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| e-docs > WebLogic Platform > WebLogic Integration > BPM Topics > Programming BPM Plug-Ins > Defining the Plug-In Session EJB |
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Programming BPM Plug-Ins
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Defining the Plug-In Session EJB
This section explains how to define the plug-in session EJB. It includes the following topics:
Overview
To define the plug-in session EJB, you must implement the three predefined interfaces described in the following table.
The following sections describe each interface and the methods that you must implement when defining the plug-in session EJB. Excerpts from the plug-in sample are included.
Session EJB Interface
By definition, a session EJB must implement the javax.ejb.SessionBean and its methods.
Note: The contents of the SessionBean interface methods may be empty, or they may simply return a message to the log; but they must be implemented.
The following table lists the session EJB methods that you must implement.
For more information about these methods, see the javax.ejb.SessionBean Javadoc. The following code listing is an excerpt from the plug-in sample that shows how to implement the javax.ejb.SessionBean interface and its methods. This excerpt is taken from the SamplePluginBean.java file in the SAMPLES_HOME/integration/samples/bpm_api/plugin/src/com/bea/wlpi/tour/po/plugin directory. Notable lines of code are shown in bold. Listing 3-1 Implementing the Session EJB Interface For more information about the plug-in sample, see BPM Plug-In Sample.
package com.bea.wlpi.tour.po.plugin;
import com.bea.wlpi.common.VersionInfo;
import com.bea.wlpi.common.plugin.*;
import com.bea.wlpi.common.plugin.PluginData;
import com.bea.wlpi.server.plugin.InstanceNotification;
import com.bea.wlpi.server.plugin.Plugin;
import com.bea.wlpi.server.plugin.PluginManagerCfg;
import com.bea.wlpi.server.plugin.PluginManagerCfgHome;
import com.bea.wlpi.server.plugin.TaskNotification;
import com.bea.wlpi.server.plugin.TemplateDefinitionNotification;
import com.bea.wlpi.server.plugin.TemplateNotification;
import java.lang.reflect.Constructor;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import java.util.Locale;
import java.net.URL;
import javax.ejb.CreateException;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.naming.InitialContext;
import javax.rmi.PortableRemoteObject;
import java.io.*
/**
* @homeInterface com.bea.wlpi.server.plugin.PluginHome
* @remoteInterface com.bea.testplugin.SamplePlugin
* @statemode Stateless
*/
public class SamplePluginBean implements SessionBean {
private SessionContext ctx;
private final static String PLUGIN_MANAGER_CFG_HOME =
"java:comp/env/ejb/PluginManagerCfg";
private static byte[] ICON_BYTE_ARRAY;
// implements javax.ejb.SessionBean
public void ejbActivate() {
} // implements javax.ejb.SessionBean
public void ejbRemove() {
}
// implements javax.ejb.SessionBean
public void ejbPassivate() {
}
// implements javax.ejb.SessionBean
public void setSessionContext(SessionContext ctx) {
this.ctx = ctx;
}
.
.
.
Plug-In Home Interface
The home interface has been defined for you by the BPM plug-in framework. The com.bea.wlpi.server.plugin.PluginHome interface extends the javax.ejb.EJBHome interface and defines the home interface for all plug-ins.
The following table describes the method defined by the PluginHome home interface.
For more information about the home interface, see the com.bea.wlpi.server.plugin.PluginHome Javadoc. The following code listing is an excerpt from the plug-in sample that shows how to implement ejbCreate() method for the single create() method that is declared in the home interface, and define a custom plug-in icon for the Studio interface view. This excerpt is taken from the SamplePluginBean.java file in the SAMPLES_HOME/integration/samples/bpm_api/plugin/src/com/bea/wlpi/tour/po/plugin directory. Listing 3-2 Implementing the Home Interface Method For more information about the plug-in sample, see BPM Plug-In Sample.
// implements javax.ejb.SessionBean
public void ejbCreate() throws CreateException {
try {
ICON_BYTE_ARRAY = InfoObject.imageStreamToByteArray(
getClass().getResourceAsStream("Sample.gif"));
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
Plug-In Remote Interface
The remote interface is defined for you by the BPM plug-in framework. The com.bea.wlpi.server.plugin.Plugin interface extends the javax.ejb.EJBObject interface and defines the remote interface for all plug-ins.
