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org.apache.cayenne.query.Ordering Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
****************************************************************/
package org.apache.cayenne.query;
import java.io.PrintWriter;
import java.io.Serializable;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import org.apache.cayenne.configuration.ConfigurationNodeVisitor;
import org.apache.cayenne.configuration.EmptyConfigurationNodeVisitor;
import org.apache.cayenne.exp.Expression;
import org.apache.cayenne.exp.ExpressionException;
import org.apache.cayenne.exp.parser.ASTDbPath;
import org.apache.cayenne.exp.parser.ASTObjPath;
import org.apache.cayenne.util.ConversionUtil;
import org.apache.cayenne.util.Util;
import org.apache.cayenne.util.XMLEncoder;
import org.apache.cayenne.util.XMLSerializable;
/**
* Defines object sorting criteria, used either for in-memory sorting of object
* lists or as a specification for building ORDER BY clause of a
* SelectQuery query. Note that in case of in-memory sorting, Ordering can be
* used with any JavaBeans, not just Persistent objects.
*/
public class Ordering implements Comparator, Serializable, XMLSerializable {
private static final long serialVersionUID = -9167074787055881422L;
protected String sortSpecString;
protected transient Expression sortSpec;
protected SortOrder sortOrder;
protected boolean pathExceptionSuppressed = false;
protected boolean nullSortedFirst = true;
/**
* Orders a given list of objects, using a List of Orderings applied
* according the default iteration order of the Orderings list. I.e. each
* Ordering with lower index is more significant than any other Ordering
* with higher index. List being ordered is modified in place.
*
* @param objects elements to sort
* @param orderings list of Orderings to be applied
*/
@SuppressWarnings("unchecked")
public static void orderList(List objects, List orderings) {
if(objects == null || orderings == null || orderings.isEmpty()) {
return;
}
Comparator comparator = orderings.get(0);
for(int i=1; i List orderedList(final Collection objects, List orderings) {
List newList = new ArrayList<>(objects);
orderList(newList, orderings);
return newList;
}
public Ordering() {
}
/**
* Create an ordering instance with a provided path and ascending sorting
* strategy.
*
* @since 4.0
*/
public Ordering(String sortPathSpec) {
this(sortPathSpec, SortOrder.ASCENDING);
}
/**
* @since 3.0
*/
public Ordering(String sortPathSpec, SortOrder sortOrder) {
setSortSpecString(sortPathSpec);
setSortOrder(sortOrder);
}
/**
* @since 4.0
*/
public Ordering(Expression sortSpec) {
this(sortSpec, SortOrder.ASCENDING);
}
/**
* @since 4.0
*/
public Ordering(Expression sortSpec, SortOrder sortOrder) {
setSortSpec(sortSpec);
setSortOrder(sortOrder);
}
@Override
public boolean equals(Object object) {
if (this == object) {
return true;
}
if (!(object instanceof Ordering)) {
return false;
}
Ordering o = (Ordering) object;
if (!Util.nullSafeEquals(sortSpecString, o.sortSpecString)) {
return false;
}
if (sortOrder != o.sortOrder) {
return false;
}
if (pathExceptionSuppressed != o.pathExceptionSuppressed) {
return false;
}
if (nullSortedFirst != o.nullSortedFirst) {
return false;
}
return true;
}
@Override
public int hashCode() {
int result = sortSpecString != null ? sortSpecString.hashCode() : 0;
result = 31 * result + (sortOrder != null ? sortOrder.hashCode() : 0);
result = 31 * result + (pathExceptionSuppressed ? 1 : 0);
result = 31 * result + (nullSortedFirst ? 1 : 0);
return result;
}
/**
* Sets sortSpec to be an expression represented by string argument.
*
* @since 1.1
*/
public void setSortSpecString(String sortSpecString) {
if (!Util.nullSafeEquals(this.sortSpecString, sortSpecString)) {
this.sortSpecString = sortSpecString;
this.sortSpec = null;
}
}
/**
* Sets sort order for whether nulls are at the top or bottom of the
* resulting list. Default is true.
* Affects only in-memory sorting.
*
* @param nullSortedFirst
* true sorts nulls to the top of the list, false sorts nulls to
* the bottom
*/
public void setNullSortedFirst(boolean nullSortedFirst) {
this.nullSortedFirst = nullSortedFirst;
}
/**
* Get sort order for nulls.
*
* @return true if nulls are sorted to the top of the list, false if sorted
* to the bottom
*/
public boolean isNullSortedFirst() {
return nullSortedFirst;
}
/**
* Sets whether a path with a null in the middle is ignored. For example, a
* sort from painting on artist.name would by
* default throw an exception if the artist was null. If set to true, then
* this is treated just like a null value. Default is false.
*
* @param pathExceptionSuppressed
* true to suppress exceptions and sort as null
*/
public void setPathExceptionSupressed(boolean pathExceptionSuppressed) {
this.pathExceptionSuppressed = pathExceptionSuppressed;
}
/**
* Is a path with a null in the middle is ignored.
*
* @return true is exception is suppressed and sorted as null
*/
public boolean isPathExceptionSuppressed() {
return pathExceptionSuppressed;
}
/**
* Returns sortSpec string representation.
*
* @since 1.1
*/
public String getSortSpecString() {
return sortSpecString;
}
/**
* Sets the sort order for this ordering.
*
* @since 3.0
*/
public void setSortOrder(SortOrder order) {
this.sortOrder = order;
}
/** Returns true if sorting is done in ascending order. */
public boolean isAscending() {
return sortOrder == null || sortOrder == SortOrder.ASCENDING || sortOrder == SortOrder.ASCENDING_INSENSITIVE;
}
/**
* Returns true if the sorting is done in descending order.
*
* @since 3.0
*/
public boolean isDescending() {
return !isAscending();
}
/**
* If the sort order is DESCENDING or DESCENDING_INSENSITIVE, sets the sort
* order to ASCENDING or ASCENDING_INSENSITIVE, respectively.
*
* @since 3.0
*/
public void setAscending() {
if (sortOrder == null || sortOrder == SortOrder.DESCENDING) {
setSortOrder(SortOrder.ASCENDING);
} else if (sortOrder == SortOrder.DESCENDING_INSENSITIVE) {
setSortOrder(SortOrder.ASCENDING_INSENSITIVE);
}
}
/**
* If the sort order is ASCENDING or ASCENDING_INSENSITIVE, sets the sort
* order to DESCENDING or DESCENDING_INSENSITIVE, respectively.
*
* @since 3.0
*/
public void setDescending() {
if (sortOrder == null || sortOrder == SortOrder.ASCENDING) {
setSortOrder(SortOrder.DESCENDING);
} else if (sortOrder == SortOrder.ASCENDING_INSENSITIVE) {
setSortOrder(SortOrder.DESCENDING_INSENSITIVE);
}
}
/** Returns true if the sorting is case insensitive */
public boolean isCaseInsensitive() {
return !isCaseSensitive();
}
/**
* Returns true if the sorting is case sensitive.
*
* @since 3.0
*/
public boolean isCaseSensitive() {
return sortOrder == null || sortOrder == SortOrder.ASCENDING || sortOrder == SortOrder.DESCENDING;
}
/**
* If the sort order is ASCENDING or DESCENDING, sets the sort order to
* ASCENDING_INSENSITIVE or DESCENDING_INSENSITIVE, respectively.
*
* @since 3.0
*/
public void setCaseInsensitive() {
if (sortOrder == null || sortOrder == SortOrder.ASCENDING) {
setSortOrder(SortOrder.ASCENDING_INSENSITIVE);
} else if (sortOrder == SortOrder.DESCENDING) {
setSortOrder(SortOrder.DESCENDING_INSENSITIVE);
}
}
/**
* If the sort order is ASCENDING_INSENSITIVE or DESCENDING_INSENSITIVE,
* sets the sort order to ASCENDING or DESCENDING, respectively.
*
* @since 3.0
*/
public void setCaseSensitive() {
if (sortOrder == null || sortOrder == SortOrder.ASCENDING_INSENSITIVE) {
setSortOrder(SortOrder.ASCENDING);
} else if (sortOrder == SortOrder.DESCENDING_INSENSITIVE) {
setSortOrder(SortOrder.DESCENDING);
}
}
/**
* Returns the expression defining a ordering Java Bean property.
