Chapter 8 Examples
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View code examples 8.25 to 8.35
8.25 8.26 8.27 8.28 8.29 8.30
8.31 8.32 8.33 8.34 8.35
Example 8.25 TaskResourceVO Class
public class TaskResourceVO {
public String projectId;
public String taskId;
public String name;
public String description;
public Date startDate;
public Date endDate;
public ResourceVO assignedResource;
...
public TaskResourceVO(String projectId,
String taskId, String name, String description,
Date startDate, Date endDate, ResourceVO
assignedResource) {
this.projectId = projectId;
this.taskId = taskId;
...
this.assignedResource = assignedResource;
}
...
}
Example 8.26 TaskVO Class
public class TaskVO {
public String projectId;
public String taskId;
public String name;
public String description;
public Date startDate;
public Date endDate;
public assignedResourceId;
public TaskVO(String projectId, String taskId,
String name, String description, Date startDate,
Date endDate, String assignedResourceId) {
this.projectId = projectId;
this.taskId = taskId;
...
this.assignedResource = assignedResource;
}
...
}
Example 8.27 ResourceVO Class
public class ResourceVO {
public String resourceId;
public String resourceName;
public String resourceEmail;
...
public ResourceVO (String resourceId, String
resourceName, String resourceEmail, ...) {
this.resourceId = resourceId;
this.resourceName = resourceName;
this.resourceEmail = resourceEmail;
...
}
}
Example 8.28 Implementing the Value Object Assembler
public class ProjectDetailsAssembler
implements javax.ejb.SessionBean {
...
public ProjectDetailsData getData(String projectId){
// Construct the composite value object
ProjectDetailsData pData = new
ProjectDetailsData();
//get the project details;
ProjectHome projectHome =
ServiceLocator.getInstance().getHome(
"Project", ProjectEntityHome.class);
ProjectEntity project =
projectHome.findByPrimaryKey(projectId);
ProjectVO projVO = project.getData();
// Add Project Info to ProjectDetailsData
pData.projectData = projVO;
//get the project manager details;
ProjectManagerHome projectManagerHome =
ServiceLocator.getInstance().getHome(
"ProjectManager", ProjectEntityHome.class);
ProjectManagerEntity projectManager =
projectManagerHome.findByPrimaryKey(
projVO.managerId);
ProjectManagerVO projMgrVO =
projectManager.getData();
// Add ProjectManager info to ProjectDetailsData
pData.projectManagerData = projMgrVO;
// Get list of TaskVOs from the Project
Collection projTaskList = project.getTasksList();
// construct a list of TaskResourceVOs
ArrayList listOfTasks = new ArrayList();
Iterator taskIter = projTaskList.iterator();
while (taskIter.hasNext()) {
TaskVO task = (TaskVO) taskIter.next();
//get the Resource details;
ResourceHome resourceHome =
ServiceLocator.getInstance().getHome(
"Resource", ResourceEntityHome.class);
ResourceEntity resource =
resourceHome.findByPrimaryKey(
task.assignedResourceId);
ResourceVO resVO = resource.getResourceData();
// construct a new TaskResourceVO using Task
// and Resource data
TaskResourceVO trVO = new TaskResourceVO(
task.projectId, task.taskId,
task.name, task.description,
task.startDate, task.endDate,
resVO);
// add TaskResourceVO to the list
listOfTasks.add(trVO);
}
// add list of tasks to ProjectDetailsData
pData.listOfTasks = listOfTasks;
// add any other data to the value object
...
// return the composite value object
return pData;
}
...
}
Example 8.29 Implementing Value List Handler Pattern
package corepatterns.apps.psa.handlers;
import java.util.*;
import corepatterns.apps.psa.dao.*;
import corepatterns.apps.psa.util.*;
import corepatterns.apps.psa.core.*;
public class ProjectListHandler
extends ValueListHandler {
private ProjectDAO dao = null;
// use ProjectVO as a template to determine
// search criteria
private ProjectVO projectCriteria = null;
// Client creates a ProjectVO instance, sets the
// values to use for search criteria and passes
// the ProjectVO instance as projectCriteria
// to the constructor and to setCriteria() method
public ProjectListHandler(ProjectVO projectCriteria)
throws ProjectException, ListHandlerException {
try {
this.projectCriteria = projectCriteria;
this.dao = PSADAOFactory.getProjectDAO();
executeSearch();
} catch (Exception e) {
// Handle exception, throw ListHandlerException
}
}
public void setCriteria(ProjectVO projectCriteria) {
this.projectCriteria = projectCriteria;
}
// executes search. Client can invoke this
// provided that the search criteria has been
// properly set. Used to perform search to refresh
// the list with the latest data.
