Apache Camel使用加载路由源码（扫描包路径方式）分析及注意事项

1.添加依赖包

gradle依赖：

compile 'org.apache.camel:camel-spring:2.20.3'

2.添加Spring配置信息

spring-camel.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
         http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
         http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">

    <camelContext xmlns="http://camel.apache.org/schema/spring">
        <packageScan>
            <package>com.chz.apps.esb.camel.routes</package>
            <excludes>**.*Excluded*</excludes>
            <includes>**.*</includes>
        </packageScan>
    </camelContext>
</beans>

com.chz.apps.esb.camel.routes包是用于存放camel的路由类

3.编写路由类（错误的类）

此处使用本地文件往ftp自动上传文件为例：

package com.chz.apps.esb.camel.routes;

import org.apache.camel.builder.RouteBuilder;
import org.springframework.stereotype.Component;

/**
 * 本地文件往服务器自动同步机制
 */
@Component
public class FileTransFtpRouteBuilder extends RouteBuilder {

    @Override
    public void configure() {
        from("file:D:\\tmp\\camel")
        .to("ftp:ftpUsername:[email protected]");
    }
}

4.问题描述

上面的builder是参考《Apache Camel Deve》第23页实例编写。每次启动的时候，会发现创建的route并没有添加到Camel的CamelContext中，也就是说路由并没有生效。

经过源码分析，Apache Camel在于Spring进行集成的时候，使用CamelContextFactoryBean进行相关Bean实例的统一管理。而使用packageScan进行启动时，需要调用如下方法：

@Override
    protected void findRouteBuildersByPackageScan(String[] packages, PackageScanFilter filter, List<RoutesBuilder> builders) throws Exception {
        // add filter to class resolver which then will filter
        getContext().getPackageScanClassResolver().addFilter(filter);

        PackageScanRouteBuilderFinder finder = new PackageScanRouteBuilderFinder(getContext(), packages, getContextClassLoaderOnStart(),
                                                                                 getBeanPostProcessor(), getContext().getPackageScanClassResolver());
        finder.appendBuilders(builders);

        // and remove the filter
        getContext().getPackageScanClassResolver().removeFilter(filter);
    }

finder.appendBuilders(builders);此方法用于扫描包路径下面所有类，如果不是Spring的bean，则使用路由初始化方法，加载到Camel容器中。而书中提到使用Component注解后，会导致此处自动过滤掉：

在dubug的时候，日志如下：

[MI TCP Connection(3)-127.0.0.1] efaultPackageScanClassResolver DEBUG Searching for implementations of org.apache.camel.RoutesBuilder in packages: [com.chz.apps.esb.camel.routes]
[MI TCP Connection(3)-127.0.0.1] efaultPackageScanClassResolver DEBUG Found: [class com.chz.apps.esb.camel.routes.FileTransFtpRouteBuilder]
[MI TCP Connection(3)-127.0.0.1] DefaultListableBeanFactory     DEBUG Returning cached instance of singleton bean 'fileTransFtpRouteBuilder'
[MI TCP Connection(3)-127.0.0.1] PackageScanRouteBuilderFinder  DEBUG Ignoring RouteBuilder class: class com.chz.apps.esb.camel.routes.FileTransFtpRouteBuilder

通过分析源码（PackageScanRouteBuilderFinder.shouldIgnoreBean方法），只要是Spring已经加载的bean，此处不会做任何处理。所以正确的方式应该是去掉Component注解。

/**
     * Appends all the {@link org.apache.camel.builder.RouteBuilder} instances that can be found on the classpath
     */
    public void appendBuilders(List<RoutesBuilder> list) throws IllegalAccessException, InstantiationException {
        Set<Class<?>> classes = resolver.findImplementations(RoutesBuilder.class, packages);
        for (Class<?> aClass : classes) {
            LOG.trace("Found RouteBuilder class: {}", aClass);

            // certain beans should be ignored
            if (shouldIgnoreBean(aClass)) {
                LOG.debug("Ignoring RouteBuilder class: {}", aClass);
                continue;
            }

            if (!isValidClass(aClass)) {
                LOG.debug("Ignoring invalid RouteBuilder class: {}", aClass);
                continue;
            }

            // type is valid so create and instantiate the builder
            @SuppressWarnings("unchecked")
            RoutesBuilder builder = instantiateBuilder((Class<? extends RoutesBuilder>) aClass);
            if (beanPostProcessor != null) {
                // Inject the annotated resource
                beanPostProcessor.postProcessBeforeInitialization(builder, builder.toString());
            }
            LOG.debug("Adding instantiated RouteBuilder: {}", builder);
            list.add(builder);
        }
    }

 protected boolean shouldIgnoreBean(Class<?> type) {
        Map<String, ?> beans = applicationContext.getBeansOfType(type, true, true);
        if (beans == null || beans.isEmpty()) {
            return false;
        }
        return true;
    }

5.编写路由类（正确的类）

package com.chz.apps.esb.camel.routes;

import org.apache.camel.builder.RouteBuilder;

/**
 * 本地文件往服务器自动同步机制
 */
public class FileTransFtpRouteBuilder extends RouteBuilder {

    @Override
    public void configure() {
        from("file:D:\\tmp\\camel")
        .to("ftp:ftpUsername:[email protected]");
    }
}