Wikipedia

Composite entity pattern: Difference between revisions

Browse history interactively
← Previous edit
Content deleted Content added
VisualWikitext
No edit summary
 
(14 intermediate revisions by 12 users not shown)
Line 1:
'''Composite entity''' is a [[Java Platform, Enterprise Edition|Java EE]] [[Software design pattern]] and it is used to model, represent, and manage a set of interrelated persistent objects rather thatthan representing them as individual fine-grained entity beans, and also a composite entity bean represents a graph of objects.<ref name=":o_cjp">{{Cite web|url = http://www.oracle.com/technetwork/java/compositeentity-141992.html|title = Core J2EE Patterns - Composite Entity|access-date = |accessdate = 6 February 2016|website = Oracle|publisher = Oracle|last = |first = }}</ref>
 
==Structure==
thereThere are a number of strategies to implement composite entity pattern. This pattern mainly composites of compsitecomposite entity, coarse-grained object, and dependent objects.<ref name=":o_cjp"/>
 
[[File:Composte entity pattern class diagram.png|center|Composite entity pattern class diagram]]
 
<!-- Deleted image removed: [[File:Composite entity pattern sequence diagram.png|center|Composite entity pattern sequence diagram]] -->
 
===Composite entity component===
Composite entity is the coarse-grained entity bean which may be the coarse-grained object, or may contain a reference to the coarse-grained object.<ref name=":o_cjp"/>
 
===Coarse-grained object===
A coarse-grained object is an object with its own life cycylecycle manages its own relationships to other objects. It can be an object contained in the composite entity, or, composite entity itself can be the coarse-grained object which holds dependent objects.<ref name=":o_cjp"/>
 
===Dependent objects===
It is an object, which can contain other dependent objects (there may be a tree of objects within the composite entity), that depends on the coarse-grained object and has its life cycle managed by the coarse-grained object.<ref name=":o_cjp"/>
 
==Consequences==
According to Oracle description of the pattern, consequences includesinclude eliminating inter-entity relationships, improving manageability by reducing entity beans, improving network performance, reducing database schema dependency, incresingincreasing object granularity, facicilitatingfacilitating composite transfer object creation and overhead of multi-level dependent object graphesgraphs.<ref name=":o_cjp"/>
 
===Drawbacks===
The fatal drawback is the requirement of bean-managed persistent (BMP) [[JavaBeans|bean]]. This involves more work for developers, and craetecreate some problems as follows:
* materializing all the data in a coarse-grained entity whenever it's is accessed, is unacceptably expensive
* In [[Java (programming language)|Java]], implementation of the ejbStore() method needs to be smart enough to avoid issuing all the updates required to persist the entire state of the object, unless the data has changed in all the persistent objects.
Composite entity pattern can only be implemented using BMP or by adding more hand-coded persistence logic to comtainercontainer managed persistancepersistence (CMP) [[JavaBeans|beans]]. These both approaches reduce the maintainability.<ref name=":eojdad">{{Cite book|title = Expert One-on-One J2EE Design and Development|last = Johnson|first = R. |publisher = Wiley Publishing, Inc|year = 2003|___location = Indianapolis|volume = |pages = 290}}</ref>
 
==Sample code==
Sample code for a Professional Service Automation application (PSA) in which the resource object is implmentedimplemented via composite entity pattern, may look like as follows (entity implements coarse-grained object):
<sourcesyntaxhighlight lang="Javajava">
package corepatterns.apps.psa.ejb;
 
Line 31 ⟶ 40:
 
public class ResourceEntity implements EntityBean {
public String employeeId;
public String lastName;
public String firstName;
public String departmentId;
public String practiceGroup;
public String title;
public String grade;
public String email;
public String phone;
public String cell;
public String pager;
public String managerId;
// Collection of BlockOutTime Dependent objects
public Collection blockoutTimes;
 
// Collection of SkillSet Dependent objects
public Collection skillSets;
 
...
 
private EntityContext context;
// Entity Bean methods implementation
public String ejbCreate(ResourceTO resource) throws
CreateException {
try {
this.employeeId = resource.employeeId;
setResourceData(resource);
getResourceDAO().create(resource);
} catch (Exception ex) {
throw new EJBException("Reason:" + ...);
}
return this.employeeId;
}
public String ejbFindByPrimaryKey(String primaryKey)
throws FinderException {
boolean result;
try {
ResourceDAO resourceDAO = getResourceDAO();
result =
resourceDAO.selectByPrimaryKey(primaryKey);
} catch (Exception ex) {
throw new EJBException("Reason:" + ...);
}
if (result) {
return primaryKey;
}
else {
throw new ObjectNotFoundException(...);
}
}
if(result) {
public void ejbRemove() {
return primaryKey;
try {
// Remove dependent objects
if (this.skillSets != null) {
 
