io.github.joeljeremy7.externalizedproperties.resolvers.database.DatabaseResolver Maven / Gradle / Ivy

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package io.github.joeljeremy7.externalizedproperties.resolvers.database;

import io.github.joeljeremy7.externalizedproperties.core.ExternalizedPropertiesException;
import io.github.joeljeremy7.externalizedproperties.core.InvocationContext;
import io.github.joeljeremy7.externalizedproperties.core.Resolver;
import io.github.joeljeremy7.externalizedproperties.resolvers.database.queryexecutors.SimpleNameValueQueryExecutor;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.Collections;
import java.util.Map;
import java.util.Optional;

/**
 * {@link Resolver} implementation which resolves requested properties 
 * from a database.
 */
public class DatabaseResolver implements Resolver {
    private final ConnectionProvider connectionProvider;
    private final QueryExecutor queryExecutor;

    /**
     * Constructor. This will use {@link SimpleNameValueQueryExecutor} to
     * execute queries when resolving properties.
     * 
     * @param connectionProvider The connection provider.
     */
    public DatabaseResolver(ConnectionProvider connectionProvider) {
        this(connectionProvider, new SimpleNameValueQueryExecutor());
    }

    /**
     * Constructor.
     * 
     * @param connectionProvider The connection provider.
     * @param queryExecutor The query executor to resolve properties from the database.
     */
    public DatabaseResolver(
            ConnectionProvider connectionProvider,
            QueryExecutor queryExecutor
    ) {
        if (connectionProvider == null) {
            throw new IllegalArgumentException("connectionProvider must not be null.");
        }
        if (queryExecutor == null) {
            throw new IllegalArgumentException("queryExecutor must not be null.");
        }
        this.connectionProvider = connectionProvider;
        this.queryExecutor = queryExecutor;
    }

    /**
     * Resolve property from database.
     * 
     * @param context The invocation context.
     * @param propertyName The property name.
     * @return The resolved property value. Otherwise, an empty {@link Optional}.
     */
    @Override
    public Optional resolve(InvocationContext context, String propertyName) {
        try {
            return getFromDatabase(propertyName);
        } catch (SQLException e) {
            throw new ExternalizedPropertiesException(
                "Exception occurred while trying to resolve properties from database.",
                e
            );
        }
    }

    private Optional getFromDatabase(String propertyName) throws SQLException {
        try (Connection connection = connectionProvider.getConnection()) {
            Map resolvedDbProperties = queryExecutor.queryProperties(
                connection, 
                Collections.singletonList(propertyName)
            );

            return Optional.ofNullable(resolvedDbProperties.get(propertyName));
        }
    }
}