沒有定義類型爲[]的唯一bean：期望單個匹配的bean但找到2：[dbImpl，DbImpl]

Question

您好我是Spring的新手：我有一個與我的項目配置有關的問題;

這是我的servlet-context.xml中：

<?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> 

這是我的控制器：

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"; 
    } 

} 

這是非常基本的，我得到這個錯誤，當我在服務器上運行它：

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

在你servlet-context.xml你寫道：

<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> 

它註冊與從XML配置的com.metmi.mmasgis.dao.DbImpl類型和DbImpl名稱的Component，並註冊該類型完全相同的，與由於元器件掃描（autodetected components naming）的dbImpl名稱。只需在config.xml中省略DbImpl bean定義即可。

Answer 2

基本問題是在spring bean池中定義了兩個相同類型的bean。有兩種方法可以解決此問題：

1. 作爲 「Khosrow」 說，從Spring配置XML文件中刪除DBImpl聲明。
2. 如果你正在使用你的DBImpl類@Component註釋，然後給一個值，註釋（如@Component（「someOtherDbImpl」）），然後在你的自動裝配把另一個註釋;像：

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