HierarchicalMap Tutorial - Intermediate Level
HierarchicalMap is an interface. So anyone can implement it. This tutorial is based on BasicHierarchicalmap, a reference implementation of HierarchicalMap.
Following subjects are covered in this tutorial:
Advanced Level12. .NET Interoperability
Working with HierarchicalMap in .Net is very simple, thanks to Jeroen Frijters with his IKVM project! Basically, all HierarchicalMap java classes were converted to .Net classes using ikvmc, a tool that compiles JVM's byte-code into CLR's byte-code. Some new classes were written in .Net to have more Microsoft fashioned behavior like ICollection, IDictionary, DictionaryEntry, Item Property and so on.
Following assemblies must be referenced to start using HierarchicalMap in .Net projects:
Note that there is no need of jar files during .Net execution. IKVM solution is not a wrapper for java classes. All the algorithms implemented in java is converted to CLR's byte-code and actually run as it was written in .Net native compiler.
Although converted classes can be used inside .Net project, like
org.dhmp.util.HierarchicalMap = new org.dhmp.util.BasicHierarchicalMap()
It is preferable to use .Net wrapper classes. Some of the differences between java implementation and .Net are listed below:
|Original (dhmp.dll)||.Net (dhmpms.dll)||Description|
|org.dhmp.util||Dhmp.Util||package org.dhmp is wrapped using namespace Dhmp|
|HierarchicalMap||IHierarchicalMap||IHierarchicalMap implements IDictionary|
|entrySet()||GetEnumerator()||.Net Enumerator is slightly different from java Iterator|
|MapInputStream||MapStreamReader||InputStream was converted to StreamReader|
|MapOutputStream||MapStreamWriter||OutputStream was converted to StreamWriter|
|BasicHierarchicalMap||BasicHierarchicalMap||Some classes name was unchanged|
The following snippet of code in C#, will create a data structure as in "2. Creating Structure" earlier presented in this tutorial. "using Dhmp.Util" must be declared in the source code:
Note that method name begins with capital letter and Item
Property, as in
address2["City"] = "São Paulo";, is equivalent to
address2.Put("City", "São Paulo");.
Iteration with map is also different from java.
IEnumerator is used instead of Iterator which is based on
MoveNext() method and
In .Net, there is a simpler way to iterate with entrySet:
Streaming HierarchicalMap from .Net to Java
Now, the most interesting part. Streaming HierarchicalMap between Java application and .Net application. Prepare the following code at java side:
Step1. Writing Server in Java
First, write a code for filling a HierarchicalMap:
Write a Main method to start a socket server:
Then, write a thread for processing accepted socket. This part is quite large and written as a single code just for showing how to stream HierarchicalMap.
The constructor of this class keeps the socket and fills a catalog, actually a HierarchicalMap, invoking the method "fillCatalog()" shown before. Then denormalize it using the algorithm presented at "5. Restructuring the Map".
The "run()" method implements the following algorithm:
Step2. Writing Client in .Net
Following snippet of code must be written in C#:
Now, start the server side and then run the client. The result will be:
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Converting .Net object to and from Java
Some objects like string and byte are automatically converted inside IKVM but other objects like DateTime, Decimal and even an integer (represented using System.Int32) must be converted to corresponding java object before streaming it. The assembly "dhmpdefaultcvt.dll" contains default conversor for most of primitive data types.
|.Net class||java class|
Writing custom converter is simple. Just implement the Dhmp.Util.IConverter interface under Dhmp.Util.Converter namespace. See below an example:
Note that class name must be the full Type name replacing "." by "_" with a literal "Cvt" as suffix. The resulting assembly name must finish with "cvt" like "myconvertercvt.dll" and must be placed within same directory where "dhmpdefaultcvt.dll" is located. The default converter is loaded as last converter inside internal cache. So any custom converter can override the converter class inside "dhmpdefaultcvt.dll". Though we do not encourage doing so nor writing complex object converter. Instead just exchange primitive types among different systems.
Continue to Advanced Level - Runtime schema validation