Java Enterprise

By Sandeep Desai (http://www.thedesai.net)

 

Java is a language and a platform. There are large number of Java, Vendor specific and open source frameworks and APIs for developing thick applications, web applications and mobile applications

Java based APIs are JDBC, Servlets, JSP, JSF, EJB and Web Services. Some of the popular open sources API and frameworks available are Struts, Spring and Hibernate. Some vendor based frameworks are Oracle ADF

 

Web Applications can be rich client AJAX based or HTML based

 

Ant for building Java Applications

JUnit Java Testing Framework (See my sample)

 

Eclipse (Open Source IDE for Java UML etc)

Oracle JDeveloper

 

Apache Tomcat ervlet and JSP Container (pache Open Source)

Apache Axis (Java Web Services)

Apache Geronimo Application J2EE Server (Apache Open Source)

 

JavaRanch Java Community

Java Blueprints

Java Memory Management and Tuning

• My Java sample that prints Garbage collection details
• Java Peformance Tuning book website (lots of articles and links)
• Java Tuning
• Diagnose using hprof

 

 

JDBC

• JDBC Logging driver useful finding out while using EJB or Hibernate what SQL queries are going to server
• JDBC Connection Pooling
• Oracle JDBC FAQ
• JDBC Sample code

 

 

J2EE Architecture

Even if you do client side validation, you should do server side validation to make sure that invalid data is not entered by customers

J2EE Patterns

Web Application Frameworks

 

• Struts, (Struts NEJUG presentation)
• Struts Shale (JSF based)
• Spring
• Tapestry

 

Apache Struts

 

Struts is a configurable MVC framework that simplifies the job of developing web applications

Struts is a Model2 Framework

Struts Components

• Action Servlet - provide by Struts, developer does not need to write one
• Form Beans – JavaBean one for each HTML form, Struts will call setters and validate()
• Action Objects – implement execute() callback, validate form and call model components
• Struts-config.xml – map request URLs to Actions, Action to Form beans and Actions to views

 

Struts

• Declarative – use XML to configure application and for validation
• Lifecycle – provide lifecycle management
• Callback – at key lifecycle events
• Custom Tags
• Data Sources
• Global Exception handling
• Internationalization support – error classes and custom tags have internationalization support (take resource bundle strings)
• Plug-ins – Validator framework initialized as plug-in has init() and destroy() method

 

Apache Struts Tutorial

Struts Powerpoint Presentation

Free Jakarts Struts Live Book PDF

 

Java Server Faces is an alternative to Struts. MyFaces is Apache implementation of Java Server Faces

 

Spring

 

Spring is a J2EE framework and aims to simplify J2EE development

• Lightweight – A non invasive container that can assemble set of loosely coupled POJOs. This allows software components to be tested in isolation
• Abstract Transaction Manager – Allows for pluggable transaction managers, not tied to J2EE environments
• JDBC abstratcion layer – meaningfull exception hierarchy (no need to extract vendor codes from SQLException) simplified error handling.
• Integrartes with Toplink, Hibernate, JDO and iBATIS SQL maps
• AOP functionality – can AOP any object and add aspects such as declarative transaction management. Transaction management can be done without EJB or JTA
• A flexible MVC architecture – Can work with Struts, WebWork or Tapestry and accomodates multiple view techonlogies like JSP, Velocity, Tiles, iText and POI

 

You can use all of Spring's functionality in any J2EE server, and most of it also in non-managed environments. A central focus of Spring is to allow for reusable business and data access objects that are not tied to specific J2EE services. Such objects can be reused across J2EE environments (web or EJB), standalone applications, test environments, etc without any hassle.

 

Spring has a layered architecture; all its functionality builds on lower levels. So you can e.g. use the JavaBeans configuration management without using the MVC framework or AOP support. But if you use the web MVC framework or AOP support, you'll find they build on the configuration framework, so you can apply your knowledge about it immediately.

