For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them. v Contents at a Glance About the Author ���������������������������������������������������������������������������������������������������������� xxxvii About the Technical Reviewers ������������������������������������������������������������������������������������� xxxix Acknowledgments ��������������������������������������������������������������������������������������������������������������xli Introduction ����������������������������������������������������������������������������������������������������������������������xliii Chapter 1: Introduction to Servlets■■ �����������������������������������������������������������������������������������1 Chapter 2: JavaServer Pages■■ ������������������������������������������������������������������������������������������53 Chapter 3: The Basics of JavaServer Faces■■ ��������������������������������������������������������������������97 Chapter 4: Facelets■■ ��������������������������������������������������������������������������������������������������������159 Chapter 5: JavaServer Faces Standard Components■■ ����������������������������������������������������199 Chapter 6: Advanced JavaServer Faces and Ajax■■ ���������������������������������������������������������255 Chapter 7: JDBC■■ �������������������������������������������������������������������������������������������������������������317 Chapter 8: Object-Relational Mapping■■ ��������������������������������������������������������������������������369 Chapter 9: Enterprise JavaBeans■■ ����������������������������������������������������������������������������������409 Chapter 10: The Query API and JPQL■■ �����������������������������������������������������������������������������447 Chapter 11: Oracle’s GlassFish■■ ��������������������������������������������������������������������������������������471 Chapter 12: Contexts and Dependency Injection■■ �����������������������������������������������������������497 Chapter 13: Java Message Service■■ �������������������������������������������������������������������������������517 Chapter 14: Authentication and Security■■ ����������������������������������������������������������������������537 Chapter 15: Java Web Services■■ �������������������������������������������������������������������������������������563 Chapter 16: Enterprise Solutions Using Alternative Programming Languages■■ ���������������597 ■ Contents at a Glance vi Chapter 17: WebSockets and JSON-P■■ ����������������������������������������������������������������������������605 Chapter 18: JavaFX in the Enterprise■■ ����������������������������������������������������������������������������615 Chapter 19: Concurrency and Batch Applications■■ ���������������������������������������������������������647 Appendix A: Java EE Development with NetBeans IDE■■ ��������������������������������������������������671 Index ���������������������������������������������������������������������������������������������������������������������������������683 xliii Introduction The Java platform is one of the most widely used platforms for application development in the world. The platform is so popular, that there are several different flavors of Java that can be used for developing applications that run on different mediums. From development of desktop or mobile, to web applications and hardware operating systems, Java can be utilized for development of just about any solution. As such, Java has become a very popular platform for development of enterprise applications, offering web services, reliability, security, and much more. Java Enterprise Edition was originally released in 1999 as Java 2 Platform, Enterprise Edition (J2EE). Although several enterprise frameworks were available for development of reliable and secure applications on the Java platform, it made sense to standardize some solutions in order to minimize customization and help to make Java Enterprise development more prevalent in the industry. The platform originally included a terse number of specifications for standardization, including Java Servlet, JavaServer Pages, RMI, Java Database Connectivity (JDBC), Java Message Service API (JMS), Java Transaction API (JTA), and Enterprise JavaBeans. Development of J2EE applications had a large learning curve, and it was cumbersome because it required the use of XML for lots of configuration. Even with these setbacks, it became popular amongst larger organizations and companies due to the prevalence of Java and its well-known security benefits. In 2001, J2EE 1.3 was released, adding more specifications to the platform, including the JavaServer Pages Standard Tag Library (JSTL) and Java Authentication and Authorization Service (JAAS). Other specifications, such as Java Servlet, also gained enhancements under the J2EE 1.3 release, making evolutionary enhancements to the platform. The release of J2EE 1.4 in 2003 marked a major milestone for Java Enterprise, as many new specifications were added to the platform, providing standards for even more Java technologies. The release of J2EE 1.4 marked the first iteration of Web Services for J2EE 1.1, JavaServer Faces (JSF), and Java APIs for XML solutions such as JAXP, JAXR, and more. Although the release of J2EE 1.4 included many specifications, it was still deemed as “difficult to learn” and “cumbersome.” Over the next few years, J2EE was reworked in an attempt to make it easier to learn and utilize. Although XML is an excellent means for configuration, it can be cumbersome and hard to manage, so configuration was a big item that was addressed for the next release. Technologies such as Enterprise JavaBeans (EJB) included some redundant characteristics, making EJB coding time-consuming and difficult to manage, so an overhaul of EJB was also in order. In May of 2006, Java EE 5 was released, leaving the J2EE acronym behind, and changing to simply