工作单元模式
package test.hella.unitwork;public interface IUnitOfWork{ void registerAdded(Object entity); void registerChanged(Object entity); void registerRemoved(Object entity); void commit();}
?然后是接口实现：
package test.hella.unitwork;import java.util.ArrayList;import java.util.List;public class UnitOfWork implements IUnitOfWork { private List<Object> newObjects = new ArrayList<Object>(); private List<Object> dirtyObjects = new ArrayList<Object>(); private List<Object> removedObjects = new ArrayList<Object>(); public void registerAdded(Object entity) { newObjects.add(entity); } public void registerChanged(Object entity) { dirtyObjects.add(entity); } public void registerRemoved(Object entity) { removedObjects.add(entity); } public void commit() { insertNew(); updateDirty(); deleteRemoved(); } private void insertNew() { for (Object newObj : newObjects) { //DO insert } } private void updateDirty() { for (Object dirtyObj : dirtyObjects) { //DO update } } private void deleteRemoved() { for (Object removedObj : removedObjects) { //DO delete } }}?调用着的调用方式：
package test.hella.unitwork;public class UnitOfWorkTest { private static final UserRepository userRepository = new UserRepository(); public static void main(String[] args) { User user1 = new User(1,"user1"); IUnitOfWork unitOfWork = new UnitOfWork(); unitOfWork.registerRemoved(user1); User user2 = userRepository.getUser(2); user2.changeName("user2Changed"); unitOfWork.registerChanged(user2); User user3 = userRepository.getUser(3); unitOfWork.registerRemoved(user3); unitOfWork.commit(); }}?2. 对象注册：
对象注册的方式，调用者无需负责注册，注册方法被置于对象方法中。
还以上面的代码距离，此时User对象需要负责注册：
package test.hella.unitwork;public class User { private final long id; private String name; public long getId() { return id; } public User(long id, String name) { this.id = id; this.name = name; } public void changeName(String name, IUnitOfWork unitOfWork) { this.name = name; unitOfWork.registerChanged(this); }}?调用者无需再向工作单元进行注册。很明显看到上例中需要将工作单元传递给User对象，这种传递显得不够简洁，更好的方式是将工作单元放到一个众所周知的地方来解决这个问题，比如java的ThreadLocal。
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package test.hella.unitwork;import java.util.ArrayList;import java.util.List;public class UnitOfWork implements IUnitOfWork { private List<Object> newObjects = new ArrayList<Object>(); private List<Object> dirtyObjects = new ArrayList<Object>(); private List<Object> removedObjects = new ArrayList<Object>(); private static ThreadLocal current = new ThreadLocal<UnitOfWork>(); public static void newCurrent() { setCurrent(new UnitOfWork()); } public static void setCurrent(UnitOfWork now) { current.set(now); } public static UnitOfWork getCurrent() { return (UnitOfWork) current.get(); } public void registerAdded(Object entity) { newObjects.add(entity); } public void registerChanged(Object entity) { dirtyObjects.add(entity); } public void registerRemoved(Object entity) { removedObjects.add(entity); } public void commit() { insertNew(); updateDirty(); deleteRemoved(); } private void insertNew() { for (Object newObj : newObjects) { //DO insert } } private void updateDirty() { for (Object dirtyObj : dirtyObjects) { //DO update } } private void deleteRemoved() { for (Object removedObj : removedObjects) { //DO delete } } }?
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3. 工作单元控制器：
这种方式调用者和DomainObject都无需小心翼翼的记得向工作单元注册变化。工作单元控制所有的数据读取，读取数据之后会产生一个拷贝，提交时按照对象的唯一标识和拷贝的对象进行对比，如果有变化则更新数据库中的数据。
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