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Welcome back to the Cosmic Cup. I hope you are enjoying our voyage through the Java universe. Last month we examined the APIs that are formally defined under the scope of the Java Platform for the Enterprise. We're going to change the course of our journey a bit. This month we will look at the APIs that define the Java Platform itself.

What is the Java Platform?
Before getting deeper into the discussion, I would like to comment on the terms "Java Platform" and the "Java Enterprise." The Java Platform is defined as "a new operating environment for delivering and running highly interactive, dynamic, distributed and secure applications on network computers." It is a layer on top of existing operating systems and hardware platforms that enables the compilation of software programs to bytecodes, which are machine instructions for a virtual machine contained in the Java Platform. The virtual machine is more than an interpreter - it provides additional services beyond the translation of byte codes to native machine code, such as garbage collection, thread synchronization and security management.

On the other hand, the Java Enterprise APIs are Java's interface into business or enterprise computing. They are a category of Java APIs that fall under the definition of the Java Platform APIs; i.e., the Enterprise APIs are a subset of the Java Platform APIs.

Components of the Java Platform
The Java Platform defines an environment that includes a virtual machine, a programming language, core class libraries and class extension libraries. In short, the Java Platform defines and encompasses Java. The greatest benefit of Java is its software platform. This platform creates a virtual operating environment that is capable of producing binary code that can be run virtually on any hardware platform that implements the Java virtual machine. The Java Platform has three basic parts:

  • The Java Virtual machine (JVM)
  • The Java Language (Language Syntax)
  • Java Class Libraries or Java Application Programming Interface (API)
The Java class libraries, which is the interface published by the Java Platform for interacting with the rest of the computing world, comprises the following:
  • The Java Core API
  • The Java Standard Extension API
  • Non-standard Java APIs
The Java Enterprise APIs discussed in last month's article focused on Java for the Enterprise (these are APIs that extend the scope of Java to the world of business computing). The current focus of this column is not on the core and extension APIs that are used for programming Java. JDJ already has several columns that have discussed these and several good texts cover them in detail. We're focusing on the APIs that extend Java beyond its core environment. Figure 1 shows the Java platform.

Figure 1
Figure 1:

This month we'll take a look at the APIs that are defined under the scope of the Java Platform. Please note that we are, for the moment, foregoing discussion on the Java APIs that focus on Java-related hardware devices, embedded Java and Java operating system APIs (JavaOS). We will also avoid discussions on Java products (Java Web Server, JavaBlend, etc.) or other APIs (JavaMail, JavaSpaces, etc.). Discussion on these products and APIs is beyond the scope of our current focus. I may cover them in future articles.

The Java Platform API Categories
The Java Platform APIs are a set of interfaces that are used by developers to build Java applications and applets. All Java Platform APIs are created primarily by JavaSoft with the help of industry-wide specialists in different technologies and market areas.

The Java Platform APIs fall under the following categories:

  • Java Base Platform
  • Commerce
  • Security
  • Media
  • Enterprise
  • Server
These API categories are described in Table 1. The next section briefly examines the Java APIs that fall into each category.

Table 1

The Java Platform Constituent APIs
Of the API domains listed in Table 1, we discussed the Enterprise APIs in the last issue of the JDJ (Vol. 3, Issue 4). The Java Base API will not be discussed here, as information about it is widely available. The APIs under the other four groups and some related products are listed in Table 2. Subsequent sections of this article briefly describe the individual APIs.

Table 2

Commerce API (Java Commerce Client)
The Java Commerce Client (JCC) is an open, extensible framework, which provides the ability to build electronic commerce applications. JCC offers a Wallet-like user interface, a database and an extensible platform that enables the use of a variety of payment instruments and protocols for E-commerce operations.

JCC provides the API for Java commerce applications. Java Wallet, on the other hand, is a family of products that uses the JCC to ensure secure electronic commerce operations. The Java Wallet incorporates the JCC, Commerce JavaBeans components, the Gateway Security Model and Java Commerce Messages to offer users an extensible platform for online commerce.

A Commerce JavaBean component is a reusable commerce component that meets specific interface requirements to enable development of commerce components that can extend the functionality of the JCC. The Commerce JavaBeans model extends the JavaBeans model to provide interface typing and support for the Gateway Security Model. JavaBeans components show some functionality within standard JavaBeans builder tools, but they only manifest full functionality in Commerce JavaBeans aware environments such as the JCC.

Commerce JavaBeans components are contained in cassettes, which package these components. When a cassette is downloaded and installed, the JCC can make use of the Commerce JavaBeans component(s) it contains to perform commerce operations.

The Java SmartCard API is the final piece that defines the building blocks for Java's electronic commerce domain. This API enables communication between portable Java applications and smart cards, independent of hardware devices. The Java Smart Card layer makes the card reader and port transparent to the Java application communicating with the smart card, providing a direct channel between application and smart card.

