I want the user to be able to specify the limit (the size of the amount returned) and offset (the first record returned / index returned) in my query method.
Here are my classes without any paging capabilities. My entity:
@Entity
public Employee {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;
@Column(name="NAME")
private String name;
//getters and setters
}
My repository:
public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
@Query("SELECT e FROM Employee e WHERE e.name LIKE :name ORDER BY e.id")
public List<Employee> findByName(@Param("name") String name);
}
My service interface:
public interface EmployeeService {
public List<Employee> findByName(String name);
}
My service implementation:
public class EmployeeServiceImpl {
@Resource
EmployeeRepository repository;
@Override
public List<Employee> findByName(String name) {
return repository.findByName(name);
}
}
Now here is my attempt at providing paging capabilities that support offset and limit. My entity class remains the same.
My "new" repository takes in a pageable parameter:
public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
@Query("SELECT e FROM Employee e WHERE e.name LIKE :name ORDER BY e.id")
public List<Employee> findByName(@Param("name") String name, Pageable pageable);
}
My "new" service interface takes in two additional parameters:
public interface EmployeeService {
public List<Employee> findByName(String name, int offset, int limit);
}
My "new" service implementation:
public class EmployeeServiceImpl {
@Resource
EmployeeRepository repository;
@Override
public List<Employee> findByName(String name, int offset, int limit) {
return repository.findByName(name, new PageRequest(offset, limit);
}
}
This however isn't what i want. PageRequest specifies the page and size (page # and the size of the page). Now specifying the size is exactly what I want, however, I don't want to specify the starting page #, I want the user to be able to specify the starting record / index. I want something similar to
public List<Employee> findByName(String name, int offset, int limit) {
TypedQuery<Employee> query = entityManager.createQuery("SELECT e FROM Employee e WHERE e.name LIKE :name ORDER BY e.id", Employee.class);
query.setFirstResult(offset);
query.setMaxResults(limit);
return query.getResultList();
}
Specifically the setFirstResult() and setMaxResult() methods. But I can't use this method because I want to use the Employee repository interface. (Or is it actually better to define queries through the entityManager?)
Is there a way to specify the offset without using the entityManager?
Below code should do it. I am using in my own project and tested for most cases.
usage:
Pageable pageable = new OffsetBasedPageRequest(offset, limit);
return this.dataServices.findAllInclusive(pageable);
and the source code:
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.commons.lang3.builder.ToStringBuilder;
import org.springframework.data.domain.AbstractPageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import java.io.Serializable;
/**
* Created by Ergin
**/
public class OffsetBasedPageRequest implements Pageable, Serializable {
private static final long serialVersionUID = -25822477129613575L;
private int limit;
private int offset;
private final Sort sort;
/**
* Creates a new {@link OffsetBasedPageRequest} with sort parameters applied.
*
* @param offset zero-based offset.
* @param limit the size of the elements to be returned.
* @param sort can be {@literal null}.
*/
public OffsetBasedPageRequest(int offset, int limit, Sort sort) {
if (offset < 0) {
throw new IllegalArgumentException("Offset index must not be less than zero!");
}
if (limit < 1) {
throw new IllegalArgumentException("Limit must not be less than one!");
}
this.limit = limit;
this.offset = offset;
this.sort = sort;
}
/**
* Creates a new {@link OffsetBasedPageRequest} with sort parameters applied.
*
* @param offset zero-based offset.
* @param limit the size of the elements to be returned.
* @param direction the direction of the {@link Sort} to be specified, can be {@literal null}.
* @param properties the properties to sort by, must not be {@literal null} or empty.
*/
public OffsetBasedPageRequest(int offset, int limit, Sort.Direction direction, String... properties) {
this(offset, limit, new Sort(direction, properties));
}
/**
* Creates a new {@link OffsetBasedPageRequest} with sort parameters applied.
*
* @param offset zero-based offset.
* @param limit the size of the elements to be returned.
*/
public OffsetBasedPageRequest(int offset, int limit) {
this(offset, limit, Sort.unsorted());
}
@Override
public int getPageNumber() {
return offset / limit;
}
@Override
public int getPageSize() {
return limit;
}
@Override
public int getOffset() {
return offset;
}
@Override
public Sort getSort() {
return sort;
}
@Override
public Pageable next() {
return new OffsetBasedPageRequest(getOffset() + getPageSize(), getPageSize(), getSort());
}
public OffsetBasedPageRequest previous() {
return hasPrevious() ? new OffsetBasedPageRequest(getOffset() - getPageSize(), getPageSize(), getSort()) : this;
}
@Override
public Pageable previousOrFirst() {
return hasPrevious() ? previous() : first();
}
@Override
public Pageable first() {
return new OffsetBasedPageRequest(0, getPageSize(), getSort());
}
@Override
public boolean hasPrevious() {
return offset > limit;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof OffsetBasedPageRequest)) return false;
OffsetBasedPageRequest that = (OffsetBasedPageRequest) o;
return new EqualsBuilder()
.append(limit, that.limit)
.append(offset, that.offset)
.append(sort, that.sort)
.isEquals();
}
@Override
public int hashCode() {
return new HashCodeBuilder(17, 37)
.append(limit)
.append(offset)
.append(sort)
.toHashCode();
}
@Override
public String toString() {
return new ToStringBuilder(this)
.append("limit", limit)
.append("offset", offset)
.append("sort", sort)
.toString();
}
}