title: create one to many relation but Foreign key value inserted null values through rest api POSTMAN
body: <p>i made following two classes bookcategory class is parent class and book class is child class. make one two many and many two one relationship but in bookcategory_id its take null values. where i am wrong please help me</p>
  <pre><code>      Book.java:
  
        @Entity
          @Table(name=&quot;book&quot;)
          public class Book
          {
              @Id
          
              @GeneratedValue(strategy = GenerationType.IDENTITY)
              private int id;
              
              @Column(name=&quot;title&quot;)
              private String title;
              private String description;
           
              @ManyToOne(fetch = FetchType.EAGER  )
              @JoinColumn(name=&quot;bookcategory_id&quot;,insertable=false,updatable=false)
              @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
              private BookCategory bookCategory;
              
          
              public Book() {
               
              }
          
          
              public Book(String title, String description) {
                  super();
                  this.title = title;
                  this.description = description;
              }
          
              
              
              public int getId() {
                  return id;
              }
          
              public void setId(int id) {
                  this.id = id;
              }
          
              public String getTitle() {
                  return title;
              }
          
              public void setTitle(String title) {
                  this.title = title;
              }
          
              public String getDescription() {
                  return description;
              }
          
              public void setDescription(String description) {
                  this.description = description;
              }
          
          
              public BookCategory getBookCategory() {
                  return bookCategory;
              }
          
          
              public void setBookCategory(BookCategory bookCategory) {
                  this.bookCategory = bookCategory;
              }
          
          
              @Override
              public String toString() {
                  return &quot;Book [id=&quot; + id + &quot;, title=&quot; + title + &quot;, description=&quot; + description + &quot;, bookCategory=&quot; + bookCategory
                          + &quot;]&quot;;
              }
           
           
              
   
     
      BookCategory.java :
  
  
  @SpringBootApplication
  @EnableJpaRepositories
  @Entity
  @Table(name= &quot;bookcategory&quot;)
  public class BookCategory  
  {
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      @Column(name=&quot;bookcategory_id&quot;,unique=true,nullable=false)
      @ColumnTransformer
      private int id;
      @NotBlank(message = &quot;name can not be empty&quot;)
      @Size(min=3, max=12, message= &quot;user name must be between 3-12 characters&quot;)
      private String name;
      @OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY)
      @JoinColumn(name = &quot;bookcategory_id&quot;, nullable = false, updatable = false)
      private Set&lt;Book&gt; books = new HashSet&lt;&gt;();
  
      public BookCategory()
      {
  
      }
  
      public BookCategory(String name)
      {
          super();
          this.name = name;
      }
  
      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;
      }
  
      @Override
      public String toString() {
          return &quot;BookCategory [id=&quot;+id+&quot;, name=&quot;+name+&quot;]&quot;;
                      }
      
  }
  </code></pre>
  <p>this is my entities classes i am trying to insert Book fields but in this fk value taking null values<a href="https://i.stack.imgur.com/jEMAf.png" rel="nofollow noreferrer">I also add image </a></p>