Spring Batch `FlatFileItemWriter` – 写入 CSV 文件

原文：https://howtodoinjava.com/spring-batch/flatfileitemwriter-write-to-csv-file/

学习使用FlatFileItemWriter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

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

public class Employee {
    String id;
    String firstName;
    String lastName;
    //public setter and getter methods
}

inputData1.csv

id,firstName,lastName
1,Lokesh,Gupta
2,Amit,Mishra
3,Pankaj,Kumar
4,David,Miller

inputData2.csv

id,firstName,lastName
5,Ramesh,Gupta
6,Vineet,Mishra
7,Amit,Kumar
8,Dav,Miller

inputData3.csv

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

<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

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

#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

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！