"Exception evaluating SpringEL expression" error while trying to iterate List(<Object>) in Thymeleaf Spring Boot

Question

I am new to spring boot and attempting to make a join between two unrelated entities (Transaction and Item) using JPA/JPQL. But I am getting the following error while using thymeleaf to display it in a table format:

2020-04-08 21:42:42.463 ERROR 73816 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "transactiondetail.tid" (template: "index" - line 27, col 21)] with root cause
org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'tid' cannot be found on object of type 'java.lang.Object[]' - maybe not public or not valid?

Following is my thymeleaf implementation:

    <tr th:each="transactiondetail : ${listTransactionDetail}">
        <td th:text="${transactiondetail.tid}">TID</td>
        <td th:text="${transactiondetail.from_uid}">From UID</td>
        <td th:text="${transactiondetail.to_uid}">To UID</td>
        <td th:text="${transactiondetail.item_name}">Item Name</td>
        <td th:text="${transactiondetail.item_count}">Count</td>
        <td th:text="${transactiondetail.status}">Status</td>

Following is the controller:

@Autowired
QueryService queryservice; 

@RequestMapping("/")
public String viewHomePage(Model model) {
    List<TransactionDetail> listTransactionDetail = queryservice.JPQLQuery();
    model.addAttribute("listTransactionDetail", listTransactionDetail);
    return "index";
    }

I am able to get the result when I simply return queryservice.JPQLQuery(), which means the joining and listing is working. Following is the service the controller is calling:

@Service
public class QueryService implements IQueryService {

    @Autowired
    EntityManagerFactory emf;

    @Override
    public List<TransactionDetail> JPQLQuery()
    {
        EntityManager em = emf.createEntityManager();

        Query query = em.createQuery("Select s.tid,s.from_uid,s.to_uid,d.item_name,s.item_count,s.status from Transaction s inner join Item d on s.item_id=d.item_id");
        @SuppressWarnings("unchecked")
        List<TransactionDetail> tranlist = (List<TransactionDetail>)query.getResultList();
        em.close();
        return tranlist;

    }

}

Shown below is the TransactionDetail class which is taking in the joined entities. As you can see, I have both constructors and getters/setters with proper names. Still not able to display the details correctly.

public class TransactionDetail {
    private Long tid;
    private int from_uid;
    private int to_uid;
    private String item_name;
    private int item_count;
    private int status;

    public TransactionDetail() {
    }

    public TransactionDetail(Long tid, int from_uid, int to_uid, String item_name, int item_count, int status) {
        super();
        this.tid = tid;
        this.from_uid = from_uid;
        this.to_uid = to_uid;
        this.item_name = item_name;
        this.item_count = item_count;
        this.status = status;
    }

    public Long getTid() {
        return tid;
    }

    public void setTid(Long tid) {    
        this.tid = tid;    
    }

    public int getFrom_uid() {    
        return from_uid;    
    }    
    public void setFrom_uid(int from_uid) {    
        this.from_uid = from_uid;    
    }

    public int getTo_uid() {    
        return to_uid;    
    }    
    public void setTo_uid(int to_uid) {    
        this.to_uid = to_uid;    
    }   

    public int getItem_count() {    
        return item_count;    
    }    
    public void setItem_count(int item_count) {    
        this.item_count = item_count;    
    }

    public int getStatus() {    
        return status;    
    }    
    public void setStatus(int status) {    
        this.status = status;    
    }

    public String getItem_name() {
        return item_name;
    }

    public void setItem_name(String item_name) {
        this.item_name = item_name;
    }

}

I am guessing the problem has to do with the way I am saving the results from query.getResultList() into List<TransactionDetail>. So any idea how I can solve this issue? Thanks in advance!

Answer 1

Turns out the issue was due my attempt to convert the result from the query (which was bits of 2 different entities) into a new class object. Hence, fixed it by changing the query to include creation of a new instance of the target object with the constructor call:

TypedQuery<TransactionDetail> query = em.createQuery("Select NEW package_name.TransactionDetail(s.tid,s.from_uid,s.to_uid,d.item_name,s.item_count,s.status) from Transaction s inner join Item d on s.item_id=d.item_id", TransactionDetail.class);
List<TransactionDetail> tranlist = query.getResultList();