Reference subquery fields in QueryDSL - sql

Question

I have to build a query in QueryDSL with a subquery, like this:
Expression<String> caseExpression = new CaseBuilder()
...;
Expression<?>[] queryProjection={
table.parameter1,
caseExpression
};
Expression<?>[] subqueryProjection={
table.parameter1.as("alias1"),
table.parameter2.as("alias2"),
table.parameter3.as("alias3"),
table.parameter4.as("alias4")
};
SQLSubQuery subQuery = new SQLSubQuery()
.from(table)
.where(...);
JPASQLQuery query = new JPASQLQuery(entityManager, ORACLE_TEMPLATE)
.from(subQuery.list(subqueryProjection));
query.list(queryProjection);
I am getting the following exception:
9/10/2014 09:45:55 AM org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() para servlet rtve-rest lanzó excepción
java.sql.SQLException: ORA-00904: "TABLE"."PARAMETER1": invalid identifier
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:331)
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:288)
at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:745)
at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:219)
at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:813)
at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1049)
at oracle.jdbc.driver.T4CPreparedStatement.executeMaybeDescribe(T4CPreparedStatement.java:854)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1154)
at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3370)
at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3415)
at org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:93)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:122)
at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81)
at $Proxy78.executeQuery(Unknown Source)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1953)
at org.hibernate.loader.Loader.doQuery(Loader.java:829)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:289)
at org.hibernate.loader.Loader.doList(Loader.java:2438)
at org.hibernate.loader.Loader.doList(Loader.java:2424)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2254)
at org.hibernate.loader.Loader.list(Loader.java:2249)
at org.hibernate.loader.custom.CustomLoader.list(CustomLoader.java:331)
at org.hibernate.internal.SessionImpl.listCustomQuery(SessionImpl.java:1784)
at org.hibernate.internal.AbstractSessionImpl.list(AbstractSessionImpl.java:229)
at org.hibernate.internal.SQLQueryImpl.list(SQLQueryImpl.java:156)
at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:257)
at com.mysema.query.jpa.sql.AbstractJPASQLQuery.list(AbstractJPASQLQuery.java:145)
This is caused because the field in my queryProjection is not the same as in my subqueryProjection. This field has to be the same as in the subquery ("alias1").
How could I reference a field by its alias? Or how could I reference a field in a subquery from outside it?
Thank you very much in advance

Answer 1

You need to use a Path instance with alias1 as the name or get rid of the aliasing. The simplest way to create that Path is
Expressions.path(Object.class, "alias1")
Replace Object with a more specific type if needed.

Answer 2

I managed to do it with Expressions.stringTemplate:
Expression<?>[] queryProjection={
Expressions.stringTemplate("alias1"),
caseExpression
};