When defining the plug-in session EJB, you must implement the Plugin remote interface, including its methods.
The Plugin remote interface defines methods in the following categories:
The following sections describe, by category, the Plugin remote interface methods that you must implement.
Note: The contents of the remote interface methods may remain empty, or they may simply return a message to the log; but they must be implemented.
Lifecycle Management Methods
The following table defines the lifecycle management methods that are defined by the remote interface that you must implement. For more information about the BPM plug-in lifecycle, see Managing Lifecycle Tasks.
For more information about the methods of managing the remote interface lifecycle, see the com.bea.wlpi.server.plugin.Plugin Javadoc. Notification Methods The following table defines the notification methods that are defined by the remote interface that you must implement. Note: In order to receive notifications, the plug-in must register as a notification listener. For more information, see Using Plug-In Notifications.
For more information about remote interface notification methods, see the com.bea.wlpi.server.plugin.Plugin Javadoc. Plug-In Information Methods The following table defines the plug-in information methods that are defined by the remote interface that you must implement.
For more information about remote interface plug-in information methods, see the com.bea.wlpi.server.plugin.Plugin Javadoc. Object Manufacturing Method The following table defines the object manufacturing method that are defined by the remote interface that you must implement.
For more information about remote interface object manufacturing method, see the com.bea.wlpi.server.plugin.Plugin Javadoc. Example of Implementing the Remote Interface The following code listing is an excerpt from the plug-in sample that shows how to implement the remote interface and its methods. This excerpt is taken from the SamplePluginBean.java file in the SAMPLES_HOME/integration/samples/bpm_api/plugin/src/com/bea/wlpi/tour/po/plugin directory. Notable lines of code are shown in bold. Listing 3-3 Implementing the Remote Interface For more information about the plug-in sample, see BPM Plug-In Sample.
// Plugin implementation
/**
* Load the Plugin. The plugin should register its
* interest in various system events at this point.
* @param pluginData Plugin configuration data.
* @see PluginManager#addTemplateListener
* @see PluginManager#addTemplateDefinitionListener
* @see PluginManager#addInstanceListener
* @see PluginManager#addTaskListener
* @throws PluginException
*/
public void load(PluginObject pluginData) throws PluginException {
log("load called");
// Enable this block to subscribe to notifications.
/*
PluginManagerCfg pm = null;
try {
pm = getPluginManagerCfg();
Plugin plugin = (Plugin)ctx.getEJBObject();
pm.addInstanceListener(plugin, PluginConstants.EVENT_NOTIFICATION_ALL);
pm.addTaskListener(plugin, PluginConstants.EVENT_NOTIFICATION_ALL);
pm.addTemplateDefinitionListener(plugin, PluginConstants.EVENT_NOTIFICATION_ALL);
pm.addTemplateListener(plugin, PluginConstants.EVENT_NOTIFICATION_ALL);
} catch (Exception e) {
e.printStackTrace();
throw new PluginException(SamplePluginConstants.PLUGIN_NAME, "Unable to get PluginManager");
} finally {
try {
if (pm != null)
pm.remove();
} catch (Exception e) {
}
}
*/
log("loaded");
}
/**
* Unload the plugin. The plugin framework will deregister the plugin
* if it had subscribed to any event notifications.
*/
public void unload() {
log("unload called");
}
public PluginDependency[] getDependencies() {
log("getDependencies called");
return null;
}
public String getName() {
return SamplePluginConstants.PLUGIN_NAME;
}
public VersionInfo getVersion() {
return SamplePluginConstants.PLUGIN_VERSION;
}
/**
* Return descriptive information about the plugin
* @param lc The locale in which to localize display strings.
* @return Descriptive information about the Plugin.
*/
public PluginInfo getPluginInfo(Locale lc) {
log("getPluginInfo called");
return createPluginInfo(lc);
}
public void setConfiguration(PluginObject config) throws PluginException {
}
/**
* Return a complete description of the plugins capabilities. To add new
* subcategories and actions, the plugin should use the category IDs
* passed in via the <code>info</code> parameter passed to identify the
* parent categories, and {@link ActionCategoryInfo#ID_PLUGIN} as the new category ID.
