autowiring bean在春天失敗了mvc jadbc webapp

Question

我正在學習使用spring。我正在開發一個使用spring和jdbc的應用程序。我在運行時遇到以下異常。

Nov 03, 2015 2:42:22 PM org.apache.catalina.core.ApplicationContext log 
SEVERE: StandardWrapper.Throwable 
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'studentController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.dao.StudentDaoImp com.controller.StudentController.studentDaoImp; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'studentDaoImp' defined in file [C:\Users\Mrunal\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\SpringMVC\WEB-INF\classes\com\dao\StudentDaoImp.class]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dao.StudentDaoImp]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Property 'dataSource' is required 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1210) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755) 
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757) 
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480) 
    at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663) 
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:629) 
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:677) 
    at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:548) 
    at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489) 
    at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136) 
    at javax.servlet.GenericServlet.init(GenericServlet.java:158) 
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1284) 
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1197) 
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1087) 
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5253) 
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5543) 
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) 
    at org.apache.catalina.core.StandardContext.reload(StandardContext.java:4020) 
    at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:425) 
    at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1344) 
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1545) 
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1555) 
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1555) 
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1523) 
    at java.lang.Thread.run(Unknown Source) 
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.dao.StudentDaoImp com.controller.StudentController.studentDaoImp; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'studentDaoImp' defined in file [C:\Users\Mrunal\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\SpringMVC\WEB-INF\classes\com\dao\StudentDaoImp.class]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dao.StudentDaoImp]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Property 'dataSource' is required 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:561) 
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331) 
    ... 31 more 
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'studentDaoImp' defined in file [C:\Users\Mrunal\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\SpringMVC\WEB-INF\classes\com\dao\StudentDaoImp.class]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dao.StudentDaoImp]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Property 'dataSource' is required 
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:275) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1139) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1042) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1120) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1044) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:942) 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533) 
    ... 33 more 
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.dao.StudentDaoImp]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Property 'dataSource' is required 
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163) 
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:122) 
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:267) 
    ... 45 more 
Caused by: java.lang.IllegalArgumentException: Property 'dataSource' is required 
    at org.springframework.jdbc.support.JdbcAccessor.afterPropertiesSet(JdbcAccessor.java:135) 
    at org.springframework.jdbc.core.JdbcTemplate.<init>(JdbcTemplate.java:169) 
    at com.dao.StudentDaoImp.<init>(StudentDaoImp.java:18) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) 
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) 
    at java.lang.reflect.Constructor.newInstance(Unknown Source) 
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147) 
    ... 47 more 

我的分發程序Servlet的樣子

<!-- declaring base package --> 
<context:component-scan base-package="com" /> 

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



<!-- declare datasource bean --> 
<bean id="dataSource" 
    class="org.springframework.jdbc.datasource.DriverManagerDataSource"> 
    <property name="driverClassName" value="com.microsoft.sqlserver.jdbc.SQLServerDriver" /> 
    <property name="url" 
     value="jdbc:sqlserver://localhost:49155;databaseName=Test;instancename=mssqlserver1;" /> 
    <property name="username" value="sa" /> 
    <property name="password" value="abc123" /> 
</bean> 

<bean id="StudentDao" class="com.dao.StudentDaoImp" > 
<constructor-arg ref="dataSource" /> 
</bean> 

and my controller class looks like 
public class StudentDaoImp { 

@Autowired 
DataSource dataSource; 

JdbcTemplate jdbcTemplateObject = new JdbcTemplate(dataSource); 

@Autowired 
public StudentDaoImp(DataSource dataSource) 
{ 
    this.dataSource = dataSource; 
} 


public void create(String name, Integer age) { 
    String SQL = "insert into Student (name, age) values (?, ?)"; 

    jdbcTemplateObject.update(SQL, name, age); 
    System.out.println("Created Record Name = " + name + " Age = " + age); 
    return; 
} 


public Student getStudent(Integer id) { 
    String SQL = "select * from Student where id = ?"; 
    Student student = jdbcTemplateObject.queryForObject(SQL, 
      new Object[]{id}, new StudentMapper()); 
    return student; 
} 

}

我試過很多的選擇，但我無法找出錯誤。任何人都可以知道答案嗎？

Answer 1

問題已解決。

由於此聲明而產生問題 JdbcTemplate jdbcTemplateObject = new JdbcTemplate（dataSource）;

實例變量在構造函數之前被初始化，因此它將空變量用於數據源。

我下面

JdbcTemplate jdbcTemplateObject; 
@Autowired 
public StudentDaoImp(DataSource dataSource) 
{ 
this.dataSource = dataSource; 
jdbcTemplateObject = new JdbcTemplate(this.dataSource); 
}