/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.mapping;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.hibernate.MappingException;
import org.hibernate.dialect.Dialect;
import org.hibernate.internal.util.StringHelper;

A foreign key constraint
Author:Gavin King
/** * A foreign key constraint * * @author Gavin King */
public class ForeignKey extends Constraint { private Table referencedTable; private String referencedEntityName; private String keyDefinition; private boolean cascadeDeleteEnabled; private List<Column> referencedColumns = new ArrayList<Column>(); private boolean creationEnabled = true; public ForeignKey() { } @Override public String getExportIdentifier() { // NOt sure name is always set. Might need some implicit naming return StringHelper.qualify( getTable().getName(), "FK-" + getName() ); } public void disableCreation() { creationEnabled = false; } public boolean isCreationEnabled() { return creationEnabled; } @Override public void setName(String name) { super.setName( name ); // the FK name "none" is a magic value in the hbm.xml binding that indicated to // not create a FK. if ( "none".equals( name ) ) { disableCreation(); } } public String sqlConstraintString( Dialect dialect, String constraintName, String defaultCatalog, String defaultSchema) { String[] columnNames = new String[getColumnSpan()]; String[] referencedColumnNames = new String[getColumnSpan()]; final Iterator<Column> referencedColumnItr; if ( isReferenceToPrimaryKey() ) { referencedColumnItr = referencedTable.getPrimaryKey().getColumnIterator(); } else { referencedColumnItr = referencedColumns.iterator(); } Iterator columnItr = getColumnIterator(); int i = 0; while ( columnItr.hasNext() ) { columnNames[i] = ( (Column) columnItr.next() ).getQuotedName( dialect ); referencedColumnNames[i] = referencedColumnItr.next().getQuotedName( dialect ); i++; } final String result = keyDefinition != null ? dialect.getAddForeignKeyConstraintString( constraintName, keyDefinition ) : dialect.getAddForeignKeyConstraintString( constraintName, columnNames, referencedTable.getQualifiedName( dialect, defaultCatalog, defaultSchema ), referencedColumnNames, isReferenceToPrimaryKey() ); return cascadeDeleteEnabled && dialect.supportsCascadeDelete() ? result + " on delete cascade" : result; } public Table getReferencedTable() { return referencedTable; } private void appendColumns(StringBuilder buf, Iterator columns) { while ( columns.hasNext() ) { Column column = (Column) columns.next(); buf.append( column.getName() ); if ( columns.hasNext() ) { buf.append( "," ); } } } public void setReferencedTable(Table referencedTable) throws MappingException { //if( isReferenceToPrimaryKey() ) alignColumns(referencedTable); // TODO: possibly remove to allow more piecemal building of a foreignkey. this.referencedTable = referencedTable; }
Validates that columnspan of the foreignkey and the primarykey is the same.

Furthermore it aligns the length of the underlying tables columns.
/** * Validates that columnspan of the foreignkey and the primarykey is the same. * <p/> * Furthermore it aligns the length of the underlying tables columns. */
public void alignColumns() { if ( isReferenceToPrimaryKey() ) { alignColumns( referencedTable ); } } private void alignColumns(Table referencedTable) { final int referencedPkColumnSpan = referencedTable.getPrimaryKey().getColumnSpan(); if ( referencedPkColumnSpan != getColumnSpan() ) { StringBuilder sb = new StringBuilder(); sb.append( "Foreign key (" ).append( getName() ).append( ":" ) .append( getTable().getName() ) .append( " [" ); appendColumns( sb, getColumnIterator() ); sb.append( "])" ) .append( ") must have same number of columns as the referenced primary key (" ) .append( referencedTable.getName() ) .append( " [" ); appendColumns( sb, referencedTable.getPrimaryKey().getColumnIterator() ); sb.append( "])" ); throw new MappingException( sb.toString() ); } Iterator fkCols = getColumnIterator(); Iterator pkCols = referencedTable.getPrimaryKey().getColumnIterator(); while ( pkCols.hasNext() ) { ( (Column) fkCols.next() ).setLength( ( (Column) pkCols.next() ).getLength() ); } } public String getReferencedEntityName() { return referencedEntityName; } public void setReferencedEntityName(String referencedEntityName) { this.referencedEntityName = referencedEntityName; } public String getKeyDefinition() { return keyDefinition; } public void setKeyDefinition(String keyDefinition) { this.keyDefinition = keyDefinition; } public String sqlDropString(Dialect dialect, String defaultCatalog, String defaultSchema) { String tableName = getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema ); final StringBuilder buf = new StringBuilder( dialect.getAlterTableString( tableName ) ); buf.append( dialect.getDropForeignKeyString() ); if ( dialect.supportsIfExistsBeforeConstraintName() ) { buf.append( "if exists " ); } buf.append( dialect.quote( getName() ) ); if ( dialect.supportsIfExistsAfterConstraintName() ) { buf.append( " if exists" ); } return buf.toString(); } public boolean isCascadeDeleteEnabled() { return cascadeDeleteEnabled; } public void setCascadeDeleteEnabled(boolean cascadeDeleteEnabled) { this.cascadeDeleteEnabled = cascadeDeleteEnabled; } public boolean isPhysicalConstraint() { return referencedTable.isPhysicalTable() && getTable().isPhysicalTable() && !referencedTable.hasDenormalizedTables(); }
Returns the referenced columns if the foreignkey does not refer to the primary key
/** * Returns the referenced columns if the foreignkey does not refer to the primary key */
public List getReferencedColumns() { return referencedColumns; }
Does this foreignkey reference the primary key of the reference table
/** * Does this foreignkey reference the primary key of the reference table */
public boolean isReferenceToPrimaryKey() { return referencedColumns.isEmpty(); } public void addReferencedColumns(Iterator referencedColumnsIterator) { while ( referencedColumnsIterator.hasNext() ) { Selectable col = (Selectable) referencedColumnsIterator.next(); if ( !col.isFormula() ) { addReferencedColumn( (Column) col ); } } } private void addReferencedColumn(Column column) { if ( !referencedColumns.contains( column ) ) { referencedColumns.add( column ); } } public String toString() { if ( !isReferenceToPrimaryKey() ) { return getClass().getName() + '(' + getTable().getName() + getColumns() + " ref-columns:" + '(' + getReferencedColumns() + ") as " + getName() + ")"; } else { return super.toString(); } } public String generatedConstraintNamePrefix() { return "FK_"; } }