[Spring] 2. Spring Batch의 ItemReader - File Item Reader

public interface ItemReader<T> {
    T read() throws Exception, UnexpectedInputException, ParseException, NonTransientResourceException;
} 

public SimpleStepBuilder<I, O> reader(ItemReader<? extends I> reader) {
    this.reader = reader;
    return this;
}   

public interface ItemStream {

	void open(ExecutionContext executionContext) throws ItemStreamException;

	void update(ExecutionContext executionContext) throws ItemStreamException;

	void close() throws ItemStreamException;
}

@Bean
public FlatFileItemReader<ItemVo> txtFileItemReader() {
    FlatFileItemReader<ItemVo> flatFileItemReader = new FlatFileItemReader<>();
    flatFileItemReader.setResource(new ClassPathResource("/sample.txt"));      flatFileItemReader.setLineMapper((line, lineNumber) -> new ItemVo(line));      return flatFileItemReader;
}

public interface LineMapper<T> {
	T mapLine(String line, int lineNumber) throws Exception;
}

@Bean
public FlatFileItemReader<CsvItemVo> csvFileItemReader() {
    FlatFileItemReader<CsvItemVo> flatFileItemReader = new FlatFileItemReader<>();
    flatFileItemReader.setResource(new ClassPathResource("/sample_data.csv"));
    flatFileItemReader.setLinesToSkip(1);    
    DefaultLineMapper<CsvItemVo> defaultLineMapper = new DefaultLineMapper<>();  
    DelimitedLineTokenizer delimitedLineTokenizer = new DelimitedLineTokenizer();
    delimitedLineTokenizer.setNames("number","item");

    BeanWrapperFieldSetMapper<CsvItemVo> beanWrapperFieldSetMapper = new BeanWrapperFieldSetMapper<>();
    beanWrapperFieldSetMapper.setTargetType(CsvItemVo.class);

    defaultLineMapper.setLineTokenizer(delimitedLineTokenizer);
    defaultLineMapper.setFieldSetMapper(beanWrapperFieldSetMapper);

    flatFileItemReader.setLineMapper(defaultLineMapper);      return flatFileItemReader;
}

    @Override
	public T mapLine(String line, int lineNumber) throws Exception {
		return fieldSetMapper.mapFieldSet(tokenizer.tokenize(line));    	}

DelimitedLineTokenizer delimitedLineTokenizer = new DelimitedLineTokenizer();
delimitedLineTokenizer.setNames("number","item");

public class DelimitedLineTokenizer extends AbstractLineTokenizer implements InitializingBean {
    
    ...

	public static final String DELIMITER_COMMA = ",";    
	public DelimitedLineTokenizer() {
		this(DELIMITER_COMMA);
	}

	public void setDelimiter(String delimiter) {    		this.delimiter = delimiter;
	}

    ...
}

BeanWrapperFieldSetMapper<CsvItemVo> beanWrapperFieldSetMapper = new BeanWrapperFieldSetMapper<>();
beanWrapperFieldSetMapper.setTargetType(CsvItemVo.class);

defaultLineMapper.setLineTokenizer(delimitedLineTokenizer);
defaultLineMapper.setFieldSetMapper(beanWrapperFieldSetMapper);

@Bean
public FlatFileItemReader<CsvItemVo> csvFileItemReader() {
    FlatFileItemReader<CsvItemVo> flatFileItemReader = new FlatFileItemReader<>();
    flatFileItemReader.setResource(new ClassPathResource("/sample_data.csv"));
    flatFileItemReader.setLinesToSkip(1);
    flatFileItemReader.setLineMapper(new DefaultLineMapper<>() {
        {
            setLineTokenizer(new DelimitedLineTokenizer() {
                {
                    setNames("number", "item");
                }
            });

            setFieldSetMapper(new BeanWrapperFieldSetMapper<>(){
                {
                    setTargetType(CsvItemVo.class);
                }
            });
        }
    });
    return flatFileItemReader;
}

<?xml version="1.0" encoding="UTF-8" ?>
<items>
    <item id="1">
        <number>1</number>
        <data>one</data>
    </item>
    <item id="2">
        <number>2</number>
        <data>two</data>
    </item>
    <item id="3">
        <number>3</number>
        <data>three</data>
    </item>
    <item id="4">
        <number>4</number>
        <data>four</data>
    </item>
</items>

dependencies {
 ...
 implementation group: 'com.thoughtworks.xstream', name: 'xstream', version: '1.4.11.1'
 implementation group: 'org.springframework', name: 'spring-oxm', version: '5.1.10.RELEASE'
 ...
}

@Data
public class XmlItemVo {
    int number;
    String data;
}

@Bean
public StaxEventItemReader<XmlItemVo> xmlFileItemReader() {
    return new StaxEventItemReaderBuilder<XmlItemVo>()
            .name("xmlFileItemReader")
            .resource(new ClassPathResource("/sample_xml_data.xml"))
            .addFragmentRootElements("item")
            .unmarshaller(itemMarshaller())            .build();
}

@Bean
public XStreamMarshaller itemMarshaller() {
    Map<String, Class<?>> aliases = Maps.newHashMap();
    aliases.put("item", XmlItemVo.class);
    aliases.put("number", Integer.class);
    aliases.put("data", String.class);
    XStreamMarshaller xStreamMarshaller = new XStreamMarshaller();
    xStreamMarshaller.setAliases(aliases);
    return xStreamMarshaller;
}

@Configuration
public class JobSecurityConfig {

    public JobSecurityConfig(XStreamMarshaller marshaller) {
        XStream xstream = marshaller.getXStream();
        XStream.setupDefaultSecurity(xstream);        xstream.allowTypes(new Class[]{XmlItemVo.class});
    }

}

[
  {
    "number" : 1,
    "data" : "one"
  },
  {
    "number" : 2,
    "data" : "two"
  },
  {
    "number" : 3,
    "data" : "three"
  },
  {
    "number" : 4,
    "data" : "four"
  }
]

@Data
@NoArgsConstructor
@AllArgsConstructor
public class JsonItemVo {
    int number;
    String data;
}

@Bean
public JsonItemReader<JsonItemVo> jsonItemReader(){
    return new JsonItemReaderBuilder<JsonItemVo>()
            .jsonObjectReader(new JacksonJsonObjectReader<>(JsonItemVo.class))            .resource(new ClassPathResource("/sample_json_data.json"))
            .name("jsonItemReader")
            .build();
}

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@Bean
@SneakyThrows
public MultiResourceItemReader<ItemVo> multiResourceItemReader(){
    MultiResourceItemReader<ItemVo> resourceItemReader = new MultiResourceItemReader<ItemVo>();
    resourceItemReader.setResources(ResourcePatternUtils.getResourcePatternResolver(this.resourceLoader).getResources("read_sample/*.txt"));      resourceItemReader.setDelegate(multiFileItemReader());      return resourceItemReader;
}


@Bean
public FlatFileItemReader<ItemVo> multiFileItemReader() {
    FlatFileItemReader<ItemVo> flatFileItemReader = new FlatFileItemReader<>();
    flatFileItemReader.setLineMapper((line, lineNumber) -> new ItemVo(line));
    return flatFileItemReader;
}

@Value("input/sample*.csv")
private Resource[] inputResources;