獲得空指針異常，而在春天MVC

它的我第一次集成Spring和Hibernate，當我調用DAO類的任何方法，我得到空指針異常獲得空指針異常，而在春天MVC

我使用抽象工廠模式抽象類中使用抽象工廠模式的源代碼：

public abstract class Content { 

    @Autowired 
    HibernateOperations ho; 

    @Transactional 
    public List<ContentDes> getContentDes(String sql,int limit){ 

     //do it with autowired 


     List<Object[]> ls = new ArrayList<Object[]>(); 
     List<ContentDes> contentDes_ls = new ArrayList<ContentDes>(); 

     System.out.println("--before invoking method---"); 
     ho.just_print(); 

     ls = ho.getResultListByLimit(sql,limit); 


     for(Object[] obj: ls){ 
       ContentDes contentDes = new ContentDes(); 
       contentDes.setCode((String)obj[0]); 
       contentDes.setContent_prv((String)obj[1]); 
       contentDes.setPricetag((String)obj[2]); 
       contentDes_ls.add(contentDes); 
      } 
     return contentDes_ls; 

    } 

    abstract List<ContentDes> getRandomContent(int limit); 
    //abstract List<ContentDes> getDistinctCat(); 

}

，我已經被延長我的內容類五級：中編碼我下面的子ID列姆之一：

public class Wallpaper extends Content{ 



    @Override 
    public List<ContentDes> getRandomContent(int limit) { 
      String sql = "select code,prv,pricetag from Wallpaper where cat not like 'Holy Deities' order by rand() limit "+limit+""; 
      List<ContentDes> contentDes_ls = new ArrayList<ContentDes>(); 
      contentDes_ls = getContentDes(sql,limit); 
     return contentDes_ls; 
    } 


}

和階級根據內容類型其返回clasess obects是：

public class GetContentFactory { 

    //use getContent method to get object of type Content 
    public Content getContent(String contentType) { 
     contentType = contentType.toLowerCase(); 

     if (contentType.equalsIgnoreCase("wallpaper")) { 

      return new Wallpaper(); 
     } else if (contentType.equalsIgnoreCase("animation")) { 

      return new Animation(); 
     } else if (contentType.equalsIgnoreCase("ringtone")) { 

      return new Ringtone(); 
     } else if (contentType.equalsIgnoreCase("video")) { 

      return new Video(); 
     } 
     else if (contentType.equalsIgnoreCase("game")) { 

      return new Game(); 
     } 
     else { 
      System.out.println(" unknow request in GetContentFactory class"); 
} 
     return null; 
    } 
}//end of GetContentFactory class.

我的主類是：

public class GetContent { 

    GetContentFactory contentFactory = new GetContentFactory(); 


    } 

    public List<ContentDes> getRandomContent(String content_type, int limit) { 
     List<ContentDes> contentDes_ls = new ArrayList<ContentDes>(); 
     Content con = contentFactory.getContent(content_type); 
     contentDes_ls = con.getRandomContent(limit); 
     for (ContentDes contentDes : contentDes_ls) { 
      System.out.println("prv----"+contentDes.getContent_prv()); 

    } 

     return contentDes_ls; 
    } 


}

我DAO類的代碼是：

@Repository 
public class HibernateOperations { 
    private SessionFactory sessionFactory; 


    public void setSessionFactory(SessionFactory sf){ 
     this.sessionFactory = sf; 
    } 

    //pass the sql query to get result for multiple column 
    public List<Object[]> getResultListByLimit(String query,int limit){ 

     System.out.println("in get result-------"); 

      Session session = this.sessionFactory.getCurrentSession(); 
      List<Object[]> ls_ob = new ArrayList<Object[]>(); 
      Query q = session.createQuery(query); 
      q.setMaxResults(limit); 
      ls_ob = (List<Object[]>)q.list(); 
      return ls_ob; 

} 


public List<Object> getListForSingleColumn(String query){ 
     Session session = this.sessionFactory.getCurrentSession(); 
      List<Object> ls_ob = new ArrayList<Object>(); 
      Query q = session.createQuery(query); 
      ls_ob = q.list(); 
      return ls_ob; 
     } 

    public void SaveObject(Object obj){ 

     Session session = this.sessionFactory.getCurrentSession(); 
     List<Object[]> ls_ob = new ArrayList<Object[]>(); 
     session.save(obj); 
     } 


    public void just_print(){ 
     System.out.println("---------in method hibenate operation------"); 
    } 

}

當我的控制器類方法調用：

的getContent GC =新的getContent（）;
List<ContentDes> contentDes_ls = new ArrayList<ContentDes>(); 
    contentDes_ls = gc.getRandomContent("wallpaper", 3); 
我有一個例外：

其打印出

--before invoking method---(its is the sout of my content class method Name "getContentDes") 

Apr 25, 2016 6:03:04 PM org.apache.catalina.core.StandardWrapperValve invoke 
SEVERE: Servlet.service() for servlet [DefaultServlet] in context with path [/slwap_sh] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause 
java.lang.NullPointerException 
    at lanka.content.get.Content.getContentDes(Content.java:37) 
    at lanka.content.get.Wallpaper.getRandomContent(Wallpaper.java:45) 
    at lanka.content.controller.ContentController.sriWap(ContentController.java:65) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:222) 
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) 
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:814) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:737) 
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) 
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:860) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:674) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Unknown Source)

