Click here to download eclipse supported ZIP file
Introduction of UUID(Universally Unique Identifier) :
I am talking about
UUID surrogate keys and
the use cases when there are more appropriate than the more common auto-incrementing identifiers.
A UUID database type
There are several ways to represent a 128-bit UUID, and whenever in doubt I like to resort to Stack Exchange for an expert advice.
Because table identifiers are usually indexed, the more compact the database type the less space will the index require. From the most efficient to the least, here are our options:
- Some databases (PostgreSQL, SQL Server) offer a dedicated UUID storage type
- Otherwise we can store the bits as a byte array (e.g. RAW(16) in Oracle or the standard BINARY(16) type)
- Alternatively we can use 2 bigint (64-bit) columns, but a composite identifier is less efficient than a single column one
- We can store the hex value in a CHAR(36) column (e.g 32 hex values and 4 dashes), but this will take the most amount of space, hence it’s the least efficient alternative
Hibernate offers many identifier strategies to choose from and for UUID identifiers we have three options:
- the assigned generator accompanied by the application logic UUID generation
- the hexadecimal “uuid” string generator
- the more flexible “uuid2” generator, allowing us to use java.lang.UUID, a 16 byte array or a hexadecimal String value
The UUID contains: IP address, startup time of the JVM that is accurate to a quarter second,
system time and a counter value that is unique within the JVM. It is not possible to obtain a MAC
address or memory address from Java code, so this is the best option without using JNI.
Here is the example code to test UUID functionality :
This is hibernate.cfg.xml file for connecting the postgreSQL database.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<!-- <session-factory> <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
hibernate word is optional <property name="connection.url">jdbc:oracle:thin:@localhost:1521:ORCL</property>
<property name="hibernate.connection.username">kcv</property> <property name="hibernate.connection.password">kcv</property>
<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>
<property name="show_sql">true</property> <mapping resource="Employee.hbm.xml"/>
</session-factory> -->
<session-factory>
<property name="hibernate.current_session_context_class">thread</property>
<property name="hbm2ddl.auto">create</property>
<property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
<property name="connection.url">jdbc:postgresql://localhost:5432/hibernate</property>
<property name="connection.username">postgres</property>
<property name="connection.password">password</property>
<property name="connection.driver_class">org.postgresql.Driver</property>
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<property name="use_sql_comments">true</property>
<mapping resource="EmployeeBean.hbm.xml" />
</session-factory>
</hibernate-configuration>
|
This is EmployeeBean.hbm.xml mapping file for map the Entity(POJO) class to columns.
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.cv.hibernate.algorithm.model.EmployeeBean"
table="EMPLOYEE_UUID">
<!-- UUID algorithm... -->
<id name="id" type="java.lang.String">
<column name="EID" />
<generator class="uuid" />
</id>
<!--GUID is not supported by the postgres database... -->
<!-- <id name="id" type="java.lang.String"> <column name="EID" length="40"
/> <generator class="guid" /> </id> -->
<property name="firstName" type="java.lang.String">
<column name="FIRSTNAME" length="29" not-null="true" />
</property>
<property name="lastName" type="java.lang.String">
<column name="LASTNAME" length="29" not-null="true" />
</property>
<property name="email" type="java.lang.String">
<column name="EMAIL" length="39" not-null="true" />
</property>
</class>
</hibernate-mapping>
|
This is EmployeeBean.java Entity(POJO) class having the fields needs to be configured in mapping file.
package com.cv.hibernate.algorithm.model;
/**
* @author Chandra Vardhan
*/
public class EmployeeBean {
private String id;
private String firstName;
private String lastName;
private String email;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
} |
This is HibernateUtil.java utility class for getting the database connection.
package com.cv.hibernate.algorithm.util;
import org.apache.log4j.Logger;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import com.cv.hibernate.algorithm.model.EmployeeBean;
/**
* Configures and provides access to Hibernate sessions, tied to the current
* thread of execution. Follows the Thread Local Session pattern, see
* {@link http://hibernate.org/42.html }.
*/
public class HibernateUtil {
private final static Logger logger = Logger.getLogger(HibernateUtil.class);
/**
* Location of hibernate.cfg.xml file. Location should be on the classpath
* as Hibernate uses #resourceAsStream style lookup for its configuration
* file. The default classpath location of the hibernate config file is in
* the default package. Use #setConfigFile() to update the location of the
* configuration file for the current session.
