sourcemediatype.java

Hiberante程序高手秘籍的源代码

package com.oreilly.hh;

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;

import net.sf.hibernate.UserType;
import net.sf.hibernate.Hibernate;
import net.sf.hibernate.HibernateException;
import net.sf.hibernate.type.Type;

/**
 * Manages persistence for the {@link SourceMedia} typesafe enumeration.
 */
public class SourceMediaType implements UserType {

    /**
     * Indicates whether objects managed by this type are mutable.
     *
     * @return <code>false</code>, since enumeration instances are immutable
     *         singletons.
     */
    public boolean isMutable() {
        return false;
    }

    /**
     * Return a deep copy of the persistent state, stopping at
     * entities and collections.
     *
     * @param value the object whose state is to be copied.
     * @return the same object, since enumeration instances are singletons.
     * @throws ClassCastException for non {@link SourceMedia} values.
     */
    public Object deepCopy(Object value) {
        return (SourceMedia)value;
    }

    /**
     * Compare two instances of the class mapped by this type for persistence
     * "equality".
     *
     * @param x first object to be compared.
     * @param y second object to be compared.
     * @return <code>true</code> iff both represent the same SourceMedia type.
     * @throws ClassCastException if x or y isn't a {@link SourceMedia}.
     */
    public boolean equals(Object x, Object y) {
        // We can compare instances, since SourceMedia are immutable singletons
        return (x == y);
    }

    /**
     * Determine the class that is returned by {@link #nullSafeGet}.
     *
     * @return {@link SourceMedia}, the actual type returned
     * by {@link #nullSafeGet}.
     */
    public Class returnedClass() {
        return SourceMedia.class;
    }

    /**
     * Determine the SQL type(s) of the column(s) used by this type mapping.
     *
     * @return a single VARCHAR column.
     */
    public int[] sqlTypes() {
        // Allocate a new array each time to protect against callers changing
        // its contents.
        int[] typeList = {
            Types.VARCHAR
        };
        return typeList;
    }

    /**
     * Retrieve an instance of the mapped class from a JDBC {@link ResultSet}.
     *
     * @param rs the results from which the instance should be retrieved.
     * @param names the columns from which the instance should be retrieved.
     * @param owner the entity containing the value being retrieved.
     * @return the retrieved {@link SourceMedia} value, or <code>null</code>.
     * @throws HibernateException if there is a problem performing the mapping.
     * @throws SQLException if there is a problem accessing the database.
     */
    public Object nullSafeGet(ResultSet rs, String[] names, Object owner)
        throws HibernateException, SQLException
    {
        // Start by looking up the value name
        String name = (String) Hibernate.STRING.nullSafeGet(rs, names[0]);
        if (name == null) {
            return null;
        }
        // Then find the corresponding enumeration value
        try {
            return SourceMedia.getInstanceByName(name);
        }
        catch (java.util.NoSuchElementException e) {
            throw new HibernateException("Bad SourceMedia value: " + name, e);
        }
    }

    /**
     * Write an instance of the mapped class to a {@link PreparedStatement}, 
     * handling null values.
     *
     * @param st a JDBC prepared statement.
     * @param value the SourceMedia value to write.
     * @param index the parameter index within the prepared statement at which
     *        this value is to be written.
     * @throws HibernateException if there is a problem performing the mapping.
     * @throws SQLException if there is a problem accessing the database.
     */
    public void nullSafeSet(PreparedStatement st, Object value, int index)
        throws HibernateException, SQLException
    {
        String name = null;
        if (value != null)
            name = ((SourceMedia)value).getName();
        Hibernate.STRING.nullSafeSet(st, name, index);
    }
}