精通Java EE 7：技术指南与实战示例

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"Java EE 7 Recipes" 本书"Java EE 7 Recipes"是一本关于Java企业版7（Java Enterprise Edition 7）技术的实践指南，旨在帮助开发者解决在开发企业级应用过程中遇到的各种问题。Java EE 7是Java平台用于构建分布式、多层的企业应用程序的标准框架，它包括一系列组件和服务，如Servlet、JSP、JSF、JDBC、ORM、EJB、JMS、JPA、JQL、WebSockets和JSON-P等。首先，书中介绍了Servlet，这是Java EE中最基本的web组件，用于处理HTTP请求和响应。读者将学习如何配置Servlet容器，创建Servlet实例，以及处理HTTP请求和响应的方法。接着，JavaServer Pages（JSP）章节深入讲解了如何使用HTML、CSS和Java脚本语言混合编写动态网页。这部分内容涵盖了JSP的基本语法、EL（Expression Language）和JSTL（JavaServer Pages Standard Tag Library）的使用。第三章涉及JavaServer Faces（JSF），这是一个用于构建用户界面的MVC（Model-View-Controller）框架。书中详细阐述了JSF的基本组件、生命周期和事件处理，以及如何利用Facelets进行视图的定义和管理。在数据库操作方面，JDBC章节讨论了如何连接到数据库、执行SQL查询和更新、处理结果集，以及事务管理。而对象-关系映射（ORM）章节则聚焦于JPA（Java Persistence API），介绍实体管理、查询语言JPQL（Java Persistence Query Language）和 Criteria API的使用。 Enterprise JavaBeans（EJB）章节讲解了EJB 3.2的核心概念，包括无状态和有状态会话bean、消息驱动bean以及实体bean，这些都是构建可扩展、事务安全的企业级服务的关键组件。在通信和数据交换部分，读者将了解到Java Message Service（JMS）用于异步消息传递，以及Java Web Services（JWS）如何实现基于SOAP或RESTful的Web服务。此外，书中还提到了WebSockets和JSON-P（JSON with Padding）技术，它们为实时双向通信和轻量级数据交换提供了支持。通过本书，开发者可以掌握Java EE 7中的核心技术和最佳实践，从而更高效地开发和部署企业级应用。每章都包含详细的示例和步骤，适合初学者和有经验的Java EE开发者参考学习。

CHAPTER 1 ■ INTRODUCTION TO SERVLETS

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

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

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.

<servlet-name>SimpleServletNoDescriptor</servlet-name>

<servlet-class>org.javaeerecipes.chapter01.recipe01_04.SimpleServletNoDescriptor</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>SimpleServletNoDescriptor</servlet-name>

<url-pattern>/SimpleServletNoDescriptor</url-pattern>

</servlet-mapping>

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

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