Java EE. The Java EE 5 platform was significantly easier to use and maintain because features such as annotations were introduced, cutting down the amount of XML configuration significantly. EJBs were made easier to develop, making EJB a marketable technology for object-relational mapping once again. Java Enterprise Edition has since become a widely adopted and mature platform for enterprise development. Java EE 6 was released in 2009, making configuration and technologies even easier, and adding more specifications to the platform. Specifications such as Contexts and Dependency Injection and Bean Validation were introduced, making usability even easier and development more productive. This latest release, Java EE 7, enhances the platform even more by adding new specifications such as WebSockets and JSON-P. Specifications such as JSF and EJB were enhanced, adding even more features to increase productivity and functionality. This book focuses on Java Enterprise as a whole, covering most of the widely used specifications that make up Java EE. You will learn how to make use of each of the major specifications, through real-world examples and solutions. This book will cover APIs that have not been updated for Java EE 7, as well as those that have been enhanced, providing complete coverage for those who are newer to the platform. It also features recipes that cover the newest features of the platform, so that seasoned Java EE developers can skip those introductory concepts and delve into newer material. ■ Introduction xliv I work with Java Enterprise on a daily basis, and I have a deep passion for the technologies involved in the platform. I hope that this book increases your passion of Java EE and the Java platform in its entirety. Who This Book Is For This book is intended for all those who are interested in learning Java Enterprise Edition (Java EE) development and/ or already know Java EE but would like some information regarding the new features included in Java EE 7. Those who are new to Java EE development can read this book, and it will allow them to start from scratch to get up and running quickly. Intermediate and advanced Java developers who are looking to update their arsenal with the latest features that Java EE 7 has to offer can also read the book to quickly update and refresh their skill sets. How This Book Is Structured This book is structured so that it does not have to be read from cover to cover. In fact, it is structured so that developers can chose which topic(s) they’d like to read about and jump right to them. Each recipe contains a problem to solve, one or more solutions to solve that problem, and a detailed explanation of how the solution works. Although some recipes may build upon concepts that have been discussed in other recipes, they will contain the appropriate references so that the developer can find other related recipes that are beneficial to the solution. The book is designed to allow developers to get up and running quickly with a solution, so that they can be home in time for dinner. Conventions Throughout the book, I’ve kept a consistent style for presenting Java code, SQL, command-line text, and results. Where pieces of code, SQL, reserved words, or code fragments are presented in the text, they are presented in fixed-width Courier font, such as this (working) example: public class MyExample { public static void main(String[] args){ System.out.println("Java EE 7 is excellent!"); } } Downloading the Code The code for the examples shown in this book is available on the Apress web site, www.apress.com. A link can be found on the book’s information page under the Source Code/Downloads tab. This tab is located underneath the “Related Titles” section of the page. Note■■ the sources for this book may change over time to provide new implementations that incorporate the most up-to-date features in Java EE. That said, if any issues are found within the sources, please submit them via the Apress web site “Errata” form, and code will be adjusted accordingly. ■ Introduction xlv Configuring a Database for the Book Sources This book’s sources have been developed using the Apache Derby database, which ships with NetBeans IDE and GlassFish. The book sources have also been optimized for use with an Oracle 11g database. Please install and configure the database for use with the book sources using either of those database choices prior to working with the sources. The database configuration involves creation of a database schema or user, as well as execution of the create_database.sql script (contained within the book sources) that goes along with the database of your choice. You must also place the appropriate database JDBC driver into the GlassFish CLASSPATH. You can do this by copying the ojdbc6.jar (Oracle) or derbyclient.jar (Apache Derby) JAR file into your Integrated Development Environment (IDE) project for the book sources, or into the \glassfish4\domains\domain1\lib\ext directory. If copying into the GlassFish lib directory, then once the JAR file has been copied into place, the GlassFish server will need to be restarted, if it is already running. Once the database has been installed/configured, and the SQL scripts contained within the book sources have been executed, please log into the GlassFish administrative console and set up a database connection pool to work with the database of your choice. For more information, please see Recipe 11-5. After a connection pool has been configured, please update the persistence.xml file that is contained within the book sources accordingly, so that the data source name aligns with the one you’ve assigned to the GlassFish JDBC resource. Setting Up a NetBeans Project Before setting up a NetBeans project for the book sources, please install and configure GlassFish v4 accordingly. For more information, please see Recipe 11-1. Note■■ Before setting up a NetBeans project for the book sources, please install and/or configure Apache Derby or Oracle Database accordingly. A note regarding dependencies: this project depends upon the use of the third-party PrimeFaces library. At the time of this book publication, the PrimeFaces 4.0 release was not yet available to the public. That said, the sources can be obtained from the Google Code repository, and the dependency JAR can be built from the sources. Please see the Google Code repository at http://code.google.com/p/primefaces/source/checkout. Please perform the following steps to set up the NetBeans project: 1. Open NetBeans IDE 7.3 or greater. 