Tech Juice

Introduction

the Java Persistence API (JPA) allows for easy managing of relational data in Java applications. It is a replacement of the much criticized EJB 2.0 and EJB 2.1 entity beans. In this post we show how to add JPA support to an existing Maven/Eclipse/JSF2 project with Java EE 6.

With JPA you can do create an entity that is backed by a table in the database. For example you can create a persisted entity (which is just a POJO with some annotations):

Name.java

import javax.persistence.Entity;
import javax.persistence.Table;
import javax.persistence.Id;
import javax.persistence.Column;
 
@Entity
@Table(name="CUSTOMER_INFORMATION")
public class Customer {
    private String name;
 
    @Id
    @Column(name="FULL_NAME")
    public int getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name= name;
    }
}

And a client class that fetches all customer names with and prints them:
Client.java

import javax.persistence.Persistence;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityManager;
 
public class Client

Introduction

Serious Java Web application development requires a lot of different applications. In addition to a JDK, an IDE and an application server you may need a Web application framework, a build system and some form of version control. Unsurprisingly, getting set up for development can be quite the task.

In this post we’ll take a look at setting up a Web application project from start to finish. The software we will use is:

What Are We Building?

Different applications come in different forms.

• A Windows application written in C++ may be compiled to a .exe file.
• Runnable Java GUI applications often come in a JAR (Java ARchive).
• Java Web applications are packaged in WAR and EAR files.

We are building a Web application, so the product of building our project will be a WAR file. The Glassfish application server extracts a WAR file and runs the application inside it. The WAR file also contains a deployment descriptor, web.xml that describes how the application server should run the WAR.

The structure of a WAR file looks like this (source):

Project Setup with Maven Archetypes

Now that we know what we are building, it is time to start setting up the project. The directory/file structure…

Introduction

When dealing with a Java Web applications, the completed application is commonly delivered as a WAR file. The Maven build system can easily be set up to create WAR files. In this post we take an in-depth look at how Maven goes from a source project to the final WAR product.

Used software: Apache Maven 3.0.4.

The structure of a WAR file looks like this (source):

Example Project

Let’s look at a very simple Mavenized Web application project in a directory named myprojectname. The contents of this folder are:

The pom.xml file looks like this:

 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/maven-v4_0_0.xsd">
  >4.0.0>
  >mygroup.com>
  >myprojectname>
  >war>
  >1.0-SNAPSHOT>
  >myprojectname Maven Webapp>
  >http://maven.apache.org

Introduction

I recently wanted to convert a number of Java projects from the Ant build system to the Maven build system. Unless you are very familiar with Ant and Maven this is not a trivial task. On this page I describe how I approached the problem, and how I dealt with the inevitable bumps in the road.

Note that the project conversions in this document are pretty much one-on-one. If you have a larger Ant project, you should consider a more modular approach for the resulting Maven projects.

Be sure to keep the Ant documentation and Maven documentation handy!

Analysing the Ant Project

As an example Ant project we look at a loader for the UniProt protein database [license].

We analyze the first two levels of the directory structure with the tree -L 2 command:

~/ant_projects$ tree -L 2
.
├── uniprot-loader
│   ├── build.xml
│   ├── docs
│   ├── etc
│   ├── lib
│   ├── src
│   └── test
└── utils
    ├── bin
    ├── src
    └── xsd
 
10 directories, 1 file

We have two directories, and the project we are after is called uniprot-loader. In the /uniprot-loader directory we see the Ant configuration file…