public void executeSearch()
throws ListHandlerException {
try {
if (projectCriteria == null) {
throw new ListHandlerException(
"Project Criteria required...");
}
List resultsList =
dao.executeSelect(projectCriteria);
setList(resultsList);
} catch (Exception e) {
// Handle exception, throw ListHandlerException
}
}
}
Example 8.30 Implementing Generic ValueListHandler Class
package corepatterns.apps.psa.util;
import java.util.*;
public class ValueListHandler
implements ValueListIterator {
protected List list;
protected ListIterator listIterator;
public ValueListHandler() {
}
protected void setList(List list)
throws IteratorException {
this.list = list;
if(list != null)
listIterator = list.listIterator();
else
throw new IteratorException("List empty");
}
public Collection getList(){
return list;
}
public int getSize() throws IteratorException{
int size = 0;
if (list != null)
size = list.size();
else
throw new IteratorException(...); //No Data
return size;
}
public Object getCurrentElement()
throws IteratorException {
Object obj = null;
// Will not advance iterator
if (list != null)
{
int currIndex = listIterator.nextIndex();
obj = list.get(currIndex);
}
else
throw new IteratorException(...);
return obj;
}
public List getPreviousElements(int count)
throws IteratorException {
int i = 0;
Object object = null;
LinkedList list = new LinkedList();
if (listIterator != null) {
while (listIterator.hasPrevious() && (i < count)){
object = listIterator.previous();
list.add(object);
i++;
}
}// end if
else
throw new IteratorException(...); // No data
return list;
}
public List getNextElements(int count)
throws IteratorException {
int i = 0;
Object object = null;
LinkedList list = new LinkedList();
if(listIterator != null){
while( listIterator.hasNext() && (i < count) ){
object = listIterator.next();
list.add(object);
i++;
}
} / / end if
else
throw new IteratorException(...); // No data
return list;
}
public void resetIndex() throws IteratorException{
if(listIterator != null){
listIterator = list.ListIterator();
}
else
throw new IteratorException(...); // No data
}
...
}
Example 8.31 ProjectDAO Class
package corepatterns.apps.psa.dao;
public class ProjectDAO {
final private String tableName = "PROJECT";
// select statement uses fields
final private String fields = "project_id, name," +
"project_manager_id, start_date, end_date, " +
" started, completed, accepted, acceptedDate," +
" customer_id, description, status";
// the methods relevant to the ValueListHandler
// are shown here.
// See Data Access Object pattern for other details.
...
private List executeSelect(ProjectVO projCriteria)
throws SQLException {
Statement stmt= null;
List list = null;
Connection con = getConnection();
StringBuffer selectStatement = new StringBuffer();
selectStatement.append("SELECT "+ fields +
" FROM " + tableName + "where 1=1");
// append additional conditions to where clause
// depending on the values specified in
// projCriteria
if (projCriteria.projectId != null) {
selectStatement.append (" AND PROJECT_ID = '" +
projCriteria.projectId + "'");
}
// check and add other fields to where clause
...
try {
stmt = con.prepareStatement(selectStatement);
stmt.setString(1, resourceID);
ResultSet rs = stmt.executeQuery();
list = prepareResult(rs);
stmt.close();
}
finally {
con.close();
}
return list;
}
private List prepareResult(ResultSet rs)
throws SQLException {
ArrayList list = new ArrayList();
while(rs.next()) {
int i = 1;
ProjectVO proj = new
ProjectVO(rs.getString(i++));
proj.projectName = rs.getString(i++);
proj.managerId = rs.getString(i++);
proj.startDate = rs.getDate(i++);
proj.endDate = rs.getDate(i++);
proj.started = rs.getBoolean(i++);
proj.completed = rs.getBoolean(i++);
proj.accepted = rs.getBoolean(i++);
proj.acceptedDate = rs.getDate(i++);
proj.customerId = rs.getString(i++);
proj.projectDescription = rs.getString(i++);
proj.projectStatus = rs.getString(i++);
list.add(proj);
}
return list;
}
...
}
Example 8.32 ValueListIterator Class
package corepatterns.apps.psa.util;
import java.util.List;
public interface ValueListIterator {
public int getSize()
throws IteratorException;
public Object getCurrentElement()
throws IteratorException;
public List getPreviousElements(int count)
throws IteratorException;
public List getNextElements(int count)
throws IteratorException;
public void resetIndex()
throws IteratorException;
// other common methods as required
...