* The PluginManager merges the CategoryInfo array returned by this call with
* the current structure (as passed via the <code>info</code> parameter), and
* replaces references to {@link ActionCategoryInfo#ID_PLUGIN} with newly-assigned
* unique category IDs. The predefined categories have the following IDs:
* {@link ActionCategoryInfo#ID_TASK}, {@link ActionCategoryInfo#ID_WORKFLOW},
* {@link ActionCategoryInfo#ID_INTEGRATION}, {@link ActionCategoryInfo#ID_MISCELLANEOUS},
* {@link ActionCategoryInfo#ID_EXCEPTION}.
* @param lc Locale in which to localize display strings.
* @param info The existing action category tree, containing
* categories and actions both predefined and plugin-defined
* (i.e., by previously loaded plugins).
* @return New categories and actions to be inserted in the tree.
*/
public PluginCapabilitiesInfo getPluginCapabilitiesInfo(Locale lc,
CategoryInfo[] info) {
PluginInfo pi;
FieldInfo orderFieldInfo;
FieldInfo confirmFieldInfo;
FieldInfo[] fieldInfo;
FunctionInfo fi;
FunctionInfo[] functionInfo;
StartInfo si;
StartInfo[] startInfo;
EventInfo ei;
EventInfo[] eventInfo;
SampleBundle bundle = new SampleBundle(lc);
log("getPluginCapabilities called");
pi = createPluginInfo(lc);
orderFieldInfo =
new FieldInfo(SamplePluginConstants.PLUGIN_NAME, 3,
bundle.getString("orderFieldName"),
bundle.getString("orderFieldDesc"),
SamplePluginConstants.ORDER_FIELD_CLASSES, false);
confirmFieldInfo =
new FieldInfo(SamplePluginConstants.PLUGIN_NAME, 4,
bundle.getString("confirmFieldName"),
bundle.getString("confirmFieldDesc"),
SamplePluginConstants.CONFIRM_FIELD_CLASSES, false);
fieldInfo = new FieldInfo[]{ orderFieldInfo, confirmFieldInfo };
ei = new EventInfo(SamplePluginConstants.PLUGIN_NAME, 6,
bundle.getString("confirmOrderName"),
bundle.getString("confirmOrderDesc"), ICON_BYTE_ARRAY,
SamplePluginConstants.EVENT_CLASSES,
confirmFieldInfo);
eventInfo = new EventInfo[]{ ei };
fi = new FunctionInfo(SamplePluginConstants.PLUGIN_NAME, 7,
bundle.getString("calcTotalName"),
bundle.getString("calcTotalDesc"),
bundle.getString("calcTotalHint"),
SamplePluginConstants.FUNCTION_CLASSES, 3, 3);
functionInfo = new FunctionInfo[]{ fi };
si = new StartInfo(SamplePluginConstants.PLUGIN_NAME, 5,
bundle.getString("startOrderName"),
bundle.getString("startOrderDesc"), ICON_BYTE_ARRAY,
SamplePluginConstants.START_CLASSES, orderFieldInfo);
startInfo = new StartInfo[]{ si };
PluginCapabilitiesInfo pci = new PluginCapabilitiesInfo(pi,
getCategoryInfo(bundle), eventInfo,
fieldInfo, functionInfo, startInfo,
null, null, null, null, null);
return pci;
}
/**
* Return a plugin-defined class. The caller retrieves the class name by
* calling on one of the plugin-supplied metadata objects.
* @param className The fully qualified Java class name to instantiate.
* @return The class with the specified name.
* @throws ClassNotFoundException if the plugin could not load the class.
* @see ActionInfo
* @see EventInfo
* @see FunctionInfo
* @see FieldInfo
* @see PluginInfo
* @see StartInfo
* @see DoneInfo
* @see VariableTypeInfo
* @see TemplatePropertiesInfo
* @see TemplateDefinitionPropertiesInfo
* @throws PluginException
*/
public Class classForName(String className)
throws ClassNotFoundException, PluginException {
log("classForName called");
return Class.forName(className);
}
/**
* Return a plugin-defined object. The caller retrieves the class name by
* calling on one of the plugin-supplied metadata objects.
* @param lc The locale in which to localize display strings.
* @param className The fully qualified Java class name to instantiate.
