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);
}

这是我的控制者：

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

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

当我尝试删除对象时，我删除了一个分离的实例时出错。

我在合并之前和之后做了sysout，两者都是假的，但我不知道为什么。为什么我的物体仍然分离？

java.lang.IllegalArgumentException：删除分离的实例kaczynski.impl.Cat＃1 在org.hibernate.jpa.event.internal.core.JpaDeleteEventListener.performDetachedEntityDeletionCheck（JpaDeleteEventListener.java:69）在org.hibernate.event.internal.DefaultDeleteEventListener.onDelete（DefaultDeleteEventListener.java:106）在org.hibernate.event.internal.DefaultDeleteEventListener.onDelete（DefaultDeleteEventListener.java:73）在org.hibernate.internal.SessionImpl.fireDelete（SessionImpl.java:920）在org.hibernate.internal.SessionImpl.delete（SessionImpl.java:896）在org.hibernate.jpa.spi.AbstractEntityManagerImpl.remove（AbstractEntityManagerImpl.java:1214） at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method） at sun.reflect.NativeMethodAccessorImpl.invoke（Unknown Source） at sun.reflect.DelegatingMethodAccessorImpl.invoke（Unknown Source） at java.lang.reflect.Method.invoke（Unknown Source）在org.springframework.orm.jpa.ExtendedEntityManagerCreator $ ExtendedEntityManagerInvocationHandler.invoke（ExtendedEntityManagerCreator.java:365）在com.sun.proxy。$ Proxy22.remove（未知来源） at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method） at sun.reflect.NativeMethodAccessorImpl.invoke（Unknown Source） at sun.reflect.DelegatingMethodAccessorImpl.invoke（Unknown Source） at java.lang.reflect.Method.invoke（Unknown Source）在org.springframework.orm.jpa.SharedEntityManagerCreator $ SharedEntityManagerInvocationHandler.invoke（SharedEntityManagerCreator.java:240）在com.sun.proxy。$ Proxy22.remove（未知来源） at kaczynski.DBaccess.AnimalDAO.deleteById（AnimalDAO.java:88） at kaczynski.DBaccess.AnimalDAO $$ FastClassBySpringCGLIB $$ 5f2786e9.invoke（）在org.springframework.cglib.proxy.MethodProxy.invoke（MethodProxy.java:204）在org.springframework.aop.framework.CglibAopProxy $ CglibMethodInvocation.invokeJoinpoint（CglibAopProxy.java:720）在org.springframework.aop.framework.ReflectiveMethodInvocation.proceed（ReflectiveMethodInvocation.java:157） at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke（PersistenceExceptionTranslationInterceptor.java:136）在org.springframework.aop.framework.ReflectiveMethodInvocation.proceed（ReflectiveMethodInvocation.java:179）在org.springframework.aop.framework.CglibAopProxy $ DynamicAdvisedInterceptor.intercept（CglibAopProxy.java:655） at kaczynski.DBaccess.AnimalDAO $$ EnhancerBySpringCGLIB $$ 53a0549d.deleteById（）在kaczynski.web.AnimalsController.dropAnimal（AnimalsController.java:48） at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method） at sun.reflect.NativeMethodAccessorImpl.invoke（Unknown Source） at sun.reflect.DelegatingMethodAccessorImpl.invoke（Unknown Source） at java.lang.reflect.Method.invoke（Unknown Source）在org.springframework.web.method.support.InvocableHandlerMethod.doInvoke（InvocableHandlerMethod.java:221）在org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest（InvocableHandlerMethod.java:136）在org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle（ServletInvocableHandlerMethod.java:110）在org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod（RequestMappingHandlerAdapter.java:817）在org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal（RequestMappingHandlerAdapter.java:731）在org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle（AbstractHandlerMethodAdapter.java:85）在org.springframework.web.servlet.DispatcherServlet.doDispatch（DispatcherServlet.java:959）在org.springframework.web.servlet.DispatcherServlet.doService（DispatcherServlet.java:893）在org.springframework.web.servlet.FrameworkServlet.processRequest（FrameworkServlet.java:968）在org.springframework.web.servlet.FrameworkServlet.doGet（FrameworkServlet.java:859）在javax.servlet.http.HttpServlet.service（HttpServlet.java:622）在org.springframework.web.servlet.FrameworkServlet.service（FrameworkServlet.java:844）在javax.servlet.http.HttpServlet.service（HttpServlet.java:729）在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:292）在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:207）在org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:240）在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:207）在org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:212）在org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:106）在org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:502） at org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:141） at org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:79）在org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:616）在org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:88）在org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:522）在org.apache.coyote.http11.AbstractHttp11Processor.process（AbstractHttp11Processor.java:1095） at org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（AbstractProtocol.java:672）在org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1500）在org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.run（NioEndpoint.java:1456） at java.util.concurrent.ThreadPoolExecutor.runWorker（Unknown Source） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（Unknown Source） at org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java:61）在java.lang.Thread.run（未知来源）

在stackTrace之前我有这条消息：

kwi 21,2016 10:47:45 AM org.apache.catalina.core.StandardWrapperValve invoke 严重：servlet [mvc-dispatcher]的Servlet.service（）在路径[/zapisywacz.baza]的上下文中引发异常[请求处理失败;嵌套异常是org.springframework.dao.InvalidDataAccessApiUsageException：删除分离的实例kaczynski.impl.Cat＃1;嵌套异常是java.lang.IllegalArgumentException：删除带有根本原因的分离实例kaczynski.impl.Cat＃1]

这是hascodes的输出：

false
1870474474
after merge
445252736
false

的persistence.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

我找到了解决方案，

弹簧配置中的

缺失，并且因为注释@Transactional，弹簧不可见。

Answer 2

合并后，该对象与会话分离并删除它，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);

从DB中删除对象，JPA

2 个答案: