相同Bean分別被Spring MVC子容器與Spring父容器初始化，致使@Value注入失敗

1 問題描述

在車保養項目開發過程當中，技術架構：Spring MVC + MyBatis；Service層接口中屬性，若是使用註解@Value注入，不可以拿到Properties文件中拿到對應的key值；但在Spring配置文件applicationContext-xxx.xml文件中配置的Properties就能夠拿到。具體項目中相關代碼以下：

Spring MVC的dispatcher-servlet.xml文件：

<?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" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <!-- 自定義的參數解析器放在第一位置 -->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
        <!-- 自定義參數解析器 -->
        <property name="customArgumentResolvers">
            <list>
                <bean class="com.qding.base.resolver.ArgumentFromJsonResolver" />
            </list>
        </property>
    </bean>

    <!-- 開啓組件掃描 -->
    <!-- 對包中的全部類進行掃描，以完成Bean建立和自動依賴注入的功能 -->
    <context:component-scan base-package="com.qding"/>

    <!-- 開啓註解 -->
    <mvc:annotation-driven />

    <!-- 啓用AspectJ對Annotation的支持 -->
    <aop:aspectj-autoproxy proxy-target-class="true"/>

    <!-- 靜態資源路徑 -->
    <mvc:resources location="/easyui/" mapping="/easyui/**"/>
    <mvc:resources location="/js/" mapping="/js/**"/>
    <mvc:resources location="/html/" mapping="/html/**"/>

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

    <!-- 配置多請求數據類型，如json xml-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- set the max upload size10MB -->
        <property name="defaultEncoding" value="UTF-8" />
        <property name="maxUploadSize" value="10485760" />
        <property name="maxInMemorySize" value="10240" />
    </bean>

    <!-- 配置Controller攔截器 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <mvc:exclude-mapping path="/remote/imessage"/>
            <mvc:exclude-mapping path="/easyui/**"/>
            <mvc:exclude-mapping path="/js/**"/>
            <mvc:exclude-mapping path="/html/**"/>
            <bean class="com.qding.base.interceptor.TransferSecurityInterceptor"/>
        </mvc:interceptor>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <mvc:exclude-mapping path="/remote/imessage"/>
            <mvc:exclude-mapping path="/easyui/**"/>
            <mvc:exclude-mapping path="/js/**"/>
            <mvc:exclude-mapping path="/html/**"/>
            <bean class="com.qding.doc.interceptor.TransferDocInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

    <!-- 切面配置：Controller方法參數校驗 -->
    <bean class="com.qding.base.aspect.ParameterValidateAspect" />
</beans>
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Spring的applicationContext-service.xml文件：

<?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:context="http://www.springframework.org/schema/context" xmlns:task="http://www.springframework.org/schema/task" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="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 http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!-- 開啓組件掃描 -->
    <!-- 對包中的全部類進行掃描，以完成Bean建立和自動依賴注入的功能 -->
    <context:component-scan base-package="com.qding.*.*.service"/>

    <!-- 定時任務 -->
    <task:annotation-driven/>

    <!-- 啓用AspectJ對Annotation的支持 -->
    <aop:aspectj-autoproxy/>

    <!-- Transaction Support -->
    <tx:advice id="useTxAdvice" transaction-manager="txManager">
        <tx:attributes>
            <tx:method name="*remove*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception"/>
            <tx:method name="*save*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="*modify*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="*update*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="create*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="fill*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="cancel*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="*chang*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />

            <tx:method name="find*" propagation="SUPPORTS"/>
            <tx:method name="get*" propagation="SUPPORTS"/>
            <tx:method name="query*" propagation="SUPPORTS"/>
            <tx:method name="page*" propagation="SUPPORTS"/>
            <tx:method name="count*" propagation="SUPPORTS"/>
        </tx:attributes>
    </tx:advice>

    <!--把事務控制在Service層-->
    <aop:config>
        <aop:pointcut id="pc" expression="execution(public * com.qding..service.*.*(..))" />
        <aop:advisor pointcut-ref="pc" advice-ref="useTxAdvice" />
    </aop:config>

    <!-- 切面配置：Service層方法執行日誌 -->
    <bean class="com.qding.aspect.ServiceVersionLogAspect" />