The Java Commerce APIs are delivered separately from JDK. They constitute a standard extension to the JDK. The Java SmartCard API is currently available as an early access release. The Java Card API is available as a 2.0 specification. The Commerce JavaBeans API specification has not been published yet.

Security API
Security in the Java Platform is provided at different levels, via core APIs as well as an extension API. JDK 1.1.x includes Javakey and Jar, which use the new JDK security APIs provided with the JDK. Javakey is used to generate keys and certificates and sign JAR files. Jar is a file archiving utility. The security APIs support hashing, digital signatures, and parsing and generating X.509 certificates.

Security support is also included in the client/server products. The Java Web Server includes security support for the server-side. The HotJava Browser offers fine-grain control for signed applets and built-in SSL support.

The Java Cryptography Extension (JCE) provides a framework for encryption and key negotiation. It includes interfaces and implementations of ciphers, secure Java streams, key generation and other features. The current version of JCE, JCE1.2, is designed so that other crypto libraries can be plugged in as service providers and new algorithms can be added. JCE1.2 supplements JDK1.2 (Java Development Kit), which already includes interfaces and implementations of message digests and digital signatures. JCE1.2 requires that you already have JDK1.2 installed.

Media APIs
The Java Media APIs support the integration of audio and video clips, animated presentations, 2D fonts, graphics and images, as well as speech input/output, 3D models and telephony. By providing standard players and integrating these supporting technologies, the Java Media APIs enable developers to distribute compelling, media-rich content.

The Java 2D API is a set of classes for advanced 2D graphics and imaging, encompassing line art, text and images in a single comprehensive model. These classes will be provided as additions to packages in the Java 1.2 AWT class libraries.

The Java 3D API is a set of classes for writing three-dimensional graphics applications and 3D applets which provide high level constructs for creating and manipulating 3D geometry and for constructing the structures used in rendering that geometry. The early access Java 3D 1.1 Alpha 2 API is available for review.

The Java Advanced Imaging API allows sophisticated, high-performance image processing to be incorporated in Java applets and applications. This API will be available as a standard extension to the Java platform. The Java Advanced Imaging API implements a set of core image processing capabilities, such as image tiling, regions of interest and deferred execution. The Java Advanced Imaging API is being developed by Sun, Autometric, Kodak and Siemens.

The Java Media Framework API (JMF) specifies a simple, unified architecture, messaging protocol and programming interface for media players, media capture and conferencing. JMF is in its first API release, which supports the synchronization, control, processing and presentation of compressed streaming and stored time-media, including video and audio. The JMF 1.0 API was developed by Sun, Silicon Graphics Inc. and Intel Corporation.

Java Sound is a very high quality 32 channel audio rendering and MIDI controlled sound synthesis engine with a new Java Sound API. Java Sound will be distributed in two phases. The first phase will be as an engine that will be a core library in JDK1.2. The second phase will be the release of a full featured Java Sound API.

The Java Speech API enables incorporation of speech technology into user interfaces of Java applications. It has a cross-platform API to support command and control recognizers, dictation systems and speech synthesizers. The beta Java Speech API is available now for review. The Java Speech API was developed by Sun, AT&T, Dragon Systems, IBM, Novell and Texas Instruments. Java Speech API is in 0.06 beta Specification.

The Java Telephony API (JTAPI) is a set of modular, abstract interface specifications for computer-telephony integrated call control. This specification was developed by Sun, Dialogic, IBM, Intel, Lucent, Nortel, Novell and Siemens. The current version of JTAPI is 1.2.

Server API
The Server API enables development of server-side applications in Java. Server-side development is done using Servlets, which are Java's server-side counterparts for applets. The Servlet API is an extension to the standard JDK. The Java Servlet Development Kit (JSDK) is used to program Java Servlets. JSDK includes a servlet engine for running and testing servlets, and support for Netscape, Microsoft and Apache Web servers.

The Java Web Server (JWS) is a product offered by Sun Microsystems that supports Servlets. JWS is used for developing network servers in the Java programming language.

The JavaServer Engine is a collection of reusable Java classes that automates connection management, security and administration. It's used for the development and deployment of network enabled, server-based applications.

Conclusion
In this article we examined the Java Platform and its constituent APIs. We briefly examined the roles played by individual APIs that make up the Java Platform. Links for detailed information on all these APIs may be obtained from Sun's Java Website at http://java.sun.com/products.

Cosmic Reflections
The APIs we discussed in the previous month, and this one, do not in any way, complete the list of APIs associated with Java. And even amongst these APIs, most are in various stages of evolution. Furthermore, new APIs are being defined every month by several different corporations in collaboration with Sun Microsystems. The growing complexity of the Java Platform is making it increasingly difficult for the average developer to comprehend the world of Java. While "simple" is one of the first white paper buzzwords that was used to define the Java programming language, the Java Platform is proving to be paradoxical to the notion of simplicity.

