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Result Handling

Once a Redis command returns a result set, dbVisitor can process it with all three result-handling interfaces. Availability depends on the API entry point.

API Support​

API entry pointRowMapperRowCallbackHandlerResultSetExtractor
Programmatic APISupportedSupportedSupported
Mapper API (method annotations)SupportedSupportedSupported
Builder APIUnsupportedUnsupportedUnsupported
Mapper filesSupportedSupportedSupported

The builder API does not translate query conditions into Redis commands, so it cannot initiate these queries. This is not a limitation of the three handlers; use native commands instead.

Programmatic API​

For example, ZRANGE scores 0 -1 WITHSCORES returns the ELEMENT and SCORE columns.

// RowMapper: map each row to a string.
List<String> members = jdbcTemplate.queryForList(
        "ZRANGE ? 0 -1 WITHSCORES", new Object[] { "scores" },
        (rs, rowNum) -> rs.getString("ELEMENT"));
// RowCallbackHandler: process each row without collecting a return list.
jdbcTemplate.query("ZRANGE ? 0 -1 WITHSCORES", new Object[] { "scores" },
        (rs, rowNum) -> System.out.println(rs.getString("ELEMENT")));

// ResultSetExtractor: collect members and scores from the entire result set.
Map<String, Double> scores = jdbcTemplate.query(
        "ZRANGE ? 0 -1 WITHSCORES", new Object[] { "scores" }, rs -> {
            Map<String, Double> result = new LinkedHashMap<>();
            while (rs.next()) {
                result.put(rs.getString("ELEMENT"), rs.getDouble("SCORE"));
            }
            return result;
        });

See Commands and Result Sets for column names.

Mapper API and Mapper Files​

Use the resultRowMapper, resultRowCallback, or resultSetExtractor attribute of @Query to specify a handler class. A Mapper file's <select> supports the same attributes.

<select id="members"
        resultRowMapper="net.hasor.dbvisitor.jdbc.mapper.ColumnMapRowMapper">
    ZRANGE #{key} 0 -1 WITHSCORES
</select>

Both entry points use native Redis commands, not SQL translations. See Result Handling for handler configuration and implementation.