package org.hibernate.id.enhanced;
import java.sql.Types;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Properties;
import java.util.HashMap;
import java.util.Map;
import java.util.Collections;
import java.io.Serializable;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.engine.TransactionHelper;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.id.PersistentIdentifierGenerator;
import org.hibernate.id.Configurable;
import org.hibernate.type.Type;
import org.hibernate.dialect.Dialect;
import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.LockMode;
import org.hibernate.mapping.Table;
import org.hibernate.util.PropertiesHelper;
import org.hibernate.util.StringHelper;
/**
* An enhanced version of table-based id generation.
* <p/>
* Unlike the simplistic legacy one (which, btw, was only ever intended for subclassing
* support) we "segment" the table into multiple values. Thus a single table can
* actually serve as the persistent storage for multiple independent generators. One
* approach would be to segment the values by the name of the entity for which we are
* performing generation, which would mean that we would have a row in the generator
* table for each entity name. Or any configuration really; the setup is very flexible.
* <p/>
* In this respect it is very simliar to the legacy
* {@link org.hibernate.id.MultipleHiLoPerTableGenerator} in terms of the
* underlying storage structure (namely a single table capable of holding
* multiple generator values). The differentiator is, as with
* {@link SequenceStyleGenerator} as well, the externalized notion
* of an optimizer.
* <p/>
* <b>NOTE</b> that by default we use a single row for all genertators (based
* on {@link #DEF_SEGMENT_VALUE}). The configuration parameter
* {@link #CONFIG_PREFER_SEGMENT_PER_ENTITY} can be used to change that to
* instead default to using a row for each entity name.
* <p/>
* Configuration parameters:
* <table>
* <tr>
* <td><b>NAME</b></td>
* <td><b>DEFAULT</b></td>
* <td><b>DESCRIPTION</b></td>
* </tr>
* <tr>
* <td>{@link #TABLE_PARAM}</td>
* <td>{@link #DEF_TABLE}</td>
* <td>The name of the table to use to store/retrieve values</td>
* </tr>
* <tr>
* <td>{@link #VALUE_COLUMN_PARAM}</td>
* <td>{@link #DEF_VALUE_COLUMN}</td>
* <td>The name of column which holds the sequence value for the given segment</td>
* </tr>
* <tr>
* <td>{@link #SEGMENT_COLUMN_PARAM}</td>
* <td>{@link #DEF_SEGMENT_COLUMN}</td>
* <td>The name of the column which holds the segment key</td>
* </tr>
* <tr>
* <td>{@link #SEGMENT_VALUE_PARAM}</td>
* <td>{@link #DEF_SEGMENT_VALUE}</td>
* <td>The value indicating which segment is used by this generator; refers to values in the {@link #SEGMENT_COLUMN_PARAM} column</td>
* </tr>
* <tr>
* <td>{@link #SEGMENT_LENGTH_PARAM}</td>
* <td>{@link #DEF_SEGMENT_LENGTH}</td>
* <td>The data length of the {@link #SEGMENT_COLUMN_PARAM} column; used for schema creation</td>
* </tr>
* <tr>
* <td>{@link #INITIAL_PARAM}</td>
* <td>{@link #DEFAULT_INITIAL_VALUE}</td>
* <td>The initial value to be stored for the given segment</td>
* </tr>
* <tr>
* <td>{@link #INCREMENT_PARAM}</td>
* <td>{@link #DEFAULT_INCREMENT_SIZE}</td>
* <td>The increment size for the underlying segment; see the discussion on {@link Optimizer} for more details.</td>
* </tr>
* <tr>
* <td>{@link #OPT_PARAM}</td>
* <td><i>depends on defined increment size</i></td>
* <td>Allows explicit definition of which optimization strategy to use</td>
* </tr>
* </table>
*
* @author Steve Ebersole
*/
public class TableGenerator extends TransactionHelper implements PersistentIdentifierGenerator, Configurable {
private static final Log log = LogFactory.getLog( TableGenerator.class );
public static final String CONFIG_PREFER_SEGMENT_PER_ENTITY = "prefer_entity_table_as_segment_value";
public static final String TABLE_PARAM = "table_name";
public static final String DEF_TABLE = "hibernate_sequences";
public static final String VALUE_COLUMN_PARAM = "value_column_name";
public static final String DEF_VALUE_COLUMN = "next_val";
public static final String SEGMENT_COLUMN_PARAM = "segment_column_name";
public static final String DEF_SEGMENT_COLUMN = "sequence_name";
