an accessible Apache Kafka™ broker (a full cluster or a local Dockerized version)
IMPORTANT NOTE: till the first major version, all releases shall be considered not stable: this means the API public, or internal, can change without notice.
First project setup
Create a new simple empty project:
dotnet new console
Entity Framework Core provider for Apache Kafka™ is available on NuGet. Execute the following command to add the package to the newly created project:
dotnet add package MASES.EntityFrameworkCore.KNet
Edit Program.cs and replace the content with the following code:
using MASES.EntityFrameworkCore.KNet.Infrastructure;
using System.Collections.Generic;
namespace MASES.EntityFrameworkCore.KNet.Test
{
class Program
{
static void Main(string[] args)
{
KEFCore.CreateGlobalInstance();
using var context = new BloggingContext()
{
BootstrapServers = "MY-KAFKA-BROKER:9092",
ApplicationId = "MyAppId",
DbName = "MyDBName",
};
// add standard EFCore queries
}
}
public class BloggingContext : KafkaDbContext { }
public class Blog
{
public int BlogId { get; set; }
public string Url { get; set; }
public int Rating { get; set; }
public List<Post> Posts { get; set; }
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public int BlogId { get; set; }
public Blog Blog { get; set; }
}
}
KEFCore shall initialize the environment before any operation can be done. The initialization is done executing the following command at first stages of your application:
KEFCore.CreateGlobalInstance();
The previous command identify the JVM™ and start it, loads the needed libraries and setup the environment. Browsing the repository within the test folder there are some examples.
KEFCore accepts many command-line switches to customize its behavior, the full list is available at Command line switch of KNet.
JVM™ identification
One of the most important command-line switch is JVMPath and it is available in JCOBridge switches: it can be used to set-up the location of the JVM™ library if JCOBridge is not able to identify a suitable JRE/JDK installation.
If a developer is using KEFCore within its own product it is possible to override the JVMPath property with a snippet like the following one:
class MyKEFCore : KEFCore
{
public override string JVMPath
{
get
{
string pathToJVM = "Set here the path to JVM library or use your own search method";
return pathToJVM;
}
}
}
JCOBridge try to identify a suitable JRE/JDK installation within the system using some standard mechanism of JRE/JDK: JAVA_HOME environment variable or Windows registry if available.
However it is possible, on Windows operating systems, that the library raises an InvalidOperationException: Missing Java Key in registry: Couldn't find Java installed on the machine.
This means that neither JAVA_HOME nor Windows registry contains information about a default installed JRE/JDK: some vendors may not setup them.
If the developer/user encounter this condition can do the following steps:
On a command prompt execute set | findstr JAVA_HOME and verify the result;
If something was reported maybe the JAVA_HOME environment variable is not set at system level, but at a different level like user level which is not visible from the KEFCore process that raised the exception;
Try to set JAVA_HOME at system level e.g. JAVA_HOME=C:\Program Files\Eclipse Adoptium\jdk-11.0.18.10-hotspot\;
Try to set JCOBRIDGE_JVMPath at system level e.g. JCOBRIDGE_JVMPath=C:\Program Files\Eclipse Adoptium\jdk-11.0.18.10-hotspot\.
IMPORTANT NOTES:
One of JCOBRIDGE_JVMPath or JAVA_HOME environment variables or Windows registry (on Windows OSes) shall be available
JCOBRIDGE_JVMPath environment variable takes precedence over JAVA_HOME and Windows registry: you can set JCOBRIDGE_JVMPath to C:\Program Files\Eclipse Adoptium\jdk-11.0.18.10-hotspot\bin\server\jvm.dll and avoid to override JVMPath in your code
After first initialization steps, JVMPath takes precedence over JCOBRIDGE_JVMPath/JAVA_HOME environment variables or Windows registry