Hibernate枚举类型数据库映射方案

在数据库里面，如果一个字段有多个固定的设定值，那么使用枚举将会简化映射，并提高开发灵活度，下面是将枚举映射到数据库的步骤：(看看这里)

1.定义一个枚举类型：

public enum Sex implements IntegerValuedEnum{女(0), 男(1);private int code;private Sex(int code) {this.code = code;}@Overridepublic int getCode() {return code;}}

2.定义一个接口：

public interface IntegerValuedEnum { int getCode();}

3.定义一个反射类

@SuppressWarnings("unchecked")public final class IntegerValuedEnumReflect { private IntegerValuedEnumReflect() { throw new UnsupportedOperationException( "This class must not be instanciated."); } private static <T extends Enum> T[] getValues(Class<T> enumClass) { return enumClass.getEnumConstants(); } public static <T extends Enum & IntegerValuedEnum> int[] getStringValues( Class<T> enumClass) { T[] values = getValues(enumClass); int[] result = new int[values.length]; for (int i = 0; i < values.length; i++) { result[i] = values[i].getCode(); } return result; } public static <T extends Enum & IntegerValuedEnum> String getNameFromValue( Class<T> enumClass, int value) { T[] values = getValues(enumClass); for (int i = 0; i < values.length; i++) { if (values[i].getCode() == value) { return values[i].name(); } } return ""; }}

4..关键类，实现了EnhancedUserType接口与ParameterizedType接口。不能用实现UserType借口，否则不能从数据库拿数据

@SuppressWarnings("unchecked")public class IntegerValuedEnumType<T extends Enum & IntegerValuedEnum> implements EnhancedUserType, ParameterizedType { /** * Enum class for this particular user type. */ private Class<T> enumClass; /** * Value to use if null. */ private Integer defaultValue; public IntegerValuedEnumType() {} public void setParameterValues(Properties parameters) { String enumClassName = parameters.getProperty("enum"); try { enumClass = (Class<T>) Class.forName(enumClassName) .asSubclass(Enum.class).asSubclass(IntegerValuedEnum.class); } catch (ClassNotFoundException e) { throw new HibernateException("Enum class not found", e); } String defaultValueStr = parameters.getProperty("defaultValue"); if (defaultValueStr != null && !defaultValueStr.isEmpty()) { try { setDefaultValue(Integer.parseInt(defaultValueStr)); } catch (NumberFormatException e) { throw new HibernateException("Invalid default value", e); } } } public Integer getDefaultValue() { return defaultValue; } public void setDefaultValue(Integer defaultValue) { this.defaultValue = defaultValue; } /** * The class returned by <tt>nullSafeGet()</tt>. * * @return Class */ public Class returnedClass() { return enumClass; } public int[] sqlTypes() { return new int[] { Types.TINYINT }; } public boolean isMutable() { return false; } /** * Retrieve an instance of the mapped class from a JDBC resultset. * Implementors should handle possibility of null values. * * @param rs a JDBC result set * @param names the column names * @param owner the containing entity * @return Object * @throws HibernateException * @throws SQLException */ public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws SQLException { Integer value = rs.getInt(names[0]); if (value == null) { value = getDefaultValue(); if (value == null) { // no default value return null; } } String name = IntegerValuedEnumReflect.getNameFromValue(enumClass, value); Object res = rs.wasNull() ? null : Enum.valueOf(enumClass, name); return res; } /** * Write an instance of the mapped class to a prepared statement. * Implementors should handle possibility of null values. A multi-column * type should be written to parameters starting from <tt>index</tt>. * * @param st a JDBC prepared statement * @param value the object to write * @param index statement parameter index * @throws HibernateException * @throws SQLException */ public void nullSafeSet(PreparedStatement st, Object value, int index) throws SQLException { if (value == null) { st.setNull(index, Types.TINYINT); } else { st.setInt(index, ((T) value).getCode()); } } public Object assemble(Serializable cached, Object owner) { return cached; } public Serializable disassemble(Object value) { return (Enum) value; } public Object deepCopy(Object value) { return value; } public boolean equals(Object x, Object y) { return x == y; } public int hashCode(Object x) { return x.hashCode(); } public Object replace(Object original, Object target, Object owner) { return original; } public String objectToSQLString(Object value) { return '/'' + String.valueOf(((T) value).getCode()) + '/''; } public String toXMLString(Object value) { return String.valueOf(((T) value).getCode()); } public Object fromXMLString(String xmlValue) { Integer value = Integer.parseInt(xmlValue); String name = IntegerValuedEnumReflect.getNameFromValue(enumClass, value); return Enum.valueOf(enumClass, name); }}

5.将枚举类型配置到配置文件中：

<property name="sex"> <column name="SEX" not-null="true"> <type name="com.ce.util.orm.enums.IntegerValuedEnumType"> <param name="enum">com.ce.demo.domain.Sex</param> </type> </column></property>