从EntityManager抛出NullPointerException [英] NullPointerException thrown from EntityManager

问题描述

我对EntityManager有问题，它引发了NullPointerException. 这是代码:

I have a problem with an EntityManager, it throws a NullPointerException. This is the code:

package com.smartpump.service.jpa;

import org.springframework.stereotype.Service;

import com.smartpump.persistent.entity.Person;
import com.smartpump.service.PersonService;

import java.util.List;

import javax.jdo.annotations.Transactional;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

@Service("personService")
public class PersonServiceJpa implements PersonService {

    private EntityManager entityManager;

    @PersistenceContext
    public void setEntityManager(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    public EntityManager getEntityManager() {
        return entityManager;
    }

    @Override
    public String getNombre() {
        return "Roberto";
    }

    @SuppressWarnings("unchecked")
    @Transactional
    public List<Person> getAll() {
        Query query = entityManager.createNamedQuery("Person.findAll");  <--Here is the problem
        List<Person> persons = null;
        persons = query.getResultList();
        return persons;
    }
}

代码 Query query = entityManager.createNamedQuery("Person.findAll"); 是NullPointerException出现在entityManager句子中的位置.

The code Query query = entityManager.createNamedQuery("Person.findAll"); is where the NullPointerException appears, in the entityManager sentence.

这是代码的其他部分.

<?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="transactions-optional">
        <provider>org.datanucleus.api.jpa.PersistenceProviderImpl</provider>
      <!--   <properties>
            <property name="datanucleus.NontransactionalRead" value="true"/>
            <property name="datanucleus.NontransactionalWrite" value="true"/>
            <property name="datanucleus.ConnectionURL" value="appengine"/>
            <property name="datanucleus.appengine.datastoreReadConsistency" value="EVENTUAL" /> 
        </properties> -->
    </persistence-unit>
</persistence>

<!-- 
transaction-type="RESOURCE_LOCAL">
         <class>com.persistent.entity.Person</class>
          -->

applicationContext

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="
            http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
            http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.5.xsd
            http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">

    <bean
    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <list>
            <value>\WEB-INF\database.properties</value>
        </list>
    </property>
    </bean>

    <bean id="dataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource"
    p:driverClassName="${jdbc.driver}" p:url="${jdbc.url}" p:username="${jdbc.username}"
    p:password="${jdbc.password}" />

    <bean id="personService"
        class="com.smartpump.service.jpa.PersonServiceJpa"></bean>

    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean"
        lazy-init="true">
        <property name="persistenceUnitName" value="transactions-optional" />
    </bean>
    <bean name="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
    </bean>
</beans>

非常感谢！

推荐答案

尝试在EntityManager本身上使用@PersistenceContext，

Try to use @PersistenceContext on EntityManager itself,

@PersistenceContext
Private EntityManager entityManager;

我不是说它可以使用setter方法

I am not that it works on setter method

这篇关于从EntityManager抛出NullPointerException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！