我是Hibernate Annotation的初学者，我想实现一个示例，但它给出了以下错误消息：
****************WRITING****************
log4j:WARN No appenders could be found for logger (org.hibernate.type.BasicTypeRegistry).
log4j:WARN Please initialize the log4j system properly.
Hibernate: insert into Node (group, name) values (?, ?)
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not insert: [com.hib.ex.entity.Node]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2345)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2852)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:320)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:713)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:701)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:697)
at com.hib.ex.dao.HibExDao.saveNode(HibExDao.java:19)
at com.hib.ex.main.Run.main(Run.java:18)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'group, name) values (null, 'zakaria')' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:532)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.Util.getInstance(Util.java:381)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3558)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3490)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2643)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2362)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2280)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2265)
at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
... 17 more
这是实体类Node：
package com.hib.ex.entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="Node")
public class Node {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
@Column
private String name;
@Column
private Integer group;
public Node() {
super();
// TODO Auto-generated constructor stub
}
public Node(Integer id, String name, Integer group) {
super();
this.id = id;
this.name = name;
this.group = group;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getGroup() {
return group;
}
public void setGroup(Integer group) {
this.group = group;
}
}
这是DAO类HibExDao：
package com.hib.ex.dao;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;
public class HibExDao {
public void saveNode(Node noeud) {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
session.save(noeud);
session.getTransaction().commit();
session.close();
}
public List listNode() {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
List nodes = session.createQuery("FROM Node").list();
session.close();
return nodes;
}
public Node readNode(Integer id) {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
Node noeud = (Node) session.get(Node.class, id);
session.close();
return noeud;
}
}
这是hibernate.cfg.xml文件：
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/exhiber</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.pool_size">1</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="current_session_context_class">thread</property>
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>
<mapping class="com.hib.ex.entity.Node" />
<mapping class="com.hib.ex.entity.HyperEdge" />
</session-factory>
</hibernate-configuration>
这是执行类Run：
package com.hib.ex.main;
import java.util.List;
import com.hib.ex.dao.HibExDao;
import com.hib.ex.entity.Node;
public class Run {
public static void main(String[] args) {
HibExDao dao = new HibExDao();
System.out.println("****************WRITING****************");
Node n1 = new Node();
n1.setName("zakaria");
dao.saveNode(n1);
System.out.println("Node saved!");
Node n2 = new Node();
n2.setName("anas");
dao.saveNode(n2);
System.out.println("Node saved!");
System.out.println("\n****************READING****************");
List nodes = dao.listNode();
System.out.println("Name in Node number 2 is: " + dao.readNode(2).getName());
}
}
有什么问题？我能解决吗？
谢谢！
答案 0 :(得分：1)
明确提到了原因：
引起：com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException： 您的SQL语法有错误;检查手册 对应于您的MySQL服务器版本，以便使用正确的语法 在第1行附近'group，name）值（null，'zakaria'）'
您的实体包含导致此问题的属性：
@Column
private Integer group;
答案很简单group是一个保留的SQL关键字（参见GROUP BY clause`）
要解决此问题，您需要重命名为列名并将其正确映射到您的实体属性。
此外，您没有填充group字段，因此它是NULL。也许MySQL不接受此列的NULL？
我希望这会有所帮助。
如果要使用保留关键字，可以使用以下规范：
在JPA 2.0中：
@Column(name="\"group\"")
在Hibernate中：
@Column(name="'group'")
答案 1 :(得分：0)
要工作，您必须设置组属性或允许它为null（nullable = true）