SpringBatch异常To use the default BatchConfigurer the context must contain no more thanone DataSource

SpringBoot整合SpringBatch项目，已将代码开源至github，访问地址：https://github.com/cmlbeliever/SpringBatch 欢迎star or fork！

在框架整合的过程中，由于需要添加db读写分离配置，因此项目中有两个DataSource，运行batch后报错如下：

java.lang.IllegalStateException: Failed to execute CommandLineRunner
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:779)
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:760)
    at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:747)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at com.cml.learning.framework.module.BaseModule.run(BaseModule.java:39)
    at com.cml.learning.module.bat00X.Bat00XModule.main(Bat00XModule.java:20)
Caused by: java.lang.IllegalStateException: To use the default BatchConfigurer the context must contain no more thanone DataSource, found 2
    at org.springframework.batch.core.configuration.annotation.AbstractBatchConfiguration.getConfigurer(AbstractBatchConfiguration.java:108)
    at org.springframework.batch.core.configuration.annotation.SimpleBatchConfiguration.initialize(SimpleBatchConfiguration.java:114)
    at org.springframework.batch.core.configuration.annotation.SimpleBatchConfiguration$ReferenceTargetSource.createObject(SimpleBatchConfiguration.java:142)
    at org.springframework.aop.target.AbstractLazyCreationTargetSource.getTarget(AbstractLazyCreationTargetSource.java:86)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:192)
    at com.sun.proxy.$Proxy55.getJobInstances(Unknown Source)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.getNextJobParameters(JobLauncherCommandLineRunner.java:131)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.execute(JobLauncherCommandLineRunner.java:212)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.executeLocalJobs(JobLauncherCommandLineRunner.java:231)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.launchJobFromProperties(JobLauncherCommandLineRunner.java:123)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.run(JobLauncherCommandLineRunner.java:117)
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:776)
    ... 5 common frames omitted

意思是要使用default BatchConfigurer，则项目中只能有一个Datasource。

根据异常堆栈信息，找到抛出此异常的源码位置和实现代码：
org.springframework.batch.core.configuration.annotation.AbstractBatchConfiguration

@Autowired(required = false)
private Collection<DataSource> dataSources;

protected BatchConfigurer getConfigurer(Collection<BatchConfigurer> configurers) throws Exception {
        if (this.configurer != null) {
            return this.configurer;
        }
        if (configurers == null || configurers.isEmpty()) {
            if (dataSources == null || dataSources.isEmpty()) {
                DefaultBatchConfigurer configurer = new DefaultBatchConfigurer();
                configurer.initialize();
                this.configurer = configurer;
                return configurer;
            } else if(dataSources != null && dataSources.size() == 1) {
                DataSource dataSource = dataSources.iterator().next();
                DefaultBatchConfigurer configurer = new DefaultBatchConfigurer(dataSource);
                configurer.initialize();
                this.configurer = configurer;
                return configurer;
            } else {
                throw new IllegalStateException("To use the default BatchConfigurer the context must contain no more than" +
                                                        "one DataSource, found " + dataSources.size());
            }
        }
        if (configurers.size() > 1) {
            throw new IllegalStateException(
                    "To use a custom BatchConfigurer the context must contain precisely one, found "
                            + configurers.size());
        }
        this.configurer = configurers.iterator().next();
        return this.configurer;
    }

根据源码得知，当数据源不存的时候，BatchConfigure会将batch数据存储到内存中，当数据源只有一个时，会根据数据源建立batch执行所需要的表。当数据源有多个的时候就抛出异常，这样难怪，因为BatchConfigure在多个数据源的时候，它根本不知道要根据哪个数据源建立batch执行所需要的表。
既然知道了原因，只需要自定义BatchConfigure，并且在多数据源的情况下指定一个默认的数据源即可解决。

实现步骤：
1、将框架SimpleBatchConfiguration，AbstractBatchConfiguration源码复制出来
2、重写AbstractBatchConfiguration.getConfigurer方法，设置默认数据源

protected BatchConfigurer getConfigurer(Collection<BatchConfigurer> configurers) throws Exception {
        if (this.configurer != null) {
            return this.configurer;
        }
        if (configurers == null || configurers.isEmpty()) {
            if (defaultDataSource == null) {
                throw new IllegalStateException("Data source can not be null!!!");
            }

            DefaultBatchConfigurer configurer = new DefaultBatchConfigurer(defaultDataSource);
            configurer.initialize();
            this.configurer = configurer;
            return configurer;
        }
        if (configurers.size() > 1) {
            throw new IllegalStateException("To use a custom BatchConfigurer the context must contain precisely one, found " + configurers.size());
        }
        this.configurer = configurers.iterator().next();
        return this.configurer;
    }

3、添加注解，将重写的BatchConfigure引入

@Import({ SimpleBatchConfiguration.class })

4、经过以上三个步骤，即可实现多数据源下SpringBatch启动报错问题

以上代码已经整合到SpringBatch，已将代码开源至github，访问地址：https://github.com/cmlbeliever/SpringBatch 欢迎star or fork！

如果有其他更好的方法，还请不吝赐教。