JPA2: Case-insensitive like matching anywhere

It may seem a little awkward at first, but it is type-safe. Building queries from strings isn’t, so you notice errors at runtime instead of at compile time. You can make the queries more readable by using indentations or taking each step separately, instead of writing an entire WHERE clause in a single line.

To make your query case-insensitive, convert both your keyword and the compared field to lower case:

query.where(
    builder.or(
        builder.like(
            builder.lower(
                root.get(
                    type.getDeclaredSingularAttribute("username", String.class)
                )
            ), "%" + keyword.toLowerCase() + "%"
        ), 
        builder.like(
            builder.lower(
                root.get(
                    type.getDeclaredSingularAttribute("firstname", String.class)
                )
            ), "%" + keyword.toLowerCase() + "%"
        ), 
        builder.like(
            builder.lower(
                root.get(
                    type.getDeclaredSingularAttribute("lastname", String.class)
                )
            ), "%" + keyword.toLowerCase() + "%"
        )
    )
);