.aFloat(), 0.0001);
+        assertEquals(6d, objects.aDouble(), 0.0001);
+        assertEquals(BigInteger.valueOf(7), objects.aBigInteger());
+        assertEquals("abc", objects.aString());
+        assertEquals(Arrays.asList("a", "b"), objects.getList());
+        Map<Integer, Double> map = new HashMap<Integer, Double>();
+        map.put(1, 2.0);
+        assertEquals(map, objects.getMap());
+        Set<Short> set = new TreeSet<Short>();
+        set.add((short) 22);
+        set.add((short) 33);
+        assertEquals(set, objects.getSortedSet());
+    }
 }