JPA：如何將本機查詢結果集轉換為POJO類集合我在我的項目中使用JPA。我來到了一個查詢，在這個查詢中，我需要對五個表進行聯接操作。因此，我創建了一個本地查詢，它返回五個字段?，F在，我想將結果對象轉換為javaPOJO類，該類包含相同的五個字符串。JPA中有任何方法直接將結果轉換為POJO對象列表嗎？我想出了以下解決方案。@NamedNativeQueries({
@NamedNativeQuery(
name = "nativeSQL",
query = "SELECT * FROM Actors",
resultClass = db.Actor.class),
@NamedNativeQuery(
name = "nativeSQL2",
query = "SELECT COUNT(*) FROM Actors",
resultClass = XXXXX) // <--------------- problem })現在結果類中，我們是否需要提供一個類，它是實際的JPA實體？或者我們可以將其轉換為包含相同列名的任何JavaPOJO類？
3 回答
明月笑刀無情
TA貢獻1828條經驗 獲得超4個贊
SqlResultSetMapping
ColumnResult
一只甜甜圈
TA貢獻1836條經驗 獲得超5個贊
使用映射實體(JPA2.0)
Query query = em.createNativeQuery("SELECT name,age FROM jedi_table", Jedi.class);@SuppressWarnings("unchecked")List<Jedi> items = (List<Jedi>) query.getResultList();Jedi
@NamedNativeQuery( name="jedisQry", query = "SELECT name,age FROM jedis_table", resultClass = Jedi.class)
TypedQuery<Jedi> query = em.createNamedQuery("jedisQry", Jedi.class);List<Jedi> items = query.getResultList();人工映射
public static <T> T map(Class<T> type, Object[] tuple){
List<Class<?>> tupleTypes = new ArrayList<>();
for(Object field : tuple){
tupleTypes.add(field.getClass());
}
try {
Constructor<T> ctor = type.getConstructor(tupleTypes.toArray(new Class<?>[tuple.length]));
return ctor.newInstance(tuple);
} catch (Exception e) {
throw new RuntimeException(e);
}}public static <T> List<T> map(Class<T> type, List<Object[]> records){
List<T> result = new LinkedList<>();
for(Object[] record : records){
result.add(map(type, record));
}
return result;}public static <T> List<T> getResultList(Query query, Class<T> type){
@SuppressWarnings("unchecked")
List<Object[]> records = query.getResultList();
return map(type, records);}Query query = em.createNativeQuery("SELECT name,age FROM jedis_table");List<Jedi> jedis = getResultList(query, Jedi.class);帶有@SqlResultSetmap的JPA2.1
@SqlResultSetMapping(name="JediResult", classes = {
@ConstructorResult(targetClass = Jedi.class,
columns = {@ColumnResult(name="name"), @ColumnResult(name="age")})})Query query = em.createNativeQuery("SELECT name,age FROM jedis_table", "JediResult");@SuppressWarnings("unchecked")List<Jedi> samples = query.getResultList();Jedi
使用XML映射
@SqlResultSetMappingMETA-INF/orm.xml
<named-native-query name="GetAllJedi" result-set-mapping="JediMapping"> <query>SELECT name,age FROM jedi_table</query></named-native-query><sql-result-set-mapping name="JediMapping"> <constructor-result target-class="org.answer.model.Jedi"> <column name="name" class="java.lang.String"/> <column name="age" class="java.lang.Integer"/> </constructor-result> </sql-result-set-mapping>
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