.NET-Java Interoperability


Designing Interoperable Classes

C#

using GigaSpaces.Core.Metadata;

namespace MyCompany.MyProject.Entities
{
   [SpaceClass(AliasName="com.mycompany.myproject.entities.Person")]
   public class Person
   {
    private string _name;
    [SpaceProperty(AliasName="name")]
    public string Name
    {
        get { return this._name; }
        set { this._name = value; }
    }
   }
}

Java

package com.mycompany.myproject.entities;

   public class Person
   {
    private String name;

    public String getName()
    {
    return this.name;
    }

    public void setName(String name)
    {
        this.name = name;
    }
   }
}

Guidelines and Restrictions

The following guidelines and restrictions should be followed in order to enable platform interoperability:

  • The full class name (including package\namespace) in all platforms should be identical.

Since java packages use a different naming convention than .NET namespaces, it is recommended to use the SpaceClass(AliasName="") feature to map a .NET class to the respective java class.

  • The properties/fields stored in the space in all platforms should be identical.

In Java, only properties are serialized into the space. In .NET, both fields and properties are serialized, so you can mix and match them.

Since java properties start with a lowercase letter, whereas .NET properties usually start with an uppercase letter, it is recommended to use the SpaceProperty(AliasName="") feature to map a property/field name from .NET to java.

  • Only the types listed in the table below are supported. If one of your fields uses a different type, you can use the class only in a homogeneous environment.

Arrays of these types are supported as well. You can also use .NET enumerations, which are treated as their underlying .NET type. Java enums are not supported. If your class contains a field whose type is not in the table, you can use SpaceExclude to exclude it from the space. Some of the types have different characteristics in .NET and Java (signed\unsigned, nullable\not nullable, precision, etc.) This can lead to runtime exceptions (e.g. trying to store null in a .NET structure) or unexpected results (e.g. copying values between signed and unsigned fields).

Supported Types for Matching and Interoperability

The following types are supported by the space for matching and interoperability:

CLS C# VB.NET Java Description
System.Byte byte Byte byte 8-bit integer.1
Nullable<Byte> byte? Nullable(Of Byte) java.lang.Byte Nullable wrapper for byte.1
System.Int16 short Short short 16-bit integer.
Nullable<Int16> short? Nullable(Of Short) java.lang.Short Nullable wrapper for short.
System.Int32 int Integer int 32-bit integer.
Nullable<Int32> int? Nullable(Of Integer) java.lang.Integer Nullable wrapper for int.
System.Int64 long Long long 64-bit integer.
Nullable<Int64> long? Nullable(Of Long) java.lang.Long Nullable wrapper for long.
System.Single float Single float Single-precision floating-point number (32 bits).
Nullable<Single> float? Nullable(Of Single) java.lang.Float Nullable wrapper for float.
System.Double double Double double Double-precision floating-point number (64 bits).
Nullable<Double> double? Nullable(Of Double) java.lang.Double Nullable wrapper for double.
System.Boolean bool Boolean boolean Boolean value (true/false).
Nullable<Boolean> bool? Nullable(Of Boolean) java.lang.Boolean Nullable wrapper for boolean.
System.Char char Char char A Unicode character (16 bits).
Nullable<Char> char? Nullable(Of Char) java.lang.Character Nullable wrapper for char.
System.String string String java.lang.String An immutable, fixed-length string of Unicode characters.
System.DateTime Nullable<DateTime> DateTime DateTime? DateTime Nullable(Of DateTime) java.util.Date An instant in time, typically expressed as a date and time of day.2,3
System.Decimal Nullable<Decimal> decimal decimal? Decimal Nullable(Of Decimal) java.math.BigDecimal A decimal number, used for high-precision calculations.2,4
System.Guid Nullable<Guid> Guid Guid? Guid Nullable(Of Guid) java.util.UUID A 128-bit integer representing a unique identifier.2
System.Object object Object java.lang.Object Any object
  1. In .NET a byte is unsigned, whereas in java a byte is signed.
  2. These types can be either nullable or not nullable in .NET, whereas in java they are always nullable.
  3. In .NET a DateTime is measured in ticks (=100 nanoseconds) since 1/1/0001, whereas in java a Date is a measured in milliseconds since 1/1/1970.
  4. The types Decimal (.NET) and BigDecimal (java) have different precision and range (see .NET and java documentation for more details). In addition, be aware that serialization/de serialization of these types is relatively slow, compared to other numeric types. As a rule of thumb these types should not be used, unless the other numeric types precision/range is not satisfactory.

Java 8’s LocalDate, LocalTime, LocalDateTime are currently not interoperable with the .NET DateTime class.

Arrays and Collections support

The following collections are mapped for interoperability:

.NET Java Description
T[] E[] Fixed-size arrays of elements.
System.Collections.Generic.List<T>
System.Collections.ArrayList
System.Collections.Specialized.StringCollection
java.util.ArrayList Ordered list of elements.
System.Collections.Generic.Dictionary<K,V>
System.Collections.HashTable
System.Collections.Specialized.HybridDictionary System.Collections.Specialized.ListDictionary
java.util.HashMap Collection of key-value pairs.
System.Collections.Specialized.OrderedDictionary java.util.LinkedHashMap Ordered collection of key-value pairs.
System.Collections.Generic.SortedDictionary<K,V> java.util.TreeMap Sorted collection of key-value pairs.
System.Collections.Specialized.NameValueCollection System.Collections.Specialized.StringDictionary java.util.Properties Collection of key-value string pairs.1

In java, the Properties type allows the user to store keys and values which are not strings.