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4

Database Schema Evolution

of an old schema is loaded into memory it is automatically converted into an instance of the up to date ... int to Date) the fields are not considered as matching and the new field is initialized ... any date type to any date type. From any collection or array type to any collection or array type, as
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FROM clause (JPQL / Criteria API)

, CHARACTER_LENGTH, CLASS, COALESCE, CONCAT, COUNT, CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP
4

Retrieving JPA Entity Objects

specifying FetchType.LAZY in either @OneToOne or @ManyToOne annotations (currently ObjectDB does not ... in @OneToMany or @ManyToMany annotations (currently ObjectDB does not distinguish between ... of the current fetch policy, as long as the EntityManager is open. This also includes fields that reference
4

Paths and Types in JPQL and Criteria API

, string, date). Simple type values are more useful in queries. They have special operators ... (number, boolean, string, date). For a path expression to be valid the user defined persistable class ... , the current FROM variable (or FROM tuple when there are multiple variables) is simply skipped
4

GROUP BY and HAVING clauses

. Only identification variables and path expressions are currently supported in the GROUP BY clause by ... the minimum of comparable values (numeric, strings, dates). MAX - returns the maximum of comparable values (numeric, strings, dates). The following query counts for every letter the number of countries
3

Index Definition

indexedField3; @Unique Integer indexedField4; // unique @Unique(name="u2") Date indexedField5 ... , Long, Float, Double. java.math.BigInteger, java.math.BigDecimal. java.lang.String. java.util.Date, java.sql.Date, java.sql.Time, java.sql.Timestamp. Any enum type. Reference to an entity object
0

Step 2: Entity Class and Persistence Unit

.Date; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax ... ; private String name; private Date signingDate; // Constructors: public Guest() { } public Guest(String name) { this.name = name; this.signingDate = new Date
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Step 2: Entity Class and Persistence Unit

.Serializable; import java.sql.Date; import javax.persistence.Entity; import javax.persistence ... Long id; private String name; private Date signingDate; // Constructors ... ; this.signingDate = new Date(System.currentTimeMillis()); } // String Representation
0

Step 2: Entity Class and Persistence Unit

with the following code: package guest; import java.io.Serializable; import java.sql.Date; import javax ... ; private Date signingDate; // Constructors: public Guest() { } public Guest(String name) { this.name = name; this.signingDate = new Date(System.currentTimeMillis
0

javax.jdo.JDOEntityManager

if the instance is a managed entity instance belonging to the current persistence context. Check if the instance is a managed entity instance belonging to the current persistence context. Parameters: entity ... is already deleted in the current transaction. This method throws JDOUserException if the instance is transient

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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