Common Git Commands

 

# initialize local Git repository

git init

# create the main branch

git checkout -b main

# add local file (eg README.md) to staging

git add README.md

# commit the staging changes with comments (eg first commit)

git commit -m "first commit"

# add a remote repository (Git HTTPS or SSH URL: git@git.abc.com:company-name/Temp_Test_Repo.git)

git remote add origin git@git.abc.com:company-name/Temp_Test_Repo.git

# push the staging changes to the (remote) repository

git push origin main

# create the new branch (eg FY23-01) from main

git checkout -b FY23-01 main

# push the latest changes from the branch (eg FY23-01)

git push origin FY23-01

# revert local commits - for SHA, only need first 5 or 6 characters to differentiate

git revert <new commit SHA>

# undo the above revert

git revert <commit SHA of the previous revert>

# or, make a copy of the original commit

git cherry-pick <original commit SHA>

# check untracked files

git diff

# check local git status for uncommitted files etc

git status

# check git history

git log

# check git history by range

git log --online <start commit SHA>..<end commit SHA>

# cherry-pick multiple commits
git cherry-pick <start commit SHA>..<end commit SHA>

# delete a new local branch (eg FY23-01) in case of recreating
git branch -D FY23-01

# delete a remote branch
git push origin --delete FY23-01

# merge branch FY23-01 back to main

# switch to the target branch (eg main)

git switch main # or git checkout main

# merge from the source branch (eg FY23-01) without fast-forward

git merge --no-ff FY23-01

# push the merged changes back to the target branch (eg main) of the (remote) repository

git push origin main

# rebase from main to the branch created before some updates in main - merged from another branch - later

git switch main

git pull origin main

git switch out-of-date-branch

git rebase main

Common Oracle DDLs

-- Table

CREATE TABLE <table name>

( <field name> <data type> NOT NULL,

  -- ... ...

  CONSTRAINT <primary key name> PRIMARY KEY (field name)

);

COMMENT ON COLUMN <table name.field name> IS 'comments...';

ALTER TABLE <table name> ADD <field name> <data type>

-- Index

CREATE INDEX <index name> ON <table name> (<field name>);

DROP INDEX <index name>;

-- View

CREATE OR REPLACE FORCE VIEW <view name> (<field name>,...)

  SELECT <field name>,...

  FROM <table/view name>;

-- Sequence

CREATE SEQUENCE <sequence name> MINVALUE 1 MAXVALUE 1000000000 INCREMENT BY 1 START WITH 1;

-- Stored Function

CREATE OR REPLACE FUNCTION <function name> (<parameter name> IN <data type>, ...)

RETURN <data type>

IS

  <local variable name> <data type>;

BEGIN

  IF <condition> THEN

    <local variable name> := <value>;

  ELSE

    -- ... ...

  END IF;

  RETURN <local variable name>;

EXCEPTION

  WHEN OTHERS THEN

    RETURN NULL;

END <function name>;

-- Stored procedure

CREATE OR REPLACE PROCEDURE <procedure name> (<parameter name> IN <data type, ...)

IS

  <local variable> <data type>;

  CURSOR <cursor name> IS

    <select query statement>;

BEGIN

  OPEN <cursor name>;

  LOOP

    FETCH <cursor name> INTO <local variable>, ...;

    EXIT WHEN <cursor name>%NOTFOUND;

    -- iterator cursor

  END LOOP;

  CLOSE <cursor name>;

EXCEPTION

  WHEN OTHERS THEN

    <local vairable> := <value>;

    DBMS_OUTPUT.PUT_LINE('SQL Error: ...');

END <procedure name>;

/

-- Package

-- Specification

CREATE OR REPLACE <package name>

AS

    FUNCTION <function name> (<parameter name> IN <data type>, ...) RETURN <data type>;

    PROCEDURE <procedure name> (<parameter name> IN <data type>, ...);

    -- ...

END <package name>;

/

-- Body

CREATE OR REPLACE BODY <package name>

AS

  FUNCTION <function name> (<parameter name> IN <data type>, ...) 

  IS

     <local variable> <data type>;

  BEGIN

  END <function name>;

  -- ... ...

