ObjectDB Database Search

The JPA Criteria API provides an alternative way for defining JPA queries , which is mainly useful for building dynamic queries whose exact structure is only known at runtime. JPA Criteria API vs JPQL JPQL queries are defined as strings, similarly to SQL. JPA criteria queries , on the other hand

The  Query and  TypedQuery interfaces define various setting and tuning methods that may affect query execution if invoked before a query is run using getResultList or getSingleResult ... defining a result window that exposes a portion of a large query result list (hiding

Query parameters enable the definition of reusable queries . Such queries can be executed with different parameter values to retrieve different results. Running the same query multiple times with different parameter values (arguments) is more efficient than using a new query string for every query

The Query interface defines two methods for running SELECT queries : Query .getSingleResult - for use when exactly one result object is expected. Query .getResultList - for general use in any ... - for general use in any other case. In addition, the Query interface defines a method for running

A named query is a statically defined query with a predefined unchangeable query string. Using named queries instead of dynamic queries may improve code organization by separating the JPQL query strings from the Java code. It also enforces the use of query   parameters

Queries are represented in JPA 2 by two interfaces - the old Query interface, which was the only interface available for representing queries in JPA 1, and the new TypedQuery interface that was introduced in JPA 2. The TypedQuery interface extends the Query interface. In JPA 2 the Query interface

Queries are represented in JPA by the Query and TypedQuery interfaces: The JPA Query API ... these interfaces to build and run JPQL queries . The TypedQuery interface (or alternatively the older Query interface) is the only neccessary interface for defining and running string based JPQL queries  

The syntax of the Java Persistence Query Language (JPQL) is very similar to the syntax of SQL. Having an SQL-like syntax in JPA queries is an important advantage because SQL is a very powerful query ... classes and objects. For example, a JPQL query can retrieve and return entity objects

DELETE queries provide an alternative way for deleting entity objects. Unlike SELECT queries , which are used to retrieve data from the database, DELETE queries do not retrieve data from ... from the database using a DELETE query may be slightly more efficient than retrieving entity objects

;within an active transaction. Applying changes to the database by calling the commit method. JPQL UPDATE queries provide an alternative way of updating entity objects. Unlike SELECT queries , which are used to retrieve data from the database, UPDATE queries do not retrieve data from the database

Query expressions are the foundations on which JPQL and criteria queries are built. Every query ... of JPQL / Criteria query expressions. Atomic Expressions The atomic query expressions are: JPQL / Criteria Variables JPQL / Criteria Parameters JPQL / Criteria Literals Every query expression consists

The JPA Query Language (JPQL) can be considered as an object oriented version of SQL. Users ... well as how to use the JPA Criteria API, which provides an alternative way for building queries in JPA ... (named) queries . It explains how to use the relevant interfaces, annotations, enums and methods

and for representing query results as tuples. SELECT Clause Elements The content of the SELECT clause in a criteria query is represented by Selection : Because Selection  is a super interface ... of Selection : See the SELECT in Criteria Queries section for more details and examples. ORDER BY

The interfaces in this group are in use for setting a criteria query FROM clause. Criteria Query Variables The FROM clause  in JPA queries (as in SQL) defines the query variables. Query variables are represented in criteria queries by descendant interfaces of the From interface: Range

Date and time expressions may appear in JPQL queries : as date and time literals - e.g. {d '2011-12 ... that are evaluated to the date and time on the database server when the query is executed: CURRENT_DATE ... to 0 . Date and Time in Criteria Queries The CriteriaBuilder interface provides three factory methods

Collections may appear in JPQL queries : as parameters - when collections are assigned as arguments ... that is passed to the query as a parameter. For example: 'English' IN :languages is TRUE if the argument ... are treated as synonyms. Criteria Query Collection Expressions JPQL collection operators and functions

). JPQL literals should be used sparingly as queries that use parameters instead of literals ... parameter values. Literals should only be embedded in JPQL queries when a single constant value ... '} Enum Literals JPA 2 adds support for enum literals. Enum literals in JPQL queries use

The following annotations are used to define static named JPA queries : The JPA Named Queries section of the ObjectDB Manual explains and demonstrates how to use these annotations to define named JPQL queries .

