ODATA-like filter expressions to JPA Criteria Queries
Filter expressions are a boolean expressions that follow a subset of javax.el.
expression := [(]property *operator* value[)][ and | or expression]
- lt, lte, gt, gte: Less Than/Greater than (or equal to). Must operate on Number or <? extends Date> fields else throws ParseException. Value for date fields can be milliseconds or ISO8601 date/time.
- eq, ne, !eq: Equals/Not Equals
- in, not in, !in: value must be quoted comma separated values
- like, not like, !like: HQL like operator with "%" as wildcard. Value must be quoted
- lower(?) or upper(?) function to perform case insensitive comparisons of strings. e.g. lower(firstName) eq "grant"
Expressions can operate across joins (M-1, 1-M and M-M). For example:
address.postCode eq "90210" // Users in beverly hills
roles.name eq "Admin" // Users who hold the admin role
contacts.type eq "facebook" // Users that have given facebook profile
- select: Limits the result to provided field names. Result class is javax.persistence.Tuple
- groupBy: Execute a group by query. Only returns enumerated fields. Result class is javax.persistence.Tuple
- getResultList(limit, skip): Returns a list of entities
- getSingleResult(): Returns a single entity. Assumes the expression is returning a single entity. Throws exception otherwise
- count(): Count of the results that would be returned by getResultList
@Entity
public class User {
@Id
String username;
String firstName;
String lastName;
@Temporal
Calendar createdDate;
String postCode;
...
}
public class Example {
EntityManager em;
Example() {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("default");
em = emf.createEntityManager();
}
public <T> List<T> filter(Class<T> entityClass, String filter, int limit, int skip) throws ParseException {
ELFilter<T> fx = new JpaELFilterImpl(em, entityClass).filter(filter);
return fx.getResultList(entityClass, limit, skip);
}
public List<Tuple> groupBy(Class entityClass, String[] select, String[] groupByFields) {
ELFilter fx = new JpaELFilterImpl(em, entityClass)
.select(select)
.groupBy(groupByFields);
return fx.getResultList(Tuple.class, 0, 0);
}
public static void main(String[] args) throws ParseException {
// All users with username starting with a
Example eg = new Example();
eg.filter(User.class, "username like \"a%\"", 0,0);
// users created in the last 24 hours
eg.filter(User.class, "createdDate gt "+(System.currentTimeMillis() - 24*60*60*1000), 0, 0);
// count the number of users in each postcode
eg.groupBy(User.class, new String[]{"postCode", "count(id)"}, new String[]{"postCode"});
}
}
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