Need to return List of Custom Object using JPA @Query

Question

I've a custom object

@Component
public class SaleReport {

    private Date date;
    private String customerName;
    private String phoneNo;
    private String productName;
    private Integer quantity;
    private Double totalAmount;

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public String getCustomerName() {
        return customerName;
    }

    public void setCustomerName(String customerName) {
        this.customerName = customerName;
    }

    public String getPhoneNo() {
        return phoneNo;
    }

    public void setPhoneNo(String phoneNo) {
        this.phoneNo = phoneNo;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public Integer getQuantity() {
        return quantity;
    }

    public void setQuantity(Integer quantity) {
        this.quantity = quantity;
    }

    public Double getTotalAmount() {
        return totalAmount;
    }

    public void setTotalAmount(Double totalAmount) {
        this.totalAmount = totalAmount;
    }
}

I need to return List of this object using a JpaRepository<Sale, Integer> The SaleRepository is as follow:

@Repository
public interface SaleRepository extends JpaRepository<Sale, Integer> {


    @Query(value = "SELECT B.order_date AS date, E.customer_name AS customerName, " +
            "E.phone_no AS phoneNo, D.product_name AS productName, C.quantity AS quantity, " +
            "C.total_price AS totalAmount " +
            "FROM SALE A " +
            "INNER JOIN A.quotation_id B " +
            "INNER JOIN B.quotation_id C " +
            "INNER JOIN C.product_id D " +
            "INNER JOIN B.customer_id E " +
            "WHERE (B.order_date BETWEEN :from_date AND :to_date)", nativeQuery = true)
    public List<SaleReport> getSaleReportByDate(@Param("from_date")String fromDate, @Param("to_date")String toDate);

}

Here is my Controller method:

@GetMapping("api/report/sale/{from_date}/{to_date}")
        public List<SaleReport> getSaleReportByDate(@PathVariable("from_date") String fromDate, @PathVariable("to_date") String toDate){
        return saleRepository.getSaleReportByDate(fromDate, toDate);
}

While I run the code it shows this error:

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'a'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_161]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_161]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_161]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_161]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) ~[mysql-connector-java-5.1.47.jar:5.1.47]
    at com.mysql.jdbc.Util.getInstance(Util.java:408) ~[mysql-connector-java-5.1.47.jar:5.1.47]
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:944) ~[mysql-connector-java-5.1.47.jar:5.1.47]

My DATABASE NAME is alright. It works perfectly while I request in other methods. Please suggest me an ideal solution.

Answer 1

Spring has an annotation called @SqlResultSetMapping This annotation can be used for above problem. Details about this annotation can be found from following link:

Annotation Type ConstructorResult

This is actually mapping a hibernate query result into a plain POJO Class. Thats what actually needed.

Example:

   Query q = em.createNativeQuery(
      "SELECT c.id, c.name, COUNT(o) as orderCount, AVG(o.price) AS avgOrder " +
      "FROM Customer c, Orders o " +
      "WHERE o.cid = c.id " +
      "GROUP BY c.id, c.name",
      "CustomerDetailsResult");

   @SqlResultSetMapping(
       name="CustomerDetailsResult",
       classes={
          @ConstructorResult(
               targetClass=com.acme.CustomerDetails.class,
                 columns={
                    @ColumnResult(name="id"),
                    @ColumnResult(name="name"),
                    @ColumnResult(name="orderCount"),
                    @ColumnResult(name="avgOrder", type=Double.class)
                    }
          )
       }
      )

Put @SqlResultSetMapping into top of any @Entity and make sure the datatype returning from database is same as your POJO Class datatype.

Hope this will help you. Enjoy :)