String values may appear in JPQL queries in various forms: as  string literals - e.g. 'abc ... expressions (which are more powerful than the LIKE operator). Criteria Query String Expressions JPQL string operators and functions (which are described above) are available also as JPA criteria query

Numeric values may appear in JPQL queries in many forms: as  numeric literals - e.g. 123 ... . Criteria Query Arithmetic Expressions JPQL arithmetic operators and functions (which are described above) are available also as JPA criteria query expressions. The CriteriaBuilder interface provides

The following interfaces are in use in representing general expressions in criteria queries : See the Query Expressions section for more details and examples.

The following JPA annotations are designated for SQL queries on relational databases: ObjectDB supports only the preferred JPA query language, JPQL, and silently ignores all the above annotations.

, the following query returns Country objects that become managed by the EntityManager em : TypedQuery query = em. createQuery ("SELECT c FROM Country c", Country.class); List results = query . getResultList ... detection , support for delete , etc. Query results are not limited to entity objects. JPA 2 adds

The FROM clause declares query identification variables that represent iteration over objects in the database. A query identification variable is similar to a variable of a Java enhanced for loop in ... are query identification variables that iterate over all the database objects of a specific entity

The GROUP BY clause enables grouping of query results. A JPQL query with a GROUP BY clause returns ... clause in the query execution order is after the FROM and WHERE clauses, but before the SELECT clause. When a GROUP BY clause exists in a JPQL query , database objects (or tuples of database objects

, derived attributes, grouping queries and aggregate queries ) which are usually missing from Object Oriented ... . Query program cache (for repeating queries with different arguments). Query result cache (for repeating queries with the same arguments). Many other internal caches. Indexing Single field and multi field

to view data in ObjectDB databases, execute JPQL and JDOQL queries and edit the content of databases ... and embeddable classes) in the database and their persistent fields and indexes. The [ Query ] window enables running JPQL and JDOQL queries , as discussed below. Closing a Database Connection Use the File Close

JPQL query that retrieves selective objects from the database. Out of the four optional clauses of JPQL queries , the WHERE clause is definitely the most frequently used. How a WHERE Clause Works The following query retrieves only countries with a population size above a population size p

The ORDER BY clause specifies a required order for the query results. Any JPQL query that does not ... Expressions The following query returns names of countries whose population size ... expressions in the SELECT clause are allowed in the ORDER BY clause. The following query , for example

JPA Interface Query Interface used to control query execution. See Also: TypedQuery StoredProcedureQuery Parameter Since: JPA 1.0 Chapter 4 - JPA Queries (JPQL / Criteria) explains how to use Query ... of entities updated or deleted Throws: IllegalStateException - if called for a Jakarta Persistence query

(which modify the database) have to be recorded. For debugging of query failure ... to accelerate the execution of relevant queries . The element The element specifies settings of the two cache mechanisms that ObjectDB manages for queries : The results attribute specifies the size

, string, date). Simple type values are more useful in queries . They have special operators ... ). Navigation through a NULL value The following query retrieves country names with their capital city names ... the equivalent JOIN query . Entity Type Expressions The TYPE operator (which is new in JPA 2) returns the type

after retrieval by a special automatic query . Note : Navigation through inverse fields is much less efficient than navigation through ordinary persistent fields, since it requires running queries . Inverse ... the following query (where :d represents the Department entity): SELECT e FROM Employee e WHERE e

 name,     Query   query ) Define the query , typed query , or stored procedure query as a named query such that future query objects can be created from it using the EntityManager ... of the query object (except for actual parameter binding) in effect when the named query is added

