title: Simple Spring @CreatedDate annotation is not working for me
body: <p>I am trying to run a simple example as below but getting an error.</p>
  
  <p>I am using @CreatedDate. However, when I save Student object using a Rest endpoint, it does not create a date and throws the given exception.</p>
  
  <p>In my Rest end point, I have</p>
  
  <pre><code> @PostMapping("/students")
   public Student createStudent(@Valid @RequestBody Student student){
      return studentRepository.save(student);
   }
  </code></pre>
  
  <p>Here is my entity...</p>
  
  <pre><code>@Entity
  @Table(name = "students")
  @EntityListeners(AuditingEntityListener.class)
  @JsonIgnoreProperties(value = {"createdAt", "updatedAt"}, allowGetters = true)
  public class Student implements Serializable {
      @Id
      @GeneratedValue(strategy = GenerationType.AUTO)
      private Long id;
  
      @NotBlank
      private String name;
      @NotBlank
      private String surname;
  
      @Column(nullable = false, updatable = false)
      @Temporal(TemporalType.TIMESTAMP)
      @CreatedDate
      private Date createdAt;
  
      @Column(nullable = false)
      @Temporal(TemporalType.TIMESTAMP)
      @LastModifiedDate
      private Date updatedAt;
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>2018-06-20 21:43:40.821 DEBUG 8844 --- [nio-8080-exec-1] org.hibernate.SQL                    
  
      : select next_val as id_val from hibernate_sequence for update
  2018-06-20 21:43:40.874 DEBUG 8844 --- [nio-8080-exec-1] org.hibernate.SQL                        : update hibernate_sequence set next_val= ? where next_val=?
  2018-06-20 21:43:40.971 DEBUG 8844 --- [nio-8080-exec-1] org.hibernate.SQL                        : insert into students (created_at, name, surname, updated_at, id) values (?, ?, ?, ?, ?)
  2018-06-20 21:43:40.978 TRACE 8844 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [TIMESTAMP] - [null]
  2018-06-20 21:43:40.979 TRACE 8844 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [2] as [VARCHAR] - [Shilpa]
  2018-06-20 21:43:40.980 TRACE 8844 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [3] as [VARCHAR] - [Manware]
  2018-06-20 21:43:40.980 TRACE 8844 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [4] as [TIMESTAMP] - [null]
  2018-06-20 21:43:40.981 TRACE 8844 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [5] as [BIGINT] - [3]
  2018-06-20 21:43:41.003  WARN 8844 --- [nio-8080-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 1048, SQLState: 23000
  2018-06-20 21:43:41.003 ERROR 8844 --- [nio-8080-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : Column 'created_at' cannot be null
  2018-06-20 21:43:41.006  INFO 8844 --- [nio-8080-exec-1] o.h.e.j.b.internal.AbstractBatchImpl     : HHH000010: On release of batch it still contained JDBC statements
  2018-06-20 21:43:41.009 ERROR 8844 --- [nio-8080-exec-1] o.h.i.ExceptionMapperStandardImpl        : HHH000346: Error during managed flush [org.hibernate.exception.ConstraintViolationException: could not execute statement]
  2018-06-20 21:43:41.041 ERROR 8844 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
  
  com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'created_at' cannot be null
      at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_112]
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_112]
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_112]
      at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_112]
      at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) ~[mysql-connector-java-5.1.45.jar:5.1.45]
      at com.mysql.jdbc.Util.getInstance(Util.java:408) ~[mysql-connector-java-5.1.45.jar:5.1.45]
      at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936) ~[mysql-connector-java-5.1.45.jar:5.1.45]
      at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973) ~[mysql-connector-java-5.1.45.jar:5.1.45]
      at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909) ~[mysql-connector-java-5.1.45.jar:5.1.45]
      at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527) ~[mysql-connector-java-5.1.45.jar:5.1.45]
  </code></pre>