Spring Batch处理数据

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在Spring Batch中，ItemReader接口用于读取数据，ItemWriter接口用于输出数据。除此之外，我们可以通过ItemProcessor接口实现数据的处理，包括：数据校验，数据过滤和数据转换等。数据处理的时机发生于ItemReader读取数据之后，ItemWriter输出数据之前。本节记录下Spring Batch中ItemProcessor的使用。

框架搭建

新建一个Spring Boot项目，版本为2.2.4.RELEASE，artifactId为spring-batch-itemprocessor，项目结构如下图所示：

QQ20200309-135557@2x

剩下的数据库层的准备，项目配置，依赖引入和Spring Batch入门文章中的框架搭建步骤一致，这里就不再赘述。

在介绍Spring Batch ItemProcessor之前，我们先准备个简单的数据读取源。在cc.mrbird.batch包下新建entity包，然后在该包下新建TestData实体类：

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public class TestData {

    private int id;
    private String field1;
    private String field2;
    private String field3;
    // get,set,toString略
}

接着在cc.mrbird.batch包下新建reader包，然后在该包下创建ItemReaderConfigure：

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@Configuration
public class ItemReaderConfigure {

    @Bean
    public ListItemReader<TestData> simpleReader() {
        List<TestData> data = new ArrayList<>();
        TestData testData1 = new TestData();
        testData1.setId(1);
        testData1.setField1("11");
        testData1.setField2("12");
        testData1.setField3("13");
        data.add(testData1);
        TestData testData2 = new TestData();
        testData2.setId(2);
        testData2.setField1("21");
        testData2.setField2("22");
        testData2.setField3("23");
        data.add(testData2);
        TestData testData3 = new TestData();
        testData3.setId(3);
        testData3.setField1("31");
        testData3.setField2("32");
        // 设置为空字符串，用于后面格式校验演示
        testData3.setField3("");
        data.add(testData3);
        return new ListItemReader<>(data);
    }
}

上面注册了一个ItemReader类型的Bean，后续都用它作为读取数据的来源。

格式校验

ItemProcessor的实现类ValidatingItemProcessor可以用于数据格式校验。举个例子，在cc.mrbird.batch包下新建job包，然后在该包下新建ValidatingItemProcessorDemo：

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@Component
public class ValidatingItemProcessorDemo {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Autowired
    private ListItemReader<TestData> simpleReader;

    @Bean
    public Job validatingItemProcessorJob() {
        return jobBuilderFactory.get("validatingItemProcessorJob")
                .start(step())
                .build();
    }

    private Step step() {
        return stepBuilderFactory.get("step")
                .<TestData, TestData>chunk(2)
                .reader(simpleReader)
                .processor(validatingItemProcessor())
                .writer(list -> list.forEach(System.out::println))
                .build();
    }

    private ValidatingItemProcessor<TestData> validatingItemProcessor() {
        ValidatingItemProcessor<TestData> processor = new ValidatingItemProcessor<>();
        processor.setValidator(value -> {
            // 对每一条数据进行校验
            if ("".equals(value.getField3())) {
                // 如果field3的值为空串，则抛异常
                throw new ValidationException("field3的值不合法");
            }
        });
        return processor;
    }
}

通过ValidatingItemProcessor我们对ItemReader读取的每一条数据进行校验，如果field3的值为空串的话，则抛出ValidationException("field3的值不合法")异常。ItemProcessor通过步骤创建工厂的processor()设置。

启动项目，控制台日志的打印如下：

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2020-03-09 14:18:47.186  INFO 17967 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=validatingItemProcessorJob]] launched with the following parameters: [{}]
2020-03-09 14:18:47.252  INFO 17967 --- [           main] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
TestData{id=1, field1='11', field2='12', field3='13'}
TestData{id=2, field1='21', field2='22', field3='23'}
2020-03-09 14:18:47.300 ERROR 17967 --- [           main] o.s.batch.core.step.AbstractStep         : Encountered an error executing step step in job validatingItemProcessorJob

