Java Enterprise Edition (JEE, which was earlier called J2EE) has been around for many years now. It is a very robust platform for developing enterprise applications. J2EE was first released in 1999, but underwent major changes in version 5, in 2006. Since version 5, it has been renamed Java Enterprise Edition (JEE). Recent versions of JEE has made developing a multi-tier distributed application a lot easier. J2EE had focused on core services and had left the tasks that made application development easier to external frameworks, for example, MVC and persistent frameworks. But JEE has brought many of these frameworks in the core services. Along with the support for annotations, these services simplify application development to a large extent.
Any runtime technology is not good without great development tools. Integrated Development Environment (IDE) plays a major part in developing applications faster, and Eclipse provides just that for JEE. Not only do you get a good editing support in Eclipse, but you also get support for build, unit testing, version control, and many other tasks important in different phases of software application development.
The goal of this book is to show how you can efficiently develop JEE application using Eclipse by using many of its features during different phases of the application development. But first, the following is a brief introduction to JEE and Eclipse.
JEE is a collection of many different specifications intended to perform specific tasks. These specifications are defined by the Java Community Process (https://www.jcp.org) program. Currently, JEE is in version 7. However, different specifications of JEE are at their own different versions.
Enterprise integration layer
Note that JEE specification does not necessarily classify APIs in such broad groups, but such classification could help in better understanding the purpose of the different standards and APIs in JEE. Before we see APIs in each of these categories, let's understand a typical JEE web application flow where each of these layers fits in.
Requests start from client. Client can be any application requesting services from a remote application â for example, it could be a browser or a desktop application. The request is first received by Web Server at the destination. Examples of Web Servers are Apache Web Server, IIS, Nginx, and so on. If it is a request for static content, then it is served by the web server(s). However, dynamic request typically requires an Application Server to process it. JEE servers are such Application Servers that handle the dynamic requests. Most JEE specification APIs execute in the application server. Examples of JEE application servers are WebLogic, WebSphere, GlassFish, JBoss, and so on.
Most non-trivial JEE applications access external systems such as database or Enterprise Integration Server (EIS) for data and process it. Response is returned from the application server to the web server and then to the clients.
The following is the brief description of each of the JEE specifications in different layers of applications that we saw previously. We will see how to use these APIs in more detail in subsequent chapters. However, note that the following is not the exhaustive list of all the specifications in JEE. We will see the most commonly used specifications here. For the exhaustive list, please visit http://www.oracle.com/technetwork/java/javaee/tech/index.html.
Now, we will take a look at some of the specifications in this group.
Java servlets are server side modules, typically used to process a request and send back response in the web applications. Servlets are useful for handling requests that do not generate large HTML markup responses. They are typically used as controllers in MVC (Model View Controller) frameworks, for forwarding/redirecting requests or for generating non-HTML responses, such as PDFs. To generate an HTML response from Servlet, you need to embed the HTML code (as Java String) in the Java code. Therefore, it is not the most convenient option for generating large HTML response. JEE 7 contains Servlet API 3.1.
Java Server Faces makes creating user interface on the server side modular by incorporating the MVC design pattern in its implementation. It also provides easy to use tags for common user interface controls that can save states across multiple request-response exchanges between the client and server. For example, if you have a page that posts form data from a browser, you can have JSF save that data in a Java Bean so that it can be used subsequently in the response to the same or different request. JSF also makes it easier to handle UI events on the server side and specify page navigation in an application.
The business layer is where you typically write code to handle the business logic of your application. The request to this layer could come from the presentation layer, directly from the client application, or from the middle layer consisting of, but not limited to, web services. Classes in this layer are executed in the application container part of JEE Server. GlassFish and WebSphere are examples of web container plus application container.
Let us take a tour of some of the specifications in this group.
Enterprise Java Beans (EJBs) are the Java classes where you can write your business logic. Though it is not a strict requirement to use EJBs to write business logic, they do provide many of the services that are essential in enterprise applications. These services are security, transaction management, component lookup, object pooling, and so on. You can have EJBs distributed across multiple servers and let the application container (also called EJB container) take care of component look up (searching component) and component pooling (useful for scalability). This can improve scalability of the application.
