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Modernizing IBM i (AS/400) with Java and JT400

By Nirmal Khatri posted yesterday

  

IBM i (AS/400) has been a trusted platform for decades, known for its security, stability, and scalability. It continues to run critical business processes at the core of many organizations. Today, however, businesses also demand speed, flexibility, and modern application experiences. 

Java provides these capabilities, offering a rich ecosystem for building web and mobile applications, seamless integration with modern frameworks but connecting Java with IBM i can be tricky. 
  

That is where JT400 comes in—a toolkit that makes integration easy, secure, and efficient. With JT400, you can access IBM i resources, run commands, call RPG programs, and work with databases—all using Java. Think of JT400 as the bridge between Java and IBM i. 

    

Key Features of JT400 

The key features of JT400 are as follows: 

  • Seamless Integration: Easily connect Java applications with IBM i systems without complex configurations. 

  • Platform Independence: Works across different operating systems, making your solution flexible. 

  • Simplified Development: Offers ready-to-use Java classes that reduce coding effort and speed up development. 

  • Enhanced Security: Built-in security features ensure safe communication between Java and IBM i. 

  • Performance Optimization: Designed for efficient operations, improving overall system performance. 

 

 

     

Prerequisites

Before using JT400, ensure your environment meets the required Java and IBM i prerequisites, as each release aligns with specific versions. 

  • JT400 10.x → Requires Java 1.1. Compatible with IBM i 7.2 or later. 

  • JT400 11.x → Requires Java 1.1. Compatible with IBM i 7.3 or later. 

  • JT400 20.x.y → Requires Java 7. Compatible with IBM i 7.3 or later. 
        

Ways to Add JT400 

  1. In Gradle project (add implementation in dependencies.) 

                      

  1. In the Maven project (add dependency in pom.xml) 

        

  1. In a normal Java project: Add the JAR file to the project's classpath. 

         

Connecting to IBM i 

Using the provided Java code, you can easily connect to an IBM i (AS/400) system. The code checks if the connection is successful and then disconnects safely. Error handling is included to manage any issues during the process. 

      

 

      

Calling RPG Programs (PCML) 

You can call RPG programs from Java using PCML (Program Call Markup Language). PCML defines the program parameters so Java can interact with IBM i programs easily. Make sure the PCML file matches the RPG program parameters exactly to avoid errors. JT400 provides APIs to run these programs smoothly. 

For further knowledge, please consider this blog: Seamlessly Integrate Java with RPG on IBM i 

      

Deploy Java on IBM i 

Here are the steps to deploy Java on IBM i: 

  • Upload the Java JAR file to the IBM i server using FTP. 

  • Submit a job to run the Java program using the appropriate command. 

                

 

                    

Benefits of Java and IBM i Integration 

  • Enhanced Data Access: Work with IBM i data easily. 
  • Cross-Platform Compatibility: Java runs everywhere. 
  • Web & Mobile Development: Build modern apps. 
  • Streamlined Processes: Improve business workflows. 
  • Rich Ecosystem: Use Java libraries and frameworks. 
  • Enterprise Support: Reliable and future ready. 

         

Security Considerations 

  • Use SSL/TLS for JT400 connections: Always configure SSL to encrypt data between Java applications and IBM i. 

  • Data Protection: Encrypt sensitive data at rest and in transit: Use IBM i's built-in encryption or Java libraries. Mask or tokenize sensitive fields 

  • Secure JT400 Usage Some JT400 APIs allow direct command execution on IBM i. Limit usage to safe, business approved classes to reduce risk. 

  • Session & Resource Management Always close JT400 connections after use to prevent resource leaks that could impact performance or availability. 

          

Conclusion 

Integrating Java with IBM i using JT400 is one of the easiest ways to modernize legacy systems without losing their reliability. JT400 provides a secure and efficient bridge between Java applications and IBM i resources, enabling you to run commands, call RPG programs, and perform database operations seamlessly. Whether you are building web applications, mobile solutions, or enterprise tools, JT400 makes the process simple and future ready. 

Modernization does not mean replacing your IBM i—it means enhancing it. And JT400 is the perfect tool to make that happen. 

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