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jdbctemplate

How JDBCTemplate queryForObject works. Specifically, the new Object[] {} part

I have this piece of example code:

public Post findById(Long id) {
    String sql = "select id, title, text from post where id = ?";

    return template.queryForObject(sql, new Object[] {id}, getPostRowMapper());

}

I don't understand what the new Object[] {id} is doing here

Solution

  • When you have a sql statement with a variable in it (the question mark sign), then you need to supply the variables that will be placed into that statement where the question marks are.

    new Object[] {id} tells us which variables should be put in places where the question marks are.

    new Object[] {} creates an empty array of objects. new Object[] {id} creates an array of objects with one item in it - the Long id, which is the function parameter.

    So, let's say id is equal to 1. In that case, the question mark

    where id = ?

    Will be replaced with 1

    where id = 1