Share My Creation [Project Template] jRDC3 Server

jRDC3 Server Template​

Version: 3.62 (based on jRDC3 Server version 3.01)

GitHub: https://github.com/pyhoon/jrdc3-server-template

Overview​

A B4J template for creating a jRDC3 remote database server — an HTTP-based middleware that bridges B4X client applications (B4A, B4i, B4J) with your database, exposing SQL operations through a simple binary-serialized protocol.

Note: Connections between clients and server are bi-directional.

Work with jRDC2 Client template and jRDC3 Client template.

 

[aeric]

Features​

• Multi-database support — SQLite, MySQL, MariaDB, MSSQL, PostgreSQL, Firebird, DBF
• Zero-config SQLite — works out of the box with a bundled sample database
• HTTP API — clients send DBCommand objects over HTTP and receive DBResult responses
• Batch transactions — execute multiple INSERT/UPDATE/DELETE statements atomically
• SSL/TLS — optional HTTPS with configurable keystore
• Auto-provisioning — creates tables and seed data on first run
• Health check — /test endpoint verifies database connectivity
• Status dashboard — browser-based UI at / with HTMX-powered auto-refresh
• Request log viewer — real-time request log via HTMX polling, shown in a modal
• Debug mode — hot-reload SQL queries from config file on each request
• 6 build configurations — one-click select the database driver in the IDE

 

[aeric]

Supported Databases​

Database	JDBC Driver	Download
SQLite	sqlite-jdbc-min-3.49.1.0	https://www.b4x.com/android/forum/threads/project-template-jrdc2-server.165712/#post-1018264 https://drive.usercontent.google.com/download?id=1YS9ldF64eMfQ8em4h6C_gxGpvEFGRMQO
MySQL	mysql-connector-j-9.3.0	https://repo1.maven.org/maven2/com/mysql/mysql-connector-j/9.3.0/mysql-connector-j-9.3.0.jar
MariaDB	mariadb-java-client-3.5.6	https://repo1.maven.org/maven2/org/...va-client/3.5.6/mariadb-java-client-3.5.6.jar
MSSQL	jtds-1.3.1 / mssql-jdbc-12.2.1	https://repo1.maven.org/maven2/net/sourceforge/jtds/jtds/1.3.1/jtds-1.3.1.jar https://repo1.maven.org/maven2/com/...jdbc/12.2.1.jre11/mssql-jdbc-12.2.1.jre11.jar
PostgreSQL	postgresql-42.6.0	https://repo1.maven.org/maven2/org/postgresql/postgresql/42.6.0/postgresql-42.6.0.jar
Firebird	jaybird-5.0.0.java11	https://repo1.maven.org/maven2/org/firebirdsql/jdbc/jaybird/5.0.0.java11/jaybird-5.0.0.java11.jar
DBF	javadbf-1.13.2 + dbschema-dbf-jdbc + H2	https://www.b4x.com/android/forum/threads/dbf-reading-visual-foxpro-dbf-using-jdbc.136840/ https://www.b4x.com/android/forum/threads/h2-database.132688/ https://repo1.maven.org/maven2/com/github/albfernandez/javadbf/1.13.2/javadbf-1.13.2.jar https://dbschema.com/download/dbschema_windows_10_2_1.zip https://github.com/h2database/h2database/releases/download/version-2.4.240/h2-2025-09-22.zip

Note: Please check vulnerabilities before download.
These versions are tested by me during development of jRDC2 Server Template. You can always download the newer versions.

 

[aeric]

Getting Started​

Using the template (end-user)​

1. Copy or install the .b4xtemplate file from release/ into your B4J Additional Libraries folder.
2. In B4J, create a new project using the jRDC3 Server template.
3. Select your database Build Configuration (SQLite is the default).
4. Open Files/config.properties and set your database connection details.
5. Press F5 (Run).
6. Visit http://127.0.0.1:17178/ to see the status dashboard.

Building the template (from source) using #Macros​

1. Clone jRDC3.b4j to $APPNAME$.b4j.
2. Open $APPNAME$.b4j in a new B4J windows.
   Remove #Macro Step 1 to Step 5 and close it.
3. Package the template to release/jRDC3 Server (3.60).b4xtemplate.
4. Copy the .b4xtemplate file to B4J's Additional Libraries directory.
5. Check the created template in target directory.

