Java Scripts

Scripts are written in pure Java and, thus, may access all resources of the machine Iotellect Server is running on, including:

  • Any in-memory objects

  • File system

  • Network and serial I/O

  • Console, logging, and even GUI

  • Multithreaded processing

Scripts are executed in the server JVM, and their permissions are not restricted in any way. See Script Security for more information.

Script Interface

Scripts are written in Java. Every script is a single Java class that must implement a Script interface:

public interface Script 
{
  public DataTable execute(ScriptExecutionEnvironment environment, DataTable parameters) throws ScriptException;
}

This interface declares a single execute() method that is called by Iotellect Server when a script is executed.

Execution Environment

Every script has access to an object implementing the ScriptExecutionEnvironment interface that is passed as an argument to the execute() method. Here is what the ScriptExecutionEnvironment interface looks like:

public interface ScriptExecutionEnvironment
{
  public abstract CallerController getCallerController();
  public abstract Context getScriptContext(); 
}

An instance of ScriptExecutionEnvironment provides access to an object implementing the CallerController interface (it is obtained by calling the getCallerController() method). This object incorporates the permissions of a user that initiated script execution. CallerController object is passed as an argument to most context-related operations (Get Context, Get/Set Variable, Call Function, Add/Remove Event Listener etc.).

When a script is launched automatically during server startup, its execution environment contains a system CallerController that suppresses all permission checking.

Context returned by getScriptContext() allows to the context tree and all its objects.

Developing Scripts

See Programming Guidelines section for common practices of developing Iotellect server scripts.

Script Template

When a new script is created, its text is not empty. It contains an auto-generated stub of a class implementing Script interface with an empty execute() method. Here is the default script text:

import com.tibbo.aggregate.common.context.*;
import com.tibbo.aggregate.common.datatable.*;
import com.tibbo.aggregate.common.script.*;

import com.tibbo.linkserver.*;
import com.tibbo.linkserver.context.*; 
import com.tibbo.linkserver.script.*;

public class %ScriptClassNamePattern% implements Script 
{
  public DataTable execute(ScriptExecutionEnvironment environment, DataTable parameters) throws ScriptException
  {
  }
}

Note, that %ScriptClassNamePattern% will be replaced by an auto-generated Java class name during compilation. Do not change this part of the script to avoid compilation problems.

After you've put some meaningful code inside the body of execute() method, you may try to execute a script. Note, that script is re-compiled by Java compiler upon every execution. Any compilation errors are reported to the user. See description of the Execute action for more information.

Script Example

Here is an example of a Java script that changes IP address of a hardware Device Server:

import com.tibbo.aggregate.common.context.*; 
import com.tibbo.aggregate.common.datatable.*; 
import com.tibbo.aggregate.common.script.*; 
import com.tibbo.linkserver.*; 
import com.tibbo.linkserver.context.*; 
import com.tibbo.linkserver.script.*; 
public class %ScriptClassNamePattern% implements Script
{
  public DataTable execute(ScriptExecutionEnvironment environment, DataTable parameters) throws ScriptException
   {
    try 
      {
       // Getting context of a Device Server Context
        con = environment.getScriptContext().getContextManager().get("users.admin.deviceservers.c1", environment.getCallerController());
        if (con == null)
        {
        throw new ScriptException("Device Server not available"); 
        } 
        // Getting IP address
        variable DataTable val = con.getVariable("IP_setting", environment.getCallerController());
        // Changing IP address
        val.rec().setValue("IP_setting", "192.168.1.235");
        // Writing new value of variable
        con.setVariable("IP_setting", environment.getCallerController(), val);
        // Rebooting Device Server
        con.callFunction("reboot", environment.getCallerController());
        return null;
        }
        catch (ScriptException ex)
        {
        throw ex; 
        } 
        catch (Exception ex) 
        { 
        throw new ScriptException(ex);
        }
    }
}

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