# Spring Batch `FlatFileItemWriter` – 写入 CSV 文件 > 原文：[https://howtodoinjava.com/spring-batch/flatfileitemwriter-write-to-csv-file/](https://howtodoinjava.com/spring-batch/flatfileitemwriter-write-to-csv-file/) 学习使用[`FlatFileItemWriter`](https://docs.spring.io/spring-batch/4.0.x/api/org/springframework/batch/item/file/FlatFileItemWriter.html)写入 CSV 数据。 它是将数据写入文件或流的项目编写器。 输出文件的位置由`Resource`定义，并且必须表示可写文件。 ## 项目结构 在这个项目中，我们将学习： 1. 使用`MultiResourceItemReader`从`input/*.csv`读取 3 个 CSV 文件。 2. 使用`FlatFileItemWriter`将整个数据写入`output/outputData.csv`文件。  项目结构 ## 使用`FlatFileItemWriter`写入数据 CSV 文件 您需要使用`FlatFileItemWriter`写入从 CSV 文件读取的行。 它将内容写入传递给`writer.setResource()`方法的任何`Resource`。 `BatchConfig.java` ```java package com.howtodoinjava.demo.config; 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.core.launch.support.RunIdIncrementer; import org.springframework.batch.item.file.FlatFileItemReader; import org.springframework.batch.item.file.FlatFileItemWriter; import org.springframework.batch.item.file.MultiResourceItemReader; import org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper; import org.springframework.batch.item.file.mapping.DefaultLineMapper; import org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor; import org.springframework.batch.item.file.transform.DelimitedLineAggregator; import org.springframework.batch.item.file.transform.DelimitedLineTokenizer; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.core.io.FileSystemResource; import org.springframework.core.io.Resource; import com.howtodoinjava.demo.model.Employee; @Configuration @EnableBatchProcessing public class BatchConfig { @Autowired private JobBuilderFactory jobBuilderFactory; @Autowired private StepBuilderFactory stepBuilderFactory; @Value("input/inputData*.csv") private Resource[] inputResources; private Resource outputResource = new FileSystemResource("output/outputData.csv"); @Bean public FlatFileItemWriter<Employee> writer() { //Create writer instance FlatFileItemWriter<Employee> writer = new FlatFileItemWriter<>(); //Set output file location writer.setResource(outputResource); //All job repetitions should "append" to same output file writer.setAppendAllowed(true); //Name field values sequence based on object properties writer.setLineAggregator(new DelimitedLineAggregator<Employee>() { { setDelimiter(","); setFieldExtractor(new BeanWrapperFieldExtractor<Employee>() { { setNames(new String[] { "id", "firstName", "lastName" }); } }); } }); return writer; } @Bean public Job readCSVFilesJob() { return jobBuilderFactory .get("readCSVFilesJob") .incrementer(new RunIdIncrementer()) .start(step1()) .build(); } @Bean public Step step1() { return stepBuilderFactory.get("step1").<Employee, Employee>chunk(5) .reader(multiResourceItemReader()) .writer(writer()) .build(); } @Bean public MultiResourceItemReader<Employee> multiResourceItemReader() { MultiResourceItemReader<Employee> resourceItemReader = new MultiResourceItemReader<Employee>(); resourceItemReader.setResources(inputResources); resourceItemReader.setDelegate(reader()); return resourceItemReader; } @SuppressWarnings({ "rawtypes", "unchecked" }) @Bean public FlatFileItemReader<Employee> reader() { //Create reader instance FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>(); //Set number of lines to skips. Use it if file has header rows. reader.setLinesToSkip(1); //Configure how each line will be parsed and mapped to different values reader.setLineMapper(new DefaultLineMapper() { { //3 columns in each row setLineTokenizer(new DelimitedLineTokenizer() { { setNames(new String[] { "id", "firstName", "lastName" }); } }); //Set values in Employee class setFieldSetMapper(new BeanWrapperFieldSetMapper<Employee>() { { setTargetType(Employee.class); } }); } }); return reader; } } ``` `Employee.java` ```java public class Employee { String id; String firstName; String lastName; //public setter and getter methods } ``` `inputData1.csv` ```java id,firstName,lastName 1,Lokesh,Gupta 2,Amit,Mishra 3,Pankaj,Kumar 4,David,Miller ``` `inputData2.csv` ```java id,firstName,lastName 5,Ramesh,Gupta 6,Vineet,Mishra 7,Amit,Kumar 8,Dav,Miller ``` `inputData3.csv` ```java id,firstName,lastName 9,Vikas,Kumar 10,Pratek,Mishra 11,Brian,Kumar 12,David,Cena ``` ## Maven 依赖 查看项目依赖项。 `pom.xml` ```java <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd; <modelVersion>4.0.0</modelVersion> <groupId>com.howtodoinjava</groupId> <artifactId>App</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>App</name> <url>http://maven.apache.org</url> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.3.RELEASE</version> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-batch</artifactId> </dependency> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <scope>runtime</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> <repositories> <repository> <id>repository.spring.release</id> <name>Spring GA Repository</name> <url>http://repo.spring.io/release</url> </repository> </repositories> </project> ``` ## 示例 在运行该应用程序之前，请查看`App.java`的完整代码，该代码将其作为 Spring Boot 应用程序运行。 `App.java` ```java package com.howtodoinjava.demo; import org.springframework.batch.core.Job; import org.springframework.batch.core.JobParameters; import org.springframework.batch.core.JobParametersBuilder; import org.springframework.batch.core.launch.JobLauncher; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.scheduling.annotation.EnableScheduling; import org.springframework.scheduling.annotation.Scheduled; @SpringBootApplication @EnableScheduling public class App { @Autowired JobLauncher jobLauncher; @Autowired Job job; public static void main(String[] args) { SpringApplication.run(App.class, args); } @Scheduled(cron = "0 */1 * * * ?") public void perform() throws Exception { JobParameters params = new JobParametersBuilder() .addString("JobID", String.valueOf(System.currentTimeMillis())) .toJobParameters(); jobLauncher.run(job, params); } } ``` `application.properties` ```java #Disable batch job's auto start spring.batch.job.enabled=false spring.main.banner-mode=off ``` #### 运行应用程序 将应用程序作为 Spring 运行应用程序运行，并观察控制台。 批处理作业将在每分钟开始时开始。 它将读取输入文件，并在控制台中打印读取的值。 `outputData.csv` ```java 1,Lokesh,Gupta 2,Amit,Mishra 3,Pankaj,Kumar 4,David,Miller 5,Ramesh,Gupta 6,Vineet,Mishra 7,Amit,Kumar 8,Dav,Miller 9,Vikas,Kumar 10,Pratek,Mishra 11,Brian,Kumar 12,David,Cena ``` 将我的问题放在评论部分。 学习愉快！