RETURN <data type>

END <package name>

-- Trigger

CREATE OR REPLACE <trigger name>

  BEFORE INSERT ON <table name> REFERENCING NEW AS NEW OLD AS OLD

  -- or AFTER INSERT OR UPDATE ON <table name> ...s

  FOR EACH ROW

DECLARE

  <local variable> <data type>;

BEGIN

  <local variable> := <value>;

  IF :NEW.id IS NULL THEN

    SELECT <sequence name>.NEXTVAL INTO <local variable> FROM DUAL;

    :NEW.id := <local variable>;

  END IF;

END;

-- Scheduled jobs

BEGIN

  DBMS_SCHEDULER.CREATE_JOB (

    job_name => '<job name>',

    job_type => 'PLSQL_BLOCK';

    job_action => 'BEGIN <stored procedure name(parameters...)> END;',

    start_date => TRUNC(SYSDATE, 'DD') + 23/24, -- starting at 23:00

    repeat_interval => 'FREQ=MONTHLY;BYMONTHDAY=22;'

    -- on 22nd every month; or FREQ=DAILY;BYHOUR=23, or FREQ=WEEKLY;BYDAY=FRI...s

  );

END;

/

-- Grant permission

GRANT SELECT,UPDATE,DELETE,INSERT,EXECUTE ON <table name> TO <user name>;

REVOKE SELECT,UPDATE,DELETE,INSERT,EXECUTE ON <table name> FROM <user name>;

-- Get environment information using system functions

SELECT SYS_CONTEXT('USERENV','OS_USER'), SYS_CONTEXT('USERENV','MODULE'), SYS_CONTEXT('USERENV','HOST') FROM DUAL;

 

Create Docker Container for SpringBoot Application

Pre-conditions:

• understand how to use Docker
• understand how to create SpringBoot applications

1. Package your SpringBoot application using Maven - "mvn clean package".
2. Create a DockerFile
• FROM openjdk:11-slim
• COPY ./target/KnowledgeBase-1.0.jar /usr/app/KnowledgeBase-1.0.jar
• WORKDIR /usr/app
• RUN sh -c "touch KnowledgeBase-1.0.jar"
• ENTRYPOINT ["java", "-jar", "KnowledgeBase-1.0.jar"]
3. Modify pom.xml to add repackage target to have a runnable .jar and maven-jar-plugin to specify mainClass in manifest.
4. Note: if your SpringBoot access a database (e.g. PostgreSQL) in another Docker container, need to change JDBC from localhost to the IP address of the database container (in application.properties).
5. Build Docker container using "docker build -t <image_name> ."
6. Verify the newly build image using "docker images"
7. Run the Docker container using "docker run --name <container_name> -p 8090:8080 <image_name>". Note: the trigger port can be different from the original one (e.g. 8090:8080)
8. the container can be stop and start using "docker container stop <container_name>" and "docker container start <container_name>" respectively.
9. check container logs using "docker container logs <container_name>"

Example of a SpringBoot data service

This is a simple database application using SpringBoot and PostgreSQL. The source code is at https://github.com/jonliu6/KnowledgeBase

1. create a Maven project template using "mvn archetype:generate".
2. fill in the application information.
• groupId, artifactId, version, package
3. open Maven project file - pom.xml and add SpringBoot and PostgreSQL dependencies.
4. create application.properties in src/main/resources with the application name, port and database connection information.
5. set up database and table(s) in PostgreSQL - scripts.
6. create SpringBoot entry application class (with @SpringBootApplication)
7. create a data model entity class (e.g. Article.java) mapping to the corresponding table (e.g. t_article).
8. create a repository interface extends from CrudRepository from Spring Data with the common method declarations (e.g. findAll(), save() and etc.).
9. create a controller class with org.springframework.web.bind.annotation.RestController.
• autowire the repository in the controller.
• create the HTTP RESTful methods in the controller.
10. build and run the SpringBoot application by running "mvn spring-boot:run"
11. test the controller method (e.g. http://<server>:<port>/<path>).