public static final String SEGMENT_VALUE_PARAM = "segment_value";
public static final String DEF_SEGMENT_VALUE = "default";
public static final String SEGMENT_LENGTH_PARAM = "segment_value_length";
public static final int DEF_SEGMENT_LENGTH = 255;
public static final String INITIAL_PARAM = "initial_value";
public static final int DEFAULT_INITIAL_VALUE = 1;
public static final String INCREMENT_PARAM = "increment_size";
public static final int DEFAULT_INCREMENT_SIZE = 1;
public static final String OPT_PARAM = "optimizer";
private Type identifierType;
private String tableName;
private String segmentColumnName;
private String segmentValue;
private int segmentValueLength;
private String valueColumnName;
private int initialValue;
private int incrementSize;
private String selectQuery;
private String insertQuery;
private String updateQuery;
private Optimizer optimizer;
private long accessCount = 0;
/**
* {@inheritDoc}
*/
public Object generatorKey() {
return tableName;
}
/**
* Type mapping for the identifier.
*
* @return The identifier type mapping.
*/
public final Type getIdentifierType() {
return identifierType;
}
/**
* The name of the table in which we store this generator's persistent state.
*
* @return The table name.
*/
public final String getTableName() {
return tableName;
}
/**
* The name of the column in which we store the segment to which each row
* belongs. The value here acts as PK.
*
* @return The segment column name
*/
public final String getSegmentColumnName() {
return segmentColumnName;
}
/**
* The value in {@link #getSegmentColumnName segment column} which
* corresponding to this generator instance. In other words this value
* indicates the row in which this generator instance will store values.
*
* @return The segment value for this generator instance.
*/
public final String getSegmentValue() {
return segmentValue;
}
/**
* The size of the {@link #getSegmentColumnName segment column} in the
* underlying table.
* <p/>
* <b>NOTE</b> : should really have been called 'segmentColumnLength' or
* even better 'segmentColumnSize'
*
* @return the column size.
*/
public final int getSegmentValueLength() {
return segmentValueLength;
}
/**
* The name of the column in which we store our persistent generator value.
*
* @return The name of the value column.
*/
public final String getValueColumnName() {
return valueColumnName;
}
/**
* The initial value to use when we find no previous state in the
* generator table corresponding to our sequence.
*
* @return The initial value to use.
*/
public final int getInitialValue() {
return initialValue;
}
/**
* The amount of increment to use. The exact implications of this
* depends on the {@link #getOptimizer() optimizer} being used.
*
* @return The increment amount.
*/
public final int getIncrementSize() {
return incrementSize;
}
/**
* The optimizer being used by this generator.
*
* @return Out optimizer.
*/
public final Optimizer getOptimizer() {
return optimizer;
}
/**
* Getter for property 'tableAccessCount'. Only really useful for unit test
* assertions.
*
* @return Value for property 'tableAccessCount'.
*/
public final long getTableAccessCount() {
return accessCount;
}
/**
* {@inheritDoc}
*/
public void configure(Type type, Properties params, Dialect dialect) throws MappingException {
identifierType = type;
tableName = determneGeneratorTableName( params );
segmentColumnName = determineSegmentColumnName( params );
valueColumnName = determineValueColumnName( params );
segmentValue = determineSegmentValue( params );
segmentValueLength = determineSegmentColumnSize( params );
initialValue = determineInitialValue( params );
incrementSize = determineIncrementSize( params );
this.selectQuery = buildSelectQuery( dialect );
this.updateQuery = buildUpdateQuery();
this.insertQuery = buildInsertQuery();
String defOptStrategy = incrementSize <= 1 ? OptimizerFactory.NONE : OptimizerFactory.POOL;
String optimizationStrategy = PropertiesHelper.getString( OPT_PARAM, params, defOptStrategy );
optimizer = OptimizerFactory.buildOptimizer( optimizationStrategy, identifierType.getReturnedClass(), incrementSize );
}
/**
* Determine the table name to use for the generator values.
