JPA Reference Card

Collection of basic types

Use @ElementCollection annotation along with @CollectionTable (if you want to control the name of table), and @Column (name of column to represent value of simple type)

@Entity
public class User {
   [...]
   public String getLastname() { ...}

   @ElementCollection
   @CollectionTable(name="Nicknames", joinColumns=@JoinColumn(name="user_id"))
   @Column(name="nickname")
   public Set<String> getNicknames() { ... } 
}

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Persistence Unit for Toplink Essentials

Minimum configurations required for persistence unit in case of Toplink essentials is given below:

<?xml version="1.0" encoding="windows-1252" ?>
<persistence xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="Model" transaction-type="RESOURCE_LOCAL">
<provider>
oracle.toplink.essentials.PersistenceProvider
</provider>
<class>org.engineers.adf.hrdemo.model.Departments</class>
<class>org.engineers.adf.hrdemo.model.Employees</class>
<properties>
<property name="toplink.logging.level" value="INFO"/>
<property name="toplink.jdbc.driver" value="oracle.jdbc.driver.OracleDriver"/>
<property name="toplink.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:XE"/>
<property name="toplink.jdbc.password" value="password"/>
<property name="toplink.jdbc.user" value="user"/>
</properties>

</persistence-unit>

</persistence>


JPA with Toplink Essentials Error Code: 17002

From this post, I am going to start to post solution for different problems or errors in java technologies which i face during development so that others also could get help from my research and don't waste time on that now.

Error is given below:

Exception [TOPLINK-4002] (Oracle TopLink Essentials - 2.1 (Build b52-fcs (09/24/2008))):
oracle.toplink.essentials.exceptions.DatabaseException
Internal Exception: java.sql.SQLException: Io exception:
Invalid number format for port number
Error Code: 17002

Cause Was: I just copied url from a web site and then pasted to persistence. Probably it appended some hidden characters due to which provider game an error about port format. I just rewrite the port number again and error resolved.

Second Error which i faced was:

Exception [TOPLINK-4002] (Oracle TopLink Essentials - 2.1 (Build b52-fcs (09/24/2008))):
oracle.toplink.essentials.exceptions.DatabaseException
Internal Exception: java.sql.SQLException:
Io exception: The Network Adapter could not establish the connection
Error Code: 17002

Cause Was: wrong port number, ip address or network disconnection