org.springframework.batch.item.validator.ValidationException: field3的值不合法
	at cc.mrbird.batch.entity.job.ValidatingItemProcessorDemo.lambda$validatingItemProcessor$1(ValidatingItemProcessorDemo.java:50) ~[classes/:na]
	at org.springframework.batch.item.validator.ValidatingItemProcessor.process(ValidatingItemProcessor.java:84) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.item.SimpleChunkProcessor.doProcess(SimpleChunkProcessor.java:134) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.item.SimpleChunkProcessor.transform(SimpleChunkProcessor.java:319) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.item.SimpleChunkProcessor.process(SimpleChunkProcessor.java:210) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:77) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:407) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:331) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140) ~[spring-tx-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.batch.core.step.tasklet.TaskletStep$2.doInChunkContext(TaskletStep.java:273) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.scope.context.StepContextRepeatCallback.doInIteration(StepContextRepeatCallback.java:82) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:375) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:145) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.tasklet.TaskletStep.doExecute(TaskletStep.java:258) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:208) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:148) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.job.AbstractJob.handleStep(AbstractJob.java:410) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.job.SimpleJob.doExecute(SimpleJob.java:136) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:319) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:147) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50) [spring-core-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.batch.core.launch.support.SimpleJobLauncher.run(SimpleJobLauncher.java:140) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) [spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) [spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) [spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.batch.core.configuration.annotation.SimpleBatchConfiguration$PassthruAdvice.invoke(SimpleBatchConfiguration.java:127) [spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) [spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) [spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at com.sun.proxy.$Proxy46.run(Unknown Source) [na:na]
	at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.execute(JobLauncherCommandLineRunner.java:192) [spring-boot-autoconfigure-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.executeLocalJobs(JobLauncherCommandLineRunner.java:166) [spring-boot-autoconfigure-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.launchJobFromProperties(JobLauncherCommandLineRunner.java:153) [spring-boot-autoconfigure-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.run(JobLauncherCommandLineRunner.java:148) [spring-boot-autoconfigure-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:784) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:768) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:322) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at cc.mrbird.batch.SpringBatchItemprocessorApplication.main(SpringBatchItemprocessorApplication.java:12) [classes/:na]

2020-03-09 14:18:47.307  INFO 17967 --- [           main] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 55ms
2020-03-09 14:18:47.335  INFO 17967 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=validatingItemProcessorJob]] completed with the following parameters: [{}] and the following status: [FAILED] in 127ms

可以看到任务处理过程中抛出了预期异常，关于任务处理中如何处理异常，可以参考后续的文章。

除了使用这种方式外，我们还可以使用BeanValidatingItemProcessor校验使用JSR-303注解标注的实体类。比如，在TestData类的field3属性上添加@NotBlank注解：

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public class TestData {

    private int id;
    private String field1;
    private String field2;
    @NotBlank
    private String field3;
    // get,set,toString略
}

使用该注解需要在pom中添加spring-boot-starter-validation依赖：

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<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

然后在job包下新建BeanValidatingItemProcessorDemo：

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@Component
public class BeanValidatingItemProcessorDemo {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Autowired
    private ListItemReader<TestData> simpleReader;

    @Bean
    public Job beanValidatingItemProcessorJob() throws Exception {
        return jobBuilderFactory.get("beanValidatingItemProcessorJob")
                .start(step())
                .build();
    }

    private Step step() throws Exception {
        return stepBuilderFactory.get("step")
                .<TestData, TestData>chunk(2)
                .reader(simpleReader)
                .processor(beanValidatingItemProcessor())
                .writer(list -> list.forEach(System.out::println))
                .build();
    }

    private BeanValidatingItemProcessor<TestData> beanValidatingItemProcessor() throws Exception {
        BeanValidatingItemProcessor<TestData> beanValidatingItemProcessor = new BeanValidatingItemProcessor<>();
        // 开启过滤，不符合规则的数据被过滤掉；
        beanValidatingItemProcessor.setFilter(true);
        beanValidatingItemProcessor.afterPropertiesSet();
        return beanValidatingItemProcessor;
    }
}

