相关demo项目查看
http://acheron.iteye.com/admin/blogs/402499
常见操作
A.查询操作
public List<Record> listAllRecord() { PersistenceManager pm = getPersistenceManager(); // Transaction tx= pm.currentTransaction(); try { // tx.begin(); Query query = pm.newQuery(Record.class); query.setOrdering("addDate DESC"); //方法1:获得查询结果,得到对象数组 // Collection entries = (Collection) query.execute(); // Object objRecord[]=(Object [])entries.toArray(); //方式2:枚举集合中的entity并作单独处理 // Collection entries = (Collection) query.execute(); // Iterator i = entries.iterator(); // while (i.hasNext()) { // Record obj = (Record) i.next(); // System.out.println("do sth on the record!"); // } //方法3:获得list,显式把返回的Collection对象转换为List对象 // Collection entries = (Collection) query.execute(); // List<Record> list = new ArrayList(entries); //方法4:直接强制转换为List返回 List<Record> list = (List<Record>) query.execute(); // tx.commit(); return list; } catch (Exception e) { e.printStackTrace(); // if (tx.isActive()) { // tx.rollback(); // } } query.execute(); return null; } public List<Record> listAllRecord(int page) { PersistenceManager pm = getPersistenceManager(); // Transaction tx= pm.currentTransaction();; try { page = (page == 0) ? 1 : page; Query query = pm.newQuery(Record.class); query.setOrdering("addDate DESC"); query.setRange(PAGE_SIZE * (page - 1), PAGE_SIZE * page); return (List<Record>) pm.detachCopyAll((Collection<Record>) query.execute()); } finally { releasePersistenceManager(pm); } } public int getPage(){ PersistenceManager pm = getPersistenceManager(); Query query = pm.newQuery(Record.class); query.setOrdering("addDate DESC"); List<Record> list = (List<Record>) query.execute(); return (int)(list.size()/10+1); }
B.删除操作
public void removeRecordById(Long id) { PersistenceManager pm = getPersistenceManager(); // Transaction tx= pm.currentTransaction(); try { // tx.begin(); Extent r = pm.getExtent (Record.class, false); String filter = "id == "+id;//注意是== Query query = pm.newQuery(r,filter); //方式1:迭代Collection获得元素然后处理 // Collection entries = (Collection) query.execute(); // Iterator i = entries.iterator(); // while (i.hasNext()) { // Record delRecord = (Record) i.next(); // pm.deletePersistent(delRecord); // } //方式2:作为list处理 List<Record> list = (List<Record>) query.execute(); // if(!list.isEmpty()){}//isEmpty是首先判断是否为空（null）,然后判断size // if(list.size()!=0){ } // if(list.iterator().hasNext()){} if(!list.isEmpty()){ Record delRecord = list.get(0); pm.deletePersistent(delRecord); } // tx.commit(); }catch (Exception e) { e.printStackTrace(); // if (tx.isActive()) { // tx.rollback(); // } } }
异常处理:
dataNucleus Enhancer (version 1.1.0) : Enhancement of classes 2009-6-1 16:02:25 org.datanucleus.metadata.MetaDataManager loadClasses 严重: Class "com.jun.demos.book.dao.RecordJdoDao" was not found in the CLASSPATH. Please check your specification and your CLASSPATH. org.datanucleus.exceptions.ClassNotResolvedException: Class "com.jun.demos.book.dao.RecordJdoDao" was not found in the CLASSPATH. Please check your specification and your CLASSPATH. at org.datanucleus.JDOClassLoaderResolver.classForName(JDOClassLoaderResolver.java:255) at org.datanucleus.JDOClassLoaderResolver.classForName(JDOClassLoaderResolver.java:420) at org.datanucleus.metadata.MetaDataManager.loadClasses(MetaDataManager.java:337) at org.datanucleus.enhancer.DataNucleusEnhancer.getFileMetadataForInput(DataNucleusEnhancer.java:723) at org.datanucleus.enhancer.DataNucleusEnhancer.enhance(DataNucleusEnhancer.java:525) at org.datanucleus.enhancer.DataNucleusEnhancer.main(DataNucleusEnhancer.java:1235) 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 com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:57) at com.google.appengine.tools.enhancer.Enhance.<init>(Enhance.java:60) at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:41) DataNucleus Enhancer completed with success for 0 classes. Timings : input=78 ms, enhance=0 ms, total=78 ms. Consult the log for full details DataNucleus Enhancer completed and no classes were enhanced. Consult the log for full details
解决方法：
这个错误是因为spring的JdoSupport依赖于spring-dao.jar ，
也就是需要spring-jdo.jar和spring-dao.jar加到构建目录中。
