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Cayenne Object Persistence Framework
/*****************************************************************
* 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
*
* http://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.map;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.SortedMap;
import java.util.StringTokenizer;
import java.util.TreeMap;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.exp.Expression;
import org.apache.cayenne.exp.ExpressionException;
import org.apache.cayenne.util.CayenneMapEntry;
import org.apache.cayenne.util.XMLSerializable;
/**
* An Entity is an abstract descriptor for an entity mapping concept. Entity can represent
* either a descriptor of database table or a persistent object.
*
* @author Andrei Adamchik
*/
public abstract class Entity implements CayenneMapEntry, XMLSerializable, Serializable {
public static final String PATH_SEPARATOR = ".";
protected String name;
protected DataMap dataMap;
protected SortedMap attributes;
protected SortedMap relationships;
/**
* Creates an unnamed Entity.
*/
public Entity() {
this(null);
}
/**
* Creates a named Entity.
*/
public Entity(String name) {
this.attributes = new TreeMap();
this.relationships = new TreeMap();
setName(name);
}
/**
* Returns entity name. Name is a unique identifier of the entity within its DataMap.
*/
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Object getParent() {
return getDataMap();
}
public void setParent(Object parent) {
if (parent != null && !(parent instanceof DataMap)) {
throw new IllegalArgumentException("Expected null or DataMap, got: " + parent);
}
setDataMap((DataMap) parent);
}
/**
* @return parent DataMap of this entity.
*/
public DataMap getDataMap() {
return dataMap;
}
/**
* Sets parent DataMap of this entity.
*/
public void setDataMap(DataMap dataMap) {
this.dataMap = dataMap;
}
/**
* Returns attribute with name attributeName or null if no attribute
* with this name exists.
*/
public Attribute getAttribute(String attributeName) {
return (Attribute) attributes.get(attributeName);
}
/**
* Adds new attribute to the entity, setting its parent entity to be this object. If
* attribute has no name, IllegalArgumentException is thrown.
*/
public void addAttribute(Attribute attribute) {
if (attribute.getName() == null) {
throw new IllegalArgumentException("Attempt to insert unnamed attribute.");
}
// block overrides
// TODO: change method signature to return replaced attribute and make sure the
// Modeler handles it...
Object existingAttribute = attributes.get(attribute.getName());
if (existingAttribute != null) {
if (existingAttribute == attribute) {
return;
}
else {
throw new IllegalArgumentException("An attempt to override attribute '"
+ attribute.getName());
}
}
// Check that there aren't any relationships with the same name as the given attribute.
Object existingRelationship = relationships.get(attribute.getName());
if (existingRelationship != null) {
throw new IllegalArgumentException(
"Attribute name conflict with existing relationship '" + attribute.getName());
}
attributes.put(attribute.getName(), attribute);
attribute.setEntity(this);
}
/** Removes an attribute named attrName. */
public void removeAttribute(String attrName) {
attributes.remove(attrName);
}
public void clearAttributes() {
attributes.clear();
}
/**
* Returns relationship with name relName. Will return null if no
* relationship with this name exists in the entity.
*/
public Relationship getRelationship(String relName) {
return (Relationship) relationships.get(relName);
}
/** Adds new relationship to the entity. */
public void addRelationship(Relationship relationship) {
if (relationship.getName() == null) {
throw new IllegalArgumentException("Attempt to insert unnamed relationship.");
}
// block overrides
// TODO: change method signature to return replaced attribute and make sure the
// Modeler handles it...
Object existingRelationship = relationships.get(relationship.getName());
if (existingRelationship != null) {
if (existingRelationship == relationship) {
return;
}
else {
throw new IllegalArgumentException(
"An attempt to override relationship '" + relationship.getName());
}
}
// Check that there aren't any attributes with the same name as the given relationship.
Object existingAttribute = attributes.get(relationship.getName());
if (existingAttribute != null) {
throw new IllegalArgumentException("Relationship name conflict with existing attribute '"
+ relationship.getName());
}
relationships.put(relationship.getName(), relationship);
relationship.setSourceEntity(this);
}
/** Removes a relationship named attrName. */
public void removeRelationship(String relName) {
relationships.remove(relName);
}
public void clearRelationships() {
relationships.clear();
}
/**
* Returns an unmodifiable map of relationships sorted by name.
