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Function library example

See the code snippet below for an example of a function library. For illustration purposes this code snippet contains only a handful of functions supported by the standard Date Function Library. 

  1. public class DateFunctionLibrary implements IFunctionLibrary
  2. {
  3.     // supported date functions
  4.     public static final String DAY_OF_WEEK_FUNCTION = "DAY_OF_WEEK";
  5.     public static final String CURRENT_YEAR_FUNCTION = "CURRENT_YEAR";
  6.  
  7.     public DateFunctionLibrary()
  8.     {
  9.     }
  10.  
  11.     /**
  12.      * @see https://docs.awareim.com/ref/p_m/getname_ifunction
  13.      */
  14.     @Override
  15.     public String getName()
  16.     {
  17.         return "DateFunctionLibrary";
  18.     }
  19.  
  20.     /**
  21.      * @see https://docs.awareim.com/ref/p_m/hasfunction
  22.      */
  23.     @Override
  24.     public boolean hasFunction(String functionName, int paramNmb)
  25.     {
  26.         if (paramNmb == 0)
  27.         {
  28.             return functionName.equalsIgnoreCase(CURRENT_YEAR_FUNCTION);
  29.         }
  30.         else if (paramNmb == 1)
  31.         {
  32.             return functionName.equalsIgnoreCase(DAY_OF_WEEK_FUNCTION);
  33.         }
  34.         return false;
  35.     }
  36.  
  37.     /**
  38.      * @see https://docs.awareim.com/ref/p_m/getavailablefunctions
  39.      */
  40.     @Override
  41.     public FunctionDescription[] getAvailableFunctions()
  42.     {
  43.         FunctionDescription[] results = new FunctionDescription[2];
  44.         results[0] = new FunctionDescription(CURRENT_YEAR_FUNCTION,
  45.             "Parameters: none\nReturn: current year as 4 digit Number");
  46.         results[1] = new FunctionDescription(DAY_OF_WEEK_FUNCTION,
  47.             "Parameters: attribute of Date type or expression producing Date" +
  48.             "\nReturn:  day of week of the provided date as Plain Text ('Monday', 'Tuesday' etc)");
  49.         return results;
  50.     }
  51.  
  52.     /**
  53.      * @see https://docs.awareim.com/ref/p_m/calculate
  54.      */
  55.     public Object calculate(String functionName, Object[] params, INodeHelper helper)
  56.     {
  57.         if (params == null || params.length == 0)
  58.         {
  59.             if (functionName.equalsIgnoreCase(CURRENT_YEAR_FUNCTION))
  60.             {
  61.                 Calendar cal = Calendar.getInstance();
  62.                 cal.setTime(new Date());
  63.                 return new Integer(cal.get(Calendar.YEAR));
  64.             }
  65.         }
  66.         else if (params != null && params.length == 1)
  67.         {
  68.             // a single parameter must be of DateHolder type
  69.             if (functionName.equalsIgnoreCase(DAY_OF_WEEK_FUNCTION))
  70.             {
  71.                 if (!(params[0] instanceof DateHolder))
  72.                     return null;
  73.                 Date date = TypeUtils.toDate((DateHolder) params[0]);
  74.                 Calendar cal = Calendar.getInstance();
  75.                 cal.setTime(date);
  76.                 SimpleDateFormat sdf = new SimpleDateFormat("E");
  77.                 return sdf.format(date);
  78.             }
  79.         }
  80.         return null;
  81.     }
  82.  
  83.     /**
  84.      * @see https://docs.awareim.com/ref/p_m/tosql
  85.      */
  86.     @Override
  87.     public String toSQL(String functionName, Collection parameters, ISQLBuilderHelper sqlHelper)
  88.         throws Exception
  89.     {
  90.         IDatabaseClientInterface dbi = sqlHelper.getDatabaseInterface();
  91.         if (parameters == null || parameters.size() == 0)
  92.         {
  93.             if (dbi instanceof MySQLClientInterface)
  94.             {
  95.                 if (functionName.equalsIgnoreCase(CURRENT_YEAR_FUNCTION))
  96.                 {
  97.                     return "YEAR(CURDATE())";
  98.                 }
  99.             }
  100.             else if (dbi instanceof MSSQLServerClientInterface)
  101.             {
  102.                 if (functionName.equalsIgnoreCase(CURRENT_YEAR_FUNCTION))
  103.                 {
  104.                     return "DATEPART (yy, GETDATE())";
  105.                 }
  106.             }
  107.         }
  108.         else if (parameters != null && parameters.size() == 1)
  109.         {
  110.             Iterator iter = parameters.iterator();
  111.             IArithmeticNode arNode = (IArithmeticNode) iter.next();
  112.             // representation of the argument
  113.             String dateArg = arNode.toSQL(sqlHelper);
  114.             if (dateArg == null || dateArg.length() == 0)
  115.                 return ""; // the expression won't be calculated
  116.             if (functionName.equalsIgnoreCase(DAY_OF_WEEK_FUNCTION))
  117.             {
  118.                 if (sqlFlavour == CommonConstants.SQL_FLAVOUR_TSQL)
  119.                     return "DATENAME(dw," + dateArg + ")";
  120.                 else if (sqlFlavour == CommonConstants.SQL_FLAVOUR_MYSQL)
  121.                     return "DAYNAME(" + dateArg + ")";
  122.             }
  123.         }
  124.         throw new UnsupportedSQLElementException(functionName);
  125.     }
  126.  
  127.     /**
  128.      * @see https://docs.awareim.com/ref/p_m/gettypeclass
  129.      */
  130.     @Override
  131.     public Class getTypeClass(String functionName, Collection params)
  132.     {
  133.         return Integer.class;
  134.     }
  135.  
  136.     /**
  137.      * @see https://docs.awareim.com/ref/p_m/getrequiredfactpatterns
  138.      */
  139.     @Override
  140.     public HashSet getRequiredFactPatterns(String functionName, Collection params)
  141.     {
  142.         return null;
  143.     }
  144. }