*/
public Expression getSortSpec() {
if (sortSpecString == null) {
return null;
}
// compile on demand .. since orderings can only be paths, avoid the
// overhead of
// Expression.fromString, and parse them manually
if (sortSpec == null) {
if (sortSpecString.startsWith(ASTDbPath.DB_PREFIX)) {
sortSpec = new ASTDbPath(sortSpecString.substring(ASTDbPath.DB_PREFIX.length()));
} else if (sortSpecString.startsWith(ASTObjPath.OBJ_PREFIX)) {
sortSpec = new ASTObjPath(sortSpecString.substring(ASTObjPath.OBJ_PREFIX.length()));
} else {
sortSpec = new ASTObjPath(sortSpecString);
}
}
return sortSpec;
}
/**
* Sets the expression defining a ordering Java Bean property.
*/
public void setSortSpec(Expression sortSpec) {
this.sortSpec = sortSpec;
this.sortSpecString = (sortSpec != null) ? sortSpec.toString() : null;
}
/**
* Orders the given list of objects according to the ordering that this
* object specifies. List is modified in-place.
*
* @param objects
* a List of objects to be sorted
*/
public void orderList(List objects) {
Collections.sort(objects, this);
}
/**
* @since 4.0
*/
public List orderedList(Collection objects) {
List newList = new ArrayList<>(objects);
orderList(newList);
return newList;
}
/**
* Comparable interface implementation. Can compare two Java Beans based on
* the stored expression.
*/
@Override
public int compare(Object o1, Object o2) {
Expression exp = getSortSpec();
Object value1 = null;
Object value2 = null;
try {
value1 = exp.evaluate(o1);
} catch (ExpressionException e) {
if (pathExceptionSuppressed && e.getCause() instanceof org.apache.cayenne.reflect.UnresolvablePathException) {
// do nothing, we expect this
} else {
// re-throw
throw e;
}
}
try {
value2 = exp.evaluate(o2);
} catch (ExpressionException e) {
if (pathExceptionSuppressed && e.getCause() instanceof org.apache.cayenne.reflect.UnresolvablePathException) {
// do nothing, we expect this
} else {
// rethrow
throw e;
}
}
if (value1 == null && value2 == null) {
return 0;
} else if (value1 == null) {
return nullSortedFirst ? -1 : 1;
} else if (value2 == null) {
return nullSortedFirst ? 1 : -1;
}
if (isCaseInsensitive()) {
// TODO: to upper case should probably be defined as a separate
// expression
// type
value1 = ConversionUtil.toUpperCase(value1);
value2 = ConversionUtil.toUpperCase(value2);
}
int compareResult = ConversionUtil.toComparable(value1).compareTo(ConversionUtil.toComparable(value2));
return (isAscending()) ? compareResult : -compareResult;
}
/**
* Encodes itself as a query ordering.
*
* @since 1.1
*/
@Override
public void encodeAsXML(XMLEncoder encoder, ConfigurationNodeVisitor delegate) {
encoder.start("ordering")
.attribute("descending", isDescending())
.attribute("ignore-case", isCaseInsensitive())
.nested(getSortSpec(), delegate)
.end();
}
@Override
public String toString() {
StringWriter buffer = new StringWriter();
PrintWriter pw = new PrintWriter(buffer);
XMLEncoder encoder = new XMLEncoder(pw);
encodeAsXML(encoder, new EmptyConfigurationNodeVisitor());
pw.close();
buffer.flush();
return buffer.toString();
}
/**
* Returns sort order for this ordering
*
* @since 3.1
*/
public SortOrder getSortOrder() {
return sortOrder;
}
/**
* Returns Orderings with this Ordering followed by the provided
* next Ordering.
*
* @param nextOrdering the next Ordering to chain to this
* @return a new Orderings with both Ordering
* @since 4.1
*/
public Orderings then(Ordering nextOrdering) {
return new Orderings(this, nextOrdering);
}
/**
* Returns Orderings with this Ordering followed by the provided
* list of next Orderings.
*
* @param nextOrderings the next Orderings to chain to this
* @return an array of sort orderings
* @since 4.1
*/
public Orderings then(Orderings nextOrderings) {
Orderings newOrderings = new Orderings(this);
return newOrderings.then(nextOrderings);
}
/**
* @see Orderings#then(Orderings)
* @param nextOrderings the next Orderings to chain to this
* @return an array of sort orderings
* @since 4.1
*/
public Orderings then(List nextOrderings) {
Orderings newOrderings = new Orderings(this);
return newOrderings.then(nextOrderings);
}
}