About the Author
Ajit Sagar is a member of the Technical Staff at i2 Technologies, Dallas, TX. He holds a B.S. in Electrical Engineering from BITS, Pilani, India and an M.S. in Computer Science from Mississippi State University. Ajit focuses on UI, networking and middleware architecture development. He has 7 and 1/2 years of programming experience, two in Java.

	

Listing 1: Cookie.java
  
// Cookie interface and derived classes  

interface Cookie {  
}  

class FortuneCookie implements Cookie{  
  public static Cookie newCookie(String str)  
  {  
    System.out.println("Fortunate " + str);  
    return new FortuneCookie();  
  }  
}  

class MisFortuneCookie implements Cookie{  
  public static Cookie newCookie(String str)  
  {  
    System.out.println("UnFortunate " + str);  
    return new MisFortuneCookie();  
  }  
}  

Listing 2: CookieFactory.java
  
import java.lang.*;  
import java.lang.reflect.*;  

public class CookieFactory {  

  // Instantiate a Cookie represented by the  
  // input String parameter.  
  public Cookie createCookie(String className)  
  {  
    // Get the class corresponding from String  
    Class c = null;  
    try {  
       c = Class.forName(className);  
    }  
     catch (ClassNotFoundException cnfe) {  
      cnfe.printStackTrace();  
    }  

    // Parameters for the "printCookie()" method  
    // of the Cookie interface.  
    Class pTypes[] = new Class[1];  
    pTypes[0] = String.class;  

    // Get "printCookie()" method for Cookie class  
    Method method = null;  
    try {  
      method = c.getMethod("newCookie", pTypes);  
    }  
    catch (NoSuchMethodException nsme) {  
      nsme.printStackTrace();  
    }  

    // Invoke "printCookie()" method to get Cookie  
    Cookie cookie = null;  
    try {  
      Object[] params = new Object[1];  
      params[0] = "Cookie";  

      cookie = (Cookie)(method.invoke(c, params));  
    }  
    catch (InvocationTargetException ite) {  
      ite.getTargetException().printStackTrace();  
    }  
    catch (IllegalAccessException iae) {  
      iae.printStackTrace();  
    }  
    return cookie;  
  }  

  // Simple test for the Cookie Factory  
  public static void main(String[] args)  
  {  
    CookieFactory cf = new CookieFactory();  
    Cookie fc = cf.createCookie("FortuneCookie");  
    Cookie mfc = cf.createCookie("MisFortuneCookie");  
  }  
}  

Listing 3: XRayBean.java
  
import java.lang.reflect.*;  
import java.beans.*;  
import java.util.*;  

public class XRayBean {  

  public Method[]  
    getMethodsFromBean(BeanInfo bi) {  

    Method[]           mList;  
    MethodDescriptor[] mDescriptorList;  

    mDescriptorList = bi.getMethodDescriptors();  
    mList = new Method[mDescriptorList.length];  

    for (int i = 0; i < mDescriptorList.length; i++) {  
      mList[i] = mDescriptorList[i].getMethod();  
    }  
    return mList;  
  }  

  public PropertyDescriptor[]  
    getPropsFromBean(BeanInfo bi) {  

    PropertyDescriptor[] pDescriptorList;  

    pDescriptorList =  
         bi.getPropertyDescriptors();  
    return pDescriptorList;  
  }  

  public EventSetDescriptor[]  
    getEventsFromBean(BeanInfo bi) {  

    EventSetDescriptor[] eDescriptorList;  

    eDescriptorList =  
        bi.getEventSetDescriptors();  
    return eDescriptorList;  
  }  

  public Method[]  
    getListenerMethods(EventSetDescriptor esd) {  

    Method mList[];  

    mList = esd.getListenerMethods();  
    return mList;  
  }  

  public static void main(String[] args) {  
    XRayBean xray = new XRayBean();  

    if (args.length != 2) {  
      System.out.println("Usage: java XRayClass " +  
       "<className> [methods | properties | events]");  
      System.exit(1);  
    }  

    try {  
      Class c     = Class.forName(args[0]);  
      BeanInfo bi = Introspector.getBeanInfo(c);  

      if (args[1].equals("methods")) {  
        Method[] mList = xray.getMethodsFromBean(bi);  

        for (int i = 0; i < mList.length; i++) {  
       System.out.println("Method[" + i +  
                          "]: " + mList[i]);  
        }  
      }  
      else if (args[1].equals("properties")) {  
     PropertyDescriptor[] pList =  
           xray.getPropsFromBean(bi);  

        for (int i = 0; i < pList.length; i++) {  
          System.out.println(  
           "---------------------------------");  
          System.out.println("Property Name: " +  
                             pList[i].getName());  
       System.out.println("Read  Method[" +  
            i + "]: " + pList[i].getReadMethod());  
       System.out.println("Write Method[" +  
         i + "]: " + pList[i].getWriteMethod());  
     }  
      }  
      else if (args[1].equals("events")) {  
     EventSetDescriptor[] eList =  
                xray.getEventsFromBean(bi);  

        for (int i = 0; i < eList.length; i++) {  
          System.out.println(  
            "--------------------------------");  
          System.out.println("Event Name: " +  
                            eList[i].getName());  

