JDBCTemplate optional parameters

问题

I am using spring JDBCTemplate.

I have a scenario, where the parameters that need to be passed into my query function, are conditional/optional. For example, I have the following code:

List<RealTimeDTO> result = jdbcTemplate.query(sql, new Object[] {custId, 
number, requestType, startDate, endDate}, new CCCRowMapper());

In the code, I passed in custId, number, requestType, etc. However, requestType is an optional parameter that may come back as null or empty so I don't want it to be passed into the Object[] if it is either null or empty.

What can I do to handle this type of situation?

I could introduce logic where I only pass in the parameters I want into the Object[], however, I was wondering if there is an already built in functionality that handles this instead of me reinventing the wheel.

回答1:

One option is to use NamedParameterJdbcTemplate, so the parameter "list" (now a Map) doesn't need to be modified, only the SQL does:

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());
}

UPDATE

If you have many conditions that may need to be skipped, and all conditions might be eliminated, then use a StringJoiner to build the WHERE clause:

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());
}

回答2:

You can use a static SQL by checking the condition like ? IS NULL OR name = ?. But you have to pass the argument twice AND pass the argument type (at.sql.Types) twice.

String sql = "SELECT foo, bar" +
              " FROM FooBar" +
             " WHERE (? IS NULL OR name = ?) ";
jdbcTemplate.query(sql, new Object[]{name, name}, new int[]{Types.VARCHAR, Types.VARCHAR}, new CCCRowMapper());

IMO not really better than using conditions.

来源：https://stackoverflow.com/questions/51160468/jdbctemplate-optional-parameters

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java

Spring

jdbctemplate