重写spring jdbcTemplate里面的queryForObject方法的问题

[Eagle昊]

最近实用jdbcTemplate里面的queryForObject方法，在返回空值的时候总是抛出异常，而我想要的是它返回null,后面看了源码，结合度娘得知重写queryForObject里面调用的requiredSingleResult方法可以解决问题，然后写了一个类重写了这个方法，代码如下

public class OverrideJdbcDao extends JdbcTemplate{

	/**
	 * 重写JdbcTemplate里面的queryForObject方法源码调用的requiredSingleResult，当查询到的结果为空时返回null(原来是抛出异常)
	 */
	@Override
	public <T> T queryForObject(String sql, Class<T> requiredType) throws DataAccessException {
		// TODO Auto-generated method stub
		return super.queryForObject(sql, requiredType);
	}
	
	public static <T> T requiredSingleResult(Collection<T> results) throws IncorrectResultSizeDataAccessException {
		int size = (results != null ? results.size() : 0); 
		if (size == 0) {
			return null; 
		} 
		if (results.size() > 1) {
			throw new IncorrectResultSizeDataAccessException(1, size); 
		} 
		return results.iterator().next(); 
	}
}

但是在使用的时候却报错了，错误如下

警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'classesDaoImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.springframework.jdbc.core.JdbcTemplate com.dao.impl.ClassesDaoImpl.db; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [org.springframework.jdbc.core.JdbcTemplate] is defined: expected single matching bean but found 2: jdbcTemplate,OverrideJdbcDao
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'classesDaoImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.springframework.jdbc.core.JdbcTemplate com.dao.impl.ClassesDaoImpl.db; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [org.springframework.jdbc.core.JdbcTemplate] is defined: expected single matching bean but found 2: jdbcTemplate,OverrideJdbcDao
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at com.frame.main.MainFrame.<init>(MainFrame.java:39)
	at com.frame.main.MainFrame$1.run(MainFrame.java:50)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.awt.EventQueue.access$200(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.springframework.jdbc.core.JdbcTemplate com.dao.impl.ClassesDaoImpl.db; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [org.springframework.jdbc.core.JdbcTemplate] is defined: expected single matching bean but found 2: jdbcTemplate,OverrideJdbcDao
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:573)
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
	... 28 more
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [org.springframework.jdbc.core.JdbcTemplate] is defined: expected single matching bean but found 2: jdbcTemplate,OverrideJdbcDao
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1126)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:545)
	... 30 more

我该怎么做才能试用我重写的那个类？

[Eagle昊]

各位前辈帮忙啊

@Repository
public class OJdbcTemplateDaoImpl implements OJdbcTemplateDao {

	@Autowired
	OverrideJdbcDao ojd;
	
	
	@Override
	public int queryforInt(String sql) {
		return ojd.queryForObject(sql,Integer.class);
	}
}

我现在在调用OverrideJdbcDao的时候报错了，最后一步了

[Eagle昊]

我自己找到解决办法了，是因为

<!--  <bean id= "jdbcTemplate" class ="org.springframework.jdbc.core.JdbcTemplate">
               <property name= "dataSource" ref ="dataSource"></property>
        </bean> -->
        
        <!--  配置spring jdbc -->
        <bean id="overrideJdbc" class="com.dao.OverrideJdbc">
         	   <property name= "dataSource" ref ="dataSource"></property>
        </bean>

原本为jdbcTemplate注入了一次dataSource,后面为overrideJdbc又注入了一遍，从而导致冲突报错

[江油儿]

怎么解决的啊，能不能说清楚，我用的是springboot