如何获得一个订单地图与AliasToEntityMapResultTransformer？ [英] How to get an order Map wih AliasToEntityMapResultTransformer ?

问题描述

我用这些东西来获取一个List>，这对于像resultSet这样的操作数据非常有趣。
我的方法是：
requeteSQL.setResultTransformer（AliasToEntityMapResultTransformer.INSTANCE）;

当我用sqldevelopper执行这个查询时，我得到了例子
|字段1 |字段2
行1 |值1 |价值2

但是我的地图不是按照顺序排列？
如何解决这个错误？为什么我的地图按此顺序有Field2 = Value2，Field1 = Value1？

解决方案

因为它是哈希映射，你怎么能期望订单检索，如果想要订单检索请实现你自己的ResultTransformer，它会返回LinkedHashMap例如

  public class AliasToEntityOrderedMapResultTransformer extends AliasedTupleSubsetResultTransformer {
 
 public static final AliasToEntityOrderedMapResultTransformer INSTANCE = new AliasToEntityOrderedMapResultTransformer（）; 
 
 / ** 
 *不允许AliasToEntityOrderedMapResultTransformer的实例化。 
 * / 
 private AliasToEntityOrderedMapResultTransformer（）{
} 
 
 / ** 
 * {@inheritDoc} 
 * / 
公共对象transformTuple（Object []元组，字符串[]别名）{
 / *请注意LinkedHashMap用于希望得到有序键* / 
 Map result = new LinkedHashMap（tuple.length） ; 
 for（int i = 0; i< tuple.length; i ++）{
 String alias = aliases [i]; 
 if（alias！= null）{
 result.put（alias，tuple [i]）; 
} 
} 
返回结果; 
 
 $ b $ ** 
 * {@inheritDoc} 
 * / 
 public boolean isTransformedValueATupleElement（String [] aliases，int tupleLength）{
返回false; 
} 
 
 / ** 
 *确保单身独特性的序列化钩子。 
 * 
 * @return单例实例：{@link #INSTANCE} 
 * / 
 private Object readResolve（）{
 return INSTANCE; 
} 
} 
  

顺便说一句，您的逻辑不应该取决于它出现在结果图中的键的顺序。

I've used this stuff to get a List>, which is very interesting to manipulate datas like a "resultSet". My method is : requeteSQL.setResultTransformer(AliasToEntityMapResultTransformer.INSTANCE);

When i execute this query with sqldevelopper, i have got for exemple | Field 1 | Field 2 Line 1 | Value 1 | Value 2

But my map is not in the righ order ? How to fix this error ? And why my map have Field2 = Value2, Field1 = Value1 in this order ?

解决方案

because it hash map, how can you expect the order retrieval,if want order retrieval please implement your own ResultTransformer which will return LinkedHashMap e.g.

public class AliasToEntityOrderedMapResultTransformer extends AliasedTupleSubsetResultTransformer {

public static final AliasToEntityOrderedMapResultTransformer INSTANCE = new AliasToEntityOrderedMapResultTransformer();

/**
 * Disallow instantiation of AliasToEntityOrderedMapResultTransformer .
 */
private AliasToEntityOrderedMapResultTransformer () {
}

/**
 * {@inheritDoc}
 */
public Object transformTuple(Object[] tuple, String[] aliases) {
            /* please note here LinkedHashMap is used so hopefully u ll get ordered key */
    Map result = new LinkedHashMap(tuple.length);
    for ( int i=0; i<tuple.length; i++ ) {
        String alias = aliases[i];
        if ( alias!=null ) {
            result.put( alias, tuple[i] );
        }
    }
    return result;
}

/**
 * {@inheritDoc}
 */
public boolean isTransformedValueATupleElement(String[] aliases, int tupleLength) {
    return false;
}

/**
 * Serialization hook for ensuring singleton uniqueing.
 *
 * @return The singleton instance : {@link #INSTANCE}
 */
private Object readResolve() {
    return INSTANCE;
}
}

by the way your logic should not be depend of the order of keys it appear in resultant map.

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