*/
public SortedMap getRelationshipMap() {
// create a new instance ... earlier attempts to cache it in the entity caused
// serialization issues (esp. with Hessian).
return Collections.unmodifiableSortedMap(relationships);
}
/**
* Returns a relationship that has a specified entity as a target. If there is more
* than one relationship for the same target, it is unpredictable which one will be
* returned.
*
* @since 1.1
*/
public Relationship getAnyRelationship(Entity targetEntity) {
if (getRelationships().isEmpty()) {
return null;
}
Iterator it = getRelationships().iterator();
while (it.hasNext()) {
Relationship r = (Relationship) it.next();
if (r.getTargetEntity() == targetEntity) {
return r;
}
}
return null;
}
/**
* Returns an unmodifiable collection of Relationships that exist in this entity.
*/
public Collection getRelationships() {
// create a new instance ... earlier attempts to cache it in the entity caused
// serialization issues (esp. with Hessian).
return Collections.unmodifiableCollection(relationships.values());
}
/**
* Returns an unmodifiable sorted map of entity attributes.
*/
public SortedMap getAttributeMap() {
// create a new instance ... earlier attempts to cache it in the entity caused
// serialization issues (esp. with Hessian).
return Collections.unmodifiableSortedMap(attributes);
}
/**
* Returns an unmodifiable collection of entity attributes.
*/
public Collection getAttributes() {
// create a new instance ... earlier attempts to cache it in the entity caused
// serialization issues (esp. with Hessian).
return Collections.unmodifiableCollection(attributes.values());
}
/**
* Translates Expression rooted in this entity to an analogous expression rooted in
* related entity.
*
* @since 1.1
*/
public abstract Expression translateToRelatedEntity(
Expression expression,
String relationshipPath);
/**
* Convenience method returning the last component in the path iterator.
*
* @since 1.1
* @see #resolvePathComponents(Expression)
*/
public Object lastPathComponent(Expression pathExp) {
Object last = null;
Iterator it = resolvePathComponents(pathExp);
while (it.hasNext()) {
last = it.next();
}
return last;
}
/**
* Processes expression pathExp and returns an Iterator of path
* components that contains a sequence of Attributes and Relationships. Note that if
* path is invalid and can not be resolved from this entity, this method will still
* return an Iterator, but an attempt to read the first invalid path component will
* result in ExpressionException.
*/
public abstract Iterator resolvePathComponents(Expression pathExp)
throws ExpressionException;
/**
* Returns an Iterator over the path components that contains a sequence of Attributes
* and Relationships. Note that if path is invalid and can not be resolved from this
* entity, this method will still return an Iterator, but an attempt to read the first
* invalid path component will result in ExpressionException.
*/
public Iterator resolvePathComponents(String path) throws ExpressionException {
return new PathIterator(path);
}
// An iterator resolving mapping components represented by the path string.
// This entity is assumed to be the root of the path.
final class PathIterator implements Iterator {
private StringTokenizer toks;
private Entity currentEnt;
private String path;
PathIterator(String path) {
super();
this.currentEnt = Entity.this;
this.toks = new StringTokenizer(path, PATH_SEPARATOR);
this.path = path;
}
public boolean hasNext() {
return toks.hasMoreTokens();
}
public Object next() {
String pathComp = toks.nextToken();
// see if this is an attribute
Attribute attr = currentEnt.getAttribute(pathComp);
if (attr != null) {
// do a sanity check...
if (toks.hasMoreTokens()) {
throw new ExpressionException(
"Attribute must be the last component of the path: '"
+ pathComp
+ "'.",
path,
null);
}
return attr;
}
Relationship rel = currentEnt.getRelationship(pathComp);
if (rel != null) {
currentEnt = rel.getTargetEntity();
return rel;
}
// build error message
StringBuffer buf = new StringBuffer();
buf
.append("Can't resolve path component: [")
.append(currentEnt.getName())
.append('.')
.append(pathComp)
.append("].");
throw new ExpressionException(buf.toString(), path, null);
}
public void remove() {
throw new UnsupportedOperationException(
"'remove' operation is not supported.");
}
}
final MappingNamespace getNonNullNamespace() {
MappingNamespace parent = getDataMap();
if (parent == null) {
throw new CayenneRuntimeException("Entity '"
+ getName()
+ "' has no parent MappingNamespace (such as DataMap)");
}
return parent;
}
}
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