Hibernate - Revision history

Rasimsen: /* Eager and Lazy Loading */

2018-11-07T15:15:43Z

‎Eager and Lazy Loading

Rasimsen at 15:13, 7 November 2018

2018-11-07T15:13:59Z

Rasimsen at 22:35, 30 July 2018

2018-07-30T22:35:56Z

Rasimsen: /* hibernate.cfg.xml */

2018-07-30T22:23:50Z

‎hibernate.cfg.xml

Rasimsen at 21:06, 21 June 2018

2018-06-21T21:06:19Z

Rasimsen at 21:05, 21 June 2018

2018-06-21T21:05:52Z

Rasimsen: /* Application main class */

2018-06-21T20:21:52Z

‎Application main class

Rasimsen: /* POJO class */

2018-06-21T20:21:06Z

‎POJO class

Rasimsen: /* POJO class */

2018-06-21T20:20:28Z

‎POJO class

Rasimsen at 20:02, 21 June 2018

2018-06-21T20:02:34Z

@@ Line 241: / Line 241: @@
 '''Eager Loading''' is a design pattern in which data initialization occurs on the spot
 '''Lazy Loading''' is a design pattern which is used to defer initialization of an object as long as it’s possible
 Let’s see how this actually works with some examples:
@@ Line 267: / Line 268: @@
 The UserLazy class:
-<syntaxhighlight>
+<syntaxhighlight lang="java">
 @Entity
 @Table(name = "USER")
@@ Line 287: / Line 288: @@
 The OrderDetail class:
-<syntaxhighlight>
+<syntaxhighlight lang="java">
 @Entity
 @Table (name = "USER_ORDER")
@@ Line 310: / Line 311: @@
 But, when '''lazy loading is enabled, if we pull up a UserLazy, OrderDetail data won’t be initialized and loaded into a memory until an explicit call is made to it.'''
 source: https://www.baeldung.com/hibernate-lazy-eager-loading
 ==JBOSS - Hibernate Tools==

← Older revision		Revision as of 15:13, 7 November 2018
Line 236:		Line 236:
	</syntaxhighlight>		</syntaxhighlight>

		+	==Eager and Lazy Loading==
		+
		+	The first thing that we should discuss here is what lazy loading and eager loading are:
		+
		+	'''Eager Loading''' is a design pattern in which data initialization occurs on the spot
		+	'''Lazy Loading''' is a design pattern which is used to defer initialization of an object as long as it’s possible
		+	Let’s see how this actually works with some examples:
		+
		+	===Lazy Loading===
		+	'''Advantages:'''
		+
		+	*Initial load time much smaller than in the other approach
		+	*Less memory consumption than in the other approach
		+
		+	'''Disadvantages:'''
		+
		+	*Delayed initialization might impact performance during unwanted moments
		+	*In some cases you need to handle lazily-initialized objects with a special care or you might end up with an exception
		+
		+	===Eager Loading:===
		+	'''Advantages:'''
		+
		+	*No delayed initialization related performance impacts
		+
		+	'''Disadvantages:'''
		+
		+	*Long initial loading time
		+	*Loading too much unnecessary data might impact performance
		+
		+
		+	The UserLazy class:
		+	<syntaxhighlight>
		+	@Entity
		+	@Table(name = "USER")
		+	public class UserLazy implements Serializable {
		+
		+	@Id
		+	@GeneratedValue
		+	@Column(name = "USER_ID")
		+	private Long userId;
		+
		+	@OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
		+	private Set<OrderDetail> orderDetail = new HashSet();
		+
		+	// standard setters and getters
		+	// also override equals and hashcode
		+
		+	}
		+	</syntaxhighlight>
		+
		+	The OrderDetail class:
		+	<syntaxhighlight>
		+	@Entity
		+	@Table (name = "USER_ORDER")
		+	public class OrderDetail implements Serializable {
		+
		+	@Id
		+	@GeneratedValue
		+	@Column(name="ORDER_ID")
		+	private Long orderId;
		+
		+	@ManyToOne(fetch = FetchType.LAZY)
		+	@JoinColumn(name="USER_ID")
		+	private UserLazy user;
		+
		+	// standard setters and getters
		+	// also override equals and hashcode
		+
		+	}
		+	</syntaxhighlight>
		+	One User can have multiple OrderDetails. '''In eager loading strategy, if we load the User data, it will also load up all orders associated with it and will store it in a memory.'''
		+
		+	But, when '''lazy loading is enabled, if we pull up a UserLazy, OrderDetail data won’t be initialized and loaded into a memory until an explicit call is made to it.'''
		+
		+	source: https://www.baeldung.com/hibernate-lazy-eager-loading

	==JBOSS - Hibernate Tools==		==JBOSS - Hibernate Tools==

← Older revision		Revision as of 22:35, 30 July 2018
Line 188:		Line 188:

