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JDBCTemplate valgfri parametre

Jdbc

En mulighed er at bruge NamedParameterJdbcTemplate , så parameteren "list" (nu en Map ) behøver ikke at blive ændret, kun SQL gør:

List<RealTimeDTO> query(String name) {
    NamedParameterJdbcTemplate jdbcTemplate = new NamedParameterJdbcTemplate(dataSource);

    String sql = "SELECT foo, bar" +
                  " FROM FooBar" +
                 " WHERE name" + (name == null ? " IS NULL" : "= :name");
    Map<String, Object> params = new HashMap<>();
    params.put("name", name);
    return jdbcTemplate.query(sql, params, new CCCRowMapper());
}

OPDATERING

Hvis du har mange tilstande, der muligvis skal springes over, og alle tilstande kan blive elimineret, så brug en StringJoiner for at bygge WHERE klausul:

List<RealTimeDTO> query(String name, String phone, int age) {
    NamedParameterJdbcTemplate jdbcTemplate = new NamedParameterJdbcTemplate(dataSource);

    StringJoiner where = new StringJoiner(" AND ", " WHERE ", "").setEmptyValue("");
    if (name != null)
        where.add("name = :name");
    if (phone != null)
        where.add("phone = :phone");
    if (age != 0)
        where.add("age = :age");
    String sql = "SELECT foo, bar" +
                  " FROM FooBar" +
                  where;
    Map<String, Object> params = new HashMap<>();
    params.put("name", name);
    params.put("phone", phone);
    params.put("age", age);
    return jdbcTemplate.query(sql, params, new CCCRowMapper());
}

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