Enable registration of custom Fix commands at runtime.

The Fix definition is parsed as soon as the Metafix instance is created, thus any custom Fix commands that are going to be used must be registered in the Metafix instance's registry at construction time.

Author: blackwinter

metafix/src/main/java/org/metafacture/metafix/Metafix.java

@@ -53,6 +53,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.function.BiConsumer;
+import java.util.function.Function;
 
 /**
  * Transforms a data stream sent via the {@link StreamReceiver} interface. Uses
@@ -119,7 +120,17 @@ public Metafix() {
      * @param vars the Fix variables as a Map
      */
     public Metafix(final Map<String, String> vars) {
-        init(vars);
+        this(m -> vars);
+    }
+
+    /**
+     * Creates an instance of {@link Metafix}.
+     *
+     * @param function an optional function that accepts the Metafix instance
+     *                 and returns the Fix variables as a Map, or {@code null}
+     */
+    public Metafix(final Function<Metafix, Map<String, String>> function) {
+        init(function);
         recordTransformer = null;
     }
 
@@ -143,7 +154,20 @@ public Metafix(final String fixDef) throws IOException {
      * @throws IOException if an I/O error occurs
      */
     public Metafix(final String fixDef, final Map<String, String> vars) throws IOException {
-        init(vars);
+        this(fixDef, m -> vars);
+    }
+
+    /**
+     * Creates an instance of {@link Metafix}.
+     *
+     * @param fixDef   the Fix definition
+     * @param function an optional function that accepts the Metafix instance
+     *                 and returns the Fix variables as a Map, or {@code null}
+     *
+     * @throws IOException if an I/O error occurs
+     */
+    public Metafix(final String fixDef, final Function<Metafix, Map<String, String>> function) throws IOException {
+        init(function);
 
         if (isFixFile(fixDef)) {
             fixFile = fixDef;
@@ -172,11 +196,22 @@ public Metafix(final Reader fixDef) {
      * @param vars   the Fix variables as a Map
      */
     public Metafix(final Reader fixDef, final Map<String, String> vars) {
-        init(vars);
+        this(fixDef, m -> vars);
+    }
+
+    /**
+     * Creates an instance of {@link Metafix}.
+     *
+     * @param fixDef   the Fix definition
+     * @param function an optional function that accepts the Metafix instance
+     *                 and returns the Fix variables as a Map, or {@code null}
+     */
+    public Metafix(final Reader fixDef, final Function<Metafix, Map<String, String>> function) {
+        init(function);
         recordTransformer = getRecordTransformer(fixDef);
     }
 
-    private void init(final Map<String, String> newVars) {
+    private void init(final Function<Metafix, Map<String, String>> function) {
         flattener.setReceiver(new DefaultStreamReceiver() {
 
             @Override
@@ -189,7 +224,12 @@ public void literal(final String name, final String value) {
 
         });
 
-        vars.putAll(newVars);
+        if (function != null) {
+            final Map<String, String> newVars = function.apply(this);
+            if (newVars != null) {
+                vars.putAll(newVars);
+            }
+        }
     }
 
     /**

metafix/src/test/java/org/metafacture/metafix/MetafixTest.java

@@ -315,6 +315,24 @@ public void shouldNotRegisterCommandWithoutClass() {
         Assertions.assertThrows(NullPointerException.class, () -> registry.registerCommand(name, clazz));
     }
 
+    @Test
+    public void shouldRegisterCommandInConstructor() {
+        final String name = "bla";
+        final Class<?> clazz = Once.class;
+
+        final Metafix metafix = new Metafix(m -> {
+            final FixRegistry registry = m.getRegistry();
+
+            Assertions.assertFalse(registry.isRegisteredCommand(name));
+            Assertions.assertTrue(registry.registerCommand(name, clazz));
+
+            return null;
+        });
+
+        final FixRegistry registry = metafix.getRegistry();
+        Assertions.assertTrue(registry.isRegisteredCommand(name));
+    }
+
     @FixCommand("test_command")
     private static class TestCommand1 implements FixFunction {