46.}
Two classes, AddressRetriever and ContactRetriever, implement the RunnableTask interface in this
example. The classes are very similar; both use RMI to request that a business object be retrieved from a server. As their names suggest, each class retrieves a specific kind of business object, making Address and Contact objects from the server available to clients.
Example A.218 AddressRetriever.java
1.import java.rmi.Naming;
2.import java.rmi.RemoteException;
3.public class AddressRetriever implements RunnableTask{
4.private Address address;
5.private long addressID;
6.private String url;
7.
8.public AddressRetriever(long newAddressID, String newUrl){
9.addressID = newAddressID;
10.url = newUrl;
11.}
12.
13.public void execute(){
14.try{
15. ServerDataStore dataStore = (ServerDataStore)Naming.lookup(url);
16. address = dataStore.retrieveAddress(addressID);
17.}
18.catch (Exception exc){
19.}
20.}
21.
22.public Address getAddress(){ return address; }
23.public boolean isAddressAvailable(){ return (address == null) ? false : true; }
24.}
Example A.219 ContractRetriever.java
1.import java.rmi.Naming;
2.import java.rmi.RemoteException;
3.public class ContactRetriever implements RunnableTask{
4.private Contact contact;
5.private long contactID;
6.private String url;
7.
8.public ContactRetriever(long newContactID, String newUrl){
9.contactID = newContactID;
10.url = newUrl;
11.}
12.
13.public void execute(){
14.try{
15. ServerDataStore dataStore = (ServerDataStore)Naming.lookup(url);
16. contact = dataStore.retrieveContact(contactID);
17.}
18.catch (Exception exc){
19.}
20.}
21.
22.public Contact getContact(){ return contact; }
23.public boolean isContactAvailable(){ return (contact == null) ? false : true; }
24.}
The RMI server in this example is defined by the ServerDataStore interface and its implementer,
ServerDataStoreImpl.
Example A.220 ServerDataStore.java
1.import java.rmi.Remote;
2.import java.rmi.RemoteException;
3.public interface ServerDataStore extends Remote{
4.public Address retrieveAddress(long addressID) throws RemoteException;
5.public Contact retrieveContact(long contactID) throws RemoteException;
6.}
Example A.221 ServerDataStoreImpl.java
1.import java.rmi.Naming;
2.import java.rmi.server.UnicastRemoteObject;
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3.public class ServerDataStoreImpl implements ServerDataStore{
4.private static final String WORKER_SERVER_SERVICE_NAME = "workerThreadServer";
6.public ServerDataStoreImpl(){
7.try {
8. |
UnicastRemoteObject.exportObject(this); |
9. |
Naming.rebind(WORKER_SERVER_SERVICE_NAME, this); |
10.}
11.catch (Exception exc){
12.System.err.println("Error using RMI to register the ServerDataStoreImpl " + exc);
13.}
14.}
15.
16.public Address retrieveAddress(long addressID){
17.if (addressID == 5280L){
18. return new AddressImpl("Fine Dining", "416 Chartres St.", "New Orleans", "LA", "51720");
19.}
20.else if (addressID == 2010L){
21. return new AddressImpl("Mystic Yacht Club", "19 Imaginary Lane", "Mystic", "CT", "46802");
22.}
23.else{
24. return new AddressImpl();
25.}
26.}
27.public Contact retrieveContact(long contactID){
28.if (contactID == 5280L){
29.return new ContactImpl("Dwayne", "Dibley", "Accountant", "Virtucon");
30.}
31.else{
32. return new ContactImpl();
33.}
34.}
36.}
The Address and Contact interfaces define the business objects used in this example, and the implementers AddressImpl and ContactImpl provide underlying functional behavior.
Example A.222 Address.java
1.import java.io.Serializable;
2.public interface Address extends Serializable{
3.public static final String EOL_STRING = System.getProperty("line.separator");
4.public static final String SPACE = " ";
5.public static final String COMMA = ",";
6.public String getType();
7.public String getDescription();
8.public String getStreet();
9.public String getCity();
10.public String getState();
11.public String getZipCode();
12.
13.public void setType(String newType);
14.public void setDescription(String newDescription);
15.public void setStreet(String newStreet);
16.public void setCity(String newCity);
17.public void setState(String newState);
18.public void setZipCode(String newZip);
19.}
Example A.223 AddressImpl.java
1.public class AddressImpl implements Address{
2.private String type;
3.private String description;
4.private String street;
5.private String city;
6.private String state;
7.private String zipCode;
8.
9.public AddressImpl(){ }
10.public AddressImpl(String newDescription, String newStreet,
11.String newCity, String newState, String newZipCode){
12.description = newDescription;
13.street = newStreet;
14.city = newCity;
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15.state = newState;
16.zipCode = newZipCode;
17.}
18.
19.public String getType(){ return type; }
20.public String getDescription(){ return description; }
21.public String getStreet(){ return street; }
22.public String getCity(){ return city; }
23.public String getState(){ return state; }
24.public String getZipCode(){ return zipCode; }
25.
