Hibernate Session 4種對象狀態
阿新 • • 發佈：2018-07-06
otf delegate trac 關閉session rop getimpl pac 方法 堅持不懈 
站在持久化的角度。Hibernate把對象分為4中狀態。 臨時狀態。 持久化狀態。遊離狀態。刪除狀態。
1：Save()方法：
//這個是驗證：1：save方法使臨時對象------>變成持久化對象。
2：為對象分配ID。
3：flush緩存時發送insert語句。
@org.junit.Test public void testSave(){ News news=new News(); news.setTitle("AA"); news.setAuthor("aa"); news.setDate(new Date(0)); System.out.println("save保存前打印："+news); session.save(news); System.out.println("save保存後打印："+news); }
//這個是驗證：ID在save方法前保存無效。
1 @org.junit.Test 2 public void testSave(){ 3 News news=new News(); 4 news.setTitle("BB"); 5 news.setAuthor("bb"); 6 news.setDate(new Date(0)); 7 news.setId(100); 8 System.out.println("save保存前打印："+news); 9 session.save(news); 10 System.out.println("save保存後打印："+news); 11 }
//這是驗證 持久化對象的ID不能進行修改。
1 @org.junit.Test 2 public void testSave(){ 3 News news=new News(); 4 news.setTitle("BB"); 5 news.setAuthor("bb"); 6 news.setDate(new Date(0)); 7 System.out.println("save保存前打印："+news); 8 session.save(news); 9 news.setId(4); 10 System.out.println("save保存後打印："+news); 11 }
org.hibernate.exception.ConstraintViolationException: could not execute statement
ConstraintViolationException 違反唯一約束條件
constraint 英 [k?n?stre?nt] n. 約束; 限制; 強制
violation 英 [?va??‘le??n] n. 違反，妨礙，侵犯; 違犯，違背; [體] 違例，犯規; 強奸，褻瀆，汙辱 at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:74) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110) at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:136) at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:96) at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:58) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2975) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3480) at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81) at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:377) at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:214) at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:194) at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:178) at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:321) at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:286) at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:192) at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:206) at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:191) at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90) at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:764) at org.hibernate.internal.SessionImpl.save(SessionImpl.java:756) at org.hibernate.internal.SessionImpl.save(SessionImpl.java:752) at com.hibernate.helloworld.Test.testSave(Test.java:54) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) 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: Duplicate entry ‘BB‘ for key ‘UK_duq2gjdo5k53otrakypw0888b‘ at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.Util.getInstance(Util.java:381) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3515) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3447) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1951) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2101) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2554) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1761) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2046) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1964) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1949) at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:133) ... 47 more org.hibernate.AssertionFailure: null id in com.hibernate.helloworld.News entry (don‘t flush the Session after an exception occurs) at org.hibernate.event.internal.DefaultFlushEntityEventListener.checkId(DefaultFlushEntityEventListener.java:79) at org.hibernate.event.internal.DefaultFlushEntityEventListener.getValues(DefaultFlushEntityEventListener.java:194) at org.hibernate.event.internal.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:156) at org.hibernate.event.internal.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:228) at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:100) at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51) at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1234) at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:404) at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101) at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:175) at com.hibernate.helloworld.Test.destroy(Test.java:34) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:37) at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) 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)
2：persist()：和save一樣。只有一個區別：
在persist()方法前設置ID會報錯。如果對象有ID。不能執行insert。而是會拋出異常
@org.junit.Test
public void testPersist(){
News news=new News();
news.setTitle("CC");
news.setAuthor("cc");
news.setDate(new Date(0));
news.setId(4);
System.out.println("save保存前打印："+news);
session.persist(news);
System.out.println("save保存後打印："+news);
