问Java eclipse tomcat HTTP错误500 Servlet执行引发异常

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   <?xml version="1.0" encoding="UTF-8"?>
    <persistence version="2.0" 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_2_0.xsd">
     <persistence-unit name="Hibernate Tutozone" transaction-type="RESOURCE_LOCAL">
     <provider>org.hibernate.ejb.HibernatePersistence</provider>
     <class>info.tutozone.food.Food</class>
     <properties>
     <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/tutozonedb"/>
     <property name="javax.persistence.jdbc.user" value="root"/>
     <property name="javax.persistence.jdbc.password" value="" />
     <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
     <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />

     </properties>
     </persistence-unit>
    </persistence>

package info.tutozone.food;

import java.io.Serializable;
import java.lang.String;
import javax.persistence.*;

/**
 * Entity implementation class for Entity: Food
 *
 */
@Entity

public class Food implements Serializable {


 @Id
 private int id;
 private String name;
 private float price;
 private int quantity;
 private static final long serialVersionUID = 1L;

 public Food() {
 super();
 } 
 public int getId() {
 return this.id;
 }

 public void setId(int id) {
 this.id = id;
 } 
 public String getName() {
 return this.name;
 }

 public void setName(String name) {
 this.name = name;
 } 
 public float getPrice() {
 return this.price;
 }

 public void setPrice(float price) {
 this.price = price;
 } 
 public int getQuantity() {
 return this.quantity;
 }

 public void setQuantity(int quantity) {
 this.quantity = quantity;
 }
 @Override
 public String toString() {
 return "Food [id=" + id + ", name=" + name + ", price=" + price
 + ", quantity=" + quantity + "]";
 }

}

    package info.tutozone.food;
 import java.io.IOException; 
 import javax.persistence.EntityManager;
 import javax.persistence.Persistence;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 /**
 * Servlet implementation class TestServlet
 */
 @WebServlet("/TestServlet")
 public class TestServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;

 /**
 * @see HttpServlet#HttpServlet()
 */
 public TestServlet() {
 super();
 // TODO Auto-generated constructor stub
 }

 /*
 * Tuto Hibernate avec Eclipse
 * author : Zied
 * www.tutozone.info
 */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub

 EntityManager manager=Persistence.createEntityManagerFactory("Hibernate Tutozone").createEntityManager();

 manager.getTransaction().begin();
 manager.getTransaction().commit();

 }
 /**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
 }

 public static void main(String[] args) {
 // TODO Auto-generated method stub
 EntityManager manager = Persistence.createEntityManagerFactory(
 "Hibernate Tutozone").createEntityManager();

 manager.getTransaction().begin();
 // add a new row in table
 Food food = new Food();
 food.setId(1);
 food.setName("Cacke");
 food.setQuantity(new Integer(20));
 food.setPrice(new Float(2500));
 manager.persist(food);

 manager.getTransaction().commit();
 manager.close();
}}