我正在构建一个Spring MVC WebApp，我使用JPA和Hibernate，在测试EntityManager时发生了一个错误，我是这样设计和配置的。
BaseController.java
public class BaseController {
public Facade facade;//it is an interface
/**
* Inject Services from Spring
*/
public void setFacade(Facade facade){
this.facade = facade;
}
}
BlogController.java
@Controller
public class BlogController extends BaseController{
@RequestMapping(value="blog/index")
public String saveValueFromEM() {
facade.saveCustomBlog();
return "blog/index";
}
@RequestMapping(value="home")
public String saveValueFromJPARep() {
//facade.saveRepositoryBlog();
return "home";
}
}
HibernateAuthenticator.java
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.transaction.annotation.Transactional;
@Transactional
public class HibernateAuthenticator {
/**
* Inject persistence layer to classes that extends this class
* */
public static EntityManager em;
@PersistenceContext
public void setEntityManager(EntityManager emf) {
em = emf;
}
}
FacadeImpl.java
public class FacadeImpl extends HibernateAuthenticator implements Facade {
private BlogService blogService;//it is an interface
@Override
public void saveCustomBlog() {
blogService.saveCustomBlog();
}
public void setBlogService(BlogService blogService) {
this.blogService = blogService;
}
}
BlogServiceImpl.java
@Transactional(readOnly = true)
public class BlogServiceImpl extends HibernateAuthenticator implements BlogService {
@Override
@Transactional(readOnly = false)
public void saveCustomBlog() {
// TODO Auto-generated method stub
Blog blog=new Blog();
blog.setId(13);
blog.setName("Fation");
em.merge(blog);
}
}
web.xml
<?xml version="1.0" encoding="utf-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<display-name>eLearning</display-name>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath*:applicationContext.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath*:spring-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
持久性.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="elearningPU">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<properties>
<property name="hibernate.search.default.optimizer.operation_limit.max" value="1000" />
<property name="hibernate.search.default.optimizer.transaction_limit.max" value="100" />
<!-- <property name="hibernate.search.default.directory_provider" value="fi.foyt.hibernate.gae.search.GaeDirectoryProvider"/> -->
<!-- <property name="hibernate.search.default.worker.backend" value="fi.foyt.hibernate.gae.search.GaeBackendQueueProcessor"/> -->
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
<property name="hibernate.connection.driver_class" value="com.mysql.cj.jdbc.Driver" />
<property name="hibernate.connection.username" value="root" />
<property name="hibernate.connection.password" value="pasw1" />
<!-- shtim -->
<property name="hibernate.enable_lazy_load_no_trans" value="true"/>
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/elearningdb" />
<property name="hibernate.max_fetch_depth" value="3" />
<!-- You may want to change this to false in production -->
<property name="hibernate.show_sql" value="true" />
<!-- You can change this to create at the first time -->
<property name="hibernate.hbm2ddl.auto" value="update" />
<!-- Set this to 0 otherwise you sometimes get errors -->
<property name="hibernate.connection.pool_size" value="0" />
</properties>
</persistence-unit>
</persistence>
applicationContext.xml
<?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:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:p="http://www.springframework.org/schema/p"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitName" value="elearningPU" />
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
<context:component-scan base-package="com.elearning.domain" />
<context:annotation-config/>
<bean id="blogService" class="com.elearning.service.BlogServiceImpl" scope="singleton"/>
<bean id="facade" class="com.elearning.service.FacadeImpl" scope="singleton">
<property name="blogService" ref="blogService"></property>
</bean>
</beans>
spring-servlet.xml
<?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:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:p="http://www.springframework.org/schema/p"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
<context:component-scan base-package="com.elearning.controller" />
<mvc:annotation-driven />
<mvc:default-servlet-handler />
<mvc:resources mapping="/resources/**" location="/resources/" />
<bean id="viewResolver" class="org.springframework.web.servlet.view.tiles3.TilesViewResolver" />
<bean id="tilesConfigurer" class="org.springframework.web.servlet.view.tiles3.TilesConfigurer">
<property name="definitions">
<list>
<value>/WEB-INF/tiles.xml</value>
</list>
</property>
</bean>
</beans>
Eclipse 控制台错误
SEVERE: Servlet.service() for servlet [spring] in context with path [/com.elearning.webapp] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at com.elearning.controller.BlogController.saveValueFromEM(BlogController.java:17)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.base/java.lang.Thread.run(Thread.java:834)
根据你的代码 facade 对象为空。您需要注入 facade 在你 BaseController:
public class BaseController {
@Autowired
public Facade facade;
/**
* Inject Services from Spring
*/
public void setFacade(Facade facade){
this.facade = facade;
}
}
你可以参考这篇类似的文章- Spring可以在抽象类里面自动布线吗？