Question

我正在使用JDO DataNucleus实现，我遇到了一个主要问题，即我无法获得我之前存储在数据库中的对象。我会给你所有相关的代码。

这是我创建新用户（通过参数传递）并将其存储在数据库中的方法。这有效，我可以创建一个用户并存储它：

public void newUser(User user) throws UserException {
    PersistenceManager pm = Repository.getFactory().getPersistenceManager();
    Transaction tx = pm.currentTransaction();
    try {
        tx.begin();

        // 1. Check required information has been set.
        if (user.getEmail() == null) throw new UserException("The email has not been set!!");
        if (user.getPassword() == null) throw new UserException("The password has not been set!!");

        // 2. Check the user has not been created before.
        Query q = pm.newQuery("SELECT count(email) FROM " + User.class.getName() + " WHERE email=='" + user.getEmail() + "'");
        Long count = (Long)q.execute();
        if (count > 0) throw new UserException("The user already exists!!");

        // 3. Everything correct: create the user
        pm.makePersistent(user);
        tx.commit();

    } finally {
        if (tx.isActive())
        {
            tx.rollback();
        }
    }
}

类Repository是一个包装器，因此我不需要每次都建立jdo.properties链接。在这里，您有检索用户的方法。这不起作用，我无法检索我之前创建的用户，消息线程中的异常“main”javax.jdo.JDOObjectNotFoundException：没有出现这样的对象：

public void updateUser(User user) throws UserException {
    PersistenceManager pm = Repository.getFactory().getPersistenceManager();
    Transaction tx = pm.currentTransaction();
    try {
        tx.begin();

        // 1. Check required information has been set.
        if (user.getEmail() == null) throw new UserException("The email has not been set!!");

        // 2. Check the user HAS BEEN created before.
        Query countQuery = pm.newQuery("SELECT count(email) FROM " + User.class.getName() + " WHERE email=='" + user.getEmail() + "'");
        Long count = (Long)countQuery.execute();
        if (count == 0) throw new UserException("The user does not exist!!");

        // 3. Update the user
        User userToUpdate = (User) pm.getObjectById(user.getEmail());

        if (!(user.getPassword() == null))
            userToUpdate.setPassword(user.getPassword());

        if (!(user.getName() == null))
            userToUpdate.setName(user.getName());

        if (!(user.getSurname() == null))
            userToUpdate.setSurname(user.getSurname());

        if (!(user.getAlias() == null))
            userToUpdate.setAlias(user.getAlias());

        if (!(user.getPicture() == null))
            userToUpdate.setPicture(user.getPicture());

        tx.commit();

    } finally {
        if (tx.isActive())
        {
            tx.rollback();
        }
    }
}

这是我的测试类，我测试方法：公共类UpdateUserTest {

static UsersImpl users = new UsersImpl();

public static void main(String[] args) {
    User user2 = new User();
    User user3 = new User();

            user2.setEmail("user4");
    user2.setPassword("pass4");

    user3.setEmail("user4");
    user3.setPassword("pass3");
    try {
        users.newUser(user2);
        users.updateUser(user3);
    } catch (UserException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

为什么我会收到此异常？提前谢谢。

堆栈跟踪：

log4j:WARN No appenders could be found for logger (DataNucleus.General).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" javax.jdo.JDOObjectNotFoundException: Objeto no existe
FailedObject:user6
at org.datanucleus.api.jdo.NucleusJDOHelper.getJDOExceptionForNucleusException(NucleusJDOHelper.java:475)
at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectById(JDOPersistenceManager.java:1727)
at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectById(JDOPersistenceManager.java:1703)
at es.diegofenollar.iap.eqp.business.UsersImpl.updateUser(UsersImpl.java:64)
at es.upv.epsa.iap.eqp.test.UpdateUserTest.main(UpdateUserTest.java:20)
NestedThrowablesStackTrace:
Objeto no existe
org.datanucleus.exceptions.NucleusObjectNotFoundException: Objeto no existe
at org.datanucleus.ExecutionContextImpl.getClassDetailsForId(ExecutionContextImpl.java:3499)
at org.datanucleus.ExecutionContextImpl.findObject(ExecutionContextImpl.java:3621)
at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectById(JDOPersistenceManager.java:1722)
at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectById(JDOPersistenceManager.java:1703)
at es.diegofenollar.iap.eqp.business.UsersImpl.updateUser(UsersImpl.java:64)
at es.upv.epsa.iap.eqp.test.UpdateUserTest.main(UpdateUserTest.java:20)

UsersImpl.java:64是：

User userToUpdate = (User) pm.getObjectById(user.getEmail());

Answer 1

使用

pm.getObjectById(User.class, idValue);

更有意义。建议您阅读JDO身份并查看pm.getObjectId(obj)

的输出

线程“main”中的异常javax.jdo.JDOObjectNotFoundException：没有这样的对象

1 个答案: