Hibernate Transformers之三种结果转换说明

在hibernate使用的过程中.我们通常需要对结果进行解释.
Hibernate为我们提供了以下3种解释方法:

Transformers.ALIAS_TO_ENTITY_MAP //把输出结果转换成map
Transformers.TO_LIST //把结果按顺序排进List
ransformers.aliasToBean(target) //把结果通过setter方法注入到指定的对像属性中

在Hibernate中Transformers的所有转换都是需要实现ResultTransformer接口

详解ALIAS_TO_ENTITY_MAP ,太简单了就是把key和值直接转换到Map当中

public Object transformTuple(Object[] tuple, String[] aliases) {
		Map result = new HashMap(tuple.length);
		for ( int i=0; i<tuple.length; i++ ) {
			String alias = aliases[i];
			if ( alias!=null ) {
				result.put( alias, tuple[i] );
			}
		}
		return result;
	}

详解TO_LIST,转换过程很简单,就是把value转换成List对像

public Object transformTuple(Object[] tuple, String[] aliases) {  
    return Arrays.asList( tuple );  
} 

详解aliasToBean,转换过程就是通过读取查询后的字段.然后通过使用setter方法注入到目标对像中

public AliasToBeanResultTransformer(Class resultClass) {  
        if ( resultClass == null ) {  
            throw new IllegalArgumentException( "resultClass cannot be null" );  
        }  
        this.resultClass = resultClass;  
        //定义属性访问器.  
        propertyAccessor = new ChainedPropertyAccessor(  
                new PropertyAccessor[] {  
                        PropertyAccessorFactory.getPropertyAccessor( resultClass, null ),  
                        PropertyAccessorFactory.getPropertyAccessor( "field" )  
                }  
        );  
    }  
  
    public Object transformTuple(Object[] tuple, String[] aliases) {  
        Object result;  
  
        try {  
            if ( setters == null ) {  
                setters = new Setter[aliases.length];  
                for ( int i = 0; i < aliases.length; i++ ) {  
                    String alias = aliases[i];  
                    if ( alias != null ) {  
                        //初始指定的setter方法  
                        setters[i] = propertyAccessor.getSetter( resultClass, alias );  
                    }  
                }  
            }  
            //实例实体对像  
            result = resultClass.newInstance();  
  
            for ( int i = 0; i < aliases.length; i++ ) {  
                if ( setters[i] != null ) {  
                    //向setter方法中指定的属性注入值  
                    setters[i].set( result, tuple[i], null );  
                }  
            }  
        }  
        catch ( InstantiationException e ) {  
            throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );  
        }  
        catch ( IllegalAccessException e ) {  
            throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );  
        }  
  
        return result;  
    } 

转自：http://gznofeng.iteye.com/blog/550705