• curl -X GET http://localhost:8080/articles/
• curl -X GET http://localhost:8080/articles/Test
• curl -X POST -H "Content-Type: application/json" -d "{"""title""":"""2nd Article for testing purpose""","""category""":"""Test""","""description""":"""This is a test record added from SpringBoot RestController again."""}" http://localhost:8080/articles/add
• curl -X DELETE http://localhost:8080/articles/10008

How to create a Docker container for PostgreSQL

1. install Docker Desktop from https://www.docker.com/get-started based on your OS.
2. create your Docker account at https://hub.docker.com and log on.
3. open a command window (in Windows), and type docker --version to check the docker version.
• c:\users\testuser>docker --version
• Docker version 19.03.8, build afacb8b
4. start Docker Desktop and log on your Docket account.
5. search postgres from  https://hub.docker.com and click postgres Office Image.
6. in the command window, type "docker pull postgres" to get the latest PostgreSQL image. Note: by default, the PostgreSQL version is the latest. To get a particular version, execute "docker pull postgres:12.2".
7. in the command window, type the following to create and start a PostgreSQL container (-p for port number <trigger port #:port# in container>):
• docker run --name containername -h localhost -p 5435:5432 -e POSTGRES_PASSWORD=mypassword -d postgres:12.2
8. use "docker ps" or "docker container ls" to show the running container status. "docker ps -a" lists all existing containers.
9. to stop a docket container, type "docker stop containername"
10. to restart an existing container, type "docker start containername"
11. get in the docker container by typing "docker exec -it containername bash"
12. within the container bash shell, you can then log in PostgreSQL as usual
• psql -U postgres postgres
13. if you specified host and port numbers when creating the docker postgres container, you can access from the local machine using postgres client
• psql -h localhost -p 5435 -U postgres -W
14. to remove the container, use "docker rm -f containername"
15. to list docker images, type "docker images" or "docker image ls"
16. to remove an image by name, use "docker image rm -f imagename", or by id using "docker image rmi -f 93d5585e579d"

Java Application accessing Oracle Database by using Hibernate

1. Download Hibernate from http://www.hibernate.org/downloads or mvnrepository.com

2. Configure Hibernate by hibernate.cfg.xml or hibernate.properties
   hibernate.cfg.xml sample for Oracle
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" 
"http://www.jboss.org/dtd/hibernate/hibernate-configuration-3.0.dtd">
 <!-- // NOTE: if accessing .dtd has a problem, download .dtd to local and refer it from CLASSPATH like below -->
 <!-- <!DOCTYPE hibernate-configuration SYSTEM "classpath://org/hibernate/hibernate-configuration-3.0.dtd"> -->
<hibernate-configuration>
<session-factory> <!-- Oracle -->
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property> 
<property name="hibernate.connection.url">jdbc:oracle:thin:@server:port:SID</property> 
<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property> 
<property name="hibernate.default_schema">schema_name</property> 
<property name="hibernate.connection.username">user_name</property> 
<property name="hibernate.connection.password">user_password</property>
<property name="hibernate.connection.pool_size">10</property>
<property name="show_sql">true</property> 
<property name="hibernate.current_session_context_class">thread</property> 
<property name="hibernate.jdbc.batch_size">30</property>
</session-factory>
</hibernate-configuration>

   hibernate.properties sample for PostgreSQL
    hibernate.connection.driver_class = org.postgresql.Driver
    hibernate.connection.url = jdbc:postgresql://localhost:5432/mydatabase
    hibernate.connection.username = myuser
    hibernate.connection.password = secret
    hibernate.c3p0.min_size=5
    hibernate.c3p0.max_size=20
    hibernate.c3p0.timeout=1800
    hibernate.c3p0.max_statements=50
    hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect

3. Create a Hibernate Java project in Maven with required dependencies, including:
    database client library files. e.g. ojdbc*.jar for Oracle, postgresql*.jar for PostgreSQL
hibernate-core
hibernate-entitymanager for Hibernate JPA implementation
hibernate-ehcache for using Hibernate cache mechenism
    e.g. in pom.xml
    <properties>
        <hibernate.version>4.3.5.Final</hibernate.version> <!-- bundled with Wildfly 8.1.0 -->
    </properties>
    <dependencies>
      <dependency>
        <groupId>com.oracle</groupId>
        <artifactId>ojdbc</artifactId>
        <version>5.0</version>
      </dependency>
      <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>${hibernate.version}</version>
      </dependency>
      <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>${hibernate.version}</version>
      </dependency>
      <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-ehcache</artifactId>
        <version>${hibernate.version}</version>
      </dependency>
  </dependencies>