}
Example 8.33 Implementing Service Locator
package corepatterns.apps.psa.util;
import java.util.*;
import javax.naming.*;
import java.rmi.RemoteException;
import javax.ejb.*;
import javax.rmi.PortableRemoteObject;
import java.io.*;
public class ServiceLocator {
private static ServiceLocator me;
InitialContext context = null;
private ServiceLocator()
throws ServiceLocatorException {
try {
context = new InitialContext();
} catch(NamingException ne) {
throw new ServiceLocatorException(...);
}
}
// Returns the instance of ServiceLocator class
public static ServiceLocator getInstance()
throws ServiceLocatorException {
if (me == null) {
me = new ServiceLocator();
}
return me;
}
// Converts the serialized string into EJBHandle
// then to EJBObject.
public EJBObject getService(String id)
throws ServiceLocatorException {
if (id == null) {
throw new ServiceLocatorException(...);
}
try {
byte[] bytes = new String(id).getBytes();
InputStream io = new
ByteArrayInputStream(bytes);
ObjectInputStream os = new
ObjectInputStream(io);
javax.ejb.Handle handle =
(javax.ejb.Handle)os.readObject();
return handle.getEJBObject();
} catch(Exception ex) {
throw new ServiceLocatorException(...);
}
}
// Returns the String that represents the given
// EJBObject's handle in serialized format.
protected String getId(EJBObject session)
throws ServiceLocatorException {
try {
javax.ejb.Handle handle = session.getHandle();
ByteArrayOutputStream fo = new
ByteArrayOutputStream();
ObjectOutputStream so = new
ObjectOutputStream(fo);
so.writeObject(handle);
so.flush();
so.close();
return new String(fo.toByteArray());
} catch(RemoteException ex) {
throw new ServiceLocatorException(...);
} catch(IOException ex) {
throw new ServiceLocatorException(...);
}
return null;
}
// Returns the EJBHome object for requested service
// name. Throws ServiceLocatorException If Any Error
// occurs in lookup
public EJBHome getHome(String name, Class clazz)
throws ServiceLocatorException {
try {
Object objref = context.lookup(name);
EJBHome home = (EJBHome)
PortableRemoteObject.narrow(objref, clazz);
return home;
} catch(NamingException ex) {
throw new ServiceLocatorException(...);
}
}
}
Example 8.34 Implementing Type Checked Service Locator Strategy
package corepatterns.apps.psa.util;
// imports
...
public class ServiceLocator {
// singleton's private instance
private static ServiceLocator me;
static {
me = new ServiceLocator();
}
private ServiceLocator() {}
// returns the Service Locator instance
static public ServiceLocator getInstance() {
return me;
}
// Services Constants Inner Class - service objects
public class Services {
final public static int PROJECT = 0;
final public static int RESOURCE = 1;
}
// Project EJB related constants
final static Class PROJECT_CLASS = ProjectHome.class;
final static String PROJECT_NAME = "Project";
// Resource EJB related constants
final static Class RESOURCE_CLASS = ResourceHome.class;
final static String RESOURCE_NAME = "Resource";
// Returns the Class for the required service
static private Class getServiceClass(int service){
switch( service ) {
case Services.PROJECT:
return PROJECT_CLASS;
case Services.RESOURCE:
return RESOURCE_CLASS;
}
return null;
}
// returns the JNDI name for the required service
static private String getServiceName(int service){
switch( service ) {
case Services.PROJECT:
return PROJECT_NAME;
case Services.RESOURCE:
return RESOURCE_NAME;
}
return null;
}
/* gets the EJBHome for the given service using the
** JNDI name and the Class for the EJBHome
*/
public EJBHome getHome( int s )
throws ServiceLocatorException {
EJBHome home = null;
try {
Context initial = new InitialContext();
// Look up using the service name from
// defined constant
Object objref =
initial.lookup(getServiceName(s));
// Narrow using the EJBHome Class from
// defined constant
Object obj = PortableRemoteObject.narrow(
objref, getServiceClass(s));
home = (EJBHome)obj;
}
catch( NamingException ex ) {
throw new ServiceLocatorException(...);
}
catch( Exception ex ) {
throw new ServiceLocatorException(...);
}
return home;
}
}
Example 8.35 Client Code for Using the Service Locator
public class ServiceLocatorTester {
public static void main( String[] args ) {
ServiceLocator serviceLocator =
ServiceLocator.getInstance();
try {
ProjectHome projectHome = (ProjectHome)
serviceLocator.getHome(
ServiceLocator.Services.PROJECT );
}
catch( ServiceException ex ) {
// client handles exception
System.out.println( ex.getMessage( ));
}
}
}
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