SimpleJdbcCallsHandler.java

package org.ovirt.engine.core.dal.dbbroker;

import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.ovirt.engine.core.dao.BaseDAODbFacade;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
import org.springframework.jdbc.core.namedparam.SqlParameterSourceUtils;
import org.springframework.jdbc.core.simple.ParameterizedRowMapper;
import org.springframework.jdbc.core.simple.SimpleJdbcCall;

public class SimpleJdbcCallsHandler {
    private static SimpleJdbcCallsHandler instance = new SimpleJdbcCallsHandler();


    private ConcurrentMap<String, SimpleJdbcCall> callsMap =
            new ConcurrentHashMap<String, SimpleJdbcCall>();

    private DbEngineDialect dialect;

    private JdbcTemplate template;

    public void setDbEngineDialect(DbEngineDialect dialect) {
        this.dialect = dialect;
    }

    public void setJdbcTemplate(JdbcTemplate template) {
        this.template = template;
    }

    private interface CallCreator {
        SimpleJdbcCall createCall();
    }

    public Map<String, Object> executeModification(final String procedureName, final MapSqlParameterSource paramSource) {
        return executeImpl(procedureName, paramSource, createCallForModification(procedureName));
    }


    public <T> T executeRead(final String procedureName,
            final ParameterizedRowMapper<T> mapper,
            final MapSqlParameterSource parameterSource) {
        List<T> results = executeReadList(procedureName, mapper, parameterSource);
        return results.isEmpty() ? null : results.get(0);
    }

    @SuppressWarnings("unchecked")
    public <T> List<T> executeReadList(final String procedureName,
            final ParameterizedRowMapper<T> mapper,
            final MapSqlParameterSource parameterSource) {
        Map<String, Object> resultsMap = executeReadAndReturnMap(procedureName, mapper, parameterSource);
        List<?> resultList = (List<?>) (resultsMap
                .get(BaseDAODbFacade.RETURN_VALUE_PARAMETER));
        return (resultList != null) ? (List<T>) resultList : null;
    }

    public <T> Map<String, Object> executeReadAndReturnMap(final String procedureName,
            final ParameterizedRowMapper<T> mapper,
            final MapSqlParameterSource parameterSource) {
        Map<String, Object> resultsMap =
                executeImpl(procedureName, parameterSource, createCallForRead(procedureName, mapper, parameterSource));
        return resultsMap;
    }

    private CallCreator createCallForRead(final String procedureName,
            final ParameterizedRowMapper<?> mapper,
            final MapSqlParameterSource parameterSource) {
        return new CallCreator() {
                @Override
                public SimpleJdbcCall createCall() {
                    SimpleJdbcCall call =
                            (SimpleJdbcCall) dialect.createJdbcCallForQuery(template).withProcedureName(procedureName);
                    call.returningResultSet(BaseDAODbFacade.RETURN_VALUE_PARAMETER, mapper);
                    // Pass mapper information (only parameter names) in order to supply all the needed
                    // metadata information for compilation.
                    call.getInParameterNames().addAll(
                            SqlParameterSourceUtils.extractCaseInsensitiveParameterNames(parameterSource).keySet());
                    return call;
                }
            };
    }

    private CallCreator createCallForModification(final String procedureName) {
        return new CallCreator() {
            @Override
            public SimpleJdbcCall createCall() {
                return new SimpleJdbcCall(template).withProcedureName(procedureName);
            }
        };
    }

    private Map<String, Object> executeImpl(String procedureName,
            MapSqlParameterSource paramsSource, CallCreator callCreator) {
        SimpleJdbcCall call = callsMap.get(procedureName);
        if (call == null) {
            // Creates a simple jdbc call object, and
            // compile its metadata.
            // The if block is not atomic - Worst case a few
            // information schema calls will be made.
            // Metada compilation is done here, in order to save it
            // the first time we actually use the stored procedure as
            // it may yield some concurrency issues.

            call = callCreator.createCall();
            call.compile();
            callsMap.putIfAbsent(procedureName,
                    call);
        }
        return call.execute(paramsSource);
    }
}