title: How to update child entity when updating parent in one to many relationship?
body: <p>I have two entities called A and B. Models are as below.</p>
  
  <pre><code>class A {    
      @OneToMany(fetch = FetchType.LAZY,mappedBy = "child", cascade={CascadeType.ALL} , orphanRemoval = true)
      private Set&lt;B&gt; children = new HashSet&lt;&gt;();
  }
  
  class B {
      @ManyToOne(fetch= FetchType.LAZY)
      @JoinColumn(name="a_id")
      @JsonIgnore
      private A child;
  }
  </code></pre>
  
  <p>I want to update class B when I am updating class A. For now lets say, I am having 3 instances of B in A. When updating I want to remove one instance from that.But now, it is not happening. But, if I need to add a new B, to A, it is working. What I am doing wrong? Please let me know.
  To update the entity I used the below.</p>
  
  <pre><code>public update A(A object){
      A existing = aDao.find(object.getID()) // retrieve the existing object A;
      for(B obj: object.getB()){  // this will create if there are new entities, but, i need to remove alreadet saved B instance if they are not in updated object
          obj.setA(existing);
      }
      existing.setB(object.getB());        
  }
  </code></pre>