4. Create an Entity object mapped with the data structure (e.g. a table or a view) in DB
    For an example of Student Table in DB, the entity class defined as Student in below:
@Entity
 @Table(name="Student_Table")
public class Student {
 @Id
@Column(name="Student_Id")
private String studentId;

@Column(name="First_Name")
private String firstName;

@Column(name="Last_Name")
private String lastName;

public String getStudentId(){ return studentId; }
public void setStudentId(String id) { this.studentId = id; }

public String getFirstName(){ return firstName; }
public void setFirstName(String name) { this.firstName = name; }

public String getLastName(){ return lastName; }
public void setLastName(String name) { this.lastName = name; }
}

5. Map the entity class in hibernate.cfg.xml by adding the following in <session-factory />
    <mapping class="org.freecode.demo.entity.Student" /> <!-- // full class name with package -->

6. Access DB through Hibernate
    public static void main(String[] args) {
String configFile = "hibernate.cfg.xml"; // load Hibernate configuration
Configuration cfg = new Configuration();
cfg.configure(configFile);
StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder();
ssrb.applySettings(cfg.getProperties());
ServiceRegistry sr = ssrb.build();
SessionFactory sf = cfg.buildSessionFactory(sr); // initialize a session factory
Session s = sf.openSession();
// Session s = sf.getCurrentSession(); // initialize a DB session
// Transaction tx = null;
try {
// tx = s.beginTransaction();
List<ProjectCause> causes = s.createQuery("FROM Student").list(); // create a Hibernate Query to get all student objects from the DB session
// tx.commit();
if (causes != null) {
for (ProjectCause c : causes) {
System.out.println("Student: " + c.getStudentId() + " - " c.getFirstName() + " " + c.getLastName());
}
}
}
catch (HibernateException he) {
he.printStackTrace();
// tx.rollback();
}
finally {
if (s.isOpen()) {
            s.close();
}
}
}

7. Use Hibernate JPA Implementation by creating JPA descriptor - persistence.xml
    <?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/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_2_0.xsd"
version="2.0">
  <persistence-unit name="Hibernate_JPA_Unit" transaction-type="RESOURCE_LOCAL"> <!-- non EJB type -->
<description>Persistence Unit for JPA Implementation</description>
<provider>org.hibernate.ejb.HibernatePersistence</provider>
  <class>org.freecode.demo.entity.Student</class> <!-- need to map the class for WAR, EAR -->
<properties>
  <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver" />
  <property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@server:port:SID" />
  <property name="javax.persistence.jdbc.user" value="db user" />
  <property name="javax.persistence.jdbc.password" value="db password" />
  <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect" />
  
  <!-- for caching, require hibernate-ehcache.jar -->
  <property name="hibernate.cache.use_second_level_cache" value="true"/>
  <property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory"></property>
  <property name="hibernate.cache.use_query_cache" value="true"></property>

  <property name="hibernate.jdbc.batch_size" value="30"/>
  <property name="hibernate.show_sql" value="true" />
  <!-- logger: org.hibernate.SQL, org.hibernate.engine.query, org.hibernate.type, org.hibernate.jdbc -->
  <property name="hibernate.format_sql" value="true"/>
  <property name="hibernate.transaction.flush_before_completion" value="true" />
</properties>
  </persistence-unit>
</persistence>

8. Access DB through Hibernate JPA
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("Hibernate_JPA_Unit"); // unit name is defined in persistence.xml
EntityManager em = emf.createEntityManager();

try {
Query qry = em.createQuery("SELECT c FROM Student c");
List<ProjectCause> students = qry.getResultList();
if (causes != null) {
for (Student std : students) {
System.out.println(std.getStudentId() + " - " + std.getFirstName() + " " + c.getLastName());
}
}
}
catch (Exception ex) {
ex.printStackTrace();
}
finally {
if (em.isOpen()) {
em.close();
}
em = null;
if (emf.isOpen()) {
emf.close();
}
emf = null;
}

