Share My Creation [Project Template] jRDC3 Server

jRDC3 Server Template​

Version: 3.60 (based on jRDC3 Server version 3.00)

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.