Factory method for easier instantiation.

Bug 14831

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@463601 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/types/EnumeratedAttribute.java

@@ -54,6 +54,32 @@ public abstract class EnumeratedAttribute {
     }
 
     /**
+     * Factory method for instantiating EAs via API in a more 
+     * developer friendly way.
+     * @param clazz             Class, extending EA, which to instantiate
+     * @param value             The value to set on that EA
+     * @return                  Configured EA
+     * @throws BuildException   If the class could not be found or the value
+     *                          is not valid for the given EA-class.
+     * @see Bug-14831                          
+     */
+    public static EnumeratedAttribute getInstance(
+    		Class/*<? extends EnumeratedAttribute>*/ clazz, 
+    		String value) throws BuildException {
+		if (!EnumeratedAttribute.class.isAssignableFrom(clazz)) {
+	    	throw new BuildException("You have to provide a subclass from EnumeratedAttribut as clazz-parameter.");
+	    }
+		EnumeratedAttribute ea = null;
+	    try {
+	        ea = (EnumeratedAttribute)clazz.newInstance();
+	    } catch (Exception e) {
+	        throw new BuildException(e);
+	    }
+	    ea.setValue(value);
+	    return ea;
+	}
+
+	/**
      * Invoked by {@link org.apache.tools.ant.IntrospectionHelper IntrospectionHelper}.
      * @param value the <code>String</code> value of the attribute
      * @throws BuildException if the value is not valid for the attribute
@@ -111,7 +137,6 @@ public abstract class EnumeratedAttribute {
         return index;
     }
 
-
     /**
      * Convert the value to its string form.
      *
@@ -121,4 +146,4 @@ public abstract class EnumeratedAttribute {
         return getValue();
     }
 
-}
+}

src/tests/junit/org/apache/tools/ant/types/EnumeratedAttributeTest.java

@@ -24,9 +24,7 @@ import org.apache.tools.ant.BuildException;
 
 /**
  * JUnit 3 testcases for org.apache.tools.ant.EnumeratedAttribute.
- *
  */
-
 public class EnumeratedAttributeTest extends TestCase {
 
     private static String[] expected = {"a", "b", "c"};
@@ -49,7 +47,22 @@ public class EnumeratedAttributeTest extends TestCase {
                !(new TestNull()).containsValue("d"));
     }
 
-    public void testExceptions() {
+    public void testFactory() {
+		EnumeratedAttributeTest_Factory ea1 = (EnumeratedAttributeTest_Factory)EnumeratedAttribute.getInstance(
+			EnumeratedAttributeTest_Factory.class, 
+			"one");
+		assertEquals("Factory didnt set the right value.", ea1.getValue(), "one");
+		try {
+	    	EnumeratedAttributeTest_Factory ea2 = (EnumeratedAttributeTest_Factory)EnumeratedAttribute.getInstance(
+	        		EnumeratedAttributeTest_Factory.class, 
+	        		"illegal");
+	    	fail("Factory should fail when trying to set an illegal value.");
+		} catch (BuildException be) {
+			// was expected
+		}
+	}
+
+	public void testExceptions() {
         EnumeratedAttribute t1 = new TestNormal();
         for (int i=0; i<expected.length; i++) {
             try {
@@ -83,4 +96,5 @@ public class EnumeratedAttributeTest extends TestCase {
             return null;
         }
     }
+    
 }

src/tests/junit/org/apache/tools/ant/types/EnumeratedAttributeTest_Factory.java

@@ -0,0 +1,7 @@
+package org.apache.tools.ant.types;
+
+public class EnumeratedAttributeTest_Factory extends EnumeratedAttribute {
+	public String[] getValues() {
+		return new String[] { "one", "two", "three" };
+	}
+}