正在从DB、JPA中删除对象

Question

这是我的DAO方法：

public void deleteById(int id){
    TypedQuery<Animal> query = entityManager.createQuery("Select e from Animal e where e.id="+id, Animal.class);
    Animal entity = query.getSingleResult();
    System.out.println(entityManager.contains(entity));
    System.out.println(entity.hashCode());
    entity = entityManager.merge(entity);
    System.out.println("after merge");
    System.out.println(entity.hashCode());
    System.out.println(entityManager.contains(entity));
    entityManager.remove(entity);
}

这是我的控制器：

@RequestMapping("{animal}/{name}/{id}/delete")
public String dropAnimal(@PathVariable("id") int id){

    animalDAO.deleteById(id);
    return "glowny";
}

当我试图删除到对象时，删除分离的实例时出错。

我在合并前后做了sysout，都是false，但我不知道为什么。为什么我的对象仍然是分离的？

在stackTrace之前，我有这样的消息：

KWI21, 2016 10:47:45AMorg.apache.catalina.core.Standard ardWrapperValve在路径[/zapisywacz.baza]抛出异常的上下文中为servlet[mvc-调度器]调用SEVERE： Servlet.service（）[请求处理失败；嵌套异常是org.springframework.dao.InvalidDataAccessApiUsageExctive：删除一个分离的实例kaczynski.impl.Cat#1；嵌套异常java.lang.IllegalArgumentExctive：删除一个分离的实例kaczynski.impl.Cat#1]具有根本原因

这是hascode的输出：

false
1870474474
after merge
445252736
false

坚持不懈xml

<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_2_0.xsd"
version="2.0">
<persistence-unit name="myDatabase" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>

    <properties>
        <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
        <property name="javax.persistence.jdbc.user" value="tutorial" />
        <property name="javax.persistence.jdbc.password" value="password" />
        <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/mojaBaza" />
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect " />
        <property name="hibernate.hbm2ddl.auto" value="update" />
    </properties>
</persistence-unit>

动物实体

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class Animal {

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    private int id;

    private String name;

    private int age;
    @Column(name="date_of_birth")
    private String dateOfBirth;

    private double weight;

    public Animal(String name, int age, String dateOfBirth, double weight) {
        this.name = name;
        this.age = age;
        this.dateOfBirth = dateOfBirth;
        this.weight = weight;
    }

    public Animal() {}

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getDateOfBirth() {
        return dateOfBirth;
    }

    public void setDateOfBirth(String dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }

    public double getWeight() {
        return weight;
    }

    public void setWeight(double weight) {
        this.weight = weight;
    }

    @Override
    public String toString() {
        return " id= " + id + " name=" + name + ", age=" + age
                + ", dateOfBirth=" + dateOfBirth + ", weight=" + weight;
    }

    public String tease() {
        return "";
    }

    public String giveVoice() {
        return "";
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
}

Answer 1

合并后，对象从会话中分离出来，要删除它，您必须再次找到它。

TypedQuery<Animal> query = entityManager.createQuery("Select e from Animal e where e.id="+id, Animal.class);
Animal entity = query.getSingleResult();
entityManager.remove(entity);

Answer 2

我找到了解决办法，

在Spring配置中缺少，并且由于注释@Transactional，Spring不可见。