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package oracle.toplink.essentials.queryframework;
import java.util.HashMap;
import java.util.Iterator;
import oracle.toplink.essentials.exceptions.DatabaseException;
import oracle.toplink.essentials.exceptions.QueryException;
import oracle.toplink.essentials.expressions.Expression;
import oracle.toplink.essentials.descriptors.ClassDescriptor;
import oracle.toplink.essentials.expressions.ExpressionBuilder;
/**
* PUBLIC:
* A Query Class used to perform a bulk update using TopLink's expression framework.
* This class is provided to help optimize performance. It can be used in place
* of reading in all the objects to be changed and issuing single updates per
* instance. With this approach a single SQL UPDATE statement can be issued and
* then, based on the Expression provided, any objects in the cache that are
* effected by the update can be invalidated.
* <p>
* Notes: <ul>
* <li>By default, if a UOW is being used, this query will be deferred until the UOW commits.
* <li>UpdateAllQuery does not support foreign key updates
* unless the relationship is 1-1 (without back pointers.)</ul>
* <p>
* <b>Example of Usage:</b> Adding an area code. <br>
* <code>
* UpdateAllQuery updateQuery = new UpdateAllQuery(Employee.class); <br>
* updateQuery.setSelectionCriteria(eb.get("areaCode").isNull()); <br>
* updateQuery.addUpdate(eb.get("areaCode"), "613"); <br>
* </code>
*
* @author Guy Pelletier
* @date March 1, 2004
*/
public class UpdateAllQuery extends ModifyAllQuery {
protected HashMap m_updateClauses;
/**
* PUBLIC:
* Constructs a default update all query.
*/
public UpdateAllQuery() {
super();
}
/**
* PUBLIC:
* Constructs an update all query for the Class type specified.
* @param referenceClass Class
*/
public UpdateAllQuery(Class referenceClass) {
super(referenceClass);
}
/**
* PUBLIC:
* Constructs an update all query for the specified Class type and selection criteria.
* @param referenceClass Class type to be considered
* @param selectionCriteria Expression
*/
public UpdateAllQuery(Class referenceClass, Expression selectionCriteria) {
super(referenceClass, selectionCriteria);
}
/**
* PUBLIC:
* Constructs an update all query for the Class type specified and the given
* ExpressionBuilder. This sets the default builder which is used for all associated
* expressions in the query.<br>
* @param referenceClass Class type to be considered
* @param builder ExpressionBuilder
*/
public UpdateAllQuery(Class referenceClass, ExpressionBuilder expressionBuilder) {
super(referenceClass);
this.defaultBuilder = expressionBuilder;
}
/**
* PUBLIC:
* Adds the update (SET) clause to the query. Uses default ExpressionBuilder.
* @param field Expression Object level representation of a database query 'where' clause
* @param value Object, the new value
*/
public void addUpdate(Expression field, Object value) {
addUpdateInternal(field, value);
}
/**
* PUBLIC:
* Adds the update (SET) clause to the query. Uses default ExpressionBuilder.
* @param attributeName String, the name of the attribute
* @param value Object, the new value
*/
public void addUpdate(String attributeName, Object value) {
addUpdateInternal(attributeName, value);
}
/**
* PUBLIC:
* Adds the update (SET) clause to the query. This method ensures that
* the builder has the session and reference class set for both given Expressions.
* Uses default ExpressionBuilder.
* @param field Expression, representation of a database query 'where' clause that describes the field
* @param value Expression, representation of a database query 'where' clause that describes the new value
*/
public void addUpdate(Expression field, Expression value) {
addUpdateInternal(field, value);
}
/**
* PUBLIC:
* Adds the update (SET) clause to the query. Uses default ExpressionBuilder.
* @param attributeName String, the name of the attribute
* @param value Expression, the new value
*/
public void addUpdate(String attributeName, Expression value) {
addUpdateInternal(attributeName, value);
}
/**
* INTERNAL:
*/
protected void addUpdateInternal(Object fieldObject, Object valueObject) {
if(fieldObject == null) {
throw QueryException.updateAllQueryAddUpdateFieldIsNull(this);
}
if(m_updateClauses == null) {
m_updateClauses = new HashMap();
}
m_updateClauses.put(fieldObject, valueObject);
}
/**
* INTERNAL:
* Issue the SQL to the database and then merge into the cache.
* If we are within a UoW, the merge to the cache must not be done until
* the UoW merges into the parent. The UoW will trigger the merge to occur
* at the correct time and will ensure the cache setting is set to none at
* that time.
*/
public Object executeDatabaseQuery() throws DatabaseException {
result = getQueryMechanism().updateAll();// fire the SQL to the database
mergeChangesIntoSharedCache();
return result;
}
/**
* INTERNAL:
* Return the updates stored for an update all query
*/
public HashMap getUpdateClauses() {
return m_updateClauses;
}
/**
* INTERNAL:
* Return true if this is an update all query.
*/
public boolean isUpdateAllQuery() {
return true;
}
/**
* INTERNAL:
*/
protected void prepare() throws QueryException {
super.prepare();// will tell the query mechanism to prepare itself as well.
Class referenceClass = getReferenceClass();
// Check the reference class, must be set
if (referenceClass == null) {
throw QueryException.referenceClassMissing(this);
}
// Check the descriptor is set, if not try to get it from the session
if (getDescriptor() == null) {
ClassDescriptor desc = getSession().getDescriptor(referenceClass);
if (desc == null) {
throw QueryException.descriptorIsMissing(referenceClass, this);
}
setDescriptor(desc);
}
ClassDescriptor descriptor = getDescriptor();
// Check the descriptor for an aggregate
if (descriptor.isAggregateDescriptor()) {
throw QueryException.aggregateObjectCannotBeDeletedOrWritten(descriptor, this);
}
// Check that the update statement is set. That is the bare minimum,
// the user can execute this query without a selection criteria though.
if ((getUpdateClauses() == null || getUpdateClauses().isEmpty()) && isExpressionQuery()) {
throw QueryException.updateStatementsNotSpecified();
}
getQueryMechanism().prepareUpdateAll();
}
/**
* INTERNAL:
* Initialize the expression builder which should be used for this query. If
* there is a where clause, use its expression builder.
* If after this method defaultBuilder is still null,
* then initializeDefaultBuilder method will generate and cache it.
*/
protected void initializeQuerySpecificDefaultBuilder() {
super.initializeQuerySpecificDefaultBuilder();
if(this.defaultBuilder == null && m_updateClauses != null) {
Iterator it = m_updateClauses.values().iterator();
while(it.hasNext() ) {
Object value = it.next();
if(value != null) {
if(value instanceof Expression) {
Expression valueExpression = (Expression)value;
this.defaultBuilder = valueExpression.getBuilder();
if(this.defaultBuilder != null) {
return;
}
}
}
}
it = m_updateClauses.keySet().iterator();
while(it.hasNext() ) {
Object field = it.next();
if(field instanceof Expression) {
Expression fieldExpression = (Expression)field;
this.defaultBuilder = fieldExpression.getBuilder();
if(this.defaultBuilder != null) {
return;
}
}
}
}
}
}
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