Configure Different Database Connections in Wildfly/JBoss Application Server

1. download and copy the database driver libraries
   For Oralce, search ojdbc from Oracle, https://www.oracle.com/technetwork/database/features/jdbc/jdbc-ucp-122-3110062.html
   For MS SQL Server, https://www.microsoft.com/en-us/download/details.aspx?id=56615
   For MySQL, https://dev.mysql.com/downloads/connector/j/
   For PostgreSQL, https://jdbc.postgresql.org/download.html

2. install and configure the database drivers in Wildfly/JBoss system modules
   For Oracle, copy ojdbc?.jar (e.g. ojdbc7.jar) to %JBOSS_HOME%/modules/system/layers/base/com/oracle/main (create folders when necessary). Create a configuration file, module.xml in the same folder with the driver file.
       <?xml version="1.0" encoding="UTF-8"?>
<module xmlns="urn:jboss:module:1.1" name="com.oracle">
  <resources>
<resource-root path="ojdbc5.jar"/>
  </resources>
  <dependencies>
<module name="javax.api"/>
<module name="javax.transaction.api"/>
  </dependencies>
</module>

   For MS SQL Server, copy mssql-jdbc-x.x.x.jre?.jar (e.g. mssql-jdbc-6.2.2.jre7) into %JBOSS_HOME%/modules/system/layers/base/com/microsoft/sqlserver/main. Create a configuration file, module.xml in the same folder with the driver file.
       <?xml version="1.0" encoding="UTF-8"?>
<module xmlns="urn:jboss:module:1.1" name="com.microsoft.sqlserver">
  <resources>
<resource-root path="mssql-jdbc-6.2.2.jre7.jar"/>
  </resources>
  <dependencies>
<module name="javax.api"/>
<module name="javax.transaction.api"/>
<module name="javax.xml.bind.api"/>
  </dependencies>
</module>

   For MySQL, copy mysql-connector-java-x.x.x.jar (e.g. mysql-connector-java-5.1.44.jar) into %JBOSS_HOME%/modules/system/layers/base/com/mysql/main. Create a configuration file, module.xml in the same folder with the driver file.
   <?xml version="1.0" encoding="UTF-8"?>
<module xmlns="urn:jboss:module:1.1" name="com.mysql">
  <resources>
<resource-root path="mysql-connector-java-5.1.44.jar"/>
  </resources>
  <dependencies>
<module name="javax.api"/>
<module name="javax.transaction.api"/>
  </dependencies>
</module>

For PostgreSQL, copy postgresql-x.x.x.jre?.jar (e.g. postgresql-9.4.1209.jre6.jar) into %JBOSS_HOME%/modules/system/layers/base/org/postgresql/main. Create a configuration file, module.xml in the same folder with the driver file.
    <?xml version="1.0" encoding="UTF-8"?>
<module xmlns="urn:jboss:module:1.1" name="org.postgresql">
  <resources>
<resource-root path="postgresql-9.4.1209.jre6.jar"/>
  </resources>
  <dependencies>
<module name="javax.api"/>
<module name="javax.transaction.api"/>
  </dependencies>
</module>

3. Configure the database drivers and data sources in Wild/JBoss Application Server.
    Open and update the Wildfly/JBoss configuration file (e.g. standalone.xml) by adding the database driver and data source information like the following: (Note: make sure the driver name, module name and etc. match with the configuration previously mentioned)

        <subsystem xmlns="urn:jboss:domain:datasources:2.0">
            <datasources>
                ... ...
<!-- // Connection Pool of Oracle. java:/jdbc/myoracle is used in applications -->
                <datasource jndi-name="java:/jdbc/myoracle" pool-name="myOraclePool" enabled="true" use-java-context="true">
                    <connection-url>jdbc:oracle:thin:@server_name:1521:SID</connection-url>
                    <driver>oracle_driver</driver>
                    <security>
                        <user-name>db_user_name</user-name>
                        <password>db_user_password</password>
                    </security>
                </datasource>

