title: aop.AopInvocationException: Null return value from
body: <p>here is the repository:</p>
  
  <pre><code>@Query(value = "select u.balance from User u where u.name=:name")
  float toGetBalance(@Param("name") String name);
  </code></pre>
  
  <p>and here is the DAO interface:</p>
  
  <pre><code>boolean checkBalance(String userName, float totalPrice);
  </code></pre>
  
  <p>and here is the service</p>
  
  <pre><code>@Transactional(readOnly = true)
  @Override
  public boolean checkBalance(String userName, float totalPrice) {
  
      if (userRepository.toGetBalance(userName) &lt; totalPrice) {
  
          return false;
  
      } else {
  
          return true;
  
      }
  
  }
  </code></pre>
  
  <p>and here is the error info:</p>
  
  <pre><code>org.springframework.aop.AopInvocationException: Null return value from advice does not match primitive return type for: public abstract float com.repository.UserRepository.toGetBalance(java.lang.String)
  </code></pre>
  
  <p>and the type of balance is float!</p>
  
  <p>what's wrong?</p>