       Method mList[] =  
         xray.getListenerMethods(eList[i]);  

          for (int j = 0; j < mList.length; j++) {  
         System.out.println("Listener Method[" +  
                       j + "]: " + mList[j]);  
          }  
     }  
      }  
      else {  
        System.out.println("ERROR:" +  
         "The selected feature is not implemented");  
      }  
    }  
    catch (java.lang.ClassNotFoundException e) {  
      e.printStackTrace();  
    }  
    catch (java.beans.IntrospectionException e) {  
      e.printStackTrace();  
    }  
  }  
}  

Listing 4: XRayClass.java
  
import java.lang.reflect.*;  
import java.util.*;  

public class XRayClass {  

  public Method[]  
    getLocalMethodsFromClass(Class c) {  

    Method[] mList;  

    mList = c.getDeclaredMethods();  
    return mList;  
  }  

  public Method[]  
    getAllMethodsFromClass(Class c) {  

    Method[] mList;  

    mList = c.getMethods();  
    return mList;  
  }  

  public Constructor[]  
    getAllConstructorsFromClass(Class c) {  

    Constructor[] cList;  

    cList = c.getDeclaredConstructors();  
    return cList;  
  }  

  public Field[] getFieldsFromClass(Class c) {  
    Field[] fList;  

    fList = c.getDeclaredFields();  
    return fList;  
  }  

  public Class[] getClassesFromClass(Class c) {  
    Vector cList = new Vector();  
    Class  cTemp;  
    Class[] aList;  

    cTemp = c;  
    while ((cTemp =  
            cTemp.getSuperclass()) != null) {  
      cList.addElement(cTemp);  
    }  

    aList = new Class[cList.size()];  
    for (int i = 0; i < cList.size(); i++) {  
      aList[i] = (Class) cList.elementAt(i);  
    }  
    return aList;  
  }  

  public Class[]  
    getInterfacesFromClass(Class c) {  

    Class[] cList;  

    cList = c.getInterfaces();  
    return cList;  
  }  

  public static void main(String[] args) {  

    XRayClass xray = new XRayClass();  

    if (args.length != 2) {  
      System.out.println("Usage: " +  
        "java XRayClass <className>" +  
        "[localMethods | allMethods | " +  
        "Constructors | fields | inheritance |" +  
        "interfaces] ");  
      System.exit(1);  
    }  

    try {  
      Class c = Class.forName(args[0]);  

      if (args[1].equals("localMethods")) {  
        Method[] mList =  
          xray.getLocalMethodsFromClass(c);  

        for (int i = 0; i < mList.length; i++) {  
       System.out.println("Method[" + i +  
                         "]: " + mList[i]);  
     }  
      }  
      else if (args[1].equals("allMethods")) {  
     Method[] mList =  
       xray.getAllMethodsFromClass(c);  

        for (int i = 0; i < mList.length; i++) {  
       System.out.println("Method[" + i +  
                        "]: " + mList[i]);  
     }  
      }  
      else if (args[1].equals("Constructors")) {  
     Constructor[] cList =  
       xray.getAllConstructorsFromClass(c);  

        for (int i = 0; i < cList.length; i++) {  
       System.out.println("Constructor[" + i + "]: " + cList[i]);  
     }  
      }  
      else if (args[1].equals("fields")) {  
        Field[] fList =  
          xray.getFieldsFromClass(c);  

        for (int i = 0; i < fList.length; i++) {  
       System.out.println("Field[" + i +  
                          "]: " + fList[i]);  
     }  
      }  
      else if (args[1].equals("inheritance")) {  
        Class[] cList =  
          xray.getClassesFromClass(c);  

        for (int i = 0; i < cList.length; i++) {  
       System.out.println("Class[" + i +  
                          "]: " + cList[i]);  
     }  
      }  
      else if (args[1].equals("interfaces")) {  
        Class[] cList =  
          xray.getInterfacesFromClass(c);  

        for (int i = 0; i < cList.length; i++) {  
          System.out.println("Interface[" + i +  
                             "]: " + cList[i]);  
     }  
      }  
      else {  
     System.out.println("ERROR:" +  
       "The selected feature is not implemented");  
      }  
    }  
    catch (java.lang.ClassNotFoundException e) {  
      e.printStackTrace();  
    }
  
      
 

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