 

Spring uses a setter based dependancy injection pattern (Inversion of Control)

 

My Spring AOP sample

An Introduction to AOP Programming with the Spring Framework by Russell Miles

Spring presentation at NEJUG

Pro Spring by Rob Harrop Jan Machacek

 

Java Server Faces

 

Java Server Faces Tutorial

 

Java Aspect Oriented Programming

 

The goal is to make the core logic simpler to write and test

 

AOP use cases

• Logging, tracing and auditing
• Security authentication and authorization
• Rules engine
• Testing and Test harness support
• Persistence and O/R mapping
• Caching, transparent to application developer
• Transaction support
• Synchronization and thread safety

 

AOP terms

 

• Join point: well defined point in program where AOP functions (advice) can intercede and affect execution
• Advice: action taken by the AOP framework at a particular join point. This functionality implemented by Java method will be called. It will transparently intercede and be executed . Types of advice are before, after and around
• Aspect: collection of one or more advice methods, typically implemented in a single Java class, an potentially accepting join point context information as a parameter to those advice methods
• Pointcut: expression that specifies which join points will be affected by one or more aspects
• Introductions: a more intrusive type of intercession that modified the structure/type of your Java application classes, for example, by implementing a new interface or adding a new member variable
• Mixin: refers to adding new class or classes to a pre existing class
• Weaving: the application/activation of an advice across one or more pointcuts so that the advice will be executed when the join points are encountered
• Target: the application object being advised (affected by the aspects) at any point in time
• Interceptor: an aspect with only one advice method named "invoke"

 

 

AOP Frameworks

 

AspectJ and Spring are the most popular AOP frameworks

 

AspectJ (1.2)

  Aspects and pointcuts are expressed in AspectJ language. Pre-compiler generates Java code. An .lst file specifies which Aspects apply to the subsystem. There is no runtime support for turning Aspects on or off. AJDT Eclipse plug-in is available

 

Spring AOP (1.2)

  Provides dynamic proxy-based approach to implementing AOP (using Java Reflection APIs). Target application classes must implemented interfaces. Uses springconfig.xml for Spring Framework and Spring AOP configuration. Uses AOP alliance. Pointcuts and advice are implemented using Spring's IOC (Inversion of control) framework. IOC is a POJO with a Java Bean setter method. Spring AOP comes with built in transaction and security support

 

JBoss AOP 1.1

 

 

http://ramnivas.com/ author of AspectJ In Action

 

Source Listings

 

See SCJP notes for Java Fundamentals

 

Fundamentals.java demonstrates primitive data types, arrays, controls etc

Objects.java inheritance, exceptions, inner classes

JavaCollections.java demonstrates how to create Lists, Sets and Hash Tables (Associative Arrays)

JavaThreads.java demonstrated how to create and use Threads

 

Java and JDBC, Oracle JDBC FAQ

 

Java 1.5 Basics

Java 1.5 Generics

Java 1.5 Enumerations

 

 

Java Basics and Sun Certified Java Programmer Notes

 

Java and XML

 

J2EE

 

J2EE is a set of API and services. The services are typically implemented in an Application server. The API/services for J2EE 1.3 are

 

• JDBC: Abstract API for connecting to any database (database vendor has to provide a JDBC driver)
• JNDI : Network wide naming service to locate objects in LDAP, JDBC, JMS, EJB Homes,
• JTA and JTS: Transaction management API and service
• Servlet : Implements CGI, creates one thread per session (unlike CGI which runs a process for each HTTP request) Accepts HTTP requests and sends HTML replies
• JSP:  Allows you to embed Java code in HTML at runtime the Application Server generates a servlet for the JSP page.  The user can access the servlet API while writing JSP.
• EJB: Enterprise Java Beans is used for implementing the business logic layer. There are three types of beans. Entity Beans, session beans, message driven beans. EJB consists of a client and a server portion which can be run on the same or different machine
• RMI-IIOP: Supports Remote Java method invocation over the IIOP protocol. The protocol is used for implementing EJB.
• JMS: Supports messaging using systems such as Oracle AQ (Advanced Queuing). Support asynchronous messaging system. JMS can work in point to point or publish/subscribe (used for multiple subscribers)
• JavaMail: email
• JAF 1.0: JavaBeans Activation Framework used in the JavaMail API. Most developers do not use this API
• JAXP:  Java API for XML Processing supports implementation independant procession of XML documents through DOM, SAX and XSLT. DOM tree based API, SAX is event driven API
• JAAS: Java Authentication and Authorization service is standard API for authentication and assigning and verifying user privileges new in J2EE 1.3
• JCA: Java Connector Architecture provides a standard abstract API for connecting EJBs to Enterprise Information System e.g ERP, CRM and legacy applications
• SOA: Service Oriented Architecture for created web services

SOA (Service Oriented Architecture)

 

SOA is a standards-based platform that lets you model, develop, find, and combine services into flexible business processes

 

Products needs for SOA

• Services - Preferably one service to one business function
• Registry - A place to store them so you can find them easily