没有定义类型 [] 的唯一 bean：预期的单个匹配 bean 但找到 2：[dbImpl，DbImpl] [重复]

Question

您好，我是 Spring 新手：我的项目配置有问题；

这是我的 servlet-context.xml：

    <?xml version="1.0" encoding="UTF-8"?>
    <beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context" 
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure -->

    <!-- Enables the Spring MVC @Controller programming model -->
    <annotation-driven />

    <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
    <resources mapping="/resources/**" location="/resources/" />

    <!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->

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

    <context:component-scan base-package="com.metmi.mmasgis" />

    <beans:bean id="DbImpl" class="com.metmi.mmasgis.dao.DbImpl">
        <beans:property name="dataSource" ref="dataSource" />

    </beans:bean>



    <beans:bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <beans:property name="driverClassName"
            value="com.mysql.jdbc.Driver">
        </beans:property>
        <beans:property name="username" value="root"></beans:property>
        <beans:property name="password" value="vilu7240"></beans:property>
        <beans:property name="url"
            value="jdbc:mysql://localhost:3306/springschema">
        </beans:property>
    </beans:bean>
</beans:beans>

这是我的控制器：

    package com.metmi.mmasgis;

import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Locale;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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 com.metmi.mmasgis.dao.DbImpl;
import com.metmi.mmasgis.model.Db;

/**
 * Handles requests for the application home page.
 */
@Controller
public class HomeController {
    @Autowired
    DbImpl dbs;
    private static final Logger logger = LoggerFactory
            .getLogger(HomeController.class);

    /**
     * Simply selects the home view to render by returning its name.
     */
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String home(Locale locale, Model model) {
        logger.info("Welcome home! The client locale is {}.", locale);

        Date date = new Date();
        DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG,
                DateFormat.LONG, locale);

        String formattedDate = dateFormat.format(date);

        model.addAttribute("serverTime", formattedDate);

        return "home";
    }

    /**
     * get the database list in Mysql
     */
    @RequestMapping(value = "/db", method = RequestMethod.GET)
    public String dbs(Locale locale, Model model) {
        ArrayList<Db> dbList = dbs.getDatabases();
        model.addAttribute("dbList", dbList);
        return "dbs";
    }

    /**
     * Simply shows ciao.
     */
    @RequestMapping(value = "/ciao", method = RequestMethod.GET)
    public String ciao(Locale locale, Model model) {
        logger.info("Welcome home! The client locale is {}.", locale);

        Date date = new Date();
        DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG,
                DateFormat.LONG, locale);

        String formattedDate = dateFormat.format(date);

        model.addAttribute("serverTime", formattedDate);

        return "ciao";
    }

}

这是非常基本的，当我在服务器上运行它时出现此错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'homeController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.metmi.mmasgis.dao.DbImpl com.metmi.mmasgis.HomeController.dbs; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [com.metmi.mmasgis.dao.DbImpl] is defined: expected single matching bean but found 2: [dbImpl, DbImpl]

Answer 1

您在servlet-context.xml 中写道：

<context:component-scan base-package="com.metmi.mmasgis" />

<beans:bean id="DbImpl" class="com.metmi.mmasgis.dao.DbImpl">
    <beans:property name="dataSource" ref="dataSource" />
</beans:bean>

它从 XML 配置中注册了一个 Component，类型为 com.metmi.mmasgis.dao.DbImpl，名称为 DbImpl，并注册了完全相同的类型，名称为 dbImpl，原因是组件扫描 (autodetected components naming)。只需在 config.xml 中省略 DbImpl bean 定义即可。

Answer 2

基本问题是在您的 Spring bean 池中定义了两个相同类型的 bean。有两种方法可以解决这个问题：

1. 正如“Khosrow”所说，从 Spring config XML 文件中删除 DBImpl 声明。
2. 如果您在 DBImpl 类上使用 @Component 注释，则为该注释指定一个值（如 @Component("someOtherDbImpl" )) 然后在你的自动装配中放另一个注释；喜欢：

    @Autowired
    @Qualifier("someOtherDbImpl")
    DbImpl dbs;