Examples of com.espertech.esper.plugin.PlugInAggregationMultiFunctionFactory

com.espertech.esper.plugin.PlugInAggregationMultiFunctionFactory

Entry point for the extension API for aggregation multi-functions.

This API allows adding one or more related aggregation functions that can share state, share parameters or exhibit related behavior.

Please use {@link com.espertech.esper.client.ConfigurationPlugInAggregationMultiFunction}to register this factory class in the engine together with one or more function names.

The engine instantiates a single instance of this class at the time it encounters the first aggregation multi-function in a given statement at the time of statement parsing or compilation from statement object model.

At the time of statement parsing, each aggregation multi-function encountered during parsing of EPL statement text results in an invocation to {@link #addAggregationFunction(PlugInAggregationMultiFunctionDeclarationContext)}. The same upon statement compilation for statement object model. For multiple aggregation functions, the order in which such calls occur is not well defined and should not be relied on by the implementation.

The engine invokes {@link #validateGetHandler(PlugInAggregationMultiFunctionValidationContext)}at the time of expression node validation. Validation occurs after statement parsing and when type information is established. For multiple aggregation functions, the order in which such calls occur is not well defined and should not be relied on by the implementation.

Usually a single {@link PlugInAggregationMultiFunctionHandler} handler class can handle the needsof all related aggregation functions. Usually you have a single handler class and return one handler object for each aggregation function expression, where the handler object takes the validation context as a parameter. Use multiple different handler classes when your aggregation functions have sufficiently different execution contexts or behaviors. Your application may want to use the expression and type information available in {@link PlugInAggregationMultiFunctionValidationContext} to decide what behavior to provide.

        }


        // try plug-in aggregation multi-function
        ConfigurationPlugInAggregationMultiFunction config = engineImportService.resolveAggregationMultiFunction(functionName);
        if (config != null) {
            PlugInAggregationMultiFunctionFactory factory = plugInAggregations.getMap().get(config);
            if (factory == null) {
                factory = (PlugInAggregationMultiFunctionFactory) JavaClassHelper.instantiate(PlugInAggregationMultiFunctionFactory.class, config.getMultiFunctionFactoryClassName());
                plugInAggregations.getMap().put(config, factory);
            }
            factory.addAggregationFunction(new PlugInAggregationMultiFunctionDeclarationContext(functionName.toLowerCase(), distinct, engineURI, config));
            return new ExprPlugInAggMultiFunctionNode(distinct, config, factory, functionName);
        }


        // try built-in expanded set of aggregation functions
        return engineImportService.resolveAggExtendedBuiltin(functionName, distinct);

        }


        // try plug-in aggregation multi-function
        ConfigurationPlugInAggregationMultiFunction config = engineImportService.resolveAggregationMultiFunction(functionName);
        if (config != null) {
            PlugInAggregationMultiFunctionFactory factory = plugInAggregations.getMap().get(config);
            if (factory == null) {
                factory = (PlugInAggregationMultiFunctionFactory) JavaClassHelper.instantiate(PlugInAggregationMultiFunctionFactory.class, config.getMultiFunctionFactoryClassName());
                plugInAggregations.getMap().put(config, factory);
            }
            factory.addAggregationFunction(new PlugInAggregationMultiFunctionDeclarationContext(functionName.toLowerCase(), distinct, engineURI, config));
            return new ExprPlugInAggMultiFunctionNode(distinct, config, factory, functionName);
        }


        // try built-in expanded set of aggregation functions
        return engineImportService.resolveAggExtendedBuiltin(functionName, distinct);

Examples of com.espertech.esper.plugin.PlugInAggregationMultiFunctionFactory

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