Skip to main content

Spring Framework Annotation - Part 4

JPA
@Repostories
@Transactional
@PersistenceContext - for @Inject Entity Manager
@Entity on class mapped to a table
@Id
@GeneratedValue (strategy = GenerationType.AUTO)
@ManyToOne many current object to one related object.
@OneToMany one current object to many other related objects.
@JoinColumn: the column used to join two objects together.

example,

@Entity
public class Item {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@ManyToOne
private Order order;
}


/**
 * An order.
 */
@Entity
@Table(name="T_ORDER")
public class Order {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;

private String customer;

@OneToMany(cascade=CascadeType.ALL)
@JoinColumn(name="ORDER_ID")
private Collection<Item> items = new LinkedHashSet<Item>();
...
}

Comments

Popular posts from this blog

Stretch a row if data overflows in jasper reports

It is very common that some columns of the report need to stretch to show all the content in that column. But  if you just specify the property " stretch with overflow' to that column(we called text field in jasper report world) , it will just stretch that column and won't change other columns, so the row could be ridiculous. Haven't find the solution from internet yet. So I just review the properties in iReport one by one and find two useful properties(the bold highlighted in example below) which resolve the problems.   example:
<band height="20" splitType="Stretch"> <textField isStretchWithOverflow="true" pattern="" isBlankWhenNull="true"> <reportElement stretchType="RelativeToTallestObject" mode="Opaque" x="192" y="0" width="183" height="20"/> <box leftPadding="2"> <pen lineWidth="0.25"/> …

JasperReports - Configuration Reference

Spring - Operations with jdbcTemplate

This class manages all the database communication and exception handling using a java.sql.Connection that is obtained from the provided DataSource. JdbcTemplate is a stateless and threadsafe class and you can safely instantiate a single instance to be used for each DAO.


Use of Callback Methods
JdbcTemplate is based on a template style of programming common to many other parts of Spring. Some method calls are handled entirely by the JdbcTemplate, while others require the calling class to provide callback methods that contain the implementation for parts of the JDBC workflow. This is another form of Inversion of Control. Your application code hands over the responsibility of managing the database access to the template class. The template class in turn calls back to your application code when it needs some detail processing filled in. These callback methods are allowed to throw a java.sql.SQLException, since the framework will be able to catch this exception and use its built-in excepti…