Jacada HostFuse

HostFuse breathes new life into your legacy systems, extending their reach and reusability. Using HostFuse, your legacy applications can be “service enabled” – that is, any and all functionality contained within an existing host application can be exposed as open standard Web services, callable from Websites, Self-service channels and applications. This process of service enablement is accomplished without requiring any modification of the application, or needing access to the source code, allowing for a rapid implementation cycle with minimal risk. Even better, the resulting transactions can be used to integrate the host application with Workspace.

With HostFuse, developers can capture data and business logic via the
screen interface to create reusable services that can be consumed by .Net, Java or mobile applications. HostFuse can “service enable” applications from IBM Mainframes, IBM System i (AS/400), UNIX and HP OpenVMS.


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You need HostFuse if…

Mainframe Automation Using RPA

  • You need to integrate multiple information sources (e.g. IBM Mainframe, AS/400, HP, Windows, Web) into a single composite application using industry standard web services
  • You need to integrate the host application with other systems, without changing host source code
  • You are implementing a Service Oriented Architecture (SOA) across the board and you want to include your legacy applications.
  • The cost of re-engineering the host application in order to integrate or modernize it is extremely expensive or unfeasible.

How Does It Work?

HostFuse is an application development tool and run-time server environment that allows you to create web services interfaces to legacy data without re-engineering the legacy applications.

The product’s point-and-click graphical modeling interface empowers developers to create these interfaces rapidly. There are 5 easy steps in the development cycle:

Jacada Hotfuse

Step 1: Navigate through the application in the Host System

Using HostFuse’s built-in emulator, you record trails of the screens to be used to build the transactions. These trails are linear (straight-line) recordings of all screens accessed, all keystrokes entered on each screen, and the keys used to transition between screens. The Map is then updated to include these trails. New trails can be recorded and added to the Map at any point.

Jacada HostFuseTrails


Step 2: Automatically Generate the Application “MAP”

Hostfuse analyzes the Trails and automatically delineates the business logic of the host application into logical Maps. It then:

  • Provides the flexibility to customize rules for screen recognition and screen combinations
  • Identifies input fields
  • Creates actions for screen-to-screen navigation
  • Warns about any unreachable screens in the recorded trails 

Step 3: Define the Data Model (Inputs/Outputs)

Once the Map is defined and HostFuse has learned how to identify and navigate between screens, you decide which fields on the screen should be used as input and output parameters to the Web Services. HostFuse lets you define the required data fields graphically with an easy point-and-click interface:

  • Data Templates identify data fields
  • Table Templates identify “repeating” data fields in a table

Hostfuse Identify

HostFuse is fully aware of host green screen formats and therefore supports sophisticated multi-columned layouts and uses table controls for tables that repeat over multiple pages. Using a powerful built-in Business Entity Editor, complex data structures can be set up to match the client data format requirements for input and output.

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Step 4: Create Methods and Web Services

This step creates Methods that will be called by Web, Java and .Net applications and groups them into services using HostFuse’s graphical modeling environment. The methods perform:

  • Application Integration Steps
    • Screen traversal, data and table input and retrieval
  • New Business Logic Steps
    • Invoke other Methods and Services
    • Conditional Logic (If-Then-Else)
    • Loops (While, For, doWhile)
    • Parallel step execution (Thread)
  • Data manipulation
    • Input and Output data mapping
    • Access to variables
    • Industry standard XPATH data manipulation
    • format transformations
    • relationships between different data types

jacada hostfuse relationships

Step 5: Deploy Services to the J2EE Application Server

The final step is to create, compile, and deploy the service. A service is simply a run-time container that contains the methods created. Once a service has been created, it can be compiled and deployed in a variety of ways:

  • HostFuse Run-Time is deployed as an EAR file on the application server.
  • Industry standard web services are created.
  • Supports and accelerates Enterprise-wide SOA initiatives.

Hostfuse Deploy

Benefits for Your Business


By not requiring programmatic access, applications are service-enabled via a graphical studio environment, reducing the development cycle to weeks not months. Any changes on the screen are easily identified and maintenance is minimal.

Low Risk

Part of the Fusion family, HostFuse enables organizations to implement significant process improvements without requiring any modification to existing business systems or infrastructure. By not modifying the application, risk is minimized, and by using existing functionality within the application, no risk is incurred trying to duplicate intricate business logic. This means a rapid, risk-free, non-intrusive approach to improving productivity with easily measured ROI.

