hibernate 批量操作

java 批量操作

网数据表里插入100 0000 条记录

EntityTransaction tx = em.getTransaction(); tx.begin(); int i=0; try { for(;i<1000000;i++){ User user = new User(); user.setAge(18); user.setUsername("sddfdf"); user.setPassword("taoge"); Account account = new Account(); account.setMoney(11111); account.setUser(user); em.persist(account); System.out.println(i); } } catch (Exception e) { System.out.println(i); e.printStackTrace(); } tx.commit();

当运行到

.............

470805
470806

的时候会抛出java.lang.OutOfMemoryError 异常：

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:2882) at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:100) at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:390) at java.lang.StringBuilder.append(StringBuilder.java:119) at java.lang.StringBuilder.append(StringBuilder.java:115) at org.hibernate.id.IdentifierGeneratorHelper.getGeneratedIdentity(IdentifierGeneratorHelper.java:87) at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:98) at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2327) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2834) 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.ejb.event.EJB3PersistEventListener.saveWithGeneratedId(EJB3PersistEventListener.java:69) at org.hibernate.event.def.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:179) at org.hibernate.event.def.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135) at org.hibernate.impl.SessionImpl.firePersist(SessionImpl.java:799) at org.hibernate.impl.SessionImpl.persist(SessionImpl.java:791) at org.hibernate.engine.EJB3CascadingAction$1.cascade(EJB3CascadingAction.java:48) at org.hibernate.engine.Cascade.cascadeToOne(Cascade.java:392) at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:335) at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:204) at org.hibernate.engine.Cascade.cascade(Cascade.java:161) at org.hibernate.event.def.AbstractSaveEventListener.cascadeBeforeSave(AbstractSaveEventListener.java:450) at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:282) at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129) at org.hibernate.ejb.event.EJB3PersistEventListener.saveWithGeneratedId(EJB3PersistEventListener.java:69) at org.hibernate.event.def.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:179) at org.hibernate.event.def.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)

此时 select 数据表 ， 数据一条没插入进去，原因很明显， 程序在 tx.commit(); 之前挂掉了

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优化：

for(;i<1000000;i++){ User user = new User(); user.setAge(18); user.setUsername("wangtao"); user.setPassword("taoge"); Account account = new Account(); account.setMoney(11111); account.setUser(user); em.persist(account); if(i % 100 == 0){ em.flush();// 将一级缓存中的数据送往二级缓存 em.clear();// 清空一级缓存 } System.out.println(i); }

当程序执循环完1000000次， tx.commit(); ok 大功告成！！！