}
org.hibernate.PersistentObjectException: detached entity passed to persist: com.hibernate.helloworld.News
persistent 英 [p??s?st?nt] adj. 持續的; 持久的; 堅持不懈的; 堅持不渝
detached 英 [d??t?t?t] adj. 超然的; 分離的，分開的; 公平的; 分遣的，派遣的
v. 派遣; 分開(detach的過去式和過去分詞); 分離，退出
persist v. 堅持; 存留; 固執; 繼續存在 at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:141) at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:78) at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:853) at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:827) at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:831) at com.hibernate.helloworld.Test.testPersist(Test.java:55) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) 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)
3：get()和load()方法的區別：
1）：get會立即加載對象。返回的是類本身。
load不會。只是去使用的時候才會執行查詢語句。返回的是一個代理對象。代理對象就是別人讓你做一件事。先答應下來。然後他需要的時候去幫他做。
get立即檢索。load延遲檢索。
@org.junit.Test
public void testGet(){
News news =(News) session.get(News.class, 1);
System.out.println(news);
}
@org.junit.Test
public void testLoad(){
News news =(News) session.load(News.class, 1);
System.out.println(news);
}
@org.junit.Test
public void testGet(){
News news =(News) session.get(News.class, 1);
// System.out.println(news);
}
@org.junit.Test
public void testLoad(){
News news =(News) session.load(News.class, 1);
// System.out.println(news);
}
get方法會有查詢語句。load方法不會執行查詢語句。
打印這個對象到底是什麽？
@org.junit.Test
public void testGet(){
News news =(News) session.get(News.class, 1);
System.out.println(news.getClass());
// System.out.println(news);
}
@org.junit.Test
public void testLoad(){
News news =(News) session.load(News.class, 1);
System.out.println(news.getClass());
// System.out.println(news);
}
get: 類自己本身。
load：是一個代理類
2）：load可能拋出一個 LazyInitializationException 異常: could not initialize proxy - no Session
因為get是先加載。然後會打印出來。 load是答應了別人。別人需要了去幫他做的時候。發現session已經關閉了。然後拋出一個懶加載異常。
@org.junit.Test
public void testGet(){
News news =(News) session.get(News.class, 1);
session.close();
System.out.println(news);
}
@org.junit.Test
public void testLoad(){
News news =(News) session.load(News.class, 1);
session.close();
System.out.println(news);
}
get會打印出來。load拋出一個懶加載異常。
1 org.hibernate.LazyInitializationException: could not initialize proxy - no Session 2 at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:164) 3 at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:285) 4 at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185) 5 at com.hibernate.helloworld.News_$$_javassist_0.toString(News_$$_javassist_0.java) 6 at java.lang.String.valueOf(String.java:2827) 7 at java.io.PrintStream.println(PrintStream.java:771) 8 at com.hibernate.helloworld.Test.testLoad(Test.java:80) 9 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 10 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 11 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 12 at java.lang.reflect.Method.invoke(Method.java:597) 13 at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) 14 at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) 15 at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) 16 at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) 17 at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) 18 at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) 19 at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) 20 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) 21 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) 22 at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) 23 at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) 24 at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) 25 at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) 26 at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) 27 at org.junit.runners.ParentRunner.run(ParentRunner.java:236) 28 at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) 29 at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) 30 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) 31 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) 32 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) 33 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
3）：查詢數據庫中沒有的對象。get返回一個null。load會拋出一個ObjectNotFoundException 異常
1 @org.junit.Test
2 public void testGet(){
3 News news =(News) session.get(News.class, 10);
4 System.out.println(news);
5 }
6 @org.junit.Test
7 public void testLoad(){
8 News news =(News) session.load(News.class, 10);
9 System.out.println(news);
10 }
