com.alexkasko.springjdbc.parallel.accessor.ImmutableAccessor Maven / Gradle / Ivy

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Processes given SQL query in parallel in multiple data sources (assuming that all data source contain the same data). Combined results from multiple queries are exposed to application as java.util.Iterator. Worker thread use spring's JdbcTemplate with named parameters support.

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package com.alexkasko.springjdbc.parallel.accessor;

import com.google.common.collect.ForwardingCollection;
import com.google.common.collect.ImmutableList;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
import org.springframework.jdbc.core.namedparam.SqlParameterSource;

import java.util.Collection;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Abstract accessor implementation as a wrapper around provided collection.
 * Copies provided collection into inner immutable one on creation. Thread-safe.
 *
 * @author alexkasko
 * Date: 6/11/12
 * @see DataSourceAccessor
 */
public abstract class ImmutableAccessor
        extends ForwardingCollection implements DataSourceAccessor {
    protected final ImmutableList delegate;

    /**
     * Protected constructor, copies provided collection into inner immutable one
     *
     * @param collection collection to wrap
     */
    protected ImmutableAccessor(Collection collection) {
        checkNotNull(collection, "Provided collection must be not null");
        checkArgument(collection.size() > 0, "Provided collection must be not empty");
        this.delegate = ImmutableList.copyOf(collection);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected Collection delegate() {
        return delegate;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        sb.append("ImmutableAccessor");
        sb.append("{delegate=").append(delegate);
        sb.append('}');
        return sb.toString();
    }
}