Binding variables
Dari supports bind variables in query strings using ? for placeholders.
In a basic scenario, placeholders refer to variables with single values or single objects, such as String, Integer, or Date.
String userName = "John Smith";
User user = Query.from(User.class)
.where("name = ?", userName).first();Referring to the previous snippet, at runtime Dari creates the following where clause:
WHERE name = 'John Smith'In the next example, the query filters on a Date object, returning all ToolUsers for which the last login date is after January 17, 2019.
String startDateString = "01/17/2019";
DateFormat df = new SimpleDateFormat("MM/dd/yyyy");
Date date = null;
try {
date = df.parse(startDateString);
}
catch (ParseException e) {
/* Error handling */
}
List<ToolUser> toolUser = Query.from(ToolUser.class)
.where("lastLoginDate > ?", date).selectAll();You can also bind a variable that is a collection, such as a or , to a query. At run time, Dari performs the operation in the .where method against all elements in the collection. In the following snippet, the query searches for all instances of User with a name value that matches any name in the list names.
List<String> names = new ArrayList<String>();
names.add("John Smith");
names.add("Jane Doe");
List<User> users = Query.from(User.class)
.where("name = ?", names).selectAll();If a .where method has more than one placeholder, Dari substitutes the placeholders for the parameters in the order they appear.
List<ToolUser> toolUser = Query.from(ToolUser.class)
.where("name = ? OR email = ?", "joe", "joe@brightspot.com")
.selectAll();Referring to the previous snippet, at runtime Dari creates the following where clause:
WHERE name = 'joe' OR email = 'joe@brightspot.com'You can indicate the value for a placeholder by specifying a position鈥攁 useful technique to avoid repeating the same value in a long list of parameters.
List<Author> authors = Query.from(Author.class)
.where("firstName = ?0 OR lastName = ?0 OR email contains ?1", "rand", "brightspot.com").selectAll();Referring to the previous snippet, at runtime Dari creates the following where clause:
WHERE firstName = 'rand'
OR lastName = 'rand'
OR email LIKE '%brightspot.com%'