 

[aeric]

Configuration​

All settings are in Files/config.properties:

Section	Key	Default
Server	ServerPort	17178
Server	SSLPort	0 (disabled)
Server	DebugQueries	True
SQLite	SQLite.DBFile	sample.db
MySQL	MySQL.JdbcUrl	jdbc:mysql://localhost:3306/{DBName}
MSSQL	MSSQL.JdbcUrl	jdbc:sqlserver://localhost:1433;databaseName={DBName}
PostgreSQL	Postgresql.JdbcUrl	jdbc:postgresql://localhost:5432/{DBName}
Firebird	Firebird.JdbcUrl	jdbc:firebirdsql://localhost:3050/{DBName}
DBF	DBF.DBFDir	(directory of .dbf files)
SQL Queries	(per-database)	Predefined CRUD for tbl_category & tbl_products

To enable SSL, set SSLPort, SSL_KEYSTORE_FILE, and SSL_KEYSTORE_PASSWORD.

 

[aeric]

API Endpoints​

Endpoint	Method	Description
/	GET	Status dashboard (HTML)
/test	GET	Health check — returns DB connection status as HTML
/rdc	POST	Execute a DBCommand (query or batch) — returns DBResult
/log	GET	Returns recent request log entries as HTML (used by dashboard modal)

/rdc Protocol​

The /rdc endpoint accepts POST requests with a binary-serialized DBCommand payload:

• method=query2 — Execute a SELECT query, returns rows via B4XSerializator
• method=batch2 — Execute multiple DML statements in a single transaction

Both client and server share the DBCommand / DBResult type definitions.

 

[aeric]

Architecture​

┌──────────────┐      HTTP (B4XSerializator)       ┌──────────────────┐
│  B4A / B4i   │  ──────────────────────────────>  │  jRDC3 Server    │
│  / B4J App   │  <──────────────────────────────  │  (B4J / Java)    │
└──────────────┘                                   └────────┬─────────┘
                                                            │ JDBC
                                                            ▼
                                                   ┌──────────────────┐
                                                   │   Database       │
                                                   │  (SQLite/MySQL/  │
                                                   │   MSSQL/etc.)    │
                                                   └──────────────────┘

The server uses B4XSerializator for binary serialization, jserver for HTTP handling, and jsql for database access.

 

[aeric]

Modules​

Module	Responsibility
IndexHandler.bas	Serves the dashboard homepage (/) and health check (/test)
RDCHandler.bas	Processes /rdc requests — query and batch execution
RDCConnector.bas	Database connection management and SQL query loading
HttpsFilter.bas	Optional HTTP-to-HTTPS redirect filter
LogHandler.bas	Returns the last 50 request log entries at /log

 

[aeric]

Version: 3.60 (rev 3)
With "Request Log" button on Index page (bottom left). Clicking the button shows a modal dialog and list of requests.
The log caps at 50 entries (FIFO).

The list is auto-refreshes every 2s via HTMX while open.

Please download the update on post #1.

 

[Mashiane]

Supported Databases​

Database	JDBC Driver
SQLite	sqlite-jdbc-min-3.49.1.0
MySQL	mysql-connector-j-9.3.0
MariaDB	mariadb-java-client-3.5.6
MSSQL	jtds-1.3.1 / mssql-jdbc-12.2.1
PostgreSQL	postgresql-42.6.0
Firebird	jaybird-5.0.0.java11
DBF	javadbf-1.13.2 + dbschema-dbf-jdbc + H2

Perhaps include download locations for the drivers. This makes everything easy to find.

 

[aeric]

Differences from original jRDC3 Server​

1. LoadSQLCommands​

Private Sub LoadSQLCommands(Config As Map)
    Dim newCommands As Map
    newCommands.Initialize
    For Each k As String In Config.Keys
        If k.StartsWith("sql.") Then
            newCommands.Put(k, Config.Get(k))
        End If
    Next
    commands = newCommands
End Sub

Private Sub LoadSQLCommands
    mCommands.Initialize
    For Each Key As String In mConfig.Keys
        If Key.StartsWith(mDbType & ".SQL.") Or Key.StartsWith("SQL.") Then
            mCommands.Put(Key, mConfig.Get(Key))
        End If
    Next
End Sub

Check config.properties to find the differences.

 

[aeric]

Version: 3.61

What's New​

1. Change dependency to jServer5 library
2. Support jrdc3-client-template v3.61

Related topic:

[B4X] jRDC3 - remote database connector

This is version 3 of the beloved RDC / jRDC feature - a middleware server that makes it simple to safely connect clients and remote SQL database servers. This update simplifies the clients API (the previous API was implemented before Resumable Subs feature was fully implemented). The data...

www.b4x.com

 

[aeric]

Version: 3.62

What's New​

1. Minor updates in code, build configuration, config.properties
2. Use jServer (version 5)
3. Compile with B4J v10.7 Beta