启动项目后，控制台日志打印如下：

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2020-03-09 14:31:14.813  INFO 18100 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=beanValidatingItemProcessorJob]] launched with the following parameters: [{}]
2020-03-09 14:31:14.873  INFO 18100 --- [           main] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
TestData{id=1, field1='11', field2='12', field3='13'}
TestData{id=2, field1='21', field2='22', field3='23'}
2020-03-09 14:31:14.959  INFO 18100 --- [           main] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 85ms
2020-03-09 14:31:14.980  INFO 18100 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=beanValidatingItemProcessorJob]] completed with the following parameters: [{}] and the following status: [COMPLETED] in 145ms
2020-03-09 14:31:15.069  INFO 18100 --- [           main]

可以看到，不符合规则的数据已经被排除了。如果不开启过滤beanValidatingItemProcessor.setFilter(false)，那么在遇到不符合注解校验规则的数据，将抛出如下异常：

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org.springframework.batch.item.validator.ValidationException: Validation failed for TestData{id=3, field1='31', field2='32', field3=''}: 
Field error in object 'item' on field 'field3': rejected value []; codes [NotBlank.item.field3,NotBlank.field3,NotBlank.java.lang.String,NotBlank]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [item.field3,field3]; arguments []; default message [field3]]; default message [不能为空]
	at org.springframework.batch.item.validator.SpringValidator.validate(SpringValidator.java:54) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.item.validator.ValidatingItemProcessor.process(ValidatingItemProcessor.java:84) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.item.SimpleChunkProcessor.doProcess(SimpleChunkProcessor.java:134) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	at org.springframework.batch.core.step.item.SimpleChunkProcessor.transform(SimpleChunkProcessor.java:319) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
	...

数据过滤

通过自定义ItemProcessor的实现类，我们也可以简单地实现数据过滤。在cc.mrbird.batch包下新建processor包，然后在该包下新建TestDataFilterItemProcessor：

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@Component
public class TestDataFilterItemProcessor implements ItemProcessor<TestData, TestData> {
    @Override
    public TestData process(TestData item) {
        // 返回null，会过滤掉这条数据
        return "".equals(item.getField3()) ? null : item;
    }
}

TestDataFilterItemProcessor实现了ItemProcessor的process()方法，在该方法内编写具体的校验逻辑，上面代码判断TestData的field3是否为空串，是的话返回null（返回null会过滤掉这条数据）。

接着在job包下新建TestDataFilterItemProcessorDemo：

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@Component
public class TestDataFilterItemProcessorDemo {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Autowired
    private ListItemReader<TestData> simpleReader;
    @Autowired
    private TestDataFilterItemProcessor testDataFilterItemProcessor;

    @Bean
    public Job testDataFilterItemProcessorJob() {
        return jobBuilderFactory.get("testDataFilterItemProcessorJob")
                .start(step())
                .build();
    }

    private Step step() {
        return stepBuilderFactory.get("step")
                .<TestData, TestData>chunk(2)
                .reader(simpleReader)
                .processor(testDataFilterItemProcessor)
                .writer(list -> list.forEach(System.out::println))
                .build();
    }
}

启动项目，控制台日志打印如下：

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2020-03-09 15:03:30.932  INFO 18690 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=testDataFilterItemProcessorJob]] launched with the following parameters: [{}]
2020-03-09 15:03:30.973  INFO 18690 --- [           main] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
TestData{id=1, field1='11', field2='12', field3='13'}
TestData{id=2, field1='21', field2='22', field3='23'}
2020-03-09 15:03:31.012  INFO 18690 --- [           main] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 39ms
2020-03-09 15:03:31.037  INFO 18690 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=testDataFilterItemProcessorJob]] completed with the following parameters: [{}] and the following status: [COMPLETED] in 95ms

数据转换

在processor包下新建一个ItemProcessor实现类TestDataTransformItemPorcessor：

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@Component
public class TestDataTransformItemPorcessor implements ItemProcessor<TestData, TestData> {
    @Override
    public TestData process(TestData item) {
        // field1值拼接 hello
        item.setField1(item.getField1() + " hello");
        return item;
    }
}

