使用Hibernate的联合主键以及遇到的问题

   使用Hibernate的联合主键composite-id

   如下：
 
   有一个类A，在类B里面，所有的字段组成联合主键， 同时在里面定义了查询语句

    <class name="com.test.A" table="T_BASE_SETTINGS">
        <composite-id name="id" class="com.test.B">
            <key-property name="name" type="com.text.util.DefaultStringType">
                <column name="NAME"/>
            </key-property> 
            <key-property name="value" type="com.text.util.DefaultStringType">
                <column name="VALUE"/>
            </key-property>               

        </composite-id>
    </class>
    
    <query name="GET_SURCHARGE_VALUE">
		FROM com.test.A a
		WHERE a.id.name =? and a.id.value=?
    </query>

   遇到的问题
   1: 查询QUERY报错，发现是需要用name替换NAME, value替换VALUE,就是不要用COLUMN
   2: 查出来的结果，虽然打log发现是有值，如：list.size() 为1 但是设置不到对象里面去， 就是因为有些字段在数据库里面是空的， 联合主键的就要保证每一个字段都不能为空，解决的办法就是自己实现string, 定义了一个类com.text.util.DefaultStringType 如下：

public class DefaultStringType implements UserType {
	
	private static final String blankChart = "";
	
	private static final int[] TYPES = new int[]{Types.VARCHAR};
	
	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#assemble(java.io.Serializable, java.lang.Object)
	 */
	public Object assemble(Serializable cached, Object owner) throws HibernateException {
		return null;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#deepCopy(java.lang.Object)
	 */
	public Object deepCopy(Object value) throws HibernateException {
		String copy = new String(value.toString());
		return copy;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#disassemble(java.lang.Object)
	 */
	public Serializable disassemble(Object value) throws HibernateException {
		return null;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#equals(java.lang.Object, java.lang.Object)
	 */
	public boolean equals(Object x, Object y) throws HibernateException {
		if (x == y) return true;
		if (x == null) return false;
		return x.equals(y);
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#hashCode(java.lang.Object)
	 */
	public int hashCode(Object x) throws HibernateException {
		return new HashCodeBuilder().append(x).toHashCode();
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#isMutable()
	 */
	public boolean isMutable() {
		return false;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#nullSafeGet(java.sql.ResultSet, java.lang.String[], java.lang.Object)
	 */
	public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws HibernateException, SQLException {
		String value = (String) Hibernate.STRING.nullSafeGet(rs, names[0]);
		return value == null ? "" : value;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#nullSafeSet(java.sql.PreparedStatement, java.lang.Object, int)
	 */
	public void nullSafeSet(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
		if (value.equals(blankChart)) {
			Hibernate.STRING.nullSafeSet(st, null, index);
		} else {
			Hibernate.STRING.nullSafeSet(st, value, index);
		}
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#replace(java.lang.Object, java.lang.Object, java.lang.Object)
	 */
	public Object replace(Object original, Object target, Object owner) throws HibernateException {
		return original;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#returnedClass()
	 */
	public Class returnedClass() {
		return String.class;
	}

	/* (non-Javadoc)
	 * @see org.hibernate.usertype.UserType#sqlTypes()
	 */
	public int[] sqlTypes() {
		return TYPES;
	}

}