    <!--memcached客戶端配置-->
    <bean name="xmemcachedClientBuilder" class="net.rubyeye.xmemcached.XMemcachedClientBuilder">
        <constructor-arg>
            <list>
                <bean class="java.net.InetSocketAddress">
                    <constructor-arg>
                        <value>${server_1}</value>
                    </constructor-arg>
                    <constructor-arg>
                        <value>${port_1}</value>
                    </constructor-arg>
                </bean>
            </list>
        </constructor-arg>
        <constructor-arg>
            <list>
                <value>${priority_1}</value>
            </list>
        </constructor-arg>
        <property name="connectionPoolSize" value="6"/>
        <property name="commandFactory">
            <bean class="net.rubyeye.xmemcached.command.BinaryCommandFactory"/>
        </property>
        <property name="sessionLocator">
            <bean class="net.rubyeye.xmemcached.impl.KetamaMemcachedSessionLocator"/>
        </property>
        <property name="transcoder">
            <bean class="net.rubyeye.xmemcached.transcoders.SerializingTranscoder" />
        </property>
    </bean>

    <bean name="xmemcachedClient" factory-bean="xmemcachedClientBuilder" factory-method="build" destroy-method="shutdown">
        <property name="opTimeout" value="3000"/>
    </bean>

    <bean id="memCacheUtil" class="com.qding.member.common.cache.MemCacheUtil">
        <!-- 過時時間 單位秒 -->
        <property name="expTime" value="3600"/>
        <!-- 操做失效時間 單位毫秒 -->
        <property name="opTime" value="3000"/>
        <property name="memcachedClient" ref="xmemcachedClient"/>
    </bean>
</beans>
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Service層OrderServiceImpl的代碼：

public class OrderServiceImpl implements OrderService {
    
        @Value("${bopai.provider_id}")
        private String bopaiProviderId;

        @Value("${bopai.provider_name}")
        private String bopaiProviderName;

        @Value("${bopai.connect.phone}")
        private String boPaiPhone;

        ......
    }
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2 排查過程

1. Spring的applicationContext-service.xml文件配置的屬性，能夠正常拿到Properties文件中的值；【正常】
2. 項目工程的Service層OrderServiceImpl實現，@Value不能拿到Properties文件中的值；【不正常】
3. 代碼斷點調試：發現OrderServiceImpl被初始化了兩次，第一次@Value能夠拿到值，第二次@Value沒有拿到值；【不正常】
4. 發現根本緣由：Spring 容器和Spring MVC容器分別都初始化了Service的實例，後者第二次初始化Service實例時，沒有拿到@Value值，該實例覆蓋掉了Spring 容器初始化的實例；

3 解決方案

經過修改兩個配置文件的<context:component-scan base-package=""/>掃包範圍，達到如下效果：

1. Spring MVC的配置文件dispatcher-servlet嚴格限制只初始化Controller層實例；
2. Spring的配置文件applicationContext-service.xml嚴格限制只初始化除Controller層的其餘層實例；

修改後的配置文件：

1. Spring MVC的dispatcher-servlet.xml文件：

<?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" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <!-- 自定義的參數解析器放在第一位置 -->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
        <!-- 自定義參數解析器 -->
        <property name="customArgumentResolvers">
            <list>
                <bean class="com.qding.base.resolver.ArgumentFromJsonResolver" />
            </list>
        </property>
    </bean>

    <!-- 開啓組件掃描 -->
    <!-- 對包中的全部類進行掃描，以完成Bean建立和自動依賴注入的功能 -->
    <context:component-scan base-package="com.qding.*.*.controller,com.qding.*.controller"/>

    <!-- 開啓註解 -->
    <mvc:annotation-driven />

    <!-- 啓用AspectJ對Annotation的支持 -->
    <aop:aspectj-autoproxy proxy-target-class="true"/>

    <!-- 靜態資源路徑 -->
    <mvc:resources location="/easyui/" mapping="/easyui/**"/>
    <mvc:resources location="/js/" mapping="/js/**"/>
    <mvc:resources location="/html/" mapping="/html/**"/>

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

    <!-- 配置多請求數據類型，如json xml-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- set the max upload size10MB -->
        <property name="defaultEncoding" value="UTF-8" />
        <property name="maxUploadSize" value="10485760" />
        <property name="maxInMemorySize" value="10240" />
    </bean>

    <!-- 配置Controller攔截器 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <mvc:exclude-mapping path="/remote/imessage"/>
            <mvc:exclude-mapping path="/easyui/**"/>
            <mvc:exclude-mapping path="/js/**"/>
            <mvc:exclude-mapping path="/html/**"/>
            <bean class="com.qding.base.interceptor.TransferSecurityInterceptor"/>
        </mvc:interceptor>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <mvc:exclude-mapping path="/remote/imessage"/>
            <mvc:exclude-mapping path="/easyui/**"/>
            <mvc:exclude-mapping path="/js/**"/>
            <mvc:exclude-mapping path="/html/**"/>
            <bean class="com.qding.doc.interceptor.TransferDocInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

    <!-- 切面配置：Controller方法參數校驗 -->
    <bean class="com.qding.base.aspect.ParameterValidateAspect" />
</beans>
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2. Spring的applicationContext-service.xml文件：

