JavaBean: creates all of the objects, a tests the service capabilities
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import java.beans.beancontext.BeanContextChildSupport;
import java.beans.beancontext.BeanContextServiceAvailableEvent;
import java.beans.beancontext.BeanContextServiceProvider;
import java.beans.beancontext.BeanContextServiceRevokedEvent;
import java.beans.beancontext.BeanContextServices;
import java.beans.beancontext.BeanContextServicesSupport;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.Iterator;
import java.util.StringTokenizer;
/**
* A test program that creates all of the objects, a tests the service
* capabilities. Run this program from the command line using java
* DocumentTester
*/
public class DocumentTester {
public static void main(String[] args) {
BeanContextServicesSupport context = new BeanContextServicesSupport(); // a
// bean
// context
DocumentBean doc1 = new DocumentBean("Test.txt");
context.add(doc1);
context.addBeanContextServicesListener(doc1); // listen for new services
WordCountServiceProvider provider = new WordCountServiceProvider();
context.addService(WordCount.class, provider); // add the service to the
// context
}
}
/**
* A JavaBean that encapsulates a text file. When added to a bean context, this
* bean listens for a WordCount service to become available. When the service
* does become available, the DocumentBean requests an instance of the service.
* The service then counts the number of words in the file, and prints a report
* to standard output.
*/
final class DocumentBean extends BeanContextChildSupport {
private File document;
private BeanContextServices context;
/**
* Creates a new DocumentBean given the name of the file to read from.
*
* @param fileName
* the name of the file to read from
*/
public DocumentBean(String fileName) {
document = new File(fileName);
}
/**
* Called when this bean detects that a new service has been registered with
* its context.
*
* @param bcsae
* the BeanContextServiceAvailableEvent
*/
public void serviceAvailable(BeanContextServiceAvailableEvent bcsae) {
System.out.println("[Detected a service being added to the context]");
// Get a reference to the context
BeanContextServices context = bcsae.getSourceAsBeanContextServices();
System.out.println("Is the context offering a WordCount service? "
+ context.hasService(WordCount.class));
// Use the service, if it's available
if (context.hasService(WordCount.class)) {
System.out.println("Attempting to use the service...");
try {
WordCount service = (WordCount) context.getService(this, this,
WordCount.class, document, this);
System.out.println("Got the service!");
service.countWords();
} catch (Exception e) {
}
}
}
/**
* Called when this bean detects that a service has been revoked from the
* context.
*
* @param bcsre
* the BeanContextServiceRevokedEvent
*/
public void serviceRevoked(BeanContextServiceRevokedEvent bcsre) {
System.out
.println("[Detected a service being revoked from the context]");
}
}
/**
* The WordCount service. Implementations of the countWords() method are
* provided by the WordCountServiceProvider class.
*/
interface WordCount {
/**
* Counts the number of words in the file.
*/
public abstract void countWords();
}
/**
* This class is the factory that delivers a word counting service. The 3
* methods defined in this class are the concrete implementations of the
* BeanContextServiceProvider interface. For this demonstration, the primary
* method of interest is getService(). The getService() methods returns a new
* WordCount instance. It is called by the bean context when a nested JavaBean
* requests the service.
*/
final class WordCountServiceProvider implements BeanContextServiceProvider {
public Object getService(BeanContextServices bcs, Object requestor,
Class serviceClass, Object serviceSelector) {
// For this demo, we know that the cast from serviceSelector
// to File will always work.
final File document = (File) serviceSelector;
/*
* Return an instance of the service. The service itself is the
* WordCount interface, which is implemented here using an anonymous
* inner class.
*/
return new WordCount() {
public void countWords() {
try {
// Create a Reader to the DocumentBean's File
BufferedReader br = new BufferedReader(new FileReader(
document));
String line = null;
int wordCount = 0;
while ((line = br.readLine()) != null) {
StringTokenizer st = new StringTokenizer(line);
while (st.hasMoreTokens()) {
System.out.println("Word " + (++wordCount)
+ " is: " + st.nextToken());
}
}
System.out
.println("Total number of words in the document: "
+ wordCount);
System.out
.println("[WordCount service brought to you by WordCountServiceProvider]");
br.close();
} catch (Exception e) {
}
}
};
}
public void releaseService(BeanContextServices bcs, Object requestor,
Object service) {
// do nothing
}
public Iterator getCurrentServiceSelectors(BeanContextServices bcs,
Class serviceClass) {
return null; // do nothing
}
}
//file: Test.txt
/*
This text will be analyzed
by the WordCount
service.
*/
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