Type conversion issue with Apache Camel and Spring

问题

I'm trying to externalize my Camel Spring (Camel 2.20.2; Spring 4.3.14) configuration into an application.properties property file. This property file has the following content:

net.sender1.port = 47000
net.sender1.address = 127.255.255.255

The application.properties file resides within src/main/resources and is copied to the target jar by the maven-shade-plugin.

My Camel context looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="..." xmlns:xsi="..." xmlns:camel="..." xsi:schemaLocation="...">
  <bean id="udpSender1" class="com.foo.MyUDPSender">
    <constructor-arg type="java.lang.String" value="${net.sender1.address}" />
    <constructor-arg type="java.lang.Integer" value="${net.sender1.port}" />
  </bean>

  <camelContext xmlns="http://camel.apache.org/schema/spring">
    ...
  </camelContext>
</beans>

When I start the application, I get the following error:

WARN | 2018-02-23 09:50:25,324 | [main]  ClassPathXmlApplicationContext.refresh  - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'udpSender1' defined in class path resource [META-INF/spring/camel-context.xml]: Unsatisfied dependency expressed through constructor parameter 1: Could not convert argument value of type [java.lang.String] to required type [java.lang.Integer]: Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "${net.sender1.port}"
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'udpSender1' defined in class path resource [META-INF/spring/camel-context.xml]: Unsatisfied dependency expressed through constructor parameter 1: Could not convert argument value of type [java.lang.String] to required type [java.lang.Integer]: Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "${net.sender1.port}"
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:723)
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:189)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1193)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1095)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
    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.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
    at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:93)
    at org.apache.camel.spring.Main.createDefaultApplicationContext(Main.java:222)
    at org.apache.camel.spring.Main.doStart(Main.java:154)
    at org.apache.camel.support.ServiceSupport.start(ServiceSupport.java:61)
    at com.foo.Server.main(Server.java:19)

It seems that the address property is parsed correctly, because it's a String. Which means that the application can find the properties-file.

Is there any way to explicitly define a type in the properties or in the spring xml?

回答1:

Your properties-file is, in fact, not found by your application. It is trying to convert the String literal "${net.sender1.port}" to an Integer, which is why you get a NumberFormatException.

You need to specify a PropertyPlaceholder in order to read your external properties-file.

<bean class="org.apache.camel.spring.spi.BridgePropertyPlaceholderConfigurer" id="bridgePropertyPlaceholder">
    <property name="location" value="classpath:application.properties"/>
</bean>

If you add the above to your application it should at least be able to read the actual properties.

回答2:

You can use also follow construction

<beans ...
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="...
         http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.5.xsd
         ">
  <context:property-placeholder properties-ref="properties"/>
  <util:properties id="properties" location="classpath:application.properties"/>

</beans>

来源：https://stackoverflow.com/questions/48944501/type-conversion-issue-with-apache-camel-and-spring