2. Choose the File ➤ New Project ➤ Java Web ➤ Web Application menu option. 3. Title the project JavaEERecipes and choose a desired Project Location. 4. Server and Settings: a. If you have not yet registered your GlassFish v4 server with NetBeans, please click the Add button in this dialog, and add the server. To do so, you will need to know the location of the GlassFish server on your file system. b. Java EE Version: Java EE 7 Web. 5. Frameworks: a. Select JavaServer Faces, and then accept all defaults. ■ Introduction xlvi 6. Click Finish. 7. Go to your file system and copy the contents from within the JavaEERecipes-BookSources\ NBProject\src directory into your new NetBeans project src directory. 8. Add the required library dependencies to your project by right-clicking the project and choosing the Properties option. Once the Properties dialog is open, select the Libraries, and add the following dependencies: a. Jython 2.5.3 or later b. Groovy 2.0.1 or later c. PrimeFaces 4.0 or later d. Database JDBC JAR file, if not already placed within the GlassFis0h lib directory 1 Chapter 1 Introduction to Servlets Java servlets were the first technology for producing dynamic Java web applications. Sun Microsystems released the first Java Servlet specification in 1997. Since then it has undergone tremendous change, making it more powerful and easing development more with each release. The 3.0 version was released as part of Java EE 6 in December 2009. Servlets are at the base of all Java EE applications. Although many developers use servlet frameworks such as Java Server Pages (JSP) and Java Server Faces (JSF), both of those technologies compile pages into Java servlets behind the scenes via the servlet container. That said, a fundamental knowledge of Java servlet technology could be very useful for any Java web developer. Servlets are Java classes that conform to the Java Servlet API, which allows a Java class to respond to requests. Although servlets can respond to any type of request, they are most commonly written to respond to web-based requests. A servlet must be deployed to a Java servlet container in order to become usable. The Servlet API provides a number of objects that are used to enable the functionality of a servlet within a web container. Such objects include the request and response objects, pageContext, and a great deal of others, and when these objects are used properly, they enable a Java servlet to perform just about any task a web-based application needs to do. As mentioned, servlets can produce not only static content but also dynamic content. Since a servlet is written in Java, any valid Java code can be used within the body of the servlet class. This empowers Java servlets and allows them to interact with other Java classes, the web container, the underlying file server, and much more. This chapter will get you started developing and deploying servlets. You will learn how to install Oracle’s GlassFish application server, a robust servlet container, which will enable you to deploy sophisticated Java enterprise applications. You will be taught the basics of developing servlets, how to use them with client web sessions, and how to link a servlet to another application. All the while, you will learn to use standards from the latest release of the Java Servlet API, which modernizes servlet development and makes it much easier and more productive than in years past. Note■■ You can run the examples within this chapter by deploying the JavaEERecipes.war file (contained in the sources) to a local Java EE application server container such as GlassFish v4. You can also set up the NetBeans project entitled JavaEERecipes that is contained in the sources, build it, and deploy to GlassFish v4. Otherwise, you can run the examples in Chapter 1 stand-alone using the instructions provided in Recipe 1-3. If you deploy the JavaEERecipes.war file to a Java EE application server container, you can visit the following URL to load the examples for this chapter: http://localhost:8080/JavaEERecipes/faces/chapter01/index.xhtml. Chapter 1 ■ Introduction to Servlets 2 1-1. Setting Up a Java Enterprise Environment Problem You want to set up an environment that you can use to deploy and run Java servlets and other Java enterprise technologies. Solution Download and install Oracle’s GlassFish application server from the GlassFish web site. The version used for this book is the open source edition, release 4.0, and it can be downloaded from http://glassfish.java.net/ in the “Download” section. Select the .zip or .tar.gz download format, and decompress the downloaded files within a directory on your workstation. I will refer to that directory as /JAVA_DEV/Glassfish. The GlassFish distribution comes prepackaged with a domain so that developers can get up and running quickly. Once the .zip file has been unpacked, you can start the domain by opening a command prompt or terminal and starting GlassFish using the following statement: /PATH_TO_GLASSFISH/Glassfish/bin/asadmin start-domain domain1 The domain will start, and it will be ready for use. You will see output from the server that looks similar to the following: Waiting for domain1 to start ............ Successfully started the domain : domain1 domain Location: /PATH_TO_GLASSFISH/glassfish/domains/domain1 Log File: /PATH_TO_GLASSFISH/glassfish/domains/domain1/logs/server.log Admin Port: 4848 Command start-domain executed successfully. How It Works The development of Java EE applications begins with a Java EE–compliant application server. A Java EE–compliant server contains all the essential components to provide a robust environment for deploying and hosting enterprise Java applications. The GlassFish application server is the industry standard for Java EE 7, and there are two versions of the server: open source, and licensed by Oracle. For the purposes of this book, the open source edition will be used. However, in a production environment, you may want to consider using the Oracle-licensed version so that technical support will be available if needed. Installing GlassFish is easy. It consists of downloading an archive and uncompressing it on your development machine. Once you’ve completed this, the application server will make use of your locally installed Java development kit (JDK) when it is started. Once the server starts, you can open a browser and go to http://localhost:4848 to gain access to the GlassFish administrative console. Most Java EE developers who deploy on GlassFish use the administrative console often. The administrative console provides developers with the tools needed to deploy web applications, register databases with Java Naming and Directory Interface (JNDI), set up security realms for a domain, and do much more. To access the GlassFish administrative console for the first time, use the user name of admin and the password of adminadmin. You should take some time to become familiar with the administrative console because the more you know about it, the easier it will be to maintain your Java EE environment. Installing the GlassFish application server is the first step toward developing Java applications for the enterprise. While other applications servers such as JBoss, Apache TomEE, and WebLogic are very well adopted, GlassFish offers developers a solid environment that is suitable for production use and easy to learn. It also has the bonus of being an open source application server and the reference implementation for Java EE 7. Chapter 1 ■ Introduction to Servlets 3 1-2. Developing a Servlet Problem You want to develop a web page that enables you to include dynamic content. Solution Develop a Java servlet class, and compile it to run within a Java servlet container. In this example, a simple servlet is created that will display some dynamic content to the web page. The following is the servlet code that contains the functionality for the servlet: package org.javaeerecipes.chapter01.recipe01_02; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Recipe 1-2: Developing a Servlet * @author juneau */ public class SimpleServlet extends HttpServlet { /** * Processes requests for both HTTP * Servlet SimpleServlet "); out.println(""); out.println(""); out.println("
Welcome to Java EE Recipes!"); ChaptER 1 ■ INtROdUCtION tO SERvLEtS 4 out.println(""); out.println(""); } finally { out.close(); } } /** * Handles the HTTP GET * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP POST * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet for documentation purposes. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; }// } The following code is the web deployment descriptor. This file is required for application deployment to a servlet container. It contains the servlet configuration and mapping that maps the servlet to a URL. In Recipe 1-4 you will learn how to omit the servlet configuration and mapping from the web.xml file to make servlet development, deployment, and maintenance easier. Chapter 1 ■ Introduction to Servlets 5 SimpleServlet org.javaeerecipes.chapter1.recipe01_02.SimpleServlet SimpleServlet /SimpleServlet /SimpleServlet Note■■ Many web applications use a page named index.html or index.xhtml as their welcome file. There is nothing wrong with doing that, and as a matter of fact, it is the correct thing to do. The use of /SimpleServlet as the welcome file in this example is to make it easier to follow for demonstration purposes. To compile the Java servlet, use the javac command-line utility. The following line was excerpted from the command line, and it compiles the SimpleServlet.java file into a class file. First, traverse into the directory containing the SimpleServlet.java file; then, execute the following: javac -cp /JAVA_DEV/Glassfish/glassfish/modules/javax.servlet-api.jar SimpleServlet.java Once the servlet code has been compiled into a Java class file, it is ready to package for deployment. Note■■ You may want to consider installing a Java integrated development environment (IDE) to increase your development productivity. There are several very good IDEs available to developers, so be sure to choose one that contains the features you find most important and useful for development. As the author of this book on Java EE 7, I recommend installing Net- Beans 7.3 or newer for development. NetBeans is an open source IDE that is maintained by Oracle, and it includes support for all the cutting-edge features that the Java industry has to offer, including EJB development with Java EE 7, JavaFX 2.0 support, and more. To learn more about working with NetBeans and Java EE 7, please see the appendix of this book. How It Works Java servlets provide developers with the flexibility to design applications using a request-response programming model. Servlets play a key role in the development of service-oriented and web application development on the Java platform. Different types of servlets can be created, and each of them is geared toward providing different functionality. The first type is the GenericServlet, which provides services and functionality. The second type, Chapter 1 ■ Introduction to Servlets 6 HttpServlet, is a subclass of GenericServlet, and servlets of this type provide functionality and a response that uses HTTP. The solution to this recipe demonstrates the latter type of servlet because it displays a