*/
private static String CONFIG_FILE_LOCATION = "hibernate.cfg.xml";
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
private static Configuration configuration = new Configuration();
private static SessionFactory sessionFactory;
static {
try {
configuration = configuration.configure(CONFIG_FILE_LOCATION);
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties());
sessionFactory = configuration.buildSessionFactory(builder.build());
logger.info("%%%% Connection successful %%%%");
} catch (Exception e) {
logger.error("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
private HibernateUtil() {
}
/**
* Returns the ThreadLocal Session instance. Lazy initialize the
* <code>SessionFactory</code> if needed.
*
* @return Session
* @throws HibernateException
*/
public static Session getSession() throws HibernateException {
Session session = (Session) threadLocal.get();
if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
session = (sessionFactory != null) ? sessionFactory.openSession() : null;
threadLocal.set(session);
}
return session;
}
/**
* Rebuild hibernate session factory
*
*/
public static void rebuildSessionFactory() {
try {
configuration = configuration.configure(CONFIG_FILE_LOCATION);
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties());
sessionFactory = configuration.buildSessionFactory(builder.build());
logger.info("%%%% Connection successful %%%%");
} catch (Exception e) {
logger.error("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
/**
* Close the single hibernate session instance.
*
* @throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
session.close();
System.exit(0);
}
}
/**
* return session factory
*
*/
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
/**
* return hibernate configuration
*
*/
public static Configuration getConfiguration() {
return configuration;
}
public static void saveOrUpdate() {
Session ses = getSession();
EmployeeBean eb = new EmployeeBean();
eb.setId("");
eb.setFirstName("chandra");
eb.setLastName("vardhan");
eb.setEmail("meetkodam@gmail.com");
ses.beginTransaction();
ses.saveOrUpdate(eb);
logger.info("Saved successful...");
ses.getTransaction().commit();
ses.close();
}
} |
This is UUID.java main class having the application business logic.
package com.cv.hibernate.algorithm;
import org.apache.log4j.Logger;
import org.hibernate.Session;
import com.cv.hibernate.algorithm.model.EmployeeBean;
import com.cv.hibernate.algorithm.util.HibernateUtil;
/**
* @author Chandra Vardhan
*/
public class UUID {
/**
* @param args
*/
private final static Logger logger = Logger.getLogger(UUID.class);
public static void main(String[] args) {
Session ses = HibernateUtil.getSession();
EmployeeBean eb = new EmployeeBean();
eb.setFirstName("chandra");
eb.setLastName("vardhan");
eb.setEmail("meetkodam@gmail.com");
ses.beginTransaction();
ses.saveOrUpdate(eb);
logger.info("Saved successful...");
ses.getTransaction().commit();
HibernateUtil.closeSession();
}
} |
This is log4j.properties file having the entries for logging the information into the console/file.
#By default enabling Console appender
# Root logger option
log4j.rootLogger=INFO, stdout
# Redirect log messages to console
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%-5p [%c]:%L -->> %m%n
# Redirect log messages to a log file
#log4j.appender.file=org.apache.log4j.RollingFileAppender
#log4j.appender.file.File=C:\\servlet-application.log
#log4j.appender.file.MaxFileSize=5MB
#log4j.appender.file.MaxBackupIndex=10
#log4j.appender.file.layout=org.apache.log4j.PatternLayout
#log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n
|
This is pom.xml file having the entries of dependency jars and information to build the application .
| <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.cv.hibernate.algorithm</groupId>
<artifactId>algorithms</artifactId>
<version>1.0</version>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.3.5.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-c3p0</artifactId>
<version>4.3.5.Final</version>
</dependency>
<dependency>
<artifactId>hibernate-core</artifactId>
<groupId>org.hibernate</groupId>
<version>4.3.5.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>4.2.0.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate.common</groupId>
<artifactId>hibernate-commons-annotations</artifactId>
<version>4.0.4.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate.javax.persistence</groupId>
<artifactId>hibernate-jpa-2.0-api</artifactId>
<version>1.0.1.Final</version>
</dependency>
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
<version>1.0.0.GA</version>
provided
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.6.4</version>
</dependency>
<dependency>
<groupId>org.jboss.logging</groupId>
<artifactId>jboss-logging</artifactId>
<version>3.1.0.CR2</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.6.4</version>
</dependency>
<dependency>
<groupId>postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>9.1-901.jdbc4</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.5</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
|
No comments:
Post a Comment