java enum 用法

/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2010, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.annotations;

import org.hibernate.cache.spi.access.AccessType;

/**
* Cache concurrency strategy.
*
* @author Emmanuel Bernard
*/
public enum CacheConcurrencyStrategy {
/**
* Indicates no concurrency strategy should be applied.
*/
NONE( null ),
/**
* Indicates that read-only strategy should be applied.
*
* @see AccessType#READ_ONLY
*/
READ_ONLY( AccessType.READ_ONLY ),
/**
* Indicates that the non-strict read-write strategy should be applied.
*
* @see AccessType#NONSTRICT_READ_WRITE
*/
NONSTRICT_READ_WRITE( AccessType.NONSTRICT_READ_WRITE ),
/**
* Indicates that the read-write strategy should be applied.
*
* @see AccessType#READ_WRITE
*/
READ_WRITE( AccessType.READ_WRITE ),
/**
* Indicates that the transaction strategy should be applied.
*
* @see AccessType#TRANSACTIONAL
*/
TRANSACTIONAL( AccessType.TRANSACTIONAL );

private final AccessType accessType;

private CacheConcurrencyStrategy(AccessType accessType) {
this.accessType = accessType;
}

/**
* Get the AccessType corresponding to this concurrency strategy.
*
* @return The corresponding concurrency strategy. Note that this will return {@code null} for
* {@link #NONE}
*/
public AccessType toAccessType() {
return accessType;
}

/**
* Conversion from {@link AccessType} to {@link CacheConcurrencyStrategy}.
*
* @param accessType The access type to convert
*
* @return The corresponding enum value. {@link #NONE} is returned by default if unable to
* recognize {@code accessType} or if {@code accessType} is {@code null}.
*/
public static CacheConcurrencyStrategy fromAccessType(AccessType accessType) {
if ( null == accessType ) {
return NONE;
}

switch ( accessType ) {
case READ_ONLY: {
return READ_ONLY;
}
case READ_WRITE: {
return READ_WRITE;
}
case NONSTRICT_READ_WRITE: {
return NONSTRICT_READ_WRITE;
}
case TRANSACTIONAL: {
return TRANSACTIONAL;
}
default: {
return NONE;
}
}
}

/**
* Parse an external representation of a CacheConcurrencyStrategy value.
*
* @param name The external representation
*
* @return The corresponding enum value, or {@code null} if not match was found.
*/
public static CacheConcurrencyStrategy parse(String name) {
if ( READ_ONLY.isMatch( name ) ) {
return READ_ONLY;
}
else if ( READ_WRITE.isMatch( name ) ) {
return READ_WRITE;
}
else if ( NONSTRICT_READ_WRITE.isMatch( name ) ) {
return NONSTRICT_READ_WRITE;
}
else if ( TRANSACTIONAL.isMatch( name ) ) {
return TRANSACTIONAL;
}
else if ( NONE.isMatch( name ) ) {
return NONE;
}
else {
return null;
}
}

private boolean isMatch(String name) {
return ( accessType != null && accessType.getExternalName().equalsIgnoreCase( name ) )
|| name().equalsIgnoreCase( name );
}
}

/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2008-2011, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.cache.spi.access;

/**
* The types of access strategies available.
*
* @author Steve Ebersole
*/
public enum AccessType {
/**
* Read-only access. Data may be added and removed, but not mutated.
*/
READ_ONLY( "read-only" ),
/**
* Read and write access (strict). Data may be added, removed and mutated.
*/
READ_WRITE( "read-write" ),
/**
* Read and write access (non-strict). Data may be added, removed and mutated. The non-strictness comes from
* the fact that locks are not maintained as tightly as in {@link #READ_WRITE}, which leads to better throughput
* but may also lead to inconsistencies.
*/
NONSTRICT_READ_WRITE( "nonstrict-read-write" ),
/**
* A read and write strategy where isolation/locking is maintained in conjunction with a JTA transaction.
*/
TRANSACTIONAL( "transactional" );

private final String externalName;

private AccessType(String externalName) {
this.externalName = externalName;
}

/**
* Get the corresponding externalized name for this value.
*
* @return The corresponding externalized name.
*/
public String getExternalName() {
return externalName;
}

@Override
public String toString() {
return "AccessType[" + externalName + "]";
}

/**
* Resolve an AccessType from its external name.
*
* @param externalName The external representation to resolve
*
* @return The access type.
*
* @throws UnknownAccessTypeException If the externalName was not recognized.
*
* @see #getExternalName()
*/
public static AccessType fromExternalName(String externalName) {
if ( externalName == null ) {
return null;
}
for ( AccessType accessType : AccessType.values() ) {
if ( accessType.getExternalName().equals( externalName ) ) {
return accessType;
}
}
throw new UnknownAccessTypeException( externalName );
}
}