* <p/>
* Called during {@link #configure configuration}.
*
* @see #getTableName()
* @param params The params supplied in the generator config (plus some standard useful extras).
* @return The table name to use.
*/
protected String determneGeneratorTableName(Properties params) {
String name = PropertiesHelper.getString( TABLE_PARAM, params, DEF_TABLE );
boolean isGivenNameUnqualified = name.indexOf( '.' ) < 0;
if ( isGivenNameUnqualified ) {
// if the given name is un-qualified we may neen to qualify it
String schemaName = params.getProperty( SCHEMA );
String catalogName = params.getProperty( CATALOG );
name = Table.qualify( catalogName, schemaName, name );
}
return name;
}
/**
* Determine the name of the column used to indicate the segment for each
* row. This column acts as the primary key.
* <p/>
* Called during {@link #configure configuration}.
*
* @see #getSegmentColumnName()
* @param params The params supplied in the generator config (plus some standard useful extras).
* @return The name of the segment column
*/
protected String determineSegmentColumnName(Properties params) {
return PropertiesHelper.getString( SEGMENT_COLUMN_PARAM, params, DEF_SEGMENT_COLUMN );
}
/**
* Determine the name of the column in which we will store the generator persistent value.
* <p/>
* Called during {@link #configure configuration}.
*
* @see #getValueColumnName()
* @param params The params supplied in the generator config (plus some standard useful extras).
* @return The name of the value column
*/
protected String determineValueColumnName(Properties params) {
return PropertiesHelper.getString( VALUE_COLUMN_PARAM, params, DEF_VALUE_COLUMN );
}
/**
* Determine the segment value corresponding to this generator instance.
* <p/>
* Called during {@link #configure configuration}.
*
* @see #getSegmentValue()
* @param params The params supplied in the generator config (plus some standard useful extras).
* @return The name of the value column
*/
protected String determineSegmentValue(Properties params) {
String segmentValue = params.getProperty( SEGMENT_VALUE_PARAM );
if ( StringHelper.isEmpty( segmentValue ) ) {
segmentValue = determineDefaultSegmentValue( params );
}
return segmentValue;
}
/**
* Used in the cases where {@link #determineSegmentValue} is unable to
* determine the value to use.
*
* @param params The params supplied in the generator config (plus some standard useful extras).
* @return The default segment value to use.
*/
protected String determineDefaultSegmentValue(Properties params) {
boolean preferSegmentPerEntity = PropertiesHelper.getBoolean( CONFIG_PREFER_SEGMENT_PER_ENTITY, params, false );
String defaultToUse = preferSegmentPerEntity ? params.getProperty( TABLE ) : DEF_SEGMENT_VALUE;
log.info( "explicit segment value for id generator [" + tableName + '.' + segmentColumnName + "] suggested; using default [" + defaultToUse + "]" );
return defaultToUse;
}
/**
* Determine the size of the {@link #getSegmentColumnName segment column}
* <p/>
* Called during {@link #configure configuration}.
*
* @see #getSegmentValueLength()
* @param params The params supplied in the generator config (plus some standard useful extras).
