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Seed.Execute

This method is invoked as a result of the CALLJAVA or a custom tag.

Syntax

public String 
Execute(FTValList vIn, 
        FTValList vOut)

Parameters

vIn

Input parameter. List of name/value pairs that appear as ARGUMENT tags in the CALLJAVA tag, or as attributes set in the custom tag.

vOut

Output parameter. List of name/value pairs that will appear as variables in the XML element upon return from the CALLJAVA tag. This is ignored when the method is called via a custom tag.

Description

When an XML element calls the CALLJAVA tag or calls a custom tag, Sites invokes the Seed.Execute method. The way this method behaves depends on whether it was triggered by CALLJAVA or by a custom tag.

Invoking the Seed Interface with CALLJAVA

When the Seed interface is invoked directly with CALLJAVA:

• The class implementing the Seed interface is instantiated every time it is called. This allows the implementing class to be written in a non-reentrant way. This can impact performance negatively, since the class is instantiated every time.

• Values are passed back to the calling Sites context by setting the value in the vOut FTValList. Elements of the FTValList are then turned into variables upon return from the CALLJAVA tag.

• There is no way to obtain a reference to the calling ICS context, so there is no way to access any of the Sites servlets.

• As a direct consequence of the previous point, there is no way to pass any complex values between the class and Sites. In particular, Sites lists cannot be accessed from the class, and lists created by the class cannot be returned to the Sites context.

Invoking the Seed Interface with a Custom Tag

When the Seed interface is invoked with a custom tag:

• The class implementing the Seed interface is instantiated only once. This requires that the class be completely re-entrant.

• Values that may be put into the vOut FTValList are not converted to variables. Variables are set using the Sites servlet.

• The following three parameters are added to the vIn FTValList by Sites when the custom tag is invoked:
  • _ICS: This is an ICS value that can be cast to an ICS object. This ICS object provides the Sites context, which allows access to the servlets provided by Sites.
  • _TAGNAME: the custom tag name used to invoke the class.
  • _CDATA: all the text found between the begin tag and the end custom tag.
• ICS methods are used to pass values between Sites and the class. The types of values handled include variables, session variables, properties, counters, and lists.

• The class and all classes it invokes must be fully re-entrant.

Returns

A string that will be inserted into the output stream at the position of the CALLJAVA tag. Null or empty strings are valid. If invoked via a custom tag, this string will be appended to any other output that may be streamed back by calls to Sites servlets, for example, by StreamEvalBytes ().

Example

The following example illustrates the use of Seed called from a custom tag:

import java.util.*;
import java.net.*;
import java.io.*;
import java.text.*;

import COM.FutureTense.XML.Template.Seed;
import COM.FutureTense.Interfaces.FTValList;
import COM.FutureTense.Interfaces.FTVAL;
import COM.FutureTense.Interfaces.ICS;

/** 
 **  This sample class just gets the Sites context and
 **  returns the tagname by which it was called in the variable 
 **  tagname.
 **/
 
public class Example implements Seed
{
    
  public Example()
  {
      // As a check that the class is getting created..
          //
          System.out.println("Example created.");
  }

  public String Execute(FTValList vIn, FTValList vOut)
  {
    ICS cs = null;
    String output = "";
    
    try
    {
      FTVAL obj = vIn.getVal("_ICS");
      cs = (ICS) obj.GetObj();
      String sTag = vIn.getValString("_TAGNAME");
      cs.SetVar("tagname", sTag);
    }
     catch
    {
      System.out.println("Example exception: " + e.getMessage());
    }
    return output;
  }
}

 

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