<!-- // Connection Pool for MS SQL Server Express -->
                <datasource jndi-name="java:/jdbc/MsSQLSvrDS" pool-name="MsSQLPool" enabled="true" use-java-context="true">
                    <connection-url>jdbc:sqlserver://server_name\SQLEXPRESS:54126;databaseName=TestDB;integratedSecurity=true;</connection-url>
                    <driver-class>com.microsoft.sqlserver.jdbc.SQLServerDriver</driver-class>
                    <driver>sqlserver_driver</driver>
                    <pool>
                        <min-pool-size>5</min-pool-size>
                        <max-pool-size>10</max-pool-size>
                    </pool>
                    <security>
                        <user-name>db_user_name</user-name>
                        <password>db_user_password</password>
                    </security>
                </datasource>

<!-- // Connection Pool for MySQL -->
                <datasource jndi-name="java:/jdbc/MySQLDS" pool-name="MySQLDS" enabled="true" use-java-context="true">
                    <connection-url>jdbc:mysql://server_name:3306/my_test_db</connection-url>
                    <driver>mysql_driver</driver>
                    <pool>
                        <min-pool-size>1</min-pool-size>
                        <max-pool-size>5</max-pool-size>
                    </pool>
                    <security>
                        <user-name>db_user_name</user-name>
                        <password>db_user_password</password>
                    </security>
                </datasource>

                <!-- // Connection Pool for MySQL -->
                <datasource jta="false" jndi-name="java:/jdbc/PostgreSQLDS" pool-name="PostgreSQLDS" enabled="true" use-ccm="false">
                    <connection-url>jdbc:postgresql://server_name:5432/my_test_db</connection-url>
                    <driver-class>org.postgresql.Driver</driver-class>
                    <driver>postgresql_driver</driver>
                    <pool>
                        <min-pool-size>1</min-pool-size>
                        <max-pool-size>5</max-pool-size>
                    </pool>
                    <security>
                        <user-name>db_user_name</user-name>
                        <password>db_user_password</password>
                    </security>
                </datasource>
                <drivers>
                    ... ...
                    <!-- // Oracle Driver -->
    <driver name="oracle_driver" module="com.oracle">
                        <driver-class>oracle.jdbc.OracleDriver</driver-class>
                    </driver>

                    <!-- // MS SQL Server Driver -->
                    <driver name="sqlserver_driver" module="com.microsoft.sqlserver">
                        <driver-class>com.microsoft.sqlserver.jdbc.SQLServerDriver</driver-class>
                    </driver>
                   
                    <!-- // MySQL Driver -->
                    <driver name="mysql_driver" module="com.mysql">
                        <driver-class>com.mysql.jdbc.Driver</driver-class>
                    </driver>

                    <!-- // PostgreSQL Driver -->
                    <driver name="postgresql_driver" module="org.postgresql">
                        <driver-class>org.postgresql.Driver</driver-class>
                    </driver>
                </drivers>
            </datasources>
        </subsystem>

4. Start the Wildfly/JBoss application server and verify the database connectivities from the server logs.

5. Use the connection pool for JPA.
    Find and update persistence.xml as following in the application folder, /src/main/resources/META-INF/persistence.xml.

<persistence-unit name="Persistence_Unit_Name"> <!-- referenced in application //-->
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <jta-data-source>PostgreSQLDS</jta-data-source> <!-- // for example of PostgreSQL datasource defined in Wildfly/JBoss -->
<properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
            <property name="hibernate.show_sql" value="false" /> <!-- Debugging purpose //-->
            <property name="hibernate.generate_statistics" value="false"/> <!-- Debugging purpose //-->
        </properties>
</persistence-unit>

If not use Connection Pool defined in Wildfly/JBoss application server, need to specify the database connection information in preperties as well.
<persistence-unit name="Persistence_Unit_Name" transaction-type="RESOURCE_LOCAL"> <!-- referenced in application //-->
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <properties>
<property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://server_name:5432/my_test_db" />
            <property name="javax.persistence.jdbc.user" value="db_user_name" />
            <property name="javax.persistence.jdbc.password" value="db_user_password" />

     <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
        </properties>
</persistence-unit>