result for the user to see within a web browser. Servlets conform to a life cycle for processing requests and posting results. First, the Java servlet container calls the servlet’s constructor. The constructor of every servlet must take no arguments. Next, the container calls the servlet init method, which is responsible for initializing the servlet. Once the servlet has been initialized, it is ready for use. At that point, the servlet can begin processing. Each servlet contains a service method, which handles the requests being made and dispatches them to the appropriate methods for request handling. Implementing the service method is optional. Finally, the container calls the servlet’s destroy method, which takes care of finalizing the servlet and taking it out of service. Every servlet class must implement the javax.servlet.Servlet interface or extend another class that does. In the solution to this recipe, the servlet named SimpleServlet extends the HttpServlet class, which provides methods for handling HTTP processes. In this scenario, a browser client request is sent from the container to the servlet; then the servlet service method dispatches the HttpServletRequest object to the appropriate method provided by HttpServlet. Namely, the HttpServlet class provides the doGet, doPut, doPost, and doDelete methods for working with an HTTP request. The HttpServlet class is abstract, so it must be subclassed, and then an implementation can be provided for its methods. In the solution to this recipe, the doGet method is implemented, and the responsibility of processing is passed to the processRequest method, which writes a response to the browser using the PrintWriter. Table 1-1 describes each of the methods available to an HttpServlet. Table 1-1. HttpServlet Methods Method Name Description doGet Used to process HTTP GET requests. Input sent to the servlet must be included in the URL address. For example: ?myName=Josh&myBook=JavaEERecipes. doPost Used to process HTTP POST requests. Input can be sent to the servlet within HTML form fields. See Recipe 1-7 for an example. doPut Used to process HTTP PUT requests. doDelete Used to process HTTP DELETE requests. doHead Used to process HTTP HEAD requests. doOptions Called by the container to allow OPTIONS request handling. doTrace Called by the container to handle TRACE requests. getLastModified Returns the time that the HttpServletRequest object was last modified. init Initializes the servlet. destroy Finalizes the servlet. getServletInfo Provides information regarding the servlet. A servlet generally performs some processing within the implementation of its methods and then returns a response to the client. The HttpServletRequest object can be used to process arguments that are sent via the request. For instance, if an HTML form contains some input fields that are sent to the server, those fields would be contained within the HttpServletRequest object. The HttpServletResponse object is used to send responses to the client browser. Both the doGet and doPost methods within a servlet accept the same arguments, namely, the HttpServletRequest and HttpServletResponse objects. Chapter 1 ■ Introduction to Servlets 7 Note■■ the doGet method is used to intercept HTTP GET requests, and doPost is used to intercept HTTP POST requests. Generally, the doGet method is used to prepare a request before displaying for a client, and the doPost method is used to process a request and gather information from an HTML form. In the solution to this recipe, both the doGet and doPost methods pass the HttpServletRequest and HttpServletResponse objects to the processRequest method for further processing. The HttpServletResponse object is used to set the content type of the response and to obtain a handle on the PrintWriter object in the processRequest method. The following lines of code show how this is done, assuming that the identifier referencing the HttpServletResponse object is response: response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); A GenericServlet can be used for providing services to web applications. This type of servlet is oftentimes used for logging events because it implements the log method. A GenericServlet implements both the Servlet and ServletConfig interfaces, and to write a generic servlet, only the service method must be overridden. 1-3. Packaging, Compiling, and Deploying a Servlet Problem You have written a Java servlet and now want to package it and deploy it for use. Solution Compile the sources, set up a deployable application, and copy the contents into the GlassFish deployment directory. From the command line, use the javac command to compile the sources. javac -cp /PATH_TO_GLASSFISH/Glassfish/glassfish/modules/javax.servlet-api.jar SimpleServlet.java After the class has been compiled, deploy it along with the web.xml deployment descriptor, conforming to the appropriate directory structure. QUICK START To quickly get started with packaging, compiling, and deploying the example application for the servlet recipes in this chapter on GlassFish or other servlet containers such as Apache Tomcat, follow these steps: 1. Create a single application named SimpleServlet by making a directory named SimpleServlet. 2. Create the WEB-INF, WEB-INF/classes, and WEB-INF/lib directories inside SimpleServlet. 3. drag the Chapter 1 sources (beginning with the org directory) in the WEB-INF/classes directory you created, as well as the contents of the web folder, into the root of your SimpleServlet directory. Chapter 1 ■ Introduction to Servlets 8 4. Copy the web.xml file that is in the source’s recipe01_02 directory into the WEB-INF directory you created. 5. download the JavaMail API code from Oracle, and copy the mail.jar file from the download into the WEB-INF/lib directory you created. This API will be used to send mail in future recipes. 6. Set your CLASSPATH to include the mail.jar file you downloaded in step 5. 