26.public void setType(String newType){ type = newType; }
27.public void setDescription(String newDescription){ description = newDescription; }
28.public void setStreet(String newStreet){ street = newStreet; }
29.public void setCity(String newCity){ city = newCity; }
30.public void setState(String newState){ state = newState; }
31.public void setZipCode(String newZip){ zipCode = newZip; }
32.
33.public String toString(){
34.return street + EOL_STRING + city + COMMA + SPACE +
35. state + SPACE + zipCode + EOL_STRING;
36.}
37.}
Example A.224 Contact.java
1.import java.io.Serializable;
2.public interface Contact extends Serializable{
3.public static final String EOL_STRING = System.getProperty("line.separator");
4.public static final String SPACE = " ";
5.public String getFirstName();
6.public String getLastName();
7.public String getTitle();
8.public String getOrganization();
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public void setFirstName(String newFirstName); |
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public void setLastName(String newLastName); |
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public void setTitle(String newTitle); |
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public void setOrganization(String newOrganization); |
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14. |
} |
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Example A.225 ContactImpl.java |
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7.public ContactImpl(){}
8.public ContactImpl(String newFirstName, String newLastName,
9.String newTitle, String newOrganization){
10. firstName = newFirstName;
11. lastName = newLastName;
12. title = newTitle;
13. organization = newOrganization;
14. }
15.
16.public String getFirstName(){ return firstName; }
17.public String getLastName(){ return lastName; }
18.public String getTitle(){ return title; }
19.public String getOrganization(){ return organization; }
21.public void setFirstName(String newFirstName){ firstName = newFirstName; }
22.public void setLastName(String newLastName){ lastName = newLastName; }
23.public void setTitle(String newTitle){ title = newTitle; }
24.public void setOrganization(String newOrganization){ organization = newOrganization; }
26.public String toString(){
27.return firstName + SPACE + lastName + EOL_STRING;
28.}
29.}
RunPattern creates a ConcreteQueue, then uses it to retrieve a sample Contact and two Addresses. The worker
thread in the queue processes these requests as |
queue. The ConcreteQueue and its |
associated worker thread can be used throughout |
client application, performing any background |
TEAM FLY PRESENTS
task required by the client as RunnableTask objects are added to its queue.
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Example A.226 RunPattern.java
1.import java.io.IOException;
2.public class RunPattern{
3.private static final String WORKER_SERVER_URL = "//localhost/ workerThreadServer";
4.public static void main(String [] arguments){
5.System.out.println("Example for the WorkerThread pattern");
6.System.out.println("In this example, a ConcreteQueue object which uses a");
7.System.out.println(" worker thread, will retrieve a number of objects from");
8.System.out.println(" the server.");
9.System.out.println();
10.
11.System.out.println("Running the RMI compiler (rmic)");
12.System.out.println();
13.try{
14. Process p1 = Runtime.getRuntime().exec("rmic ServerDataStoreImpl");
15. p1.waitFor();
16.}
17.catch (IOException exc){
18.System.err.println("Unable to run rmic utility. Exiting application.");
19. System.exit(1);
20.}
21.catch (InterruptedException exc){
22.System.err.println("Threading problems encountered while using the rmic utility.");
23.}
24.
25.System.out.println("Starting the rmiregistry");
26.System.out.println();
27.Process rmiProcess = null;
28.try{
29. rmiProcess = Runtime.getRuntime().exec("rmiregistry");
30. Thread.sleep(15000);
31.}
32.catch (IOException exc){
33.System.err.println("Unable to start the rmiregistry. Exiting applica-
tion.");
34. System.exit(1);
35.}
36.catch (InterruptedException exc){
37.System.err.println("Threading problems encountered when starting the rmiregistry.");
38.}
39.
40.System.out.println("Creating the queue, which will be managed by the worker thread");
41.System.out.println();
42.ConcreteQueue workQueue = new ConcreteQueue();
43.
44.System.out.println("Creating the RMI server object, ServerDataStoreImpl");
45.System.out.println();
46.ServerDataStore server = new ServerDataStoreImpl();
47.
48.System.out.println("Creating AddressRetrievers and ContactRetreivers.");
49.System.out.println(" These will placed in the queue, as tasks to be");
50.System.out.println(" performed by the worker thread.");
51.System.out.println();
52.AddressRetriever firstAddr = new AddressRetriever(5280L, WORKER_SERVER_URL);
53.AddressRetriever secondAddr = new AddressRetriever(2010L, WORKER_SERVER_URL);
54.ContactRetriever firstContact = new ContactRetriever(5280L, WORKER_SERVER_URL);
56.workQueue.put(firstAddr);
57.workQueue.put(firstContact);
58.workQueue.put(secondAddr);
60.while (!secondAddr.isAddressAvailable()){
61. |
try{ |
62. |
Thread.sleep(1000); |
63. |
} |
64. |
catch (InterruptedException exc){} |
65. |
} |
66. |
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67.System.out.println("WorkerThread completed the processing of its Tasks");
68.System.out.println("Printing out the retrieved objects now:");
69.System.out.println();
70.System.out.println(firstAddr.getAddress());
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71.System.out.println(firstContact.getContact());
72.System.out.println(secondAddr.getAddress());
74. }
75.
76.}
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