SkillSetDAO skillSetDAO = getSkillSetDAO();
skillSetDAO.setResourceID(employeeId);
skillSetDAO.deleteAll();
skillSets = null;
}
if (this.blockoutTime != null) {
BlockOutTimeDAO blockouttimeDAO =
getBlockOutTimeDAO();
blockouttimeDAO.setResourceID(employeeId);
blockouttimeDAO.deleteAll();
blockOutTimes = null;
}
 
// Remove the resource from the persistent store
ResourceDAO resourceDAO = new
ResourceDAO(employeeId);
resourceDAO.delete();
} catch (ResourceException ex) {
throw new EJBException("Reason:"+...);
} catch (BlockOutTimeException ex) {
throw new EJBException("Reason:"+...);
} catch (Exception exception) {
...
}
}
public void setEntityContext(EntityContext context)
else {
{
throw new ObjectNotFoundException(...);
this.context = context;
}
}
public void unsetEntityContext() {
context = null;
public void ejbRemove() {
try {}
// Remove dependent objects
public void ejbActivate() {
if(this.skillSets != null) {
employeeId = (String)context.getPrimaryKey();
}
public void ejbPassivate() {
employeeId = null;
}
public void ejbLoad() {
try {
// load the resource info from
ResourceDAO resourceDAO = getResourceDAO();
setResourceData((ResourceTO)
resourceDAO.load(employeeId));
// Load other dependent objects, if necessary
...
} catch (Exception ex) {
throw new EJBException("Reason:" + ...);
}
}
public void ejbStore() {
try {
// Store resource information
getResourceDAO().update(getResourceData());
 
// Store dependent objects as needed
SkillSetDAO skillSetDAO = getSkillSetDAO();
...
skillSetDAO.setResourceID(employeeId);
} catch (SkillSetException ex) {
skillSetDAO.deleteAll();
throw new EJBException("Reason:" + ...);
skillSets = null;
} catch (BlockOutTimeException ex) {
}
throw new EJBException("Reason:" + ...);
if(this.blockoutTime != null) {
}
BlockOutTimeDAO blockouttimeDAO =
getBlockOutTimeDAO();...
blockouttimeDAO.setResourceID(employeeId);
blockouttimeDAO.deleteAll();
blockOutTimes = null;
}
 
// Remove the resource from the persistent store
ResourceDAO resourceDAO = new
ResourceDAO(employeeId);
resourceDAO.delete();
} catch(ResourceException ex) {
throw new EJBException("Reason:"+...);
} catch(BlockOutTimeException ex) {
throw new EJBException("Reason:"+...);
} catch(Exception exception) {
...
}
public void ejbPostCreate(ResourceTO resource) {
}
public void setEntityContext(EntityContext context)
{
this.context = context;
}
public void unsetEntityContext() {
context = null;
}
public void ejbActivate() {
employeeId = (String)context.getPrimaryKey();
}
public void ejbPassivate() {
employeeId = null;
}
public void ejbLoad() {
try {
// load the resource info from
ResourceDAO resourceDAO = getResourceDAO();
setResourceData((ResourceTO)
resourceDAO.load(employeeId));
// Load other dependent objects, if necessary
...
} catch(Exception ex) {
throw new EJBException("Reason:" + ...);
}
}
public void ejbStore() {
try {
// Store resource information
getResourceDAO().update(getResourceData());
 
// StoreMethod to dependentGet objectsResource asTransfer neededObject
public ResourceTO getResourceTO() {
...
// create a new Resource Transfer Object
} catch(SkillSetException ex) {
ResourceTO resourceTO = new
throw new EJBException("Reason:" + ...);
ResourceTO(employeeId);
} catch(BlockOutTimeException ex) {
 
throw new EJBException("Reason:" + ...);
// copy all values
resourceTO.lastName = lastName;
resourceTO.firstName = firstName;
resourceTO.departmentId = departmentId;
...
return resourceTO;
}
...
}
public void ejbPostCreate(ResourceTO resource) {
}
 
public void setResourceData(ResourceTO resourceTO) {
// Method to Get Resource Transfer Object
// copy values from Transfer Object into entity bean
public ResourceTO getResourceTO() {
employeeId = resourceTO.employeeId;
// create a new Resource Transfer Object
lastName = resourceTO.lastName;
ResourceTO resourceTO = new
ResourceTO(employeeId);...
}
 