<?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:context="http://www.springframework.org/schema/context" xmlns:task="http://www.springframework.org/schema/task" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="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 http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!-- 開啓組件掃描 -->
    <!-- 對包中的全部類進行掃描，以完成Bean建立和自動依賴注入的功能 -->
    <context:component-scan base-package="com.qding.*.*.service,com.qding.*.*.imessage,com.qding.*.quartz,com.qding.remote.service"/>

    <!-- 定時任務 -->
    <task:annotation-driven/>

    <!-- 啓用AspectJ對Annotation的支持 -->
    <aop:aspectj-autoproxy/>

    <!-- Transaction Support -->
    <tx:advice id="useTxAdvice" transaction-manager="txManager">
        <tx:attributes>
            <tx:method name="*remove*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception"/>
            <tx:method name="*save*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="*modify*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="*update*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="create*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="fill*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="cancel*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />
            <tx:method name="*chang*" propagation="REQUIRED" read-only="false" rollback-for="java.lang.Exception" />

            <tx:method name="find*" propagation="SUPPORTS"/>
            <tx:method name="get*" propagation="SUPPORTS"/>
            <tx:method name="query*" propagation="SUPPORTS"/>
            <tx:method name="page*" propagation="SUPPORTS"/>
            <tx:method name="count*" propagation="SUPPORTS"/>
        </tx:attributes>
    </tx:advice>

    <!--把事務控制在Service層-->
    <aop:config>
        <aop:pointcut id="pc" expression="execution(public * com.qding..service.*.*(..))" />
        <aop:advisor pointcut-ref="pc" advice-ref="useTxAdvice" />
    </aop:config>

    <!-- 切面配置：Service層方法執行日誌 -->
    <bean class="com.qding.aspect.ServiceVersionLogAspect" />

    <!--memcached客戶端配置-->
    <bean name="xmemcachedClientBuilder" class="net.rubyeye.xmemcached.XMemcachedClientBuilder">
        <constructor-arg>
            <list>
                <bean class="java.net.InetSocketAddress">
                    <constructor-arg>
                        <value>${server_1}</value>
                    </constructor-arg>
                    <constructor-arg>
                        <value>${port_1}</value>
                    </constructor-arg>
                </bean>
            </list>
        </constructor-arg>
        <constructor-arg>
            <list>
                <value>${priority_1}</value>
            </list>
        </constructor-arg>
        <property name="connectionPoolSize" value="6"/>
        <property name="commandFactory">
            <bean class="net.rubyeye.xmemcached.command.BinaryCommandFactory"/>
        </property>
        <property name="sessionLocator">
            <bean class="net.rubyeye.xmemcached.impl.KetamaMemcachedSessionLocator"/>
        </property>
        <property name="transcoder">
            <bean class="net.rubyeye.xmemcached.transcoders.SerializingTranscoder" />
        </property>
    </bean>

    <bean name="xmemcachedClient" factory-bean="xmemcachedClientBuilder" factory-method="build" destroy-method="shutdown">
        <property name="opTimeout" value="3000"/>
    </bean>

    <bean id="memCacheUtil" class="com.qding.member.common.cache.MemCacheUtil">
        <!-- 過時時間 單位秒 -->
        <property name="expTime" value="3600"/>
        <!-- 操做失效時間 單位毫秒 -->
        <property name="opTime" value="3000"/>
        <property name="memcachedClient" ref="xmemcachedClient"/>
    </bean>
</beans>
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4 問題總結

Spring MVC容器是Spring容器的一個子容器，它一樣可以初始化實體類。因爲SpringMVC容器的初始化是在Spring容器初始化以後，因此它會替換Spring中已經存在的類，這樣可能會致使衝突。所以在Spring的配置文件中SpringMVC和Spring容器各司其職，在使用ComponentScan進行掃描時，各自掃描各自的實體類。以下配置：

1. Spring容器掃描配置：

<context:component-scan base-package="com.projects.system">
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller" />         
    </context:component-scan>
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2. SpringMVC容器掃描配置：

<context:component-scan base-package="com.projects.system">
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Service"/>
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
    </context:component-scan>
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以上配置在使用Spring xml-based配置時是沒有問題的。若是在項目中引入java-base配置時，同時引入了@Configuration註解，@Configuration註解是在Spring容器初始化時進行實體類的初始化工做，所以在Spring MVC掃描配置中要將其過濾掉，不然會致使SpringMVC 的rest地址不可訪問的問題。新的配置以下：

<context:component-scan base-package="com.projects.system">
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Service"/>
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
        <!-- 不掃描配置文件類，避免重複初始化 -->
        <context:exclude-filter type="annotation" expression="org.springframework.context.annotation.Configuration"/>
    </context:component-scan>
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