7. at the command prompt, change directories so that you are in the classes directory you created in step 2. Compile each recipe with the command javac org\javaeerecipes\ chapter01\recipe1_x\*.java, where x is equal to the recipe number. 8. Copy your SimpleServlet application directory to the /JAVA_DEV/Glassfish/ glassfish/domains/domain1/autodeploy directory for GlassFish or the /Tomcat/webapps directory for Tomcat. Test the application by launching a browser and going to http://localhost:8080/SimpleServlet/servlet_name, where servlet_name corresponds to the servlet name in each recipe. If using Tomcat, you may need to restart the server in order for the application to deploy. How It Works To compile the sources, you can use your favorite Java IDE such as NetBeans or Eclipse, or you can use the command line. For the purposes of this recipe, I will do just that. If you’re using the command line, you must ensure you are using the javac command that is associated with the same Java release that you will be using to run your servlet container. In this example, we will say that the location of the Java SE 7 installation is at the following path: /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home This path may differ in your environment if you are using a different operating system and/or installation location. To ensure you are using the Java runtime that is located at this path, set the JAVA_HOME environment variable equal to this path. On OS X and *nix operating systems, you can set the environment variable by opening the terminal and typing the following: export JAVA_HOME=/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home If you are using Windows, use the SET command within the command line to set up the JAVA_HOME environment variable. set JAVA_HOME=C:\your-java-se-path\ Next, compile your Java servlet sources, and be sure to include the javax.servlet-api.jar file that is packaged with your servlet container (use servlet-api.jar for Tomcat) in your CLASSPATH. You can set the CLASSPATH by using the –cp flag of the javac command. The following command should be executed at the command line from within the same directory that contains the sources. In this case, the source file is named SimpleServlet.java. javac -cp /path_to_jar/javax.servlet-api.jar SimpleServlet.java Chapter 1 ■ Introduction to Servlets 9 Next, package your application by creating a directory and naming it after your application. In this case, create a directory and name it SimpleServlet. Within that directory, create another directory named WEB-INF. Traverse into the WEB-INF directory, and create another directory named classes. Lastly, create directories within the classes directory in order to replicate your Java servlet package structure. For this recipe, the SimpleServlet.java class resides within the Java package org.javaeerecipes.chapter01.recipe01_02, so create a directory for each of those packages within the classes directory. Create another directory within WEB-INF and name it lib; any JAR files containing external libraries should be placed within the lib directory. In the end, your directory structure should resemble the following: SimpleServlet |_WEB-INF |_classes |_org |_javaeerecipes |_chapter01 |_recipe01_02 |_lib Place your web.xml deployment descriptor within the WEB-INF directory, and place the compiled SimpleServlet.class file within the recipe01_02 directory. The entire contents of the SimpleServlet directory can now be copied within the deployment directory for your application server container to deploy the application. Restart the application server if using Tomcat, and visit the URL http://localhost:8080/SimpleServlet/SimpleServlet to see the servlet in action. 1-4. Registering Servlets Without WEB-XML Problem Registering servlets in the web.xml file is cumbersome, and you want to deploy servlets without modifying web.xml at all. Solution Use the @WebServlet annotation to register the servlet, and omit the web.xml registration. This will alleviate the need to modify the web.xml file each time a servlet is added to your application. The following adaptation of the SimpleServlet class that was used in Recipe 1-2 includes the @WebServlet annotation and demonstrates its use: package org.javaeerecipes.chapter01.recipe01_04; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; Chapter 1 ■ Introduction to Servlets 10 /** * Recipe 1-4 - Registering Servlets without WEB-XML * @author juneau */ @WebServlet(name = "SimpleServletNoDescriptor", urlPatterns = {"/SimpleServletNoDescriptor"}) public class SimpleServletNoDescriptor extends HttpServlet { /** * Processes requests for both HTTP * Servlet SimpleServlet "); out.println(""); out.println(""); out.println("
Look ma, no WEB-XML!"); out.println(""); out.println(""); } finally { out.close(); } } /** * Handles the HTTP SimpleServletNoDescriptor org.javaeerecipes.chapter01.recipe01_04.SimpleServletNoDescriptor SimpleServletNoDescriptor /SimpleServletNoDescriptor 1-5. Displaying Dynamic Content with a Servlet Problem You want to display some content to a web page that may change depending upon server-side activity or user input. Solution Define a field within your servlet to contain the dynamic content that is to be displayed. Post the dynamic content on the page by appending the field containing it using the PrintWriter println method. The following example servlet declares a Date field and updates it with the current Date each time the page is loaded: package org.javaeerecipes.chapter01.recipe01_05; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Recipe 1-5: Displaying Dynamic Content with a Servlet * * @author juneau */ Chapter 1 ■ Introduction to Servlets 13 @WebServlet(name = "CurrentDateAndTime", urlPatterns = {"/CurrentDateAndTime"}) public class CurrentDateAndTime extends HttpServlet { Date currDateAndTime; /** * Processes requests for both HTTP * Servlet CurrentDateAndTime "); out.println(""); out.println(""); out.println("