1 org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.hibernate.helloworld.News#10] 2 at org.hibernate.internal.SessionFactoryImpl$1$1.handleEntityNotFound(SessionFactoryImpl.java:244) 3 at org.hibernate.proxy.AbstractLazyInitializer.checkTargetState(AbstractLazyInitializer.java:261) 4 at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:175) 5 at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:285) 6 at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185) 7 at com.hibernate.helloworld.News_$$_javassist_0.toString(News_$$_javassist_0.java) 8 at java.lang.String.valueOf(String.java:2827) 9 at java.io.PrintStream.println(PrintStream.java:771) 10 at com.hibernate.helloworld.Test.testLoad(Test.java:78) 11 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 12 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 13 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 14 at java.lang.reflect.Method.invoke(Method.java:597) 15 at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) 16 at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) 17 at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) 18 at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) 19 at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) 20 at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) 21 at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) 22 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) 23 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) 24 at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) 25 at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) 26 at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) 27 at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) 28 at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) 29 at org.junit.runners.ParentRunner.run(ParentRunner.java:236) 30 at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) 31 at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) 32 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) 33 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) 34 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) 35 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
4：update()方法：
1）：若更新一個持久化對象。不需要顯示的調用update方法。因為在調用事務中的commit()方法的時候，先執行session的flush()方法。
這個是驗證把遊離對象變成一個持久化對象。因為查詢出來news對象。有OID。但是session緩存中沒有這個對象。所以是遊離對象。執行了update對象。session就有這個對象了。
關閉session。重新打開的時候。不會執行update語句。 因為news對象是查詢出來了。放在session緩存中。然後關閉了。又重新打開了一個session中。
但是新打開的session中沒有news對象。所以修改對象不會執行update。需要顯示的調用update方法。
1 @org.junit.Test 2 public void testUpdate(){ 3 News news =(News) session.get(News.class, 1); 4 transaction.commit(); 5 session.close(); 6 7 session=sessionFactory.openSession(); 8 transaction=session.beginTransaction(); 9 10 news.setAuthor("YI"); 11 12 }
1 @org.junit.Test
2 public void testUpdate(){
3 News news =(News) session.get(News.class, 1);
4 transaction.commit();
5 session.close();
6
7 session=sessionFactory.openSession();
8 transaction=session.beginTransaction();
9
10 news.setAuthor("YI");
11 session.update(news);
12 }
但是顯示調用update方法。有個小缺點。
無論更新的遊離對象和數據表中的記錄是否一樣。都會執行update語句。Hibernate有個觸發器。每執行一個update方法。都會觸發一次。影響效率。
可以在.hbm.xml文件中class 節點下 select-before-update="true" 。就不會盲目的觸發update語句。但是不常用。
2）：若數據表中沒有對應的記錄。但還調用了update方法。會拋出異常。
1 查詢一個news對象。然後修改ID 。拋出StaleObjectStateException 異常
2 @org.junit.Test
3 public void testUpdate(){
4 News news =(News) session.get(News.class, 1);
5 transaction.commit();
6 session.close();
7
8 session=sessionFactory.openSession();
9 transaction=session.beginTransaction();
10
11 news.setId(10);
12 session.update(news);
13 }
1 查詢一個根本不存在的對象 拋出IllegalArgumentException異常
2 @org.junit.Test
3 public void testUpdate(){
4 News news =(News) session.get(News.class, 10);
5 transaction.commit();
6 session.close();
7
8 session=sessionFactory.openSession();
9 transaction=session.beginTransaction();
10
11 // news.setId(10);
12 session.update(news);
13 }
3）：當update()方法關聯一個遊離對象時。如果session的緩存中已經存在相同OID的持久化對象。會拋出異常。因為在Session緩存中不能有兩個相同OID的對象。
@org.junit.Test
public void testUpdate(){
News news =(News) session.get(News.class, 1);
transaction.commit();
session.close();
session=sessionFactory.openSession();
transaction=session.beginTransaction();
News news2 =(News) session.get(News.class, 1);
session.update(news);
}
4：saveOrUpdate()方法。
5：delete()方法。
只要OID和數據表中一條記錄對應。就刪除。若OID沒有對應的。拋出異常。
1 @org.junit.Test
2 public void testDelete(){
3 News news =(News) session.get(News.class, 1);
4 session.delete(news);
5 System.out.println(news);
6 }
刪除後這個OID還是有值的。刪除後OID為空。可以在hibernate.cfg.xml中設置。
<property name="hibernate.use_identifier_rollback">true</property>
刪除一個沒有的。拋出IllegalArgumentException異常。
java.lang.IllegalArgumentException: attempt to create delete event with null entity
at org.hibernate.event.spi.DeleteEvent.<init>(DeleteEvent.java:45)
at org.hibernate.internal.SessionImpl.delete(SessionImpl.java:936)
at com.hibernate.helloworld.Test.testDelete(Test.java:95)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
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)
6：evict():把一個對象從session緩存中移除。
@org.junit.Test
public void testEvict(){
News news1 =(News) session.get(News.class, 1);
News news2 =(News) session.get(News.class, 2);
news1.setTitle("XX");
news2.setTitle("YY");
session.evict(news1);
}
只修改了2.
轉載自https://www.cnblogs.com/bulrush/p/7786973.html
Hibernate Session 4種對象狀態