// Method to get dependent Transfer Objects
// copy all values
public Collection getSkillSetsData() {
resourceTO.lastName = lastName;
// If skillSets is not loaded, load it first.
resourceTO.firstName = firstName;
// See Lazy Load strategy implementation.
resourceTO.departmentId = departmentId;
 
return skillSets;
}
...
return resourceTO;
}
 
// other get and set methods as needed
public void setResourceData(ResourceTO resourceTO) {
// copy values from Transfer Object into entity bean
employeeId = resourceTO.employeeId;
lastName = resourceTO.lastName;
...
}
 
// Entity bean business methods
// Method to get dependent Transfer Objects
public Collectionvoid getSkillSetsDataaddBlockOutTimes(Collection moreBOTs) {
throws BlockOutTimeException {
// If skillSets is not loaded, load it first.
// Note: moreBOTs is a collection of
// See Lazy Load strategy implementation.
// BlockOutTimeTO objects
try {
Iterator moreIter = moreBOTs.iterator();
while (moreIter.hasNext()) {
BlockOutTimeTO botTO = (BlockOutTimeTO)
moreIter.next();
if (! (blockOutTimeExists(botTO))) {
// add BlockOutTimeTO to collection
botTO.setNew();
blockOutTime.add(botTO);
} else {
// BlockOutTimeTO already exists, cannot add
throw new BlockOutTimeException(...);
}
}
} catch (Exception exception) {
throw new EJBException(...);
}
}
 
public void addSkillSet(Collection moreSkills)
return skillSets;
throws SkillSetException {
}
// similar to addBlockOutTime() implementation
...
...
 
// other get and set methods as needed
...
 
// Entity bean business methods
public void addBlockOutTimes(Collection moreBOTs)
throws BlockOutTimeException {
// Note: moreBOTs is a collection of
// BlockOutTimeTO objects
try {
Iterator moreIter = moreBOTs.iterator();
while(moreIter.hasNext()) {
BlockOutTimeTO botTO = (BlockOutTimeTO)
moreIter.next();
if (! (blockOutTimeExists(botTO))) {
// add BlockOutTimeTO to collection
botTO.setNew();
blockOutTime.add(botTO);
} else {
// BlockOutTimeTO already exists, cannot add
throw new BlockOutTimeException(...);
}
}
} catch(Exception exception) {
throw new EJBException(...);
}
}
 
public void addSkillSet(Collection moreSkills)
throws SkillSetException {
// similar to addBlockOutTime() implementation
...
}
 
public void updateBlockOutTime(Collection updBOTs)
...
throws BlockOutTimeException {
 
try {
public void updateBlockOutTime(Collection updBOTs)
Iterator botIter = blockOutTimes.iterator();
throws BlockOutTimeException {
Iterator updIter = updBOTs.iterator();
try {
Iterator botIter = blockOutTimes while (updIter.iteratorhasNext();) {
BlockOutTimeTO botTO = (BlockOutTimeTO)
Iterator updIter = updBOTs.iterator();
while ( updIter.hasNextnext()) {;
BlockOutTimeTO botTO = while (BlockOutTimeTObotIter.hasNext()) {
updIter.next(); BlockOutTimeTO existingBOT =
while (BlockOutTimeTO) botIter.hasNextnext()) {;
// compare key values to locate BlockOutTime
BlockOutTimeTO existingBOT =
(BlockOutTimeTO) botIter if (existingBOT.nextequals(botTO);) {
// compare key values to locate // Found BlockOutTime in collection
// replace old BlockOutTimeTO with new one
if (existingBOT.equals(botTO)) {
botTO.setDirty(); //modified old dependent
// Found BlockOutTime in collection
// replace old BlockOutTimeTO with botTO.resetNew(); //not a new onedependent
botTO.setDirty(); //modified old dependent existingBOT = botTO;
botTO.resetNew(); //not a new dependent }
existingBOT = botTO; }
}
} catch (Exception exc) {
throw new EJBException(...);
}
}
} catch (Exception exc) {
throw new EJBException(...);
}
}
 
public void updateSkillSet(Collection updSkills)
throws CommitmentException {
// similar to updateBlockOutTime...
...
}
 
...
 
}
</syntaxhighlight><ref name=":o_cjp"/>
 
 
</source><ref name=":o_cjp"/>
==See also==
* [[Data transfer object]]
Line 272 ⟶ 280:
 
{{Design Patterns patterns}}
 
[[Category:Software design patterns]]
[[Category:Articles with example Java code]]
Retrieved from "https://en.wikipedia.org/wiki/Composite_entity_pattern"