title: Hibernate :Save Parent automatically before saving Child
body: <p>I have a parent-child relationship:</p>
  
  <pre><code>@Entity
  @Table(name = "user")
  public final class User
  {
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Integer userID;
  
      @Column(name = "username")
      private String userName;
  
      @OneToMany(cascade = CascadeType.ALL, mappedBy = "admin")
      private Set&lt;News&gt; news;
  }
  
  @Entity
  @Table(name = "news")
  public final class News
  {
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private int newsID;
  
      @ManyToOne(cascade = CascadeType.PERSIST)
      @JoinColumn(name = "userID")
      private User admin;
  
      @Column(name = "newsText")
      private String newsText;
  
      @Column(name = "dateOfPost")
      private Date dateOfPost;
  }
  </code></pre>
  
  <p>Here <code>User</code> is the parent and <code>News</code> is the child. The reason that I have the cascade operations such is because I want all <code>News</code> objects to be deleted/persisted when I delete/persist the corresponding <code>User</code>. Also when I persist a <code>News</code> object I want the corresponding <code>User</code> to be persisted [but not deleted if the <code>News</code> is deleted]. I have a service method that saves a <code>News</code> object as follows:</p>
  
  <pre><code>User u = new User("administrator");
  News n = new News("News text");
  n.setUser(u);       
  u.addNews(n);
  
  session.save(n);
  </code></pre>
  
  <p>For the above code I get the following exception:</p>
  
  <pre><code>org.hibernate.exception.ConstraintViolationException: could not insert: [com.maximus.db.model.News]
      at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
      at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
      at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
      at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2345)
      at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2852)
      at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
      at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
      at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:320)
      at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
      at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
      at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
      at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
      at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
      at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
      at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
      at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:713)
      at org.hibernate.impl.SessionImpl.save(SessionImpl.java:701)
      at org.hibernate.impl.SessionImpl.save(SessionImpl.java:697)
      at com.maximus.db.dao.NewsDAOImpl.addNews(NewsDAOImpl.java:17)
      at com.maximus.db.service.NewsServiceImpl.addNews(NewsServiceImpl.java:31)
      at com.maximus.test.db.service.NewsServiceTest.testAddNewsWithNewUser(NewsServiceTest.java:36)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99)
      at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81)
      at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
      at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75)
      at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45)
      at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66)
      at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35)
      at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42)
      at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
      at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
  Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'userId' cannot be null
      at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
      at java.lang.reflect.Constructor.newInstance(Unknown Source)
      at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
      at com.mysql.jdbc.Util.getInstance(Util.java:384)
      at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1041)
      at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3566)
      at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3498)
      at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
      at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113)
      at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
      at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2113)
      at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2409)
      at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2327)
      at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2312)
      at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
      at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
      ... 38 more
  </code></pre>
  
  <p>What could be the issue here?</p>
  
  <p>Am I incorrect in having a service method that tries to save a child? Should I always save the parent instead?</p>
  
  <p>Thanks.</p>
  
  <p>UPDATE: If I instead save the user as <code>session.save(u)</code> instead of the news, everything is fine. So the question that remains is, is it incorrect to save the child instead of the parent? If not, then how do I achieve it?</p>