Spring Batch应用出现JobRestController与SpringBatchConfig循环依赖如何解决

Spring Boot 2.6+ 版本默认禁用了循环依赖支持，你当前项目的依赖循环路径如下：

• JobRestController 启动初始化时，需要注入 Job 实例
• Job 是 SpringBatchConfig 配置类中通过 @Bean 方法声明的Bean，初始化Job前需要先完成SpringBatchConfig类的实例化
• SpringBatchConfig 加了@AllArgsConstructor注解，需要通过构造函数注入ItemReader、ItemProcessor、ItemWriter三个Bean，而其中ItemReader的实现也是当前SpringBatchConfig类中声明的@Bean，必须等配置类实例化完成才能创建，二者形成初始化死锁，触发循环依赖报错。

方案1（推荐：彻底消除循环） #

修改SpringBatchConfig的写法，不要将依赖注入到配置类的成员变量中，改为将依赖声明为@Bean方法的入参，Spring会自动注入方法入参的Bean实例，修改后的代码参考：

import lombok.RequiredArgsConstructor;
import org.springframework.batch.core.Job;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
import org.springframework.batch.item.ItemProcessor;
import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.LineMapper;
import org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper;
import org.springframework.batch.item.file.mapping.DefaultLineMapper;
import org.springframework.batch.item.file.transform.DelimitedLineTokenizer;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.Resource;

@Configuration
@EnableBatchProcessing
// 只注入两个工厂类即可，无需注入其他业务组件
@RequiredArgsConstructor
public class SpringBatchConfig {

    private final JobBuilderFactory jobBuilderFactory;
    private final StepBuilderFactory stepBuilderFactory;

    // 把Step依赖直接声明为方法入参
    @Bean
    public Job bankJob(Step stepLoadData) {
        return jobBuilderFactory.get("bank-data-loader-job")
                .start(stepLoadData)
                .build();
    }

    // 把批量处理组件直接声明为方法入参
    @Bean
    public Step stepLoadData(ItemReader<BankTransaction> bankTransactionItemReader,
                             ItemProcessor<BankTransaction, BankTransaction> bankTransactionItemProcessor,
                             ItemWriter<BankTransaction> bankTransactionItemWriter) {
        return stepBuilderFactory.get("step-load-data")
                .<BankTransaction, BankTransaction>chunk(100)
                .reader(bankTransactionItemReader)
                .processor(bankTransactionItemProcessor)
                .writer(bankTransactionItemWriter)
                .build();
    }

    @Bean
    public ItemReader<BankTransaction> flatFileItemReader(@Value("${inputFile}") Resource inputFile) {
        FlatFileItemReader<BankTransaction> flatFileItemReader = new FlatFileItemReader<>();
        flatFileItemReader.setName("CSV-READER");
        flatFileItemReader.setLinesToSkip(1);
        flatFileItemReader.setResource(inputFile);
        flatFileItemReader.setLineMapper(lineMapper());
        return flatFileItemReader;
    }

    @Bean
    public LineMapper<BankTransaction> lineMapper() {
        DefaultLineMapper<BankTransaction> lineMapper = new DefaultLineMapper<>();
        DelimitedLineTokenizer lineTokenizer = new DelimitedLineTokenizer();
        lineTokenizer.setDelimiter(",");
        lineTokenizer.setStrict(false);
        lineTokenizer.setNames("id", "accountID", "strTransactionDate", "transactionType", "amount");
        lineMapper.setLineTokenizer(lineTokenizer);
        BeanWrapperFieldSetMapper<BankTransaction> fieldSetMapper = new BeanWrapperFieldSetMapper<>();
        fieldSetMapper.setTargetType(BankTransaction.class);
        lineMapper.setFieldSetMapper(fieldSetMapper);
        return lineMapper;
    }
}

如果你的ItemProcessor和ItemWriter是在其他配置类中声明的，确保Bean类型匹配，或者添加@Qualifier指定Bean名称即可。

方案2（快速修复，不推荐） #

直接在项目的application.properties配置文件中添加如下配置，开启循环依赖支持：

spring.main.allow-circular-references=true

方案3（临时修复） #

在JobRestController中注入Job的位置添加@Lazy注解，延迟Job的初始化时机：

@RestController
@AllArgsConstructor
public class JobRestController {

    private JobLauncher jobLauncher;
    @Lazy
    private Job job;

    // 其余代码保持不变
}

内容的提问来源于stack exchange，提问作者Elhilali Yassine