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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
*
* 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 org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.util.ToStringBuilder;
import org.apache.cayenne.util.XMLEncoder;
import org.apache.cayenne.util.XMLSerializable;
/**
* Defines a join between two attributes of a given relationship.
*
* @since 1.1
*/
public class DbJoin implements XMLSerializable, Serializable {
protected DbRelationship relationship;
protected String sourceName;
protected String targetName;
protected DbJoin() {
}
public DbJoin(DbRelationship relationship) {
this.relationship = relationship;
}
public DbJoin(DbRelationship relationship, String sourceName, String targetName) {
this.relationship = relationship;
this.sourceName = sourceName;
this.targetName = targetName;
}
/**
* Returns a "reverse" join. Join source relationship is not set and must be
* initialized by the caller.
*/
public DbJoin createReverseJoin() {
DbJoin reverse = new DbJoin();
reverse.setTargetName(sourceName);
reverse.setSourceName(targetName);
return reverse;
}
/**
* Returns DbAttribute on on the left side of the join.
*/
public DbAttribute getSource() {
if (sourceName == null) {
return null;
}
Relationship r = getNonNullRelationship();
Entity entity = r.getSourceEntity();
if (entity == null) {
return null;
}
return (DbAttribute) entity.getAttribute(sourceName);
}
public DbAttribute getTarget() {
if (targetName == null) {
return null;
}
Relationship r = getNonNullRelationship();
Entity entity = r.getTargetEntity();
if (entity == null) {
return null;
}
return (DbAttribute) entity.getAttribute(targetName);
}
/**
* Prints itself as XML to the provided XMLEncoder.
*/
public void encodeAsXML(XMLEncoder encoder) {
encoder.print("<db-attribute-pair");
// sanity check
if (getSourceName() != null) {
encoder.print(" source=\"");
encoder.print(getSourceName());
encoder.print("\"");
}
if (getTargetName() != null) {
encoder.print(" target=\"");
encoder.print(getTargetName());
encoder.print("\"");
}
encoder.println("/>");
}
public DbRelationship getRelationship() {
return relationship;
}
public String getSourceName() {
return sourceName;
}
public String getTargetName() {
return targetName;
}
public void setRelationship(DbRelationship relationship) {
this.relationship = relationship;
}
public void setSourceName(String string) {
sourceName = string;
}
public void setTargetName(String string) {
targetName = string;
}
private final DbRelationship getNonNullRelationship() {
if (relationship == null) {
throw new CayenneRuntimeException("Join has no parent Relationship.");
}
return relationship;
}
@Override
public String toString() {
ToStringBuilder builder = new ToStringBuilder(this);
builder.append("source", getSourceName());
builder.append("target", getTargetName());
return builder.toString();
}
}