EJBs are of two types:
JMS and message driven beans can be used for handling asynchronous requests. In a typical asynchronous request processing scenario, the client puts a request in a messaging queue or a topic and does not wait for immediate response. Server application gets the request message, either directly using JMS APIs or by using MDB. It processes the request and may put response in a different queue or topic to which the client would listen and get the response.
JDBC is a specification to access relational database in a common and consistent way. Using JDBC you can execute SQL statements and get results on different databases using common APIs. Database specific driver sits between the JDBC call and the database, which translates JDBC calls to database vendor specific API calls. JDBC can be used in both the Presentation and Business layers directly, but it is recommended to separate the database calls from both UI and the business code. Typically, this is done by creating Data Access Objects (DAO) which encapsulate logic to access the database.
JEE 7 contains JDBC specification 4.0.
One of the problems of using JDBC APIs directly is that you have to constantly map the data between Java Objects and the data in columns of rows in relational database. Frameworks such as Hibernate and Spring have made this process simpler by using a concept known as Object Relationship Mapping (ORM). ORM is incorporated in JEE in the form of Java Persistent API (JPA). JPA gives you the flexibility to map the objects to the tables in relational database and execute the queries with or without using Structured Query Language (SQL). Though when used in the content of JPA, query language is called Java Persistence Query Language. JPA specification 2.1 is a part of JEE.
JCA APIs can be used in JEE applications for communicating with Enterprise Integration Systems, such as SAP, Salesforce, and so on. Just like you have database drivers to broker communication between JDBC APIs and relational database, you have JCA adapters between JCA calls and EIS. Most EIS applications now provide REST APIs, which are lightweight and easy to use, so REST could replace JCA in some cases. However, if you use JCA, you get transaction and pooling support from JEE application server.
Simple Object Access Protocol (SOAP)
Representational State Transfer (REST)
JEE provides many specifications to simplify development and consumption of both types of web services, for example, JAX-WS (Java API for XML â web services) and JAX-RS (Java API for RESTful web services).
The preceding are just some of the specifications that are part of JEE. There are many other independent specifications, such as web services, and many enabling specifications, such as dependency injection and concurrency utilities, that we will see in subsequent chapters.
As mentioned earlier, a good IDE is essential for better productivity while coding. Eclipse is one such IDE, which has great editor features and many integration points with JEE technologies. The primary purpose of this book is to show you how to develop JEE applications using Eclipse. So following is a quick introduction to Eclipse, if you are not already familiar with it.
Eclipse is an open source IDE for developing applications in many different programming languages. It is quite popular for developing many different types of Java applications. Its architecture is pluggable â there is a core IDE and many different plugins can be added to it. In fact, support for many languages is added as Eclipse plugins, including support for Java.
Along with editor support, Eclipse has plugins to interact with many of the external systems used during development. For example, source control systems such as SVN and Git, build tools such as Apache Ant and Maven, file explorer for remote systems using FTP, managing servers such as Tomcat and GlassFish, database explorer, memory and CPU profiler, and so on. We will see many of these features in the subsequent chapters.
The Eclipse workspace is a collection of projects, settings, and preferences. Workspace is a folder where Eclipse stores this information. You must create a workspace to use Eclipse. You can create multiple workspaces, but at a time only one can be opened by one running instance of Eclipse. However, you can launch multiple instances of Eclipse with different workspaces.
Eclipse has pluggable architecture. Many of the features of Eclipse are implemented as plugins, for example, editor plugins for Java and many other languages, plugins for SVN and Git, and many others. Default installation of Eclipse comes with many built-in plugins and you can add more plugins for the features you want later.
Most windows in Eclipse can be classified either as editor or views. Editor is something where you can change the information displayed in it. View just displays the information and does not allow you to change it. An example of an editor is the Java editor where you write a code. An example of view is the outline view that displays the hierarchical structure of the code you are editing (in case of Java editor, it shows classes in a file, and methods in them).
