Using EntityManager you can achieve this .
Suppose your entity class is like bellow:
import javax.persistence.*;
import java.math.BigDecimal;
@Entity
@Table(name = "USER_INFO_TEST")
public class UserInfoTest {
private int id;
private String name;
private String rollNo;
public UserInfoTest() {
}
public UserInfoTest(int id, String name) {
this.id = id;
this.name = name;
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ID", nullable = false, precision = 0)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Basic
@Column(name = "name", nullable = true)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Basic
@Column(name = "roll_no", nullable = true)
public String getRollNo() {
return rollNo;
}
public void setRollNo(String rollNo) {
this.rollNo = rollNo;
}
}
And your query is "**select id, name from users where roll_no = 1001**".
Here query will return an object with id and a name column. Your Response class is like below:
Your Response class is like:
public class UserObject{
int id;
String name;
String rollNo;
public UserObject(Object[] columns) {
this.id = (columns[0] != null)?((BigDecimal)columns[0]).intValue():0;
this.name = (String) columns[1];
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRollNo() {
return rollNo;
}
public void setRollNo(String rollNo) {
this.rollNo = rollNo;
}
}
here UserObject constructor will get an Object Array and set data with the object.
public UserObject(Object[] columns) {
this.id = (columns[0] != null)?((BigDecimal)columns[0]).intValue():0;
this.name = (String) columns[1];
}
Your query executing function is like bellow :
public UserObject getUserByRoll(EntityManager entityManager,String rollNo) {
String queryStr = "select id,name from users where roll_no = ?1";
try {
Query query = entityManager.createNativeQuery(queryStr);
query.setParameter(1, rollNo);
return new UserObject((Object[]) query.getSingleResult());
} catch (Exception e) {
e.printStackTrace();
throw e;
}
}
Here you have to import bellow packages:
import javax.persistence.Query;
import javax.persistence.EntityManager;
Now your main class, you have to call this function. First get EntityManager and call this `getUserByRoll(EntityManager entityManager,String rollNo)` function. Calling procedure is given below:
**Here is the Imports**
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
get `EntityManager` from this way:
@PersistenceContext
private EntityManager entityManager;
UserObject userObject = getUserByRoll(entityManager,"1001");
Now you have data in this userObject.
**Note**:
`query.getSingleResult()` return a object array. You have to maintain the column position and data type with query column position.
**select id,name from users where roll_no = 1001**
query return a array and it's [0] --> id and [1] -> name.
More info visit [this thread][1] .
[1]: https://stackoverflow.com/a/50365522/3073945
YES, You can do this in bellow ways:
**1. By CrudRepository (Projection)**
Spring Data Repositories usually return the domain model when using query methods. However, sometimes, you may need to alter the view of that model for various reasons.
Suppose your entity is like this :
import javax.persistence.*;
import java.math.BigDecimal;
@Entity
@Table(name = "USER_INFO_TEST")
public class UserInfoTest {
private int id;
private String name;
private String rollNo;
public UserInfoTest() {
}
public UserInfoTest(int id, String name) {
this.id = id;
this.name = name;
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ID", nullable = false, precision = 0)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Basic
@Column(name = "name", nullable = true)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Basic
@Column(name = "roll_no", nullable = true)
public String getRollNo() {
return rollNo;
}
public void setRollNo(String rollNo) {
this.rollNo = rollNo;
}
}
Now your Projection class is like below. It can those fields that you needed.
public interface IUserProjection {
int getId();
String getName();
String getRollNo();
}
And `Your Data Access Object(Dao) is like bellow` :
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import java.util.ArrayList;
public interface UserInfoTestDao extends CrudRepository<UserInfoTest,Integer> {
@Query(value = "select id,name,roll_no from USER_INFO_TEST where rollNo = ?1", nativeQuery = true)
ArrayList<IUserProjection> findUserUsingRollNo(String rollNo);
}
Now `ArrayList<IUserProjection> findUserUsingRollNo(String rollNo)` will give you the list of user.
**2. Using EntityManager**
Suppose your query is "***select id,name from users where roll_no = 1001***".
Here query will return an object with id and name column. Your Response class is like bellow:
Your Response class is like this:
public class UserObject{
int id;
String name;
String rollNo;
public UserObject(Object[] columns) {
this.id = (columns[0] != null)?((BigDecimal)columns[0]).intValue():0;
this.name = (String) columns[1];
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRollNo() {
return rollNo;
}
public void setRollNo(String rollNo) {
this.rollNo = rollNo;
}
}
here UserObject constructor will get an Object Array and set data with the object.
public UserObject(Object[] columns) {
this.id = (columns[0] != null)?((BigDecimal)columns[0]).intValue():0;
this.name = (String) columns[1];
}
Your query executing function is like bellow :
public UserObject getUserByRoll(EntityManager entityManager,String rollNo) {
String queryStr = "select id,name from users where roll_no = ?1";
try {
Query query = entityManager.createNativeQuery(queryStr);
query.setParameter(1, rollNo);
return new UserObject((Object[]) query.getSingleResult());
} catch (Exception e) {
e.printStackTrace();
throw e;
}
}
Here you have to import bellow packages:
import javax.persistence.Query;
import javax.persistence.EntityManager;
Now your main class, you have to call this function. First get EntityManager and call this `getUserByRoll(EntityManager entityManager,String rollNo)` function. The calling procedure is given below:
**Here is the Imports**
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
get `EntityManager` from this way:
@PersistenceContext
private EntityManager entityManager;
UserObject userObject = getUserByRoll(entityManager,"1001");
Now you have data in this userObject.
**Note:**
**query.getSingleResult()** return a object array. You have to maintain the column position and data type with the query column position.
select id,name from users where roll_no = 1001
query return a array and it's `[0] --> id and [1] -> name`.
More info visit this [thread][1] and [this Thread][1]
Thanks :)
[1]: https://stackoverflow.com/a/50367467/3073945