"); synchronized(currDateAndTime){ currDateAndTime = new Date(); out.println("The current date and time is: " + currDateAndTime); } out.println(""); out.println(""); } finally { out.close(); } } /** * Handles the HTTP *Test Math Servlet "); out.println("\t"); out.println(""); out.println(""); try { int solution = Integer.valueOf(numA) + Integer.valueOf(numB); /* * Display some response to the user */ out.println("
"); out.println("Add Two More Numbers"); out.println(""); out.close(); } } 4 Chapter 1 ■ Introduction to Servlets 17 Note■■ to run the example, copy the previous HTML code into an HTML file within the web root of your JavaEERecipes application named recipe1_6.html, and then enter the following address into your browser: http://localhost:8080/ JavaEERecipes/recipe1_6.html. This assumes you are using default port numbers for your application server installation. If using the NetBeans project that was packaged with the sources, you do not need to worry about copying the code as everything is pre-configured. How It Works Servlets make it easy to create web applications that adhere to a request and response life cycle. They have the ability to provide HTTP responses and also process business logic within the same body of code. The ability to process business logic makes servlets much more powerful than standard HTML code. The solution to this recipe demonstrates a standard servlet structure for processing requests and sending responses. An HTML web form contains parameters that are sent to a servlet. The servlet then processes those parameters in some fashion and publishes a response that can be seen by the client. In the case of an HttpServlet object, the client is a web browser, and the response is a web page. Values can be obtained from an HTML form by using HTML tags embedded within an HTML
GET and * POST methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { // Place page output here out.println(""); out.println(""); out.println("Servlet SimpleServlet at " + request.getContextPath() + "
"); out.println("Welcome to Java EE Recipes!"); ChaptER 1 ■ INtROdUCtION tO SERvLEtS 4 out.println(""); out.println(""); } finally { out.close(); } } /** * Handles the HTTP GET * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP POST * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet for documentation purposes. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; }// } The following code is the web deployment descriptor. This file is required for application deployment to a servlet container. It contains the servlet configuration and mapping that maps the servlet to a URL. In Recipe 1-4 you will learn how to omit the servlet configuration and mapping from the web.xml file to make servlet development, deployment, and maintenance easier. Chapter 1 ■ Introduction to Servlets 5
GET and * POST methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* * TODO output your page here. You may use following sample code. */ out.println(""); out.println(""); out.println("Servlet SimpleServlet at " + request.getContextPath() + "
"); out.println("Look ma, no WEB-XML!"); out.println(""); out.println(""); } finally { out.close(); } } /** * Handles the HTTP
GET method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } Chapter 1 ■ Introduction to Servlets 11 /** * Handles the HTTP POST method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } In the end, the servlet will be accessible via a URL in the same way that it would if the servlet were registered within web.xml. Note■■ Remove the existing servlet mapping within the web.xml file in order to make use of the @WebServlet annotation. How It Works There are a couple of ways to register servlets with a web container. The first way is to register them using the web.xml deployment descriptor, as demonstrated in Recipe 1-2. The second way to register them is to use the @WebServlet annotation. The Servlet 3.0 API introduced the @WebServlet annotation, which provides an easier technique to use for mapping a servlet to a URL. The @WebServlet annotation is placed before the declaration of a class, and it accepts the elements listed in Table 1-2. Table 1-2. @WebServlet Annotation Elements Element Description description Description of the servlet displayName The display name of the servlet initParams Accepts list of @WebInitParam annotations largeIcon The large icon of the servlet loadOnStartup Load on start-up order of the servlet name Servlet name smallIcon The small icon of the servlet urlPatterns URL patterns that invoke the servlet Chapter 1 ■ Introduction to Servlets 12 In the solution to this recipe, the @WebServlet annotation maps the servlet class named SimpleServletNoDescriptor to the URL pattern of /SimpleServletNoDescriptor, and it also names the servlet SimpleServletNoDescriptor. @WebServlet(name="SimpleServletNoDescriptor", urlPatterns={"/SimpleServletNoDescriptor"}) The new @WebServlet can be used rather than altering the web.xml file to register each servlet in an application. This provides ease of development and manageability. However, in some cases, it may make sense to continue using the deployment descriptor for servlet registration, such as if you do not want to recompile sources when a URL pattern changes. If you look at the web.xml listing in Recipe 1-2, you can see the following lines of XML, which map the servlet to a given URL and provide a name for the servlet. These lines of XML perform essentially the same function as the @WebServlet annotation in this recipe. GET and * POST methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { out.println(""); out.println(""); out.println("Servlet CurrentDateAndTime at " + request.getContextPath() + "
"); out.println(""); synchronized(currDateAndTime){ currDateAndTime = new Date(); out.println("The current date and time is: " + currDateAndTime); } out.println(""); out.println(""); } finally { out.close(); } } /** * Handles the HTTP *
