최대 절전 모드를 통해 데이터베이스에 액세스하려고 시도한 후 NullPointerException이 발생했습니다.

Question

간단한 웹 응용 프로그램을 개발하려고하지만 웹 프런트 엔드에서 실수의 가능성을 모두 배제하기 위해 명령 프롬프트에서 실행하는 작은 클래스를 작성했습니다 .

package org.vadim.testmvc; 

import org.vadim.testmvc.model.*; 
import org.vadim.testmvc.service.*; 
public class TestMain { 
    public static void main(String[] args){ 
     Strings s = new Strings(); 
     TestService ts = new TestService(); 
     s.setText("StrText"); 
     ts.addStrings(s); 
     System.out.println(ts.listStrings()); 
    } 
} 

TestService.java (그들은 원래 목록에 존재해야하지만, import 문없이) :

package org.vadim.testmvc.service; 

@Service 
public class TestService implements TestServiceInterface { 

    //@Autowired 
    TestDAO testdao = new TestDAO(); 

    @Transactional 
    public List<Strings> listStrings(){ 
     return testdao.listStrings(); 
    } 

    @Transactional 
    public void addStrings(Strings strings){ 
     testdao.addStrings(strings); 
    } 
} 

TestDAO.java :

package org.vadim.testmvc.dao; 

@Transactional 
@Repository 
public class TestDAO implements TestDAOInterface { 

    @Autowired 
    private SessionFactory sessionFactory; 

    public void addStrings(Strings strings){ 
     sessionFactory.getCurrentSession().save(strings); 
    } 

    @SuppressWarnings("unchecked") 
    public List<Strings> listStrings(){ 
     return sessionFactory.getCurrentSession().createQuery("from Strings").list(); 
    } 
} 

엔티티 클래스 :

package org.vadim.testmvc.model; 

@Entity 
@Table(name="STRINGS") 
public class Strings { 

    @Id 
    @Column(name="ID") 
    @GeneratedValue(strategy=GenerationType.AUTO) 
    private Integer id; 

    @Column(name="TEXT") 
    private String text; 

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

    public Integer getId(){ 
     return id; 
    } 

    public String getText(){ 
     return text; 
    } 

    public void setText(String text){ 
     this.text=text; 
    } 
} 

hibernate.cfg.xm L :

Exception in thread "main" java.lang.NullPointerException 
    at org.vadim.testmvc.dao.TestDAO.listStrings(TestDAO.java:23) 
    at org.vadim.testmvc.service.TestService.listStrings(TestService.java:18) 
    at org.vadim.testmvc.TestMain.main(TestMain.java:11) 

동일한 께 :

<?xml version='1.0' encoding='utf-8'?> 
<!DOCTYPE hibernate-configuration PUBLIC 
    "-//Hibernate/Hibernate Configuration DTD//EN" 
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 
<hibernate-configuration> 
<session-factory> 
<mapping class="org.vadim.testmvc.model.Strings"/> 
</session-factory> 
</hibernate-configuration> 

루트의 context.xml

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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:lang="http://www.springframework.org/schema/lang" xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd"> 

<context:annotation-config/> 
<context:component-scan base-package="org.vadim.testmvc.dao"/> 
<context:component-scan base-package="org.vadim.testmvc.service"/> 
<import resource="data.xml"/> 
</beans> 

인 data.xml는

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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:lang="http://www.springframework.org/schema/lang" xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd"> 

<tx:annotation-driven transaction-manager="transactionManager"/> 

<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> 
<property name="sessionFactory" ref="sessionFactory"/> 
</bean> 

<bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource"> 
<property name="basename" value="classpath:messages"/> 
<property name="defaultEncoding" value="UTF-8"/> 
</bean> 

    <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" p:location="/WEB-INF/jdbc.properties"/> 

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

    <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> 
    <property name="dataSource" ref="dataSource"/> 
    <property name="configLocation"> 
    <value>classpath:hibernate.cfg.xml</value> 
    </property> 
    <property name="configurationClass"> 
    <value>org.hibernate.cfg.AnnotationConfiguration</value> 
    </property> 
    <property name="hibernateProperties"> 
    <props> 
    <prop key="hibernate.show_sql">true</prop> 
    <prop key="hibernate.dialect">${jdbc.dialect}</prop> 
    <prop key="hibernate.connection.charSet">UTF-8</prop> 
    </props> 
    </property> 
    </bean> 
    </beans> 

이 예외 만남 후 스택 트레이스이고 TestDAO.addStrings를 실행하려고하면 발생합니다. (문자열 문자열) 메서드는, 즉 문제가 listStrings() 반환 결과가 아니라 데이터베이스에 액세스 할 수 있습니다. mysql 명령 프롬프트에서 일부 항목을 추가하여 비어 있지 않게하려고 시도했습니다. 나는 그것을 성공하지만 그것이 프로그램의 행동에 영향을 미치지는 않았다. 여기

그냥 당신이 @Autowired을 주석 이유

ERROR: org.springframework.web.context.ContextLoader - Context initialization failed 
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'testService': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.vadim.testmvc.dao.TestDAO org.vadim.testmvc.service.TestService.testdao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [org.vadim.testmvc.dao.TestDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1074) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:291) 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:580) 
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895) 
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425) 
    at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:276) 
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:197) 
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47) 
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4723) 
    at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5226) 
    at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5221) 
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) 
    at java.util.concurrent.FutureTask.run(FutureTask.java:166) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) 
    at java.lang.Thread.run(Thread.java:722) 
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.vadim.testmvc.dao.TestDAO org.vadim.testmvc.service.TestService.testdao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [org.vadim.testmvc.dao.TestDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:502) 
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:84) 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:282) 
    ... 21 more 
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [org.vadim.testmvc.dao.TestDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:920) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:789) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:703) 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:474) 
    ... 23 more 

Answer 1

@Bozho와 @ smp7d 답변의 조합이라고 생각합니다. 스프링 구성을로드해야하며 해당 구성에서 TestDao에 대한 bean을 정의하고 @Autowired의 주석을 제거하십시오.

Answer 2

내가 모르는 @Autowire 주석을 TestService testservice;를 선언하는 경우 내가 무엇을 얻을이지만, 문제가 발생합니다

//@Autowired 
TestDAO testdao = new TestDAO(); 

당신은 수동으로 TestDAO을 생성합니다. 봄은 TestDAO.sessionFactory을 삽입 할 수 없으며, 왼쪽은 null입니다. 의 주석이 주석 제거 = new TestDAO() : 당신의 주요 방법은

@Autowired 
private TestDAO testdao; 

Answer 3

, 당신은 스프링 구성을로드하지 않습니다 ... 그래서 반원를 자동 설정할 수 없습니다.

컨텍스트를로드하고 컨텍스트/bean 팩토리에서 TestService Bean을 가져 와서 TestDao를 autowire해야합니다.

Answer 4

dao에 추가해주세요.

공개 HibernateTemplate hibernateTemplate; 공개 세션 = null;

@Autowired 
public void setSessionFactory(SessionFactory sessionFactory) { 
    hibernateTemplate = new HibernateTemplate(sessionFactory); 
} 

Answer 5

ı 일을 대신 sessionFactory.getCurrentSession()