Leverages investment in legacy applications

HostFuse allows legacy applications to be “service enabled” – that is, any and all functionality contained within an existing host application can be exposed as open standard Web services, without requiring any modification of the application, and no access to the source code is required. Access to the host machine is only at the application (user) level. In addition any host security mechanism can be leveraged as well.

SOA Enablement

The industry trend today is to deploy Service Oriented Architectures as an enterprise-wide initiative to allow companies to build composite applications — that is, applications that are rapidly assembled from pieces and parts of existing applications. As the inventory of available services within a company grows, the requirement for writing code or applications from scratch will diminish. Indeed, the full benefit of an SOA is only reached when existing services can be used, assembled and orchestrated into new composite applications. Composite application development provides for much faster delivery of applications and increased business value. The biggest challenge in moving to an SOA is not the implementation of the architecture, but the ability to rapidly provide services to be used within this framework. Applications in use today are not “SOA ready” and do not transform easily, if at all, into a set of reusable services. By using HostFuse, the organization is able to capture and reuse all the existing application functionality within the new SOA framework, without requiring changes to a single line of code or access or ownership to the existing applications. This allows the business to not only continue, but to increase the ROI on application development and software purchases. Complex business logic inherent in these applications and or processes can remain untouched, yet be reused by new composite applications and processes


Non-Invasive:  Does not require any changes to the host screens

HostFuse enables organizations to implement significant process improvements without requiring any modification to existing business systems or infrastructure. By not modifying the application, risk is minimized by not introducing possible defects, and by using existing functionality within the application, no risk is incurred trying to duplicate intricate business logic.

“Maps” the Host:  Development tool records host navigation with a built in emulator

The HostFuse tool allows you to create interfaces to legacy applications by mapping the legacy application screens, the navigational information required to traverse the through a sequence of screens, and the tags and fields included on each screen into JAVA services.  HostFuse contains a built-in 3270/5250/VTXXX emulator which enables development and run-time from one product.

Graphical IDE: Visual Tool with Drag and Drop Modeling and integrated debugging

Developers use the HostFuse graphical tool to encapsulate legacy functions—including data elements and screen navigations—as components. With over 15 years of experience in the field, HostFuse is the easiest and best product in its class.

jacada hostfuse drapdrop

Automated Error Handling:  Allows for error handling to be automated for known errors or the error messages can be returned to the client

Developing the successful Trail is easy. However, in many cases there are error messages on the screen, random popup windows or requirements for multiple key strokes. HostFuse has significant capabilities to analyze errors/messages and act upon them. HostFuse can automatically perform the right action upon an error or return it to the user with the WebService while maintaining the application state.

Service Enablement:  Industry standard web services are automatically generated

HostFuse generates Web Services which can be consumed both by Java and ASP.Net applications. This includes support for Web Services Description Language (WSDL) and Simple Object Access Protocol (SOAP).

HostFuse’s XML support provides for XML over HTTP and XML via the client specific interfaces (APIs).

J2EE Deployment: Deployed as an EAR/WAR file on a J2EE application server

For Java and J2EE environments, HostFuse supports Java Applications, Java Servlets, Java Beans, Java Server Pages, EJBs, and Web Services. HostFuse is deployed within application servers like WebSphere, WebLogic or Tomcat.

Access data on a variety of host systems, including IBM Mainframes and AS/400s, VAX/Open VMS, Solaris, and other ASCII hosts

HostFuse is used to integrate legacy applications which can be running on a mainframe, an AS/400, or UNIX host. For mainframe systems, HostFuse supports TN3270 and TN3270E model 2-5 terminal connections. For AS/400 systems, HostFuse uses TN5250 and supports both 80 column and 132 column displays. HostFuse can also be used to access other Telnet systems running on UNIX, DEC/VAX, and Data General platforms using VT100, VT220, VT320, and DG400 type protocols.

 jacada Hostfuse Legacy

Create new portal or web applications that contain business-critical mainframe functionality

HostFuse’s level of abstraction from the host enables you to create new applications that are independent of the host-application workflow, for real improvement of your business processes.

Advanced Data Transformation

HostFuse has extensive capabilities to manipulate legacy systems data and adapt it to another format. In addition, HostFuse enables XPATH data manipulation and to map the relationship between different data types.

jacada Hostfuse DataTrans