Implementing Conversational Services in Java

Generating PDF417 in Java Implementing Conversational Services
Implementing Conversational Services
PDF 417 Maker In Java
Using Barcode creation for Java Control to generate, create PDF 417 image in Java applications.
persisted in a particular way Implementations that manage their own state must correlate the current conversation ID with any conversation state This will usually involve obtaining the conversation ID and performing a lookup of the conversational state based on that ID In this scenario, the conversation ID is still system-generated, and it is passed in a message header rather than as a parameter (using whatever approach to headers is appropriate for the binding being used) Because of this, the interface is still considered to be conversational The fact that the conversational state is explicitly retrieved through application logic, rather than automatically maintained by the infrastructure, is an implementation detail that does not need to be visible to the client of the service The fact that it is conversational, however, is still visible, because the client needs to know that a sequence of operations will be correlated to each other without being based on any information from the messages The current conversation ID can be obtained through injection via the @ConversationID annotation The following version of the CreditComponent uses the conversation ID to manually store state using a special ConversationalStorageService The latter could store the information in memory using a simple map or persistently using a database (see Listing 44)
Generating Bar Code In Java
Using Barcode creator for Java Control to generate, create barcode image in Java applications.
Listing 44
Scan Barcode In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
Manually Maintaining Conversational State
PDF417 Creator In C#.NET
Using Barcode generator for VS .NET Control to generate, create PDF 417 image in .NET applications.
import orgosoascaannotationsScope; public class CreditComponent implements CreditService { private ConversationalStorageService storageService; private String conversationID; public CreditComponent(@Reference (name="storageService") service){ thisstorageService = storageService; } @ConversationID public void setConversationID(String id){ thisconversationID = id; } public void apply(LoanApplicant applicant){ storageServicestoreApplicant(conversationID, applicant); } int getStatus() {
PDF-417 2d Barcode Drawer In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create PDF-417 2d barcode image in ASP.NET applications.
Conversational Interactions Using Java return storageServicegetStatus(conversationID); } void cancel() { storageServiceremoveApplicant(conversationID); }
PDF 417 Maker In .NET
Using Barcode maker for VS .NET Control to generate, create PDF-417 2d barcode image in VS .NET applications.
Similar to other injectable SCA-related information, the @ConversationID annotation may be used on public and protected elds or setter methods Expiring Conversations In loosely coupled systems, conversational services cannot rely on clients to be well behaved and call an operation marked with @EndsConversation to signal that conversational resources can be released Clients can fail or a network interruption could block an invocation from reaching its target service To handle these scenarios, SCA provides mechanisms for expiring a conversation using the @ConversationAttributes annotation @Conversation Attributes is placed on a Java class and can be used to specify a maximum idle time and maximum age of a conversation The maxIdleTime of a conversation de nes the maximum time that can pass between operation invocations within a single conversation The maxAge of a conversation denotes the maximum time a conversation can remain active If the container is managing conversational state, it may free resources, including removing implementation instances, associated with an expired conversation In the example shown in Listing 45, the maxIdleTime between invocations in the same conversation is set to 30 days
Paint PDF-417 2d Barcode In VB.NET
Using Barcode encoder for VS .NET Control to generate, create PDF 417 image in VS .NET applications.
Listing 45
Barcode Creator In Java
Using Barcode drawer for Java Control to generate, create bar code image in Java applications.
Setting Conversation Expiration Based on Idle Time
Creating Barcode In Java
Using Barcode creation for Java Control to generate, create bar code image in Java applications.
import orgosoascaannotationsConversationAttributes; @ConversationAttributes(maxIdleTime="30 days") public class CreditComponent implements CreditService { // }
EAN-13 Supplement 5 Creation In Java
Using Barcode encoder for Java Control to generate, create EAN13 image in Java applications.
Conversational Services and Asynchronous Interactions
Code 128 Code Set B Generation In Java
Using Barcode drawer for Java Control to generate, create Code 128A image in Java applications.