* @return
* @see ActionInfo
* @see EventInfo
* @see FunctionInfo
* @see FieldInfo
* @see PluginInfo
* @see StartInfo
* @see DoneInfo
* @see VariableTypeInfo
* @see TemplateInfo
* @see TemplateDefinitionInfo
* @throws ClassNotFoundException
* @throws PluginException
*/
public Object getObject(Locale lc, String className)
throws ClassNotFoundException, PluginException {
log("getObject called with class name " + className);
try {
Class cls = Class.forName(className);
Object obj;
try {
// see if there is a ctor that takes a Locale object
Class[] paramType = new Class[]{ lc.getClass() };
Constructor ctor = cls.getConstructor(paramType);
Object[] param = new Object[]{ lc };
obj = ctor.newInstance(param);
return (obj);
} catch (Exception e) {
}
// if not ctor takes a Locale just call the no-arg ctor
return Class.forName(className).newInstance();
} catch (InstantiationException ie) {
throw new PluginException(SamplePluginConstants.PLUGIN_NAME,
"Unable to instantiate class: " + ie);
} catch (IllegalAccessException iae) {
throw new PluginException(SamplePluginConstants.PLUGIN_NAME,
"Unable to instantiate class: " + iae);
}
}
/**
* Notifies a plugin of a change in a template.
* @param e An event object describing the change.
*/
public void templateChanged(TemplateNotification e) {
log("templateChanged called");
}
/**
* Notifies a plugin of a change in a template definition.
* @param e An event object describing the change.
*/
public void templateDefinitionChanged(TemplateDefinitionNotification e) {
log("templateDefinitionChanged called");
}
/**
* Notifies a plugin of a change in a workflow instance.
* @param e An event object describing the change.
*/
public void instanceChanged(InstanceNotification e) {
log("instanceChanged called");
}
/**
* Notifies a plugin of a change in a task instance.
* @param e An event object describing the change.
*/
public void taskChanged(TaskNotification e) {
log("taskChanged called");
} private PluginInfo createPluginInfo(Locale lc) {
HelpSetInfo helpSet;
PluginInfo pi;
SampleBundle bundle = new SampleBundle(lc);
String name = bundle.getString("pluginName");
String desc = bundle.getString("pluginDesc");
String helpName = bundle.getString("helpName");
String helpDesc = bundle.getString("helpDesc");
helpSet = new HelpSetInfo(SamplePluginConstants.PLUGIN_NAME, helpName,
helpDesc,
new String[]{ "htmlhelp/Sample", "index" },
HelpSetInfo.HELP_HTML);
pi = new PluginInfo(SamplePluginConstants.PLUGIN_NAME, name, desc, lc,
SamplePluginConstants.VENDOR_NAME,
SamplePluginConstants.VENDOR_URL,
SamplePluginConstants.PLUGIN_VERSION,
SamplePluginConstants.PLUGIN_FRAMEWORK_VERSION,
null, null, helpSet);
return pi;
}
// It is necessary to create these objects afresh each time, because we
// relinquish ownership of the result and the plugin framework assigns
// a system ID to each item. Reassignment will cause an
// IllegalStateException.
private CategoryInfo[] getCategoryInfo(SampleBundle bundle) {
ActionInfo checkInventoryAction =
new ActionInfo(SamplePluginConstants.PLUGIN_NAME, 1,
bundle.getString("checkInventoryName"),
bundle.getString("checkInventoryDesc"), ICON_BYTE_ARRAY,
ActionCategoryInfo.ID_NEW,
ActionInfo.ACTION_STATE_ALL,
SamplePluginConstants.CHECKINV_CLASSES);
ActionInfo sendConfirmAction =
new ActionInfo(SamplePluginConstants.PLUGIN_NAME, 2,
bundle.getString("sendConfirmName"),
bundle.getString("sendConfirmDesc"), ICON_BYTE_ARRAY,
ActionCategoryInfo.ID_NEW,
ActionInfo.ACTION_STATE_ALL,
SamplePluginConstants.SENDCONF_CLASSES);
ActionCategoryInfo[] actions =
new ActionCategoryInfo[]{ checkInventoryAction, sendConfirmAction };
CategoryInfo[] catInfo =
new CategoryInfo[]{ new CategoryInfo(SamplePluginConstants.PLUGIN_NAME,
0, bundle.getString("catName"),
bundle.getString("catDesc"),
ActionCategoryInfo.ID_NEW,
actions) };
return catInfo;
}
private void log(String msg) {
System.out.println("SamplePlugin: " + msg);
}
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