java.lang.NumberFormatException: For input string: "${jdbc.maxActive}"

1、問題

使用SpringMVC和MyBatis整合，將jdbc配置隔離出來的時候出現下面的錯誤，百度了好久沒有找到解決方法，回家谷歌下，就找到解決方法了，不得不說谷歌就是強大，不廢話，下面是具體的錯誤：

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mySqlDataSource' defined in ServletContext resource [/WEB-INF/classes/config/spring/daoSource.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type [java.lang.String] to required type [int] for property 'maxActive'; nested exception is java.lang.NumberFormatException: For input string: "${jdbc.maxActive}"
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351)
    ... 41 more
Caused by: org.springframework.beans.TypeMismatchException: Failed to convert property value of type [java.lang.String] to required type [int] for property 'maxActive'; nested exception is java.lang.NumberFormatException: For input string: "${jdbc.maxActive}"
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:596)
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertForProperty(AbstractNestablePropertyAccessor.java:603)
    at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:216)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1527)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1486)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1226)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
    ... 47 more
Caused by: java.lang.NumberFormatException: For input string: "${jdbc.maxActive}"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:569)
    at java.lang.Integer.valueOf(Integer.java:766)
    at org.springframework.util.NumberUtils.parseNumber(NumberUtils.java:208)
    at org.springframework.beans.propertyeditors.CustomNumberEditor.setAsText(CustomNumberEditor.java:113)
    at org.springframework.beans.TypeConverterDelegate.doConvertTextValue(TypeConverterDelegate.java:468)
    at org.springframework.beans.TypeConverterDelegate.doConvertValue(TypeConverterDelegate.java:441)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:199)
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:576)
    ... 53 more

 2、出現緣由

　　這個問題是沒法識別佔位符，就是在加載過程當中直接把 ${jdbc.maxActive }當作字符串處理了。myabatis使用MapperScannerConfigurer掃描模式後他會優先於PropertyPlaceholderConfigurer執行，因此這個時候，${jdbc.maxActive }尚未被properties文件裏面的值所替換，就出現TypeMismatchException，而後就異常了。

3、解決方法

    <!-- 配置sqlSessionFactory -->
    <bean id="mysqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="mySqlDataSource" />
         <property name="configLocation" value="/WEB-INF/classes/config/db/mybatis-config.xml" />
        <property name="mapperLocations">
            <list>
                <value>classpath:com/xsjt/dao/**/*Mapper.xml</value>
            </list>
        </property>
    </bean>

     <!-- DAO接口所在包名，Spring會自動查找其下的類 -->
     <bean name="mysqlMapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="annotationClass" value="org.springframework.stereotype.Repository" />
        <property name="basePackage" value="com.rxwx.dao" />
        <!-- 這裏 用sqlSessionFactoryBeanName，而不是sqlSessionFactory，接下來用value而不是ref -->
        <property name="sqlSessionFactoryBeanName" value="masterSqlSessionFactory" />
    </bean>

MapperScannerConfigurer掃描Dao的 配置中要使用sqlSessionFactoryBeanName，而不是sqlSessionFactory，接下來用value而不是ref。