在job包下新建TestDataTransformItemPorcessorDemo：

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@Component
public class TestDataTransformItemPorcessorDemo {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Autowired
    private ListItemReader<TestData> simpleReader;
    @Autowired
    private TestDataTransformItemPorcessor testDataTransformItemPorcessor;

    @Bean
    public Job testDataTransformItemPorcessorJob() {
        return jobBuilderFactory.get("testDataTransformItemPorcessorJob")
                .start(step())
                .build();
    }

    private Step step() {
        return stepBuilderFactory.get("step")
                .<TestData, TestData>chunk(2)
                .reader(simpleReader)
                .processor(testDataTransformItemPorcessor)
                .writer(list -> list.forEach(System.out::println))
                .build();
    }
}

启动项目，控制台日志打印如下：

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2020-03-09 15:08:55.628  INFO 18775 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=testDataTransformItemPorcessorJob]] launched with the following parameters: [{}]
2020-03-09 15:08:55.694  INFO 18775 --- [           main] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
TestData{id=1, field1='11 hello', field2='12', field3='13'}
TestData{id=2, field1='21 hello', field2='22', field3='23'}
TestData{id=3, field1='31 hello', field2='32', field3=''}
2020-03-09 15:08:55.757  INFO 18775 --- [           main] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 63ms
2020-03-09 15:08:55.781  INFO 18775 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=testDataTransformItemPorcessorJob]] completed with the following parameters: [{}] and the following status: [COMPLETED] in 144ms

聚合处理

在创建Step的时候，除了制定一个ItemProcess外，我们可以通过CompositeItemProcessor聚合多个processor处理过程。

在job包下新建CompositeItemProcessorDemo：

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@Component
public class CompositeItemProcessorDemo {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;
    @Autowired
    private StepBuilderFactory stepBuilderFactory;
    @Autowired
    private ListItemReader<TestData> simpleReader;
    @Autowired
    private TestDataFilterItemProcessor testDataFilterItemProcessor;
    @Autowired
    private TestDataTransformItemPorcessor testDataTransformItemPorcessor;

    @Bean
    public Job compositeItemProcessorJob() {
        return jobBuilderFactory.get("compositeItemProcessorJob")
                .start(step())
                .build();
    }

    private Step step() {
        return stepBuilderFactory.get("step")
                .<TestData, TestData>chunk(2)
                .reader(simpleReader)
                .processor(compositeItemProcessor())
                .writer(list -> list.forEach(System.out::println))
                .build();
    }

    // CompositeItemProcessor组合多种中间处理器
    private CompositeItemProcessor<TestData, TestData> compositeItemProcessor() {
        CompositeItemProcessor<TestData, TestData> processor = new CompositeItemProcessor<>();
        List<ItemProcessor<TestData, TestData>> processors = Arrays.asList(testDataFilterItemProcessor, testDataTransformItemPorcessor);
        // 代理两个processor
        processor.setDelegates(processors);
        return processor;
    }
}

上面代码中，我们通过CompositeItemProcessor聚合了前面定义的连个processor：TestDataFilterItemProcessor和TestDataTransformItemPorcessor。

启动项目，控制台日志打印如下：

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2020-03-09 15:21:24.960  INFO 18882 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=compositeItemProcessorJob]] launched with the following parameters: [{}]
2020-03-09 15:21:25.005  INFO 18882 --- [           main] o.s.batch.core.job.SimpleStepHandler     : Executing step: [step]
TestData{id=1, field1='11 hello', field2='12', field3='13'}
TestData{id=2, field1='21 hello', field2='22', field3='23'}
2020-03-09 15:21:25.065  INFO 18882 --- [           main] o.s.batch.core.step.AbstractStep         : Step: [step] executed in 60ms
2020-03-09 15:21:25.104  INFO 18882 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [SimpleJob: [name=compositeItemProcessorJob]] completed with the following parameters: [{}] and the following status: [COMPLETED] in 128ms

从结果可以看到，数据不但进行了过滤，还进行了转换（拼接hello）。

本节源码链接：https://github.com/wuyouzhuguli/SpringAll/tree/master/70.spring-batch-itemprocessor。

请作者喝瓶肥宅水🥤
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