	</syntaxhighlight>		</syntaxhighlight>
		+
		+	===Example of @ForeignKey in Hibernate===
		+	Hibernate allows to keep foreign key name. Hibernate overrides the foreign key name by '''@ForeignKey'''. It has the attribute name that should be defined. Find the example.
		+
		+	<source>
		+	- @ForeignKey(name="FK_COUNTRY")
		+	- @ManyToOne
		+	- @OneToMany(cascade=CascadeType.ALL)
		+	- @JoinColumn(name="country_id")
		+	</source>
		+
		+	<syntaxhighlight lang="java">
		+
		+	@Entity
		+	@Table(name = "state")
		+	public class State {
		+	@Id
		+	@Column(name = "id")
		+	private int id;
		+
		+	@Column(name = "name")
		+	private String name;
		+
		+	@ManyToOne
		+	@ForeignKey(name="FK_COUNTRY")
		+	private Country country;
		+	}
		+
		+	</syntaxhighlight>
		+
		+
		+	<syntaxhighlight lang="java">
		+	@Entity
		+	public class Country implements Serializable {
		+	private static final long serialVersionUID = 1L;
		+	@Id
		+	@Column(name="id")
		+	private int id;
		+
		+	@Column(name="name")
		+	private String name;
		+
		+	@OneToMany(cascade=CascadeType.ALL)
		+	@JoinColumn(name="country_id")
		+	private Set<State> states;
		+	}
		+	</syntaxhighlight>
		+

	==JBOSS - Hibernate Tools==		==JBOSS - Hibernate Tools==

@@ Line 63: / Line 63: @@
      <session-factory>
          <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
-         <property name="hibernate.connection.url">jdbc:mysql://testmysql.oasissofttech.com:3306/oasis_test_db</property>
+         <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/oasis_test_db</property>
          <property name="hibernate.connection.username">oasisdbtestuser</property>
-         <property name="hibernate.connection.password">test97531</property>
+         <property name="hibernate.connection.password">passwd</property>
          <!--  <property name="hbm2ddl.auto">create</property>  - deletes table and create new -->
          <!--  <property name="hbm2ddl.auto">update</property>  - if exist run the query, otherwise create table first-->

@@ Line 225: / Line 225: @@
 ==Resource==
 [http://hibernate.org http://hibernate.org]
 Hibernate eclipse plugin - JBOSS : [https://tools.jboss.org/features/hibernate.html https://tools.jboss.org/features/hibernate.html]

← Older revision		Revision as of 21:05, 21 June 2018
Line 223:		Line 223:


		+	==Resource==
		+	[http://hibernate.org http://hibernate.org]
	Hibernate eclipse plugin - JBOSS : [https://tools.jboss.org/features/hibernate.html https://tools.jboss.org/features/hibernate.html]		Hibernate eclipse plugin - JBOSS : [https://tools.jboss.org/features/hibernate.html https://tools.jboss.org/features/hibernate.html]

@@ Line 166: / Line 166: @@
 	public static void main(String[] args) {
-		Alien alien = new Alien();
+		ParameterTable prm = new ParameterTable();
-		alien.setAid(1);
+		prm.setPid(1);
-		alien.setAname("rasim");
+		prm.setParameterName("Country");
-		alien.setAcolor("green");
+		prm.setParameterDesc("Countries description");
-		Configuration con = new Configuration().configure().addAnnotatedClass(Alien.class);
+		Configuration con = new Configuration().configure().addAnnotatedClass(ParameterTable.class);
 		SessionFactory buildSessionFactory = con.buildSessionFactory();
 		Session session = buildSessionFactory.openSession();
 		Transaction transaction = session.beginTransaction();
-		session.save(alien);
 		transaction.commit();
@@ Line 183: / Line 188: @@
 </syntaxhighlight>
 ==JBOSS - Hibernate Tools==

@@ Line 89: / Line 89: @@
 @Entity
-@Table(name = "metric")
+@Table(name = "PARAMETER_TABLE")
 public class ParameterTable {
 	@Id

@@ Line 80: / Line 80: @@
 package com.oasissofttech.springmvc;
 import javax.persistence.Entity;
 import javax.persistence.Id;
 @Entity
-public class Alien {
+@Table(name = "metric")
 	@Id
-	private int aid;
+	@GeneratedValue(strategy = GenerationType.AUTO)
-	private String aname;
+	@Column(name = "PRM_ID")
-	private String acolor;
+	private int pid;
-	public Alien() {
+	@Column(name = "PRM_DESC")
+	}
-	public Alien(int aid, String aname, String acolor) {
+	public ParameterTable(int pid, String parameterName, String parameterDesc) {
 		super();
-		this.aid = aid;
+		this.pid = pid;
-		this.aname = aname;
+		this.parameterName = parameterName;
-		this.acolor = acolor;
+		this.parameterDesc = parameterDesc;
+	}
-	public int getAid() {
+	public void setPid(int pid) {
-		return aid;
+		this.pid = pid;
+	}
-	public void setAid(int aid) {
+	public String getParameterName() {
-		this.aid = aid;
+		return parameterName;
+	}
-	public String getAname() {
+	public void setParameterName(String parameterName) {
-		return aname;
+		this.parameterName = parameterName;
+	}
-	public void setAname(String aname) {
+	public String getParameterDesc() {
-		this.aname = aname;
+		return parameterDesc;
+	}
-	public String getAcolor() {
+	public void setParameterDesc(String parameterDesc) {
-		return acolor;
+		this.parameterDesc = parameterDesc;
+	}
-	public void setAcolor(String acolor) {
+	public String getDoNotCreateThisColumnInTable() {
-		this.acolor = acolor;
+		return doNotCreateThisColumnInTable;
+	}
+}
 </syntaxhighlight>

@@ Line 55: / Line 55: @@
 <syntaxhighlight lang="xml">
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE hibernate-configuration PUBLIC
@@ Line 65: / Line 66: @@
          <property name="hibernate.connection.username">oasisdbtestuser</property>
          <property name="hibernate.connection.password">test97531</property>
      </session-factory>
 </hibernate-configuration>
 </syntaxhighlight>