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Session: Querying: How to query?
Database can be queried using QueryDSL-enabled query method with few custom extension that will be described later.
Syntax
public <T> IRavenQueryable<T> query(Class<T> clazz); // perform query on a dynamic index
public <T> IRavenQueryable<T> query(Class<T> clazz, String indexName);
public <T> IRavenQueryable<T> query(Class<T> clazz, String indexName, boolean isMapReduce);
public <T> IRavenQueryable<T> query(Class<T> clazz, Class<? extends AbstractIndexCreationTask> indexCreator);| Parameters | ||
|---|---|---|
| indexName | String | Name of an index to perform query on |
| isMapReduce | boolean | Indicates if queried index is a map/reduce index (modifies how we treat identifier properties). |
| Return Value | |
|---|---|
| IRavenQueryable | Instance implementing IRavenQueryable interface containing additional query methods. |
Safe By Default
The default value of a page size for a query is 128 results. In order to retrieve a different number of results in a single query use .Take(pageSize) method.
Example I - Basic
// load up to 128 entities from 'Employees' collection
List<Employee> employees = session
.query(Employee.class)
.toList();Notice that by specifying Employee as a class parameter, we are not only defining a result type, but also marking name of collection that will be queried.
Example II - Syntax
Queries can be performed using strongly typed syntax.
// load up to 128 entities from 'Employees' collection
// where FirstName equals 'Robert'
QEmployee e = QEmployee.employee;
List<Employee> employees = session
.query(Employee.class)
.where(e.firstName.eq("Robert"))
.toList();Example III - Querying specified index
// load up to 128 entities from 'Employees' collection
// where FirstName equals 'Robert'
// using 'My/Custom/Index'
QEmployee e = QEmployee.employee;
List<Employee> employees = session
.query(Employee.class, "My/Custom/Index")
.where(e.firstName.eq("Robert"))
.toList();or
// load up to 128 entities from 'Employees' collection
// where FirstName equals 'Robert'
// using 'My/Custom/Index'
QEmployee e = QEmployee.employee;
List<Employee> employees = session
.query(Employee.class, MyCustomIndex.class)
.where(e.firstName.eq("Robert"))
.toList();Custom methods and extensions
Available custom methods and extensions:
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