无法通过反射设置字段值

Question

I have a problem with a many to many relationship. The tables are: ingredient and nutional value. I created a table of relations between the 2 entities, in which there are the external keys of ingredient and nutrional value (which form the compound key) and some attributes.

Class JoinedNutrionalValueIngredient :

import lombok.Data;
import javax.persistence.*;
import javax.validation.constraints.NotNull;
import java.io.Serializable;

@Entity @Data
public class JoinedNutrionalValueIngredient implements Serializable {

    @EmbeddedId
    private NutrionalValueIngredientId id;

    @ManyToOne(fetch= FetchType.LAZY)
    @MapsId("ingredient_id")
    private Ingredient ingredient;

    @ManyToOne(fetch=FetchType.LAZY)
    @MapsId("nutrional_value_id")
    private NutrionalValue nutrionalValue;

    @NotNull
    String matrixUnit;

    @NotNull
    int value;

    @NotNull
    String valueType;
}

Class NutrionalValueIngredientId :

import javax.persistence.*;
import java.io.Serializable;
import java.util.Objects;

@Embeddable
@Getter
@Setter
public class NutrionalValueIngredientId implements Serializable{

    @Column(name = "ingredient_id")
    private Long ingredient_id;

    @Column(name = "nutrional_value_id")
    private Long nutrional_value_id;

    public NutrionalValueIngredientId() {
        
    }   
   
    public NutrionalValueIngredientId(Long ingredient, Long nutrionalValue){
        this.ingredient_id=ingredient;
        this.nutrional_value_id=nutrionalValue;
    }
    
    public boolean equals(Object o) {
        if (this == o) return true;
    
        if (o == null || getClass() != o.getClass())
            return false;
    
        NutrionalValueIngredientId that = (NutrionalValueIngredientId) o;
        return Objects.equals(ingredient_id, that.ingredient_id) &&
                    Objects.equals(nutrional_value_id, that.nutrional_value_id);
    }
    
    @Override
    public int hashCode() {
        return Objects.hash(ingredient_id, nutrional_value_id);
    }
}

When I try to insert a new field inside the relationship table I get this error:

{
  "timestamp": 1542653896247,
  "status": 500,
  "error": "Internal Server Error",
  "message": "Could not set field value [1] value by reflection : [class com.whateat.reciper.model.NutrionalValueIngredientId.ingredient_id] setter of com.whateat.reciper.model.NutrionalValueIngredientId.ingredient_id; nested exception is org.hibernate.PropertyAccessException: Could not set field value [1] value by reflection : [class com.whateat.reciper.model.NutrionalValueIngredientId.ingredient_id] setter of com.whateat.reciper.model.NutrionalValueIngredientId.ingredient_id",
  "path": "/v1/joinedNutrionalValueIngredients"
}

Edit: I added constructor and annotation @Getter and @Setter , but I have the same error.

class NutritionalValue :

@Data
@Entity
public class NutrionalValue implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotNull
    private String name;

    @NotNull
    private String unit;

    @NotNull
    private String source;

    @ManyToOne
    @NotNull
    @JoinColumn(name = "category_id")
    private NutrionalValueCategory category;

    @OneToMany(mappedBy = "nutrionalValue")
    private Set<JoinedNutrionalValueIngredient> joined = new HashSet<JoinedNutrionalValueIngredient>();

}

edit: after Debopam's answer, this error came out.

{
  "timestamp": 1542657216244,
  "status": 500,
  "error": "Internal Server Error",
  "message": "null id generated for:class com.whateat.reciper.model.JoinedNutrionalValueIngredient; nested exception is org.hibernate.id.IdentifierGenerationException: null id generated for:class com.whateat.reciper.model.JoinedNutrionalValueIngredient",
  "path": "/v1/joinedNutrionalValueIngredients"
}

Answer 1

Change the variable Names as below

Long ingredient_id to Long ingredientid nutrional_value_id to nutrionalvalueid

Example

  @Column(name = "ingredient_id")
  Long ingredient_id;

to

@Column(name = "ingredient_id")
Long ingredientid;

Then generate getter setter for all the fields. Hibernate is unable to set the fields because there is no public getter/setter.

Answer 2

 @Entity @Data
 public class JoinedNutrionalValueIngredient implements Serializable {
    
        @EmbeddedId
        private NutrionalValueIngredientId id = new NutrionalValueIngredientId();
    
    // ... rest of class  
 }

In the JoinedNutrionalValueIngredient class the compound id NutrionalValueIngredientId shall be instansiated.

Answer 3

Set values for the the id entity 'NutrionalValueIngredientId ' then try to insert that as embedded id for 'JoinedNutrionalValueIngredient'. refer below example:

package com.example;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Embeddable;

@Embeddable
public class EmployeeId implements Serializable
{
private static final long serialVersionUID = 1L;
@Column(name = "EMP_ID")
private int empId;
@Column(name = "DEPARTMENT")
private String department;

public EmployeeId()
{
    super();
}
public EmployeeId(int empId, String department)
{
    super();
    this.empId = empId;
    this.department = department;
}

public int getEmpId()
{
    return empId;
}
public void setEmpId(int empId)
{
    this.empId = empId;
}
public String getDepartment()
{
    return department;
}
public void setDepartment(String department)
{
    this.department = department;
}
@Override
public int hashCode()
{
    final int prime = 31;
    int result = 1;
    result = prime * result + ((department == null) ? 0 : department.hashCode());
    result = prime * result + empId;
    return result;
}
@Override
public boolean equals(Object obj)
{
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    EmployeeId other = (EmployeeId) obj;
    if (department == null)
    {
        if (other.department != null)
            return false;
    } else if (!department.equals(other.department))
        return false;
    if (empId != other.empId)
        return false;
    return true;
}
 }

Refer above Embedded Id class(EmployeeId). which is primary key of Employee class. So, We need to set the values in Id class(EmployeeId) Then, inject that id class to Employee as primary key. Then it will work. Without primary key that value is null.

package com.example;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Employee implements Serializable
{
private static final long serialVersionUID = 1L;
@EmbeddedId
EmployeeId id;
@Column(name="EMP_NAME")
private String empName;

public Employee()
{
    super();
}
public Employee(EmployeeId id, String empName)
{
    super();
    this.id = id;
    this.empName = empName;
}
public EmployeeId getId()
{
    return id;
}
public void setId(EmployeeId id)
{
    this.id = id;
}
public String getEmpName()
{
    return empName;
}
public void setEmpName(String empName)
{
    this.empName = empName;
}
} 

Set Values for Id class and other field like below.

 //Create a new Employee object   
 Employee employee = new Employee();

 EmployeeId employeeId = new EmployeeId(1,"DailyNews");
 employee.setEmpName("CompositeKey");
 employee.setId(employeeId);

 session.save(employee);

Answer 4

Check you are setting the instance for embedded id. I was not and getting this error.

I change this

@EmbeddedId
ProductUserId id;    

ProductUser(Integer productId, Integer UserId, Double rating){
    this.rating = rating
}

to

@EmbeddedId
ProductUserId id;    

ProductUser(Integer productId, Integer userId, Double rating){
    this.id = new ProductUserId(productId, userId);
    this.rating = rating
}