Issue-374 Add unit tests & docs

py4j-java/src/test/java/py4j/commands/DirCommandTest.java

@@ -69,8 +69,8 @@ public class DirCommandTest {
 	{
 		// Defined in ExampleClass
 		ExampleClassMethods.addAll(Arrays.asList(new String[] { "method1", "method2", "method3", "method4", "method5",
-				"method6", "method7", "method8", "method9", "method10", "method11", "getList", "getField1", "setField1",
-				"getStringArray", "getIntArray", "callHello", "callHello2", "static_method", "getInteger",
+				"method6", "method7", "method8", "method9", "method10", "method11", "method12", "getList", "getField1",
+				"setField1", "getStringArray", "getIntArray", "callHello", "callHello2", "static_method", "getInteger",
 				"getBrokenStream", "getStream", "sleepFirstTimeOnly" }));
 		// Defined in Object
 		ExampleClassMethods.addAll(Arrays

py4j-java/src/test/java/py4j/examples/ExampleClass.java

@@ -37,6 +37,7 @@
 import java.nio.channels.Channels;
 import java.nio.channels.ReadableByteChannel;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 
 public class ExampleClass {
@@ -174,6 +175,20 @@ public BigInteger method11(BigInteger bi) {
 		return bi.add(new BigInteger("1"));
 	}
 
+	public int method12(HashSet<Object> set) {
+		Object element = set.stream().findAny().get();
+		if (element instanceof Long) {
+			return 4;
+		}
+		if (element instanceof Integer) {
+			return 1;
+		}
+		if (element instanceof String) {
+			return 2;
+		}
+		return 3;
+	}
+
 	@SuppressWarnings("unused")
 	private int private_method() {
 		return 0;

py4j-python/src/py4j/protocol.py

@@ -21,8 +21,6 @@
 from base64 import standard_b64encode, standard_b64decode
 
 from decimal import Decimal
-from enum import Enum
-from collections import namedtuple
 
 from py4j.compat import (
     long, basestring, unicode, bytearray2,
@@ -72,11 +70,12 @@
 ITERATOR_TYPE = "g"
 PYTHON_PROXY_TYPE = "f"
 
-class JavaType(Enum):
-    PRIMITIVE_INT = INTEGER_TYPE
-    PRIMITIVE_LONG = LONG_TYPE
-
-TypeInt = namedtuple('TypeInt', ['value', 'java_type'])
+class TypeHint:
+    """Enables users to provide a hint to the Python to Java converter specifying the accurate data type for a given value.
+    Essential to enforce i.e. correct number type, like Long."""
+    def __init__(self, value, java_type):
+        self.value = value
+        self.java_type = java_type
 
 # Protocol
 END = "e"
@@ -281,12 +280,12 @@ def get_command_part(parameter, python_proxy_pool=None):
 
     if parameter is None:
         command_part = NULL_TYPE
+    elif isinstance(parameter, TypeHint):
+        command_part = parameter.java_type + smart_decode(parameter.value)
     elif isinstance(parameter, bool):
         command_part = BOOLEAN_TYPE + smart_decode(parameter)
     elif isinstance(parameter, Decimal):
         command_part = DECIMAL_TYPE + smart_decode(parameter)
-    elif isinstance(parameter, TypeInt):
-        command_part = parameter.java_type.value + smart_decode(parameter.value)
     elif isinstance(parameter, int) and parameter <= JAVA_MAX_INT\
             and parameter >= JAVA_MIN_INT:
         command_part = INTEGER_TYPE + smart_decode(parameter)

py4j-python/src/py4j/tests/java_dir_test.py

@@ -30,6 +30,7 @@
     # overloaded
     "method10",
     "method11",
+    "method12",
     "getList",
     "getField1",
     "setField1",

py4j-python/src/py4j/tests/java_gateway_test.py

@@ -33,8 +33,8 @@
     set_default_callback_accept_timeout, GatewayConnectionGuard,
     get_java_class)
 from py4j.protocol import (
-    Py4JError, Py4JJavaError, Py4JNetworkError, decode_bytearray,
-    encode_bytearray, escape_new_line, unescape_new_line, smart_decode)
+    Py4JError, Py4JJavaError, Py4JNetworkError, TypeHint, LONG_TYPE,
+    decode_bytearray, encode_bytearray, escape_new_line, unescape_new_line, smart_decode)
 
 
 SERVER_PORT = 25333
@@ -607,7 +607,7 @@ def internal():
 class TypeConversionTest(unittest.TestCase):
     def setUp(self):
         self.p = start_example_app_process()
-        self.gateway = JavaGateway()
+        self.gateway = JavaGateway(auto_convert=True)
 
     def tearDown(self):
         safe_shutdown(self)
@@ -619,6 +619,8 @@ def testLongInt(self):
         self.assertEqual(4, ex.method7(2147483648))
         self.assertEqual(4, ex.method7(-2147483649))
         self.assertEqual(4, ex.method7(long(2147483648)))
+        self.assertEqual(4, ex.method7(TypeHint(1, LONG_TYPE)))
+        self.assertEqual(4, ex.method12({TypeHint(1, LONG_TYPE)}))
         self.assertEqual(long(4), ex.method8(3))
         self.assertEqual(4, ex.method8(3))
         self.assertEqual(long(4), ex.method8(long(3)))

py4j-web/advanced_topics.rst

@@ -726,6 +726,27 @@ Java methods slightly less efficient because in the worst case, Py4J needs to
 go through all registered converters for all parameters. This is why automatic
 conversion is disabled by default.
 
+.. _explicit_conversion:
+
+Explicit converting Python objects to Java primitives
+-----------------------------------------------------
+
+Sometimes, especially when ``auto_convert=True`` it is difficult to enforce correct type 
+passed from Python to Java. Then, ``TypeHint`` from ``py4j.protocol`` may be used. 
+``java_type`` argument of constructor should be one of Java types defined in ``py4j.protocol``.
+
+So if you have method in Java like:
+
+.. code-block:: java
+
+  void method(HashSet<Long> longs) {}
+
+Then you can pass arguments with correct type to this method with ``TypeHint``
+
+::
+
+  >>> set_with_longs = { TypeHint(1, LONG_TYPE), TypeHint(2, LONG_TYPE) }
+  >>> gateway.jvm.my.Class().method(set_with_longs)
 
 .. _py4j_exceptions: