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Strings in JPQL and Criteria Queries

String values may appear in JPQL queries in various forms: as string literals - e.g. 'abc', ''. as parameters - when string values are assigned as arguments. as path expressions - in navigation to persistent string fields. as results of predefined JPQL string manipulation functions. LIKE - String

Memory consumption of empty Strings

of objectdb: My program has several entities which contain many String. Often some of these String are empty (""). To avoid unnecessary memory consumption, the String within the entities are initialized like: String firstName = ""; In this case every "empty" attribute shares the same String

Inserted entities with strings as keys and indices needs more and more ram memory in comparing to primitive integers as keys and indices

Hello, I have a problem with inserting of many entities. We use strings as primary key and indices ... . Can you explain this and do you have an idea for the case that strings are used for keys and indices? See both examples. btc_es BTC EmbeddedSystems Correction. The case with strings as primary key and indices

String Encoding Issue

Hi all Encounter a character encoding issue when i try to retrieve a String column containing Chinese character. Retrieve a String column on odb file. em = emf.createEntityManager(); Query query ... ();) {     System.out.println(itr.next().getName()); // name is a string column } Result: å?‹å–„å

Possible issue with String fields

to commit transaction: String index out of range: 5 (error 613) at com.objectdb.jpa.EMImpl.commit ... .StringIndexOutOfBoundsException: String index out of range: 5 at java.lang.String.charAt(String.java:695) at com.objectdb ... :276) ... 1 more Java Result: 1 When I comment out the fields that are strings all works out fine. I


Enum Constant javax.persistence.DiscriminatorType STRING String as the discriminator type. Since: JPA 1.0


Enum Constant javax.persistence.EnumType STRING Persist enumerated type property or field as a string. Since: JPA 1.0

Literals in JPQL and Criteria Queries

including NULL, boolean literals (TRUE and FALSE), numeric literals (e.g. 100), string literals (e.g ... ), a feature that is not currently supported by all JPA implementations. String Literals JPQL follows the syntax of SQL for string literals in which strings are always enclosed in single quotes (e.g

JPA Persistable Types

, Mapped superclasses, Embeddable classes. Simple Java data types: Primitive types, Wrappers, String ... public class Address { String street; String city; String state; String country; String zip; } Instances of embeddable classes are always embedded in other entity objects

JPA Query Expressions (JPQL / Criteria)

, sqrt). String expressions (like, length, locate, lower, upper, concat, substring, ...). Data

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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