Skip to main content

Tomcat Database Connection Pooling (JPA)

Follow these simple steps to setup Database Connection Pooling inside Tomcat 6.x

Step 1

Add following element to conf/context.xml file. This Resource will be avaible to all Applications deployed

<Resource name="jdbc/SampleDb" auth="Container" type="javax.sql.DataSource"
maxActive="50" maxIdle="3" maxWait="10000"
username="" password=""
driverClassName=""
url=""/>

provide values for all attributes (username, password, driverClassName, url etc)

Step 2
Add following to web.xml of your Application

<resource-ref>
<description>DB Connection</description>
<res-ref-name>jdbc/SampleDB</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>

Step 3
Refer JNDI Data source inside your persistence.xml

If you want to use JTA use this configuration

<persistence-unit name="SamplePU" transaction-type="JTA">
<jta-data-source>java:/comp/env/jdbc/SampleDB</jta-data-source>
..
</persistence-unit>

and for non JTA
<persistence-unit name="SamplePU" transaction-type="RESOURCE_LOCAL">
<non-jta-data-source>java:/comp/env/jdbc/SampleDB</non-jta-data-source>
..
</persistence-unit>

Comments

Anonymous said…
Many thanks for the information. It was very useful.
Anonymous said…
Thank you. It is very useful.

Popular posts from this blog

Access multiple Databases in JPA

According to JPA specification we can define multiple "persistence-unit" elements (i.e. like below) in persistence.xml file and can easily refer them inside Dao layers as this. public class PolarDaoImpl {     @PersistenceContext(unitName="PolarPU")     protected EntityManager entityManager; -- } public class BearDaoImpl {     @PersistenceContext(unitName="BearPU")     protected EntityManager entityManager; -- } Checkout sample persistence.xml <?xml version="1.0" encoding="UTF-8"?> <persistence version="2.0" 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">     <!-- Database 1 -->     <persistence-unit name="PolarPU" transaction-type="RESOURCE_LOCAL">         <

JPA 2 new feature @ElementCollection explained

@ElementCollection is new annotation introduced in JPA 2.0, This will help us get rid of One-Many and Many-One shitty syntax. Example 1: Stores list of Strings in an Entity @Entity public class Users implements Serializable {     private static final long serialVersionUID = 1L;     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Long id;     @ElementCollection     private List<String> certifications = new ArrayList <String> ();     public Long getId() {         return id;     }     public void setId(Long id) {         this.id = id;     }     public List <String> getCertifications() {         return certifications;     }     public void setCertifications(List <String> certifications) {         this.certifications = certifications;     } .. }         Users u = new Users();         u.getCertifications().add("Sun Certified Java Programmer");         em.persist(u); Generated Tables    Users    Co

Reuse JPA Entities as DTO

Note : Major design advantages of JPA Entities are they can detached and used across tiers and networks and later can by merged. Checkout this new way of querying entities in JPA 2.0 String ql = " SELECT new prepclass2.Employee (e.firstname, e.lastname) FROM Employee e "; List<Employee> dtos = em.createQuery(ql).getResultList(); The above query loads all Employee entities but with subset of data i.e. firstname, lastname. Employee entity looks like this. @Entity @Table(name="emp") public class Employee implements Serializable {     private static final long serialVersionUID = 1L;     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Long id;     @Column     private String firstname;     @Column     private String lastname;     @Column     private String username;     @Column     private String street;     @Column     private String city;     @Column     private String state;     @Column     private String zipc