我無法打電話給我的任何DAO類的方法，我得到空指針當我叫任我的Dao的方法（HibernateOperations.java）類

任何人都可以ASE幫我找出我的錯誤
DefaultServlet-servlet.xml中的
編碼是象下面這樣：

<?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:mvc="http://www.springframework.org/schema/mvc" 
    xmlns:tx="http://www.springframework.org/schema/tx" 
    xmlns:aop="http://www.springframework.org/schema/aop" 
    xsi:schemaLocation="http://www.springframework.org/schema/beans 

http://www.springframework.org/schema/beans/spring-beans.xsd 
http://www.springframework.org/schema/context 
http://www.springframework.org/schema/context/spring-context.xsd 
http://www.springframework.org/schema/mvc 
http://www.springframework.org/schema/mvc/spring-mvc.xsd 
http://www.springframework.org/schema/tx 
http://www.springframework.org/schema/tx/spring-tx.xsd 
http://www.springframework.org/schema/aop 
http://www.springframework.org/schema/aop/spring-aop.xsd"> 


    <mvc:annotation-driven /> 
    <mvc:annotation-driven enable-matrix-variables="true" /> 
    <context:component-scan base-package="lanka.content.controller" /> 
    <context:component-scan base-package="lanka.content.domain" /> 
    <context:component-scan base-package="lanka.content.utility" /> 

    <bean 
     class="org.springframework.web.servlet.view.InternalResourceViewResolver"> 
     <property name="prefix" value="/WEB-INF/jsp/" /> 
     <property name="suffix" value=".jsp" /> 
    </bean> 

<!-- start of languages xml code --> 


<!-- lang param is defined in the mvc interceptor --> 

    <bean id="messageSource" 
     class="org.springframework.context.support.ReloadableResourceBundleMessageSource"> 
     <property name="basename" value="WEB-INF/propFiles/content" /> 
     <property name="defaultEncoding" value="UTF-8" /> 

    </bean> 

    <bean id="localeResolver" 
     class="org.springframework.web.servlet.i18n.CookieLocaleResolver"> 
     <property name="defaultLocale" value="en" /> 

    </bean> 


    <!-- end of languages xml code --> 

    <mvc:interceptors> 
     <mvc:interceptor> 
      <mvc:mapping path="/**" /> 

     <bean 
      class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor"> 
      <property name="paramName" value="lang" /> 
     </bean> 
     </mvc:interceptor> 




     <!-- <mvc:interceptor> 
      <mvc:mapping path="/**" /> 
      <mvc:exclude-mapping path="/resources/**"/> 
      <bean id="storingWapHits" 
       class="vodafone.interceptor.StroringHits"> 

      </bean> 
     </mvc:interceptor> --> 

     </mvc:interceptors> 

    <mvc:resources mapping="/resources/**" location="/resources/design/" /> 

<!-- start of hibernate integration --> 


    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" 
     destroy-method="close"> 
     <property name="driverClassName" value="com.mysql.jdbc.Driver" /> 
     <property name="url" value="jdbc:mysql://localhost:3306/wapsite" /> 
     <property name="username" value="root" /> 
     <property name="password" value="" /> 
    </bean> 


<!-- hibernate4AnnotatedSessionFactory is a session fectory--> 
    <!-- Hibernate 4 SessionFactory Bean definition --> 
    <bean id="hibernate4AnnotatedSessionFactory" 
     class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> 
     <property name="dataSource" ref="dataSource" /> 
     <property name="annotatedClasses"> 
      <list> 

       <value>lanka.content.table.Game</value> 
       <value>lanka.content.table.Scrsaver</value> 
       <value>lanka.content.table.Video</value> 
       <value>lanka.content.table.Wallpaper</value> 



      </list> 
     </property> 
     <property name="hibernateProperties"> 
      <props> 
       <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect 
       </prop> 
       <prop key="hibernate.show_sql">true</prop> 
      </props> 
     </property> 
    </bean> 

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


    <bean id="transactionManager" 
     class="org.springframework.orm.hibernate4.HibernateTransactionManager"> 
     <property name="sessionFactory" ref="hibernate4AnnotatedSessionFactory" /> 
    </bean> 

    <!-- <bean id="personService" class="com.journaldev.spring.service.PersonServiceImpl"> 
     <property name="personDAO" ref="personDAO"></property> 
    </bean>--> 


     <bean id="HibernateOperations" class="lanka.content.utility.HibernateOperations"> 
     <property name="sessionFactory" ref="hibernate4AnnotatedSessionFactory" /> 
    </bean> 




</beans>

來源

2016-04-25 Kunal Batra

你'@ Autowired'在'Content'類引用名稱浩'HibernateOperations'類。但是bean的id不存在於bean.xml文件中。 '@ Autowired'註釋後面添加'@Qualifier（「HibernateOperations」）''。 –

這樣做：

new Wallpaper();

你是不是讓春天做他的工作，也就是說在物體中注入東西：

@Autowired 
HibernateOperations ho;

ho將始終爲空。

每Content子類應春豆，你必須擺脫你的GetContentFactory，只有自動裝配的每一個春天豆

編輯：抽象工廠設計

定義你的bean是這樣的：

@Component 
@Scope(BeanDefinition.SCOPE_PROTOTYPE) 
public class Wallpaper extends Content {

聲明GetContentFactory作爲彈簧豆，以及：

@Component 
public class GetContentFactory { 

    @Autowired 
    private Wallpaper wallpaper;

這必須避免還有：

GetContentFactory contentFactory = new GetContentFactory();

來源

2016-04-25 13:12:28 Pras

那麼有什麼方法可以在我的代碼中使用抽象工廠設計parttern？ –

我應該改變我的編碼風格嗎？ –

對不起，讓我編輯我的答案... 5分鐘;-) – Pras

獲得空指針異常，而在春天MVC

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