Perspective is a collection of editors and views, and how they are laid out or arranged in the main Eclipse window. At different stages of development, you need different views to be displayed. For example, when you are editing a code, you need to see the Project Explorer and Task views, but when you are debugging an application, you don't need those views, but instead want to see the variables and breakpoints view. So, the editing perspective displays, among other views and editor, the Project Explorer and Task view and the Debug perspective displays views and editors relevant to the debugging activities. You can change the default perspectives to suit your purpose, though.
In the subsequent chapters, we will see how to develop JEE applications using different APIs in Eclipse. But the applications are going to need a JEE application server and a database. We are going to use Tomcat web container for the initial few chapters and then use GlassFish JEE application server. We are going to use MySQL database. We are going to need these products for most of the applications that we are going to develop. So the following sections describe how to install and configure Eclipse, Tomcat, GlassFish, and MySQL.
You can download Eclipse from https://eclipse.org/downloads/. You will see many different packages for Eclipse. Make sure you install the Eclipse IDE for Java EE Developers package. Select an appropriate package based on your OS and JVM architecture (32 or 64 bit). You may want to run the command java âversion to know if the JVM is 32-bit or 64-bit.
Unzip the downloaded zip file and then run the Eclipse application (you need to install JDK before you run Eclipse). The first time you run Eclipse, you will be asked to specify a workspace. Create a new folder in your file system and select that as the initial workspace folder. If you intend to use the same folder for workspace on every launch of Eclipse, then check the Use this as the default and do not ask again check box.
Tomcat is a Web Container. It supports APIs in the presentation layer described earlier. In addition, it supports JDBC and JPA also. It is easy to use and configure, and could be a good option if you do not want to use EJBs.
Download Tomcat from http://tomcat.apache.org/. At the time of writing, the latest version of Tomcat available was 8. Download the zip file and unzip in a folder. Set the
JAVA_HOME environment variable to point to the folder where JDK is installed (the folder path should be the JDK folder, which has
bin as one of the sub folders). Then run
startup.bat at the Command Prompt on Windows and
startup.sh in a Terminal window on Mac and Linux, to start the Tomcat server. If there are no errors, then you should see the message
Server startup in --ms or
Default Tomcat installation is configured to use port
8080. If you want to change the port, open
server.xml under the
conf folder and look for connector declaration like:
<Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" />
Change the port value to any port number you want, though in this book we will be using the default
port 8080. Before we open the default page of Tomcat, we will add a user for administration of the Tomcat server. Open
tomcat-users.xml under the
conf folder in any text editor. At the end of the file you will see commented example of how to add users. Add the following configuration before closure of the
<role rolename="manager-gui"/> <user username="admin" password="admin" roles="manager-gui"/>
Here we are adding a user
admin, with password also as
admin, to a role called
'manager-gui'. This role has access to web pages for managing an application in Tomcat. This and other security roles are defined in
web.xml of the
manager application. You can find it at
webapps/manager/WEB-INF/web.xml. For more information for managing Tomcat server, see http://tomcat.apache.org/tomcat-8.0-doc/manager-howto.html.
After making the preceding changes, open a web browser and browse to
http://localhost:8080 (modify port number if you have changed the default port as described previously). You will see the following default Tomcat page:
Click on the Manager App button on the right. You will be asked for the user name and password. Enter the user name and password you configured in
manager-gui, as described earlier. After you are successfully logged in, you will see the Tomcat Web Application Manager page, as shown in the following image. You can see the applications deployed in Tomcat in this page. You can also deploy your applications from this page.
Download GlassFish from https://glassfish.java.net/download.html. GlassFish comes in two flavors: Web Profile and Full Platform. Web Profile is like Tomcat, which does not include EJB support. So download Full Platform. See https://glassfish.java.net/webprofileORfullplatform31x.html for comparison of Web Profile and Full Platform.
Unzip the downloaded file in a folder. Default port of GlassFish server is also
8080. If you want to change that, open
glassfish/domains/domain1/config/domain.xml in a text editor (you could open it in Eclipse too, using the File | Open File menu option) and look for
8080. You should see it in one of the
<network-listener>. Change the port if you want to (which may be the case if some other application is already using that port).
