我在尝试自动装配扩展JdbcDaoSupport的类时收到错误。我把我的DAO类和Controller类分成了两个不同的弹簧上下文。 DAO类位于根上下文中，Controller类位于servlet上下文中。我已经设置了组件扫描，以便在两个上下文之间的bean中没有重叠（这是正确的模式吗？）。所有这些因素加上我的DAO扩展JdbcDaoSupport的事实似乎导致了这个问题，我不明白为什么。我只是学习春天，所以我还没有完全理解所有的概念。
编辑：此行为似乎是由JdbcDaoSupport / DaoSupport实现InitializingBean接口引起的。但仍然感到困惑。
Error creating bean with name 'homeController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.test.dao.CustomerDAO2 org.test.servlet.HomeController.customerDAO; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.test.dao.CustomerDAO2] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
HomeController.java
package org.test.servlet;
import java.util.Locale;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.test.dao.*;
@Controller
public class HomeController
{
@Autowired
CustomerDAO2 customerDAO;
@RequestMapping(value = "/", method = RequestMethod.GET)
public String home(Locale locale, Model model)
{
model.addAttribute("customer", customerDAO.getCustomer());
return "home";
}
}
CustomerDAO2.java
package org.test.dao;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.sql.DataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.*;
import org.springframework.jdbc.core.support.JdbcDaoSupport;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.*;
import org.test.dto.Customer;
@Repository
public class CustomerDAO2 extends JdbcDaoSupport
{
public CustomerDAO2()
{
}
@Autowired
public CustomerDAO2(DataSource datasource)
{
this.setDataSource(datasource);
}
@Transactional
public Customer getCustomer()
{
JdbcTemplate jdbcTemplate = new JdbcTemplate(getDataSource());
Customer customer = jdbcTemplate.queryForObject("select * from customer", new CustomerMapper());
return customer;
}
public static class CustomerMapper implements RowMapper<Customer>
{
public Customer mapRow(ResultSet rs, int rowNum) throws SQLException
{
Customer customer = new Customer();
customer.setCustomerId(rs.getInt("customerId"));
customer.setCustomerNumber(rs.getString("customerNumber"));
return customer;
}
}
}
应用context.xml中
<?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:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<!-- Scans within the base package of the application for @Components to configure as beans -->
<!-- @Controller, @Service, @Configuration, etc. -->
<context:component-scan base-package="org.test">
<context:exclude-filter expression="org.springframework.stereotype.Controller" type="annotation"/>
</context:component-scan>
<!-- Enables the configuration of transactional behavior based on annotations -->
<tx:annotation-driven transaction-manager="transactionManager"/>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost/crm?user=root&password=password" />
</bean>
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
</beans>
servlet的context.xml中
<?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:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<!-- Scans within the base package of the application for @Components to configure as beans -->
<!-- @Controller, @Service, @Configuration, etc. -->
<context:component-scan base-package="org.test.servlet"/>
<!-- Enables the Spring MVC @Controller programming model -->
<mvc:annotation-driven />
<!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/views/" />
<property name="suffix" value=".jsp" />
</bean>
</beans>
答案 0 :(得分：1)
我在这篇文章中找到了答案：
Spring expected at least 1 bean which qualifies as autowire candidate for this dependency
基本上，我需要为我的DAO类创建一个接口。像这样：
public interface ICustomerDAO {
Customer getCustomer();
}
注意：制作更通用的CRUD界面可能会更好。
然后使用接口类型进行依赖注入，而不是使用类类型：
@Autowired
ICustomerDAO customerDAO;
这是必要的原因是因为Spring创建了底层代理类：
http://insufficientinformation.blogspot.com/2007/12/spring-dynamic-proxies-vs-cglib-proxies.html
http://docs.spring.io/spring/docs/2.5.x/reference/aop.html#aop-proxying