，为什么表建不起来

<?xml version="1.0" encoding="utf-8"?>
<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="msg" transaction-type="RESOURCE_LOCAL">
		<provider>org.hibernate.ejb.HibernatePersistence</provider>
		<properties>
		 <property name="hibernate.dialect" value="org.hibernate.dialect.OracleDialect"/>   
		  <!-- 建表方式，value值为creat-drop时表示创建应用的时候建表，结束应用的时候表自动删除；
     				值为update表示如果映射元数据不存在则建立表，如果映射元数据存在并新增加了字段则会添加到数据库表中 -->
         <property name="hibernate.hbm2ddl.auto" value="update"/>
          <property name="hibernate.show_sql" value="true"/>
         <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/>
         <property name="hibernate.connection.username" value="....没错...."/>
         <property name="hibernate.connection.password" value=".......没错...."/>
         <property name="hibernate.connection.url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>    
		</properties>
	</persistence-unit>
</persistence>

package com.demo.entity;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;

@Entity
@Table(name = "User")
public class User implements Serializable {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue(strategy = GenerationType.SEQUENCE)
	@SequenceGenerator(name = "ID_sqe")
	private int id;
	@Column(name = "User_name", length = 20, nullable = true)
	private String username;
	@Column(name = "User_pwd", length = 40, nullable = true)
	private String password;
	@Column(name = "User_lev", length = 1, nullable = true)
	private int level=0;//0为普通用户，1管理员

	public User() {}
	public User(int id, String name, String password) {
		this.id = id;
		this.username = name;
		this.password = password;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public int getLevel() {
		return level;
	}

	public void setLevel(int level) {
		this.level = level;
	}

	@Override
	public String toString() {
		return "User [id=" + id + ", username=" + username + ", password=" + password
				+ ", level=" + level + "]";
	}

}

2013-11-19 10:27:08 org.apache.catalina.core.AprLifecycleListener init
信息: Loaded APR based Apache Tomcat Native library 1.1.27 using APR version 1.4.6.
2013-11-19 10:27:08 org.apache.catalina.core.AprLifecycleListener init
信息: APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random [true].
2013-11-19 10:27:09 org.apache.catalina.core.AprLifecycleListener initializeSSL
信息: OpenSSL successfully initialized (OpenSSL 1.0.1d 5 Feb 2013)
2013-11-19 10:27:09 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["http-apr-8080"]
2013-11-19 10:27:09 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["ajp-apr-8009"]
2013-11-19 10:27:09 org.apache.catalina.startup.Catalina load