如何将会话变量作为Mule中回滚异常策略组件中MaxRedeliveryAttents字段的参数传递？

下面是Mule配置XML

<http:listener-config name="HTTP_Listener_Configuration" host="localhost" port="8090" doc:name="HTTP Listener Configuration"/>
<flow name="testflowFlow">
    <http:listener config-ref="HTTP_Listener_Configuration" path="/test" doc:name="HTTP"/>
    <set-session-variable variableName="count" value="#[message.inboundProperties.'http.query.params'.retrycount]" doc:name="count Session Variable"/>
    <set-payload value="#[sessionVars.count]" doc:name="Set Payload"/>
    <file:outbound-endpoint path="C:\Users\y0134079\Desktop" responseTimeout="10000" doc:name="File"/>
    <set-payload value="#[sessionVars.count]" doc:name="Set Payload"/>
    <rollback-exception-strategy maxRedeliveryAttempts="#[sessionVars.count]" doc:name="Rollback Exception Strategy"/>
</flow>

我尝试在HTTP请求中的一个查询参数（retrycount）中传递最大重试次数。但是MaxRedeliveryAttents字段需要一个整数，并且由于提供的查询参数是字符串，构建失败，因为它无法从字符串转换为整数。有什么建议吗

错误：

*****原因：org.springframework.beans.typemischException:未能将类型为“java.lang.String”的属性值转换为属性“MaxRedeliveryAttents”所需的类型“java.lang.Integer”；嵌套异常是java.lang.NumberFormatException:对于输入字符串：“[sessionVars.count]” 在org.springframework.beans.BeanWrapperImpl.convertifrequired（BeanWrapperImpl.java:468）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE]***** 在org.springframework.beans.BeanWrapperImpl.convertForProperty（BeanWrapperImpl.java:494）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.BeanWrapperImpl.convertForProperty（BeanWrapperImpl.java:488）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty（AbstractAutowireCapableBeanFactory.java:1464）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues（AbstractAutowireCapableBeanFactory.java:1423）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean（AbstractAutowireCapableBeanFactory.java:1159）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean（AbstractAutowireCapableBeanFactory.java:519）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean（AbstractAutowireCapableBeanFactory.java:458）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean（BeanDefinitionValueResolver.java:276）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.beandDefinitionValueResolver.ResolveValueIfNeeded（beandDefinitionValueResolver.java:129）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues（AbstractAutowireCapableBeanFactory.java:1418）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean（AbstractAutowireCapableBeanFactory.java:1159）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean（AbstractAutowireCapableBeanFactory.java:519）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean（AbstractAutowireCapableBeanFactory.java:458）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject（AbstractBeanFactory.java:293）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton（DefaultSingletonBeanRegistry.java:223）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean（AbstractBeanFactory.java:290）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.AbstractBeanFactory.getBean（AbstractBeanFactory.java:191）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.beans.factory.support.DefaultListableBeanFactory.PreInstanceSingleton（DefaultListableBeanFactory.java:633）~[spring-beans-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization（AbstractApplicationContext.java:932）~[spring-context-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.springframework.context.support.AbstractApplicationContext.refresh（AbstractApplicationContext.java:479）~[spring-context-3.2.10.RELEASE.jar:3.2.10.RELEASE] 在org.mule.config.spring.SpringRegistry.doInitialise（SpringRegistry.java:86）~[mule-module-spring-config-3.6.1.jar:3.6.1] 在org.mule.registry.AbstractRegistry.initialise（AbstractRegistry.java:105）~[mule-core-3.6.1.jar:3.6.1] 在org.mule.config.spring.SpringXmlConfigurationBuilder.createSpringRegistry（SpringXmlConfigurationBuilder.java:135）~[mule-module-spring-config-3.6.1.jar:3.6.1] 在org.mule.config.spring.SpringXmlConfigurationBuilder.doConfigure（SpringXmlConfigurationBuilder.java:90）~[mule-module-spring-config-3.6.1.jar:3.6.1] 在org.mule.config.builders.AbstractConfigurationBuilder.configure（AbstractConfigurationBuilder.java:43）~[mule-core-3.6.1.jar:3.6.1] 在org.mule.config.builders.AbstractResourceConfigurationBuilder.configure（AbstractResourceConfigurationBuilder.java:69）~[mule-core-3.6.1.jar:3.6.1] 在org.mule.config.builders.AutoConfigurationBuilder.autoConfigure（AutoConfigurationBuilder.java:101）~[mule-core-3.6.1.jar:3.6.1] 在org.mule.config.builders.AutoConfigurationBuilder.doConfigure（AutoConfigurationBuilder.java:52）~[mule-core-3.6.1.jar:3.6.1] 在org.mule.config.builders.AbstractConfigurationBuilder.configure（AbstractConfigurationBuilder.java:43）~[mule-core-3.6.1.jar:3.6.1] 在org.mule.config.builders.AbstractResourceConfigurationBuilder.configure（AbstractResourceConfigurationBuilder.java:69）~[mu