Querying without indexes requires iteration over entity objects in the database one by ... indexes the iteration can be avoided and complex queries over millions of objects can be executed quickly ... firstName; String lastName; Address address; : } Indexes in Queries ObjectDB manages a BTree

. Starting Online Backup The online backup can be started by executing a special query on an EntityManager ... ; em.createQuery("objectdb backup").getSingleResult(); The backup query string is always exactly ... directory can be specified by setting the target parameter before executing the backup query :  

JPA Method in jakarta.persistence. Query Query setLockMode (    LockModeType  lockMode ) Set the lock mode type to be used for the query execution. Parameters: lockMode - lock mode Return: the same query instance Throws: IllegalStateException - if the query is found not

JPA Method in jakarta.persistence. Query Stream getResultStream () Execute a SELECT query and return the query results as an untyped java.util.stream.Stream . By default, this method delegates ... Throws: IllegalStateException - if called for a Jakarta Persistence query language UPDATE or DELETE

JPA Method in jakarta.persistence. Query List getResultList () Execute a SELECT query and return the query results as an untyped List. Return: a list of the results, or an empty list if there are no results Throws: IllegalStateException - if called for a Jakarta Persistence query language UPDATE or

JPA Method in jakarta.persistence. Query Object getSingleResult () Execute a SELECT query ... Persistence query language UPDATE or DELETE statement QueryTimeoutException - if the query execution exceeds the query timeout value set and only the statement is rolled back TransactionRequiredException

JPA Method in jakarta.persistence. Query LockModeType getLockMode () Get the current lock mode for the query . Returns null if a lock mode has not been set on the query object. Return: lock mode Throws: IllegalStateException - if the query is found not to be a Jakarta Persistence query language

JPA Method in jakarta.persistence. Query Object getSingleResultOrNull () Execute a SELECT query ... Persistence query language UPDATE or DELETE statement QueryTimeoutException - if the query execution exceeds the query timeout value set and only the statement is rolled back TransactionRequiredException

JPA Method in jakarta.persistence. Query int executeUpdate () Execute an update or delete statement ... for a Jakarta Persistence query language SELECT statement or for a criteria query ... QueryTimeoutException - if the statement execution exceeds the query timeout value set

JPA Method in jakarta.persistence. Query Parameter getParameter (   String name ... of the given name and type. This method is required to be supported for criteria queries ... IllegalStateException - if invoked on a native query or Jakarta Persistence query language query when the implementation does not support this use Since: JPA 2.0

JPA Method in jakarta.persistence. Query Query setFlushMode (    FlushModeType  flushMode ) Set the flush mode type to be used for the query execution. The flush mode type applies to the query regardless of the flush mode type in use for the entity manager. Parameters: flushMode

JPA Method in jakarta.persistence. Query Set getParameters () Get the parameter objects corresponding to the declared parameters of the query . Returns empty set if the query has no parameters. This method is not required to be supported for native queries . Return: set of the parameter objects

JPA Method in jakarta.persistence. Query Query setHint (   String hintName,    Object value ) Set a query property or hint. The hints elements may be used to specify query properties and hints. Properties defined by this specification must be observed by

;String message,    Throwable cause,     Query   query ) Constructs a new QueryTimeoutException exception with the specified detail message, cause, and query . Parameters: message - the detail message. cause - the cause. query - the query . Since: JPA 2.0

JPA Constructor in jakarta.persistence.QueryTimeoutException QueryTimeoutException (    Query   query ) Constructs a new QueryTimeoutException exception with the specified query . Parameters: query - the query . Since: JPA 2.0

JPA Method in jakarta.persistence. Query Query setTimeout (   Integer timeout ) Set the query timeout, in milliseconds. This is a hint, and is an alternative to plain jakarta.persistence. query .timeout . Parameters: timeout - the timeout, in milliseconds, or null to indicate no timeout Return: the same query instance Since: JPA 3.2