我在java webapp项目的Service部分编写了这段代码:
@Service
@Transactional
public class PersonService extends BaseService {
@PersistenceContext
private EntityManager entityManager;
public void insert(Person person) {
entityManager.persist(person);
}
public boolean checkUserName(String userName) {
try {
System.out.println("Entity null ni");
Person person = (Person) entityManager.createQuery("select entity from person entity where entity.USER_NAME=:userName")
.setParameter("userName", userName)
.getSingleResult();
if (person == null)
return true;
else {
return false;
}
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
}
当我尝试不使用checkUserName方法插入新记录时,记录将正确插入并且entityManager在此条件下不为null但是当我想检查重复的userName时,我得到了NullPointerException.I检查了我的代码中的每个Object最后我理解entityManager是null。为什么entityManager在Spring Transaction中是null。这是spring.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd">
<!--SpringMVC-->
<context:component-scan base-package="Laitec.Doctor"/>
<mvc:annotation-driven/>
<mvc:resources mapping="/resources/**" location="/resources/"/>
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/"/>
</bean>
<!-- SpringTransaction-->
<bean id="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="packagesToScan" value="Laitec.Doctor.model.entity"/><!--ToPackageAddress-->
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
</property>
<property name="jpaProperties">
<props>
<prop key="hibernate.hbm2ddl.auto">update</prop>
<!--<prop key="hibernate.hbm2ddl.auto">create-drop</prop>-->
<prop key="hibernate.show_sql">false</prop>
<prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
</props>
</property>
</bean>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"/>
<property name="url" value="jdbc:oracle:thin:@localhost:1521:XE"/>
<property name="username" value="username"/>
<property name="password" value="password"/>
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactoryBean"/>
</bean>
<tx:annotation-driven/>
</beans>
答案 0 :(得分:0)
也许您正在实例化调用新PersonService()的PersonService?在这种情况下,Spring没有执行任何操作,因此字段实体管理器&#39;一片空白。您必须从应用程序上下文中获取一个bean
applicationContext.getBean(PersonService.class);
或者从测试或控制器中调用它
@RestController
@GetMapping("people")
public class PersonController() {
@Autowired
private PersonService personService;
@PostMapping
public void home(@RequestBody Person person) {
personService.insert(person);
}
}