9.7 Engine and query configuration

Use DatawayConfig to configure engine and query creation:

• configureHost: runs when Dataway is created to register imported objects, fragment processors and other engine settings.
• configureQuery: runs for each new query to set shared variables, Hints and compiler options.
• attachment: stores an application object for Java extensions to retrieve by type, such as the ConnectionProvider used for SQL execution.

Supply application settings to queries

This example stores application settings with attachment, then uses configureQuery to expose the application name as the script variable application.

ApplicationInfo.java

package com.example.dataway;

public class ApplicationInfo {
    private final String name;

    public ApplicationInfo(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }
}

ApplicationQueryCustomizer.java

package com.example.dataway;

import java.util.function.Consumer;
import net.hasor.dataql.host.QueryBuilder;

public class ApplicationQueryCustomizer implements Consumer<QueryBuilder> {
    @Override
    public void accept(QueryBuilder builder) {
        ApplicationInfo application = builder.getHostContext().getAttachment(ApplicationInfo.class);
        builder.addShareVar("application", application::getName);
    }
}

Register the extensions

config is the application’s DatawayConfig; apply these settings before creating Dataway.

import com.example.dataway.ApplicationInfo;
import com.example.dataway.ApplicationQueryCustomizer;
import com.example.dataway.GreetingUdf;

config.attachment(ApplicationInfo.class, new ApplicationInfo("orders"))
        .configureHost(host -> host.addImport("app.greeting", GreetingUdf::new))
        .configureQuery(new ApplicationQueryCustomizer());

Call from a script

import 'app.greeting' as greeting;
return greeting(application);

Returns "Hello orders". See Custom functions for GreetingUdf.

Configuration timing

• configureHost: runs in registration order whenever Dataway is created, registering imported objects, fragment processors and other engine settings.
• configureQuery: runs in registration order whenever a query builder is created; configure variables, Hints and compiler options here.
• attachment: retrieve application objects with HostContext.getAttachment(type). The first registration for a type is retained. The application manages object creation and resource cleanup.

Convenience methods such as function, library and importSource already wrap these registrations. Use callbacks for additional native configuration. SQL obtains connections through attachment(ConnectionProvider.class, provider); see Data source integration.