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- Business Delegate
- Forces
- Solution
- Consequences
- Sample Code
- Related Patterns
From the book
Sample Code
From the book
From the book
Sample Code
Implementing the Business Delegate Pattern
Consider a professional services application (PSA), which has resources (consultants) assigned to projects (engagements). The presentation-tier component must access a Session Façde (341). Apply the Business Delegate pattern to implement a ResourceDelegate object, which encapsulates the details of dealing with the ResourceSession Session Façde (341).
The ResourceDelegate implementation for this example is shown in Example 7.1, and the corresponding remote interface for the ResourceSession Session Façde (341) is shown in Example 7.2.
Example 7.1 Implementing Business Delegate pattern – ResourceDelegate
1
2 // imports
3 ...
4
5 public class ResourceDelegate {
6
7 // Remote reference for Session Facade
8 private ResourceSession session;
9
10 // Class for Session Facade's Home object
11 private static final Class homeClazz =
12 corepatterns.apps.psa.ejb.ResourceSessionHome.class;
13
14 // Default Constructor. Looks up home and connects to
15 // session by creating a new one.
16 public ResourceDelegate() throws ResourceException {
17 try {
18 ResourceSessionHome home =
19 (ResourceSessionHome) ServiceLocator.getInstance().
20 getRemoteHome("Resource", homeClazz);
21 session = home.create();
22 } catch (ServiceLocatorException ex) {
23 // Translate Service Locator exception into
24 // application exception
25 throw new ResourceException(...);
26 } catch (CreateException ex) {
27 // Translate the Session create exception into
28 // application exception
29 throw new ResourceException(...);
30 } catch (RemoteException ex) {
31 // Translate the Remote exception into application
32 // exception
33 throw new ResourceException(...);
34 }
35 }
36
37 // Constructor that accepts an ID (Handle id) and
38 // reconnects to the prior session bean instead of creating
39 // a new one
40 public ResourceDelegate(String id)
41 throws ResourceException {
42 // reconnect to the session bean for the given id
43 reconnect(id);
44 }
45
46 // Returns a String ID the client can use at a later time
47 // to reconnect to the session bean
48 public String getID() {
49 try {
50 return ServiceLocator.getId(session);
51 } catch (Exception e) {
52 // Throw an application exception
53 }
54 }
55
56 // method to reconnect using String ID
57 public void reconnect(String id) throws ResourceException {
58 try {
59 session =
60 (ResourceSession) ServiceLocator.getService(id);
61 } catch (RemoteException ex) {
62 // Translate the Remote exception into application
63 // exception
64 throw new ResourceException(...);
65 }
66 }
67
68 // The following are the business methods proxied to the
69 // Session Facade. If any service exception is encountered,
70 // these methods convert them into application exceptions
71 // such as ResourceException, SkillSetException, and so on.
72 public ResourceTO setCurrentResource(String resourceId)
73 throws ResourceException {
74 try {
75 return session.setCurrentResource(resourceId);
76 } catch (RemoteException ex) {
77 // Translate the service exception into
78 // application exception
79 throw new ResourceException(...);
80 }
81 }
82
83 public ResourceTO getResourceDetails()
84 throws ResourceException {
85
86 try {
87 return session.getResourceDetails();
88 } catch (RemoteException ex) {
89 // Translate the service exception into application
90 // exception
91 throw new ResourceException(...);
92 }
93 }
94
95 public void setResourceDetails(ResourceTO to)
96 throws ResourceException {
97 try {
98 session.setResourceDetails(to);
99 } catch (RemoteException ex) {
100 throw new ResourceException(...);
101 }
102 }
103
104 public void addNewResource(ResourceTO to)
105 throws ResourceException {
106 try {
107 session.addResource(to);
108 } catch (RemoteException ex) {
109 throw new ResourceException(...);
110 }
111 }
112
113 // all other proxy method to session bean
114 ...
115 }
Example 7.2 Remote Interface for ResourceSession
1 // imports
2 ...
3 public interface ResourceSession extends EJBObject {
4
5 public ResourceTO setCurrentResource(String resourceId)
6 throws RemoteException, ResourceException;
7
8 public ResourceTO getResourceDetails()
9 throws RemoteException, ResourceException;
10
11 public void setResourceDetails(ResourceTO resource)
12 throws RemoteException, ResourceException;
13
14 public void addResource(ResourceTO resource)
15 throws RemoteException, ResourceException;
16
17 public void removeResource()
18 throws RemoteException, ResourceException;
19
20 // methods for managing blockout time by the resource
21 public void addBlockoutTime(Collection blockoutTime)
22 throws RemoteException, BlockoutTimeException;
23
24 public void updateBlockoutTime(Collection blockoutTime)
25 throws RemoteException, BlockoutTimeException;
26
27 public void removeBlockoutTime( Collection blockoutTime)
28 throws RemoteException, BlockoutTimeException;
29
30 public void removeAllBlockoutTime()
31 throws RemoteException, BlockoutTimeException;
32
33 // methods for resource skillsets time by the resource
34 public void addSkillSets(Collection skillSet)
35 throws RemoteException, SkillSetException;
36
37 public void updateSkillSets(Collection skillSet)
38 throws RemoteException, SkillSetException;
39
40 public void removeSkillSet(Collection skillSet)
41 throws RemoteException, SkillSetException;
42
43 ...
44 }
45