编写JPA项目 测试生成数据库表 报错

实体类
package com.yl.jpa;import java.util.HashSet;
import java.util.Set;import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.OneToMany;@Entity
public class Orders { private String orderId;
private float amount = 0f ;
private Set<OrderItems> items = new HashSet<OrderItems>();
@Id 
public String getOrderId() {
return orderId;
}
public void setOrderId(String orderId) {
this.orderId = orderId;
}
public float getAmount() {
return amount;
}
public void setAmount(float amount) {
this.amount = amount;
}
@OneToMany(cascade={CascadeType.REFRESH,CascadeType.MERGE,CascadeType.REMOVE,CascadeType.PERSIST},
fetch = FetchType.LAZY,mappedBy = "order")
public Set<OrderItems> getItems() {
return items;
}
public void setItems(Set<OrderItems> items) {
this.items = items;
}

}package com.yl.jpa;import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
public class OrderItems { private Integer id;
private String prodouctName;
private float sellPrice = 0f;
private Orders order ;
@Id @GeneratedValue
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(nullable = false,length = 40)
public String getProdouctName() {
return prodouctName;
}
public void setProdouctName(String prodouctName) {
this.prodouctName = prodouctName;
}
public float getSellPrice() {
return sellPrice;
}
public void setSellPrice(float sellPrice) {
this.sellPrice = sellPrice;
}
@ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},fetch = FetchType.EAGER,optional = false)
@JoinColumn(name = "order_id")
public Orders getOrder() {
return order;
}
public void setOrder(Orders order) {
this.order = order;
}

}persistence.xml 配置文件
<?xml version="1.0"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">
 <persistence-unit name="jpa" transaction-type="RESOURCE_LOCAL">
   <provider>org.hibernate.ejb.HibernatePersistence</provider>
   <properties>
         <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
         <property name="hibernate.connection.driver_class" value="org.gjt.mm.mysql.Driver"/>
         <property name="hibernate.connection.username" value="root"/>
         <property name="hibernate.connection.password" value="sa"/>
         <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/jpa?useUnicode=true&amp;characterEncoding=UTF-8"/>
         <property name="hibernate.max_fetch_depth" value="3"/>
         <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.jdbc.fetch_size" value="18"/>
      <property name="hibernate.jdbc.batch_size" value="10"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.format_sql" value="false"/>
    </properties>
 </persistence-unit>
</persistence>
测试生成表
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;import org.junit.BeforeClass;
import org.junit.Test;public class JunitTest { @BeforeClass
public static void setUpBeforeClass() throws Exception {
}

//测试
@Test public void save()
{
EntityManagerFactory emf = Persistence.createEntityManagerFactory("jpa");
emf.close();
}
}错误信息
javax.persistence.PersistenceException: [PersistenceUnit: jpa] Unable to configure EntityManagerFactory
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:374)
at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:56)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:32)
at com.yl.junitTest.JunitTest.save(JunitTest.java:18)
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:585)
at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99)
at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75)
at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45)
at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66)
at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35)
at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany targeting an unmapped class: com.yl.jpa.Orders.items[com.yl.jpa.OrderItems]
at org.hibernate.cfg.annotations.CollectionBinder.bindManyToManySecondPass(CollectionBinder.java:1168)
at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:693)
at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:628)
at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:65)
at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1686)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1393)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1345)
at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1477)
at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:193)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:1096)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:278)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:362)
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