Implement #5064 (automatic type detection)

src/main/java/tools/jackson/databind/ObjectMapper.java

@@ -983,6 +983,28 @@ public <T> T readValue(JsonParser p, Class<T> valueType) throws JacksonException
         return (T) _readValue(_deserializationContext(p), p, _typeFactory.constructType(valueType));
     }
 
+    /**
+     * Factory method for constructing {@link ObjectReader} that will
+     * read or update instances automatically
+     */
+    public <T> ObjectReader forAutomaticType(T... reified) {
+        Type type = getClassOf(reified);
+        _assertNotNull("type", type);
+        return _newReader(deserializationConfig(), _typeFactory.constructType(type), null,
+                null, _injectableValues);
+    }
+
+    /**
+     * Utility method to get the class type from a varargs array.
+     *
+     * @param <T> the generic type
+     * @param array the varargs array
+     * @return the class of the array component
+     */
+    private static <T> Class<T> getClassOf(T[] array) {
+        return (Class<T>) array.getClass().getComponentType();
+    }
+
     /**
      * Method to deserialize JSON content into a Java type, reference
      * to which is passed as argument. Type is passed using so-called

src/test/java/tools/jackson/databind/ObjectReaderTest.java

@@ -53,6 +53,18 @@ public void testSimpleViaParser() throws Exception
         assertTrue(ob instanceof List<?>);
     }
 
+    @Test
+    public void testSimpleViaParserForAutomaticType() throws Exception
+    {
+        final String JSON = "[1]";
+        JsonParser p = MAPPER.createParser(JSON);
+        List<Integer> ob = MAPPER.forAutomaticType()
+                .readValue(p);
+        p.close();
+        assertTrue(ob != null);
+        assertEquals(1, ob.get(0));
+    }
+
     @Test
     public void testSimpleAltSources() throws Exception
     {