使用MyBatis的Java Mapper上的NullPointerException
[英]NullPointerException on java Mapper with MyBatis
问题描述
I'm getting the NullPointerException and I can't figure out where are my mistakes. 
我收到了NullPointerException ，我不知道我的错误在哪里。
The error is in selectByExample function. 错误在selectByExample函数中。 The code is: 代码是：
package com.service.test;
@Service
public class TestService {
[...]
@Autowired
private TestMapper TestMapper;
[...]
public List<Short> test(){
List<Short> lista = new ArrayList<Short>();
testExample me = new testExample();
me.or().andTestEqualTo(1);
List<test> listTest = TestMapper.selectByExample(me); //line 81
for(int i=0; i<listTest.size(); i++){
lista.add(listTest.get(i).getNuovoDb());
}
return lista;
}
Controller.java Controller.java
TestService ms = new TestService();
List<Short> listTest = ms.sediMigrate(); //line 46
The applicationContext is the follow: applicationContext是以下内容：
<!-- enable autowire -->
<context:annotation-config />
<context:component-scan base-package="com.service.test"/>
[...]
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.test.**"/>
<property name="sqlSessionFactoryBeanName" value="exSqlSessionFactory"/>
</bean>
Here there is the error: 这里有错误：
[11/07/14 11.19.33:848 CEST] 0000004f servlet E com.ibm.ws.webcontainer.servlet.ServletWrapper service SRVE0068E: Generata eccezione non rilevata in uno dei metodi di servizio del servlet dispatcher nell'applicazione TestEAR.
[11/07/14 11.19.33:856 CEST] 0000004f FfdcProvider W com.ibm.ws.ffdc.impl.FfdcProvider logIncident FFDC1003I: Emesso evento FFDC in C:\\Program Files\\IBM\\WebSphere\\AppServer\\profiles\\AppSrv01\\logs\\ffdc\\server1_5e0b5e0b_14.07.11_11.19.33.8537970037945028520402.txt com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest() 309 [11/07/14 11.19.33:857 CEST] 0000004f webapp E com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Errore servlet]-[dispatcher]: java.lang.NullPointerException at com.service.test.TestService.test(TestService.java:81) at com.test.controller.ReturnPage(controller.java:46) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:600) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(Handler
1 个解决方案
解决方案1
2 已采纳 2014-07-11 10:09:49
As you use Spring you should avoid explicitly creating your beans (using new operator) - the framework should do it for you. 使用Spring时，应避免显式创建bean（使用new运算符）-框架应为您完成。 And the bean instance should be already in Spring context. 并且bean实例应该已经在Spring上下文中。 If you instantiate your service bean with new nothing will be autowired. 如果用new实例化服务Bean，则不会自动装配任何东西。 Thats why you will have null instead of your mapper instance. 这就是为什么您将使用null而不是您的mapper实例的原因。
Please look info the Spring documentation about dependency injection and beans lifecycle in Spring applications http://docs.spring.io/spring/docs/3.0.x/reference/beans.html#beans-factory-collaborators 请查看有关Spring应用程序中的依赖项注入和bean生命周期的Spring文档http://docs.spring.io/spring/docs/3.0.x/reference/beans.html#beans-factory-collaborators
Update: 更新：
Autowiring TestService into your controller may solve your issue. 将TestService自动TestService到控制器中可能会解决您的问题。
@Controller
public class Controller {
@Autowired private TestService testService;
...
@RequestMapping
public String returnPage() {
...
testService.sediMigrate();
...
}
}
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