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Hibernate's core ORM functionality
/*
* 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 .
*/
package org.hibernate.mapping;
import java.io.Serializable;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import org.hibernate.HibernateException;
import org.hibernate.annotations.common.util.StringHelper;
import org.hibernate.boot.model.relational.Exportable;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.spi.Mapping;
/**
* A relational constraint.
*
* @author Gavin King
* @author Brett Meyer
*/
public abstract class Constraint implements RelationalModel, Exportable, Serializable {
private String name;
private final ArrayList columns = new ArrayList();
private Table table;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
/**
* If a constraint is not explicitly named, this is called to generate
* a unique hash using the table and column names.
* Static so the name can be generated prior to creating the Constraint.
* They're cached, keyed by name, in multiple locations.
*
* @return String The generated name
*/
public static String generateName(String prefix, Table table, Column... columns) {
// Use a concatenation that guarantees uniqueness, even if identical names
// exist between all table and column identifiers.
StringBuilder sb = new StringBuilder( "table`" + table.getName() + "`" );
// Ensure a consistent ordering of columns, regardless of the order
// they were bound.
// Clone the list, as sometimes a set of order-dependent Column
// bindings are given.
Column[] alphabeticalColumns = columns.clone();
Arrays.sort( alphabeticalColumns, ColumnComparator.INSTANCE );
for ( Column column : alphabeticalColumns ) {
String columnName = column == null ? "" : column.getName();
sb.append( "column`" ).append( columnName ).append( "`" );
}
return prefix + hashedName( sb.toString() );
}
/**
* Helper method for {@link #generateName(String, Table, Column...)}.
*
* @return String The generated name
*/
public static String generateName(String prefix, Table table, List columns) {
return generateName( prefix, table, columns.toArray( new Column[columns.size()] ) );
}
/**
* Hash a constraint name using MD5. Convert the MD5 digest to base 35
* (full alphanumeric), guaranteeing
* that the length of the name will always be smaller than the 30
* character identifier restriction enforced by a few dialects.
*
* @param s
* The name to be hashed.
* @return String The hased name.
*/
public static String hashedName(String s) {
try {
MessageDigest md = MessageDigest.getInstance( "MD5" );
md.reset();
md.update( s.getBytes() );
byte[] digest = md.digest();
BigInteger bigInt = new BigInteger( 1, digest );
// By converting to base 35 (full alphanumeric), we guarantee
// that the length of the name will always be smaller than the 30
// character identifier restriction enforced by a few dialects.
return bigInt.toString( 35 );
}
catch ( NoSuchAlgorithmException e ) {
throw new HibernateException( "Unable to generate a hashed Constraint name!", e );
}
}
private static class ColumnComparator implements Comparator {
public static ColumnComparator INSTANCE = new ColumnComparator();
public int compare(Column col1, Column col2) {
return col1.getName().compareTo( col2.getName() );
}
}
public void addColumn(Column column) {
if ( !columns.contains( column ) ) {
columns.add( column );
}
}
public void addColumns(Iterator columnIterator) {
while ( columnIterator.hasNext() ) {
Selectable col = (Selectable) columnIterator.next();
if ( !col.isFormula() ) {
addColumn( (Column) col );
}
}
}
/**
* @return true if this constraint already contains a column with same name.
*/
public boolean containsColumn(Column column) {
return columns.contains( column );
}
public int getColumnSpan() {
return columns.size();
}
public Column getColumn(int i) {
return columns.get( i );
}
//todo duplicated method, remove one
public Iterator getColumnIterator() {
return columns.iterator();
}
public Iterator columnIterator() {
return columns.iterator();
}
public Table getTable() {
return table;
}
public void setTable(Table table) {
this.table = table;
}
public boolean isGenerated(Dialect dialect) {
return true;
}
public String sqlDropString(Dialect dialect, String defaultCatalog, String defaultSchema) {
if ( isGenerated( dialect ) ) {
final String tableName = getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema );
return String.format(
Locale.ROOT,
"%s evictData constraint %s",
dialect.getAlterTableString( tableName ),
dialect.quote( getName() )
);
}
else {
return null;
}
}
public String sqlCreateString(Dialect dialect, Mapping p, String defaultCatalog, String defaultSchema) {
if ( isGenerated( dialect ) ) {
// Certain dialects (ex: HANA) don't support FKs as expected, but other constraints can still be created.
// If that's the case, hasAlterTable() will be true, but getAddForeignKeyConstraintString will return
// empty string. Prevent blank "alter table" statements.
String constraintString = sqlConstraintString( dialect, getName(), defaultCatalog, defaultSchema );
if ( !StringHelper.isEmpty( constraintString ) ) {
final String tableName = getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema );
return dialect.getAlterTableString( tableName ) + " " + constraintString;
}
}
return null;
}
public List getColumns() {
return columns;
}
public abstract String sqlConstraintString(
Dialect d,
String constraintName,
String defaultCatalog,
String defaultSchema);
public String toString() {
return getClass().getName() + '(' + getTable().getName() + getColumns() + ") as " + name;
}
/**
* @return String The prefix to use in generated constraint names. Examples:
* "UK_", "FK_", and "PK_".
*/
public abstract String generatedConstraintNamePrefix();
}