带接口的自动装配中的空指针异常

Question

@Service("ProductRestImpl")
@Path("/product")
@Produces(MediaType.APPLICATION_JSON)
public class ProductRestImpl{

 private Logger logger = LoggerFactory.getLogger(ProductRestImpl.class);

    @Autowired
    IProductService productService;

    @GET
    @Path("/getone")
    public Product productById(){

        return productService.getProduct();

    }

    @GET
    @Path("/AllProduct")
    public List<Product> get(){
        logger.info("inside @class ProductRestImpl @method getallProduct entry...");
        try{
              return productService.getAllProduct();
        }catch(Exception e){
            e.printStackTrace();
            logger.error("inside @class ProductRestImpl  @method getallProduct cause:"+e.toString());

            return null;
        }
    }


}  

服务类是：

@Service
@Transactional
public class ProductServiceImpl implements IProductService {
    private Logger logger = LoggerFactory.getLogger(ProductServiceImpl.class);

    @Autowired
    IProductDAO productDAO;

    @Override
    public void addProduct(Product product) {
        // TODO Auto-generated method stub

    }

    @Override
    public void deleteProduct(Integer productId) {
        // TODO Auto-generated method stub

    }


    @Override
    public Product getProduct(){
        return null;
    }

    @Override
    public List<Product> getAllProduct() {
        logger.info("inside @class ProductServiceImpl  @method  getAllProduct entry...");
        try{
            return productDAO.getAllProducts();
        }
        catch(Exception e){
            e.printStackTrace();
            logger.error("inside @class ProductServiceImpl  @method  getAllProduct cause:"+e.toString());
            return null;

        }
    }
   }

道类是：

@Repository
@Transactional
public class ProductDaoImpl implements IProductDAO{

    private final Logger logger = LoggerFactory.getLogger(ProductDaoImpl.class);

    @PersistenceContext
    private EntityManager manager;

    @Override
    public void addProduct(Product product) {
        logger.info("inside @class ProductDaoImpl  @method addProduct entry... ");
        manager.persist(product);
    }

    @Override
    public List<Product> getAllProducts() {

        logger.info("inside @class ProductDaoImpl  @method getAllProducts entry... ");
        try{
            return manager.createQuery("Select p From Product p", Product.class).getResultList();

        }catch(Exception e){
            e.printStackTrace();
            logger.error("inside @class ProductDaoImpl  @method addProduct cause:"+e.toString());

        }
        return null;
    }

    @Override
    public void deleteProduct(Integer productId) {
}

}  

application.xml条目是：

<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.xsds">

    <context:annotation-config/>
    <tx:annotation-driven />
    <context:property-placeholder location="classpath*:*.properties"/>
    <context:component-scan base-package="com.petCart" />

    <bean id="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <!-- This makes /META-INF/persistence.xml is no longer necessary -->
        <property name="packagesToScan" value="com.petCart.model" />
        <!-- JpaVendorAdapter implementation for Hibernate EntityManager.
        Exposes Hibernate's persistence provider and EntityManager extension interface -->
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
        </property>
        <property name="jpaProperties">
        <props>
            <prop key="hibernate.hbm2ddl.auto">create-drop</prop>
            <prop key="hibernate.dialect">${db.dialect}</prop>
        </props>
        </property>
    </bean>

    <!-- Simple implementation of the standard JDBC DataSource interface,
    configuring the plain old JDBC DriverManager via bean properties -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${db.driverClassName}" />
        <property name="url" value="${db.connection.url}" />
        <property name="username" value="${db.connection.username}" />
        <property name="password" value="${db.connection.password}" />
    </bean>

    <!-- This transaction manager is appropriate for applications that use a single JPA EntityManagerFactory for transactional data access.
    JTA (usually through JtaTransactionManager) is necessary for accessing multiple transactional resources within the same transaction. -->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactoryBean" />
    </bean>
    <bean  class="com.petCart.rest.impl.ProductRestImpl"/>


</beans>  

web.xml条目是：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_3_0.xsd"
    version="3.0">
    <display-name>petCart</display-name>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/classes/application.xml</param-value>
    </context-param>

    <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>

    <servlet>
        <servlet-name>rest-ws</servlet-name>
        <servlet-class>
            com.sun.jersey.spi.container.servlet.ServletContainer
        </servlet-class>
        <init-param>
            <param-name>com.sun.jersey.config.property.packages</param-name>
            <param-value>com.petCart.rest</param-value>
        </init-param>
        <init-param>
            <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
            <param-value>true</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>rest-ws</servlet-name>
        <url-pattern>/rest/*</url-pattern>
    </servlet-mapping>


</web-app>  

当我运行此代码时，从命中浏览器获取空指针异常。我厌倦了main方法，它在从自动连接接口调用时给我空指针。

这是我的stacktrace：

java.lang.NullPointerException
    at com.petCart.rest.impl.ProductRestImpl.productById(ProductRestImpl.java:45)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
    at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$TypeOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:185)
    at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
    at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1542)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1473)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1419)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1409)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:409)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:540)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:715)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1008)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

Dec 01, 2015 1:33:46 PM com.sun.jersey.spi.container.ContainerResponse mapMappableContainerException
SEVERE: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container
java.lang.NullPointerException
    at com.petCart.rest.impl.ProductRestImpl.productById(ProductRestImpl.java:45)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
    at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$TypeOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:185)
    at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
    at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1542)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1473)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1419)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1409)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:409)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:540)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:715)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1008)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)