To start the server, run the
startserv script (
.sh depending on the OS you use). Once the server has started, open a web browser and browse to
http://localhost:8080. You should see a page like the following screenshot:
This page is located at
glassfish/domains/domain1/docroot/index.html. Click on the go to the Administration Console link in the preceding page to open GlassFish administrator. For details on administrating GlassFish server, see https://glassfish.java.net/docs/4.0/administration-guide.pdf.
To stop the GlassFish server, run the
stopserv script in the
Download MySQL Community Server from http://dev.mysql.com/downloads/mysql/. You can either download the web installer or the all in one installer. The web installer would download only those components that you have selected. Following instructions show the download options using the web installer.
We would like to install MySQL Workbench too, which is a client application to manage MySQL Server. As of writing this chapter, MySQL Workbench required Visual C++ 2013 Runtime for Windows installation. If you don't have it already installed, you can download it from http://www.microsoft.com/en-in/download/details.aspx?id=40784.
Select the Custom option and click on Next.
Select MySQL Server and MySQL Workbench products and complete the installation. During the installation of Server, you will be asked to set the
rootpassword and given the option to add more users. It is always a good idea to add user other than root for applications to use.
Run MySQL Workbench after installation. You will find that the default connection to the local MySQL instance is already created for you.
Click on the local connection and you will be asked to enter the
rootpassword. Enter the
rootpassword that you typed during the installation of MySQL server. MySQL Workbench opens and displays the default test schema.
OS X versions before 10.7 had MySQL server installed by default. See http://dev.mysql.com/doc/mysql-macosx-excerpt/5.7/en/macosx-installation-server.html to know which version of MySQL was installed for different versions of OS X. If you are using OS X 10.7 or later, then you will have to download and install MySQL Community Server from http://dev.mysql.com/downloads/mysql/.
There are many different ways to install MySQL on OS X. See http://dev.mysql.com/doc/refman/5.7/en/osx-installation.html for installation instruction for OS X. Note that users on OS X should have administrator privileges to install the MySQL server.
Once you install the server, you can start it either from the Command Prompt or from the system preferences.
To start it from the Command Prompt, execute the following command in Terminal:
sudo /usr/local/mysql/support-files/mysql.server start
To start it from System Preferences, open the preferences and click the MySQL icon.
Click the Start MySQL Server button.
Next, download MySQL Workbench for OSX from http://dev.mysql.com/downloads/workbench/.
There are many different ways to install MySQL on Linux. Refer to https://dev.mysql.com/doc/refman/5.7/en/linux-installation.html for details.
To execute SQL and other commands from the Command Prompt, open Terminal and type the following:
mysql -u root -p <root_password>
Once logged in successfully, you will see the
To create a user, first select the
mysql>user mysql; Database changed mysql>insert into user (host, user, password, select_priv, insert_priv, update_priv) values ('%', 'user1', password('usper1_pass'),'Y','Y','Y');
The preceding command will create a user named
'user1' with password 'user1_pass' having privileges to insert, update, and select. And because we have specified host as
'%', this user can access the server from any host.
If you prefer a graphical user interface to manage the users, then run MySQL Workbench, connect to the local MySQL server (see Figure 1.13 MySQL Workbench Connections), and click on Users and Privileges under the Management section.
Having installed all the above products, you should be in a position to start developing JEE applications. We may need a few additional software, but we will see how to install and configure them at appropriate time.
In this chapter, we had a brief introduction to different JEE APIs for the presentation layer, business layer, and Enterprise integration layer. We learnt some of the important terminologies in Eclipse IDE. We then learned how to install Eclipse, Tomcat, GlassFish, MySQL, and MySQL Workbench. We are going to use these products in this book to develop JEE applications.
In the next chapter, we will configure the JEE server and database in Eclipse, and create a simple application using Servlet, JSP, and Java Server Faces.
We will also see how to crate JEE Web Applications using Servlet, JSP, and JSF. Along with that, we will learn how to use Maven to build and package the JEE applications.