Lecture 3A

Question 1

JSP XML syntax possible in JSP 2.x Benefits?

Answer 1

Conforms with XHTML, XML validation against schema, can use XML tools. However, verbose.

Question 2

What are JSP directives?

Answer 2

They don’t produce output into current output stream. use them to add imports, include or taglib.

Question 3

What are JSP actions?

Answer 3

Tell web container what to do as opposed to directives which give new information. Fuzzy difference. Use directive only if included file changes rarely, use action which guarantees latest content.

Question 4

How to forward JSP?

Answer 4

Use forward action-

Question 5

What are JSP implicit objects?

Answer 5

Available without declaring - provided by EE web container. ie request, response, session, out

Question 6

JSTL?

Answer 6

JSP Standard Tag Library.

Question 7

What does JPA stand for?

Answer 7

Java Persistence API. Application Programming Interface. Used for storing and retrieving objects to/from relational database. It provides ORM - maps Java classes to database tables. Javax.persistence

Question 8

What is a Java process?

Answer 8

A Java program which is currently running.

Question 9

JPA is a specification. Hibernate is an implementation of that specification.

Answer 9

Hibernate made by RedHat.

Question 10

JDBC?

Answer 10

Java Database Connectivity. Non enterprise standard java framework. Allows SQL queries into Java code.

Question 11

JPA entity classes vs entities?

Answer 11

Entity class annotated with @Entity. An entity is an instance of such a class. As an entity a Java object can be stored as a database.

Question 12

What is a POJO?

Answer 12

Plain Old Java Object. Items stored in db rows using JPA are POJO’s (minus methods).

Question 13

Entity classes need what to work?

Answer 13

@entity, import javax.persistence.Entity, a public or protected no argument constructor, no Finals, must be serializable sometimes, persistence instance variables (non static fields) must be private, protected or package private.

Question 14

List some common JPA annotations

Answer 14

@Id @Table @Column

Question 15

What is the JPA entity manager?

Answer 15

Responsible for storing retrieving Java objects in database. @PersistenceUnit(unitName=”customerPersistenceUnit”) private EntityManagerDactory entityManagerFactory;
EntityManager entityManager = entityManagerFactory.createEntityManager();

Question 16

What is a persistence context?

Answer 16

The set of Java objects which are controlled by an entity manager instance. It is also a session, the time period during which an entity manager manages these objects.

Question 17

What is JSP declaration?

Answer 17

Used to define variable / method that gets inserted into main body.

Question 18

What is the persistent identity?

Answer 18

The primary of an object. Only one entity with a certain persistent identity in the PC.

Question 19

List some entity manager methods:

Answer 19

Persist(), remove(), refresh(), merge(), createQuery() - using JPQL, flush() - force sync to db

Question 20

Difference between remove() and detach()

Answer 20

A removed entity is marked for removal from database but not from PC. Detached has A Persistent identity no longer associated with a persistence context.

Question 21

What happens when close() method called on an entityManager?

Answer 21

Detached all managed entities from PC

Question 22

What is a transaction?

Answer 22

Calls of entityManager methods must be embedded in a transaction (apart from find()). It’s a set of operations that either fail or succeed as a unit. @Resource UserTransaction object using dependency injection.

Question 23

Open and close transaction:

Answer 23

@Resource
UserTransaction userTransaction;
UserTransaction.begin();
UserTransaction.commit();