一个简单的依赖注入

Question

我想问下，能不能使用内部bean实现构造注入啊？<bean id="personService" class="cn.itcast.service.impl.PersonServiceBean" >
<constructor-arg index="0" ref="personDao" type="cn.itcast.dao.PersonDao" />
<constructor-arg index="1" value="构造注入" type="java.lang.String"/>
<property name="personDao1">
<bean class="cn.itcast.dao.impl.PersonDaoBean" /> 
</property>
</bean>
这时配置文件，执行报错了；Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personService' defined in class path resource [applicationContext.xml]: Cannot resolve reference to bean 'personDao' while setting constructor argument; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'personDao' is defined
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:275)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:104)
at org.springframework.beans.factory.support.ConstructorResolver.resolveConstructorArguments(ConstructorResolver.java:479)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:162)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:925)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:835)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:440)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
at java.security.AccessController.doPrivileged(Native Method)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
at test.SpringTest.main(SpringTest.java:16)
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'personDao' is defined
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:387)
at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:971)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:246)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269)
... 20 more

Answer 1

<constructor-arg index="0" ref="personDao" type="cn.itcast.dao.PersonDao" />
这句有问题
可以这么写
<constructor-arg index="0" ref="personDao" />
<bean class="cn.itcast.dao.impl.PersonDaoBean" id="personDao"/>  

Answer 2

不行，报错了
No constructor with 1 argument defined in class 'cn.itcast.service.impl.PersonServiceBean'

Answer 3

No bean named 'personDao' is defined

Answer 4

能不能使用内部bean实现构造注入啊?有没有这个功能的，在spring里面，我知道有内部bean实现set注入，但是构造注入就不知道了

Answer 5

personDao 访问不到。可能在访问不到的文件里 也有可能是顺序问题。

Answer 6

能不能使用内部bean实现构造注入啊?有没有这个功能的，在spring里面，我知道有内部bean实现set注入，但是构造注入就不知道了

Answer 7

为什么要构造注入呢 set注入是普遍的比较好的

Answer 8

++1
另外这类配置文件 要细心。
'personDao' 这个东西在这里找不到配置

Answer 9

所谓构造注入，创建对象调用相应的构造函数。应该是你的配置和你的所想注入的构造函数不匹配的缘故。
比如
public class Person{
   private Car car;
   public Person(){}
   public Person(Car car){this.car=car;}
……
}
现在你应该想构造注入 public Person(Car car)
那么配置应该是
<bean id="person" class=....>
   <Constructor-arg><ref bean="宝马"/> </Constructor-arg>
</bean>
<bean id="宝马" class=..../>