The abstract schema type 'Entity' is unknown.

异常栈:

An exception occurred while creating a query in EntityManager: Exception Description: Problem compiling [SELECT u FROM User u WHERE u.name=:Name AND u.pswd=:Pswd]. [14, 18] The abstract schema type 'User' is unknown.[27, 33] The state field path 'u.name' cannot be resolved to a valid type.[46, 52] The state field path 'u.pswd' cannot be resolved to a valid type.java.lang.IllegalArgumentException    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1605)    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:366)    at com.sun.proxy.$Proxy16.createQuery(Unknown Source)    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:241)    at com.sun.proxy.$Proxy16.createQuery(Unknown Source)    at net.lab.dao.impl.UserDaoImpl.getUser(UserDaoImpl.java:45)    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)    at com.sun.proxy.$Proxy17.getUser(Unknown Source)    at net.lab.test.UserTest.hello(UserTest.java:45)    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)    at org.eclipse.persistence.internal.jpa.jpql.HermesParser.buildException(HermesParser.java:155)    at org.eclipse.persistence.internal.jpa.jpql.HermesParser.validate(HermesParser.java:347)    at org.eclipse.persistence.internal.jpa.jpql.HermesParser.populateQueryImp(HermesParser.java:278)    at org.eclipse.persistence.internal.jpa.jpql.HermesParser.buildQuery(HermesParser.java:163)    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:142)    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:116)    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:102)    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:86)    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1603)

用Junit测试jpa时的代码:

package net.lab.test;import java.util.List;import net.lab.dao.UserDao;import net.lab.entity.User;import static org.junit.Assert.assertTrue;import org.junit.Before;import org.junit.Test;import org.springframework.beans.BeansException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;/** * * @author xiaofanku */public class UserTest extends AbstractTests implements ApplicationContextAware{    private ApplicationContext applicationContext;    private UserDao ud;    @Before    public void init(){        ud=applicationContext.getBean(UserDao.class);    }    // TODO add test methods here.    // The methods must be annotated with annotation @Test. For example:    //ngunit    @Test    public void hello() {        User qu=ud.getUser("pktmandy", "12345");        assertTrue(qu.getId()>0);    }    @Override    public void setApplicationContext(ApplicationContext ac) throws BeansException {        applicationContext=ac;    }}

实体类:

package net.lab.entity;import java.io.Serializable;import java.util.Objects;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;/** * 购买者 * @author xiaofanku */@Entity(name="king_user")public class User implements Serializable {    private static final long serialVersionUID = 1L;    @Id    @GeneratedValue(strategy = GenerationType.AUTO)    private Long id;    /**     * 用户名     */    @Column    private String name;    /**     * 密码     */    @Column    private String pswd;    //GET/SET    @Override    public int hashCode() {        int hash = 7;        hash = 11 * hash + Objects.hashCode(this.id);        hash = 11 * hash + Objects.hashCode(this.name);        return hash;    }    @Override    public boolean equals(Object obj) {        if (this == obj) {            return true;        }        if (obj == null) {            return false;        }        if (getClass() != obj.getClass()) {            return false;        }        final User other = (User) obj;        if (!Objects.equals(this.name, other.name)) {            return false;        }        if (!Objects.equals(this.pswd, other.pswd)) {            return false;        }        if (!Objects.equals(this.id, other.id)) {            return false;        }        return true;    }}

DAO实现类:

package net.lab.dao.impl;import java.util.List;import javax.persistence.EntityManager;import javax.persistence.PersistenceContext;import javax.persistence.TypedQuery;import net.lab.dao.UserDao;import net.lab.entity.User;import org.springframework.stereotype.Repository;import org.springframework.transaction.annotation.Propagation;import org.springframework.transaction.annotation.Transactional;/** * * @author xiaofanku */@Repositorypublic class UserDaoImpl implements UserDao{    private EntityManager em;    @PersistenceContext    public void setEntityManager(EntityManager em) {         this.em=em;    }       @Transactional(propagation=Propagation.REQUIRES_NEW)    @Override    public long add(User user) {        em.persist(user);        return user.getId();    }    @Override    public List<User> getAll() {        return em.createQuery("SELECT u FROM User u").getResultList();    }    @Override    public User getUser(String name, String pswd) {        TypedQuery<User> q=em.createQuery("SELECT u FROM User u WHERE u.name=:Name AND u.pswd=:Pswd",User.class);        q.setParameter("Name", name);        q.setParameter("Pswd",pswd);        return q.getResultList().get(0);    }    @Override    public User getUser(long uid) {        return em.find(User.class, uid);    }}

只需要改下User实体的注解,修改后：

package net.lab.entity;import java.io.Serializable;import java.util.Objects;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;/** * 购买者 * @author xiaofanku */@Entity@Table(name="king_user")public class User implements Serializable {//...}

再运行测试文件

注意:
如果没有@Table注解(也就是表名加在Entity注解中),Dao中的以下方法是不会报异常的:

    @Transactional(propagation=Propagation.REQUIRES_NEW)    @Override    public long add(User user) {        em.persist(user);        return user.getId();    }    @Override    public User getUser(long uid) {        return em.find(User.class, uid);    }

其它两个方法报异常的共同点它们都使用了 Java Persistence query language (JPQL)，在EE中有如下介绍:

Query Language Terminology

The following list defines some of the terms referred to in this chapter:

• Abstract schema: The persistent schema abstraction (persistent entities, their state, and their >relationships) over which queries
  operate. The query language translates queries over this >persistent
  schema abstraction into queries that are executed over the database
  schema to which >entities are mapped.

• Abstract schema type: The type to which the persistent property of an entity evaluates in the >abstract schema. That is, each
  persistent field or property in an entity has a corresponding state
  field of the same type in the abstract schema. The abstract schema type of an entity is derived >from the entity class and the metadata
  information provided by Java language annotations.

• Backus-Naur Form (BNF): A notation that describes the syntax of high-level languages. The >syntax diagrams in this chapter are in BNF
  notation.

• Navigation: The traversal of relationships in a query language expression. The navigation >operator is a period.

• Path expression: An expression that navigates to a entity’s state or relationship field.

• State field: A persistent field of an entity.

• Relationship field: A persistent relationship field of an entity whose type is the abstract schema type of the related entity.

环境:
JDK: 1.7.0_79
Spring: 3.2.7
EclipseLink: 2.1
JUnit: 4.12

参考网址:
JPA’s Nasty “Unknown abstract schema type” Error
The Java EE 6 Tutorial