Similarly, the example in Listing 46 demonstrates setting the maxAge of a conversation to 30 days
Painting UPC Symbol In Java
Using Barcode drawer for Java Control to generate, create GS1 - 12 image in Java applications.
Listing 46
Code 2/5 Maker In Java
Using Barcode creator for Java Control to generate, create 2 of 5 Industrial image in Java applications.
Setting Conversation Expiration Based on Duration
Generating Barcode In VS .NET
Using Barcode creation for VS .NET Control to generate, create bar code image in VS .NET applications.
import orgosoascaannotationsConversationAttributes; @ConversationAttributes(maxAge="30 days") public class CreditComponent implements CreditService { // }
USS Code 39 Printer In Visual C#
Using Barcode creator for .NET Control to generate, create Code 39 Full ASCII image in VS .NET applications.
The @ConversationAttributes annotation allows maxAge and maxIdleTime to be speci ed in seconds, minutes, hours, days, or years The value of the attribute is an integer followed by the scale, as in 15 minutes
Print Barcode In VS .NET
Using Barcode generator for Visual Studio .NET Control to generate, create bar code image in Visual Studio .NET applications.
Conversational Services and Asynchronous Interactions
Data Matrix Creator In C#
Using Barcode printer for .NET Control to generate, create ECC200 image in .NET applications.
Conversational services can be used in conjunction with nonblocking operations and callbacks to create loosely coupled interactions that share state between the client and service provider Non-Blocking Invocations Operations can be made non-blocking on a conversational service using the @OneWay annotation discussed in 3 (see Listing 47)
Scanning Code-39 In .NET Framework
Using Barcode reader for VS .NET Control to read, scan read, scan image in VS .NET applications.
Conversational services can be used in conjunction with non-blocking operations and callbacks to create loosely coupled interactions that share state between the client and service provider
Printing ANSI/AIM Code 39 In .NET Framework
Using Barcode drawer for ASP.NET Control to generate, create Code39 image in ASP.NET applications.
Listing 47 import import import import
Code 39 Full ASCII Drawer In .NET
Using Barcode creator for VS .NET Control to generate, create ANSI/AIM Code 39 image in .NET framework applications.
Using Conversations with Non-Blocking Operations
orgosoascaannotationsRemotable; orgosoascaannotationsEndsConversation; orgosoascaannotationsConversational; orgosoascaannotationsOneWay;
@Remotable @Conversational public interface CreditService
@OneWay void apply(LoanApplicant applicant);
Conversational Interactions Using Java int getStatus(); @OneWay @EndsConversation void cancel();
Without the @OneWay annotation, the client developer knows if the operation returns without throwing an exception
The preceding example makes the CreditServiceapply() and CreditServicecancel() operations non-blocking, where control is returned immediately to the client, even before the operation request has been sent to the service provider This is different from just having the operation return void without having been marked with the @OneWay annotation Without the @OneWay annotation, the client doesn t regain control until the operation completes, so the client developer knows that if the operation returns without throwing an exception, the operation has successfully completed By contrast, a @OneWay operation may not be started until well after the client program has moved well beyond the place where the operation had been called This means that the client cannot assume that the operation has successfully completed, or even that the operation request has been able to reach the service provider Often, in this scenario, it will be advisable to require reliable delivery of the message so that the request is not lost merely because the client or the service provider crashes at an inopportune time Reliable delivery can be guaranteed by using SCA s policy intent mechanism In this case, the annotation would be @Requires ("ExactlyOnce") This will constrain the deployer to con gure the runtime to use some form of reliable delivery Policy intents are described in more detail in 6, Policy Using reliable delivery will not, however, help with the fact that the client code can t see exceptions that are raised by the @OneWay operation When developing these operations, if an error is discovered in the way the client has invoked the service (an invalid parameter, for example), the error must be sent back to the client through the callback interface, which is described in the next section