* @return The size of the segment column
*/
protected int determineSegmentColumnSize(Properties params) {
return PropertiesHelper.getInt( SEGMENT_LENGTH_PARAM, params, DEF_SEGMENT_LENGTH );
}
protected int determineInitialValue(Properties params) {
return PropertiesHelper.getInt( INITIAL_PARAM, params, DEFAULT_INITIAL_VALUE );
}
protected int determineIncrementSize(Properties params) {
return PropertiesHelper.getInt( INCREMENT_PARAM, params, DEFAULT_INCREMENT_SIZE );
}
protected String buildSelectQuery(Dialect dialect) {
final String alias = "tbl";
String query = "select " + StringHelper.qualify( alias, valueColumnName ) +
" from " + tableName + ' ' + alias +
" where " + StringHelper.qualify( alias, segmentColumnName ) + "=?";
HashMap lockMap = new HashMap();
lockMap.put( alias, LockMode.UPGRADE );
Map updateTargetColumnsMap = Collections.singletonMap( alias, new String[] { valueColumnName } );
return dialect.applyLocksToSql( query, lockMap, updateTargetColumnsMap );
}
protected String buildUpdateQuery() {
return "update " + tableName +
" set " + valueColumnName + "=? " +
" where " + valueColumnName + "=? and " + segmentColumnName + "=?";
}
protected String buildInsertQuery() {
return "insert into " + tableName + " (" + segmentColumnName + ", " + valueColumnName + ") " + " values (?,?)";
}
/**
* {@inheritDoc}
*/
public synchronized Serializable generate(final SessionImplementor session, Object obj) {
return optimizer.generate(
new AccessCallback() {
public long getNextValue() {
return ( ( Number ) doWorkInNewTransaction( session ) ).longValue();
}
}
);
}
/**
* {@inheritDoc}
*/
public Serializable doWorkInCurrentTransaction(Connection conn, String sql) throws SQLException {
int result;
int rows;
do {
SQL.debug( selectQuery );
PreparedStatement selectPS = conn.prepareStatement( selectQuery );
try {
selectPS.setString( 1, segmentValue );
ResultSet selectRS = selectPS.executeQuery();
if ( !selectRS.next() ) {
PreparedStatement insertPS = null;
try {
result = initialValue;
SQL.debug( insertQuery );
insertPS = conn.prepareStatement( insertQuery );
insertPS.setString( 1, segmentValue );
insertPS.setLong( 2, result );
insertPS.execute();
}
finally {
if ( insertPS != null ) {
insertPS.close();
}
}
}
else {
result = selectRS.getInt( 1 );
}
selectRS.close();
}
catch ( SQLException sqle ) {
log.error( "could not read or init a hi value", sqle );
throw sqle;
}
finally {
selectPS.close();
}
SQL.debug( updateQuery );
PreparedStatement updatePS = conn.prepareStatement( updateQuery );
try {
long newValue = optimizer.applyIncrementSizeToSourceValues()
? result + incrementSize : result + 1;
updatePS.setLong( 1, newValue );
updatePS.setLong( 2, result );
updatePS.setString( 3, segmentValue );
rows = updatePS.executeUpdate();
}
catch ( SQLException sqle ) {
log.error( "could not update hi value in: " + tableName, sqle );
throw sqle;
}
finally {
updatePS.close();
}
}
while ( rows == 0 );
accessCount++;
return new Integer( result );
}
/**
* {@inheritDoc}
*/
public String[] sqlCreateStrings(Dialect dialect) throws HibernateException {
return new String[] {
new StringBuffer()
.append( dialect.getCreateTableString() )
.append( ' ' )
.append( tableName )
.append( " ( " )
.append( segmentColumnName )
.append( ' ' )
.append( dialect.getTypeName( Types.VARCHAR, segmentValueLength, 0, 0 ) )
.append( " not null, " )
.append( valueColumnName )
.append( ' ' )
.append( dialect.getTypeName( Types.BIGINT ) )
.append( ", primary key ( " )
.append( segmentColumnName )
.append( " ) ) " )
.toString()
};
}
/**
* {@inheritDoc}
*/
public String[] sqlDropStrings(Dialect dialect) throws HibernateException {
StringBuffer sqlDropString = new StringBuffer().append( "drop table " );
if ( dialect.supportsIfExistsBeforeTableName() ) {
sqlDropString.append( "if exists " );
}
sqlDropString.append( tableName ).append( dialect.getCascadeConstraintsString() );
if ( dialect.supportsIfExistsAfterTableName() ) {
sqlDropString.append( " if exists" );
}
return new String[] { sqlDropString.toString() };
}
}
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