GET method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } ChaptER 1 ■ INtROdUCtION tO SERvLEtS 14 /** * Handles the HTTP * POST method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } Note Servlets are mutithreaded, and many client requests may be using a servlet concurrently. When a field is declared as a Servlet class member (not within a method) as you have done with currDateAndTime, you have to assure that only one client request can manipulate the field at any instance. You do this by synchronizing around the use of the field, as shown in the processRequest() method. You synchronize around the smallest block of code you can manage in order to minimize latency. synchronized( currDateAndTime ) { currDateAndTime = new Date(); out.println("The current date and time is: " + currDateAndTime); } The resulting output from this servlet will be the current date and time. How It Works One of the reasons why Java servlets are so useful is because they allow dynamic content to be displayed on a web page. The content can be taken from the server itself, a database, another web site, or many other web-accessible resources. Servlets are not static web pages; they are dynamic, and that is arguably their biggest strength. In the solution to this recipe, a servlet is used to display the current time and date on the server. When the servlet is processed, the doGet method is called, which subsequently makes a call to the processRequest method, passing the request and response objects. Therefore, the processRequest method is where the bulk of the work occurs. The processRequest method creates a PrintWriter by calling the response.getWriter method, and the PrintWriter is used to display content on the resulting web page. Next, the current date and time are obtained from the server by creating a new Date and assigning it to the currDateAndTime field. Lastly, the processRequest method sends the web content through the out.println method, and the contents of the currDateAndTime field are concatenated to a String and sent to out.println as well. Each time the servlet is processed, it will display the current date and time at the time in which the servlet is invoked because a new Date is created with each request. This example just scratches the surface of what is possible with a Java servlet. Although displaying the current date and time is trivial, you could alter that logic to display the contents of any field contained within the servlet. Whether it be an int field that displays a calculation that was performed by the servlet container or a String field containing some information, the possibilities are endless. Chapter 1 ■ Introduction to Servlets 15 1-6. Handling Requests and Responses Problem You want to create a web form that accepts user input and supply a response based upon the input that has been received. Solution Create a standard HTML-based web form, and when the submit button is clicked, invoke a servlet to process the end-user input and post a response. To examine this technique, you will see two different pieces of code. The following code is HTML that is used to generate the input form. This code exists within the file recipe01_06.html. Please browse to /SimpleServlet/recipe01_06.html to execute the example. Pay particular attention to the Next, take a look at the following code for a servlet named MathServlet. This is the Java code that receives the input from the HTML code listed earlier, processes it accordingly, and posts a response. package org.javaeerecipes.chapter01.recipe01_06; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; /** * Recipe 1-6: Handling Requests and Responses */ // Uncomment the following line to run example stand-alone //@WebServlet(name="SessionServlet", urlPatterns={"/MathServlet"}) Chapter 1 ■ Introduction to Servlets 16 // The following will allow the example to run within the context of the JavaEERecipes example // enterprise application (JavaEERecipes.war distro or Netbeans Project @WebServlet(name = "MathServlet", urlPatterns = {"/chapter01/MathServlet"})public class MathServlet extends HttpServlet { public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { res.setContentType("text/html"); // Store the input parameter values into Strings String numA = req.getParameter("numa"); String numB = req.getParameter("numb"); PrintWriter out = res.getWriter(); out.println(""); out.println("Solution: " + numA + " + " + numB + " = " + solution + "
"); } catch (java.lang.NumberFormatException ex) { // Display error if an exception is raised out.println("Please use numbers only. . .try again.
"); } out.println(""); out.println("Add Two More Numbers"); out.println(""); out.close(); } } 4 Chapter 1 ■ Introduction to Servlets 17 Note■■ to run the example, copy the previous HTML code into an HTML file within the web root of your JavaEERecipes application named recipe1_6.html, and then enter the following address into your browser: http://localhost:8080/ JavaEERecipes/recipe1_6.html. This assumes you are using default port numbers for your application server installation. If using the NetBeans project that was packaged with the sources, you do not need to worry about copying the code as everything is pre-configured. How It Works Servlets make it easy to create web applications that adhere to a request and response life cycle. They have the ability to provide HTTP responses and also process business logic within the same body of code. The ability to process business logic makes servlets much more powerful than standard HTML code. The solution to this recipe demonstrates a standard servlet structure for processing requests and sending responses. An HTML web form contains parameters that are sent to a servlet. The servlet then processes those parameters in some fashion and publishes a response that can be seen by the client. In the case of an HttpServlet object, the client is a web browser